JP5532649B2 - Node device, node processing program, and content storage method - Google Patents

Description

  The present invention relates to a technical field of a peer-to-peer (P2P) type communication system including a plurality of node devices that can communicate with each other via a network.

  This type of peer-to-peer communication system includes a plurality of node devices. Data files of various contents are distributed and stored in a plurality of node devices as duplicate data (hereinafter referred to as “replicas”) of a plurality of data files. The data file is a data file such as a movie and music. In general, a distributed storage system is known in which a replica can be used between node devices. This improves fault tolerance and access dispersibility. The location of the replicas thus distributed and stored can be efficiently searched using a distributed hash table (hereinafter referred to as DHT (Distributed Hash Table)) as disclosed in, for example, Patent Document 1.

  When the above-described node device acquires desired content, a message (query) for searching for the location of the replica of the content is transmitted to the other node devices. As a result, the message is transferred to the managing node device of the replica of the content according to the DHT. Then, the node device that has transmitted the message acquires information indicating the location of the replica from the management source node device. As a result, the node device that has transmitted the message can access the node device that stores the replica of the content related to the search. Then, the replica can be obtained (downloaded).

JP 2006-197400 A

  In a general peer-to-peer communication system, a node device that has acquired a content replica stores the replica as a cache in various storage means. Then, the node device deletes the cached content replica from the cache when a predetermined condition is satisfied. Among node devices participating in the communication system described above, a node device that does not cache a replica cannot respond to a content request from another node device, and the cache usage efficiency is reduced. . As a result, the node device has a low contribution to the system. Since each node device deletes a replica from the cache according to each determination, there is a problem in that the use efficiency of the cache is lowered as a whole peer-to-peer communication system.

  The present invention has been made in view of the above points. An object of the present invention is to provide a node device, a node processing program, and a content data storage method for determining whether there is free capacity in a cache of another node device and improving the cache usage efficiency as a whole peer-to-peer communication system. Is to provide.

  According to the first aspect of the present invention, there is provided a distributed content storage system including a plurality of node devices that can communicate with each other via a network, and a plurality of content data are distributed and stored in the plurality of node devices, The node device in the content distributed storage system in which the content data can be used between the node devices, the location information indicating the location of the node device participating in the content distributed storage system, and the node indicated by the location information Node information acquisition means for acquiring node information associated with capacity information for specifying the free storage capacity of the apparatus, storage means for storing the content data usable in the content distributed storage system, and the storage Content data stored in the means based on a predetermined condition. Delete means for deleting data, and determination means for determining whether or not there is a node device having the free storage capacity of a predetermined capacity or more based on the node information when the content data is deleted by the delete means When the determination unit determines that there is a free capacity, the content data deleted by the deletion unit is transmitted to the node device indicated by the node device identification information determined to have the free capacity. And a content transmission means.

  According to a second aspect of the present invention, the content transmission unit transmits the content deleted by the deletion unit to the node device having the largest available capacity.

  According to the invention of claim 3, a routing table acquisition unit that acquires a routing table including the location information of a node device capable of transmitting a message including content for processing a predetermined request from the node device, and the deletion Search message transmission means for transmitting a search message for searching for the capacity information of the node device indicated by the location information described in the routing table according to the routing table when the content data is deleted by means; The node information acquisition unit acquires the node information in which the location information and the capacity information are associated with each other from the node device that has received the search message, and the determination unit uses the node information acquisition unit. More than a predetermined capacity based on the acquired node information Wherein the come storage capacity is a node device determines whether or not there.

  According to a fourth aspect of the present invention, the node information acquisition unit includes the location information in a routing table including the location information of a node device capable of transmitting a message including content for processing a predetermined request from the node device. And the free space are stored in association with each other, and the determination unit determines whether or not the free space of the node device described in the routing table is greater than or equal to a predetermined capacity, and the determination unit includes the free space When it is determined that there is capacity, the content transmission means transmits the content to be deleted to a node device described in the routing table and having free capacity.

  According to the invention described in claim 5, the storage means stores publication time information in which a publication time for publishing the content data is described. The storage means stores the publication time information based on the publication time information. A disclosure time determination unit that determines whether or not the publication time of the content data that has been released has ended, and when the publication time determination unit determines that the publication time has ended, the deletion unit deletes the content data However, the determination unit does not perform the determination, or the content transmission unit does not transmit the content to be deleted.

  According to the invention described in claim 6, the storage means stores the content data stored in the storage means in association with the evaluation value of the content data, and the deletion means stores the predetermined data As a condition, content having the evaluation value lower than a predetermined value in the content data stored in the storage unit is deleted from the storage unit.

  According to the seventh aspect of the present invention, the participation processing determination unit that determines whether or not a new node device participates in the content distribution storage system, and the participation processing determination unit causes the new node device to perform the content distribution. When it is determined to participate in the storage system, the determination unit determines whether the new node device has the free storage capacity equal to or greater than a predetermined capacity, and the determination unit determines whether the free storage capacity is in the new node. If it is determined that there is a content, the content transmission means transmits the deleted content to the new node.

According to the invention described in claim 8, it is a content distributed storage system comprising a plurality of node devices that can communicate with each other via a network, a plurality of content data is distributed and stored in the plurality of node devices, Location information indicating the location of a node device participating in the content distributed storage system and a node indicated by the location information in a computer of the node device in the content distributed storage system in which the content data can be used between the node devices Node information acquisition step for acquiring node information associated with capacity information for specifying the free storage capacity of the device, and storage means for storing the content data usable in the content distributed storage system Content based on predetermined conditions of content data A determination step for determining whether or not there is a node device having the free storage capacity equal to or larger than a predetermined capacity based on the node information when the content data is deleted by the deletion step. And when the determination step determines that there is a node device when there is the free capacity, the content data deleted by the deletion step to the node device indicated by the node device identification information determined to have the free capacity A content transmission step for transmission and a program executed by a computer .

  According to the ninth aspect of the present invention, there is provided a content distributed storage system including a plurality of node devices that can communicate with each other via a network, and a plurality of content data are distributed and stored in a plurality of node devices, A content distributed storage system that enables the content data to be used between the node devices, wherein the location information indicating the location of the node device participating in the content distributed storage system, and the free storage capacity of the node device indicated by the location information Node information acquisition means for acquiring node information associated with capacity information for specifying the content, storage means for storing the content data usable in the content distributed storage system, and stored in the storage means Deletion that deletes content data based on specified conditions And determining means for determining whether or not there is a node device having the free storage capacity of a predetermined capacity or more based on the node information when the content data is deleted by the deleting means; Content acquisition means for acquiring content data to be deleted by the deletion means when the node apparatus indicated by the node apparatus identification information determined to have free capacity is A content distributed storage system comprising:

According to the invention described in claim 10, a content distributed storage system including a plurality of node devices that can communicate with each other via a network, a plurality of content data is distributed and stored in the plurality of node devices, A content storage method in a content distributed storage system in which the content data can be used between the node devices, wherein the location information indicates the location of a node device participating in the content distributed storage system, and the node indicated by the location information Node information acquisition step for acquiring node information associated with capacity information for specifying the free storage capacity of the device, and storage means for storing the content data usable in the content distributed storage system Content data based on predetermined conditions And a determination step of determining whether or not there is a node device having the free storage capacity of a predetermined capacity or more based on the node information when the content data is deleted by the deletion step. When the determination step determines that there is a node device having the free capacity, the node device indicated by the node device identification information determined to have the free capacity acquires the content data to be deleted by the deletion step. A content acquisition method comprising: a content acquisition step.

  According to the first aspect of the present invention, the node information acquisition means includes the location information indicating the location of the node device participating in the distributed content storage system, and the capacity for specifying the free storage capacity of the node device indicated by the location information. Node information associated with information is acquired. When the determination unit determines that there is free space, the content transmission unit transmits content data to the node device indicated by the node device identification information determined to have free space. Accordingly, the content deleted from the node device is transmitted to the node device having a low contribution to the system. As a result, the content that is originally deleted is transmitted to a node device with a low contribution that has a sufficient free space. Since the contents that should have been deleted can be used in the distributed storage system, the cache usage efficiency of the entire system can be improved.

  According to the second aspect of the present invention, the content transmitting unit transmits the content deleted by the deleting unit to the node device having the largest available capacity. The node device with the largest available capacity is a node device with a low contribution to the system. For this reason, the content that should have been deleted is transmitted to the node device having a low contribution, so that the contribution of each node device to the system is greatly improved.

  According to the third aspect of the present invention, when the content data is deleted by the deletion unit, the search message transmission unit searches the capacity information of the node device indicated by the location information described in the routing table according to the routing table. Send a search message. The determination unit determines whether there is a node device having a free storage capacity of a predetermined capacity or more based on the node information acquired by the node information acquisition unit. Therefore, when content is deleted, a node device having a predetermined free storage capacity is searched using the routing table. At the timing when the content is deleted, a node device having a low contribution to the content distributed storage system is searched. As a result, the content to be deleted is transmitted to the node device having a low contribution when the content is deleted, so that the cache usage efficiency of the entire system can be reliably improved.

  According to a fourth aspect of the present invention, the node information acquisition means associates a free space with a routing table including location information of a node device capable of transmitting a message including content for processing a predetermined request from the node device. Remember. When the determination unit determines that there is free space, the content transmission unit transmits the content to be deleted to the node device described in the routing table and having free space. As a result, it is possible to determine, from the plurality of node devices constituting the distributed storage system, a node device that can be connected to the node device from which the content is deleted, without searching for free space by a search message. .

  According to the invention described in claim 5, the storage means stores the publication time information in which the publication time for publishing the content data is described. When the publication time determination unit determines that the publication time has ended, the deletion unit deletes the content data, and the determination unit does not perform the determination, or the content transmission unit does not transmit the deleted content. As a result, even if the content whose publication time has ended is sent to a node device having a sufficient storage capacity, the content whose publication time has ended will not be used in the future. As a result, even if the node device has a sufficient storage capacity, the content data that will not be used in the future after the release period ends is not transmitted. As a result, content that will not be used in the future is not transmitted, so that the cache usage efficiency of the entire system can be improved.

  According to the sixth aspect of the present invention, the storage unit stores the content data stored in the storage unit and the evaluation value of the content data in association with each other. The deletion unit deletes content having an evaluation value lower than a predetermined value from the storage unit in the content data stored in the storage unit as a predetermined condition. If there is a node device with a sufficient storage capacity, even content with a low evaluation value is stored in the storage means. As a result, the contribution of the entire system can be improved, and contents with a low evaluation value that should have been deleted can be used in the distributed storage system.

  According to the seventh aspect of the present invention, the participation process determination means determines whether or not a new node device participates in the content distributed storage system. When the determination unit determines that the new node has free storage capacity, the content transmission unit transmits the content to be deleted to the new node. As a result, even if a node device newly participates in the distributed storage system, if there is enough free space, the content that should originally be deleted is transmitted. As soon as a new node joins, it becomes a node device with a high degree of contribution, so the contribution of each node device to the system is also improved.

According to the eighth aspect of the present invention, the content deleted from the node device is transmitted to the node device having a low contribution to the system. As a result, the content that is originally deleted is transmitted to a node device with a low contribution that has a sufficient free space. Since the contents that should have been deleted can be used in the distributed storage system, the cache usage efficiency of the entire system can be improved.

  According to the ninth aspect of the present invention, the node information acquisition means includes the location information indicating the location of the node device participating in the distributed content storage system, and the capacity for specifying the free storage capacity of the node device indicated by the location information. Node information associated with information is acquired. When the determination unit determines that there is a node device having free capacity, the content acquisition unit acquires content data to be deleted by the deletion unit from the node device indicated by the node device identification information determined to have free space. Therefore, the content deleted from the node device is acquired by the node device having a low contribution to the system. As a result, the content that is originally deleted is acquired to a node device with a low contribution that has a sufficient free space. Since the contents that should have been deleted can be used in the distributed storage system, the cache usage efficiency of the entire system can be improved.

According to the tenth aspect of the present invention, the node information acquisition step includes the location information indicating the location of the node device participating in the distributed content storage system and the capacity for specifying the free storage capacity of the node device indicated by the location information. Node information associated with information is acquired. In the content transmission step, when the determination step determines that there is a node device having free capacity, the node device indicated by the node device identification information determined to have free space acquires the content data deleted by the deletion step. . Therefore, the content deleted from the node device is acquired by the node device having a low contribution to the system. As a result, the content that is originally deleted is transmitted to a node device with a low contribution that has a sufficient free space. Since the contents that should have been deleted can be used in the distributed storage system, the cache usage efficiency of the entire system can be improved.

It is a figure which shows an example of the connection aspect of each node apparatus Nn in the content distribution storage system of this embodiment. It is a conceptual diagram which shows an example of the routing table which the node N2 hold | maintains. It is a conceptual diagram which shows an example of ID space of DHT. It is a conceptual diagram which shows an example of the production | generation procedure of the routing table at the time of participating in the content distribution storage system S. It is a conceptual diagram which shows the mode of the message transferred between each node Nn. It is a figure which shows an example of the index cache which node N2 hold | maintains. It is a conceptual diagram which shows the mode of the publish message transferred between each node Nn. It is a conceptual diagram which shows the electric constitution of the node apparatus Nn. It is a flowchart which shows the main process operation | movement of node apparatus Nn.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best embodiment of the invention will be described based on the drawings.

[Configuration of distributed content storage system]
FIG. 1 shows a distributed content storage system S of this embodiment. The content distributed storage system S is composed of multiple node devices Nn (n = 1, 2, 3...).

  As shown in a lower frame 101 of FIG. 1, a general network 8 such as the Internet includes an IX (Internet eXchange) 3, ISP (Internet Service Provider) 4a and 4b, and a DSL (Digital Subscriber Line) line provider device. 5a and 5b, an FTTH (Fiber To The Home) line provider apparatus 6, a communication line 7, and the like. For example, the communication line 7 is a telephone line or an optical cable. Note that a router for transferring data (packets) is appropriately inserted into the network 8 in the example of FIG.

  The network 8 is composed of a large number of node devices Nn (n = 1, 2, 3,...). A large number of node devices Nn are connected via the Internet via a router or the like. Each node device Nn is assigned a unique manufacturing number and an IP (Internet Protocol) address. The content distributed storage system S of this embodiment is a peer-to-peer network system. As shown in the upper frame 100 of FIG. 1, the peer-to-peer network system is formed by the participation of any one of the node devices Nn among these node devices Nn.

  A P2P network 9 shown in the upper frame 100 of FIG. 1 is a P2P network formed using the existing network 8. The P2P network is constructed by virtually linking a plurality of node devices in the upper frame 100 of FIG. The P2P network 9 is an overlay network or a logical network. The P2P network 9 is constructed by a specific algorithm. For example, the P2P network 9 is constructed by an algorithm using DHT described in Japanese Patent Application Laid-Open No. 2006-197400.

  A node ID is assigned to each node device Nn constituting the P2P network 9. The node ID is unique identification information consisting of a predetermined number of digits. Specifically, the node ID is generated based on the IP address or the serial number assigned individually to each node device Nn. The node ID is a value obtained by hashing the above-described IP address or manufacturing number with a common hash function. For example, a hash value having a bit length of 160 bits is generated by a hash function such as SHA-1. Each node ID is distributed in a certain ID space without any deviation.

  As shown in FIG. 1, the content distribution storage system S includes a content input server CS. The content input server CS is a server for inputting new content data into the content distributed storage system S. The content input server CS inputs a replica obtained by duplicating the content data to the content distributed storage system S.

  In participation in the distributed content storage system S, a node device Nn not currently participating in the P2P network 9 transmits a participation message indicating a participation request to any node device Nn currently participating. The node device that receives the participation message is a node device that always participates in the distributed content storage system S. In this embodiment, a node device that is always participating is used as a contact node. For example, when the node device not participating in the P2P network 9 is the node device N8, the node device N8 transmits a transmission request message to the contact node of the content distributed storage system S. The contact node transmits information necessary for participating in the P2P network 9 to the node device N8 that is the transmission source of the request message. Details of the necessary information will be described later.

  Each node device Nn stores a routing table using DHT described in Patent Document 1 in a storage unit of each node device Nn. The routing table defines transmission destination candidate destinations of various messages on the content distribution storage system S. Specifically, node information is described in the routing table. In this embodiment, “node ID”, “IP address and port number”, and “free recording capacity” of the message transmission destination candidate are described as the node information. The “node ID” of the message destination candidate is the “node ID” of the node Nn that is moderately separated in the ID space. The “IP address or port number” of the message destination candidate is the IP address and port number of the node indicated by the node ID. The “free recording capacity” of the message transmission destination candidate is the free capacity of the storage means for storing the content and the replica. Specifically, the free space is configured by an HD (Hard Disk) which is an example of content recording means.

  The “IP address or port number” is an example of address information. The “free recording capacity” is an example of “information for specifying the free recording capacity” in the storage unit. The “information for specifying the free recording capacity” of the storage unit is not limited to the free recording capacity of the storage unit as long as it is information that can specify the free recording capacity of the storage unit of the node device Nn. For example, it may be information indicating the total operating time of the node device Nn as a device. Alternatively, it may be information indicating the number of times the node device Nn has acquired a replica in the past (download count). Alternatively, it may be information indicating the number of times (viewing number) of reproduction of the replica acquired by the node device Nn. Alternatively, it may be information indicating the number of save instructions (pre-distribution count) received in the past from another node device Nn or the content input server CS by the node device Nn. Alternatively, it may be information indicating the number of times that the node device Nn has made the replica available to other node devices Nn (the number of times of disclosure). It can be specified that the smaller the total operating time is, the larger the free recording capacity of the storage unit is. It can be specified that the smaller the number of downloads, the number of viewings, etc., the larger the available recording capacity of the storage unit.

  The routing table of a node device Nn participating in the content distributed storage system S describes at least a part of node information of the node device Nn participating in the content distributed storage system S. As described in Patent Document 1, a node device Nn whose node information is not described in the DHT table transfers various messages between the node devices Nn to be delivered.

  In the present embodiment, when various messages are transmitted or transferred to the above-described other node device Nn using the routing table, the message transmission source or the free recording capacity of the transfer source node Nn is included in the message. Sent. Each node device Nn that has received this message registers and updates the received node information in the routing table and index cache held by each node device Nn. With this configuration, each node device Nn can grasp the free recording capacity of other node devices. A detailed description of how to register and update the routing table and index cache will be given later.

[Routing table overview]
Hereinafter, the function of each node device Nn in the content distributed storage system S will be described. The “routing table” stored in each node device Nn will be described in detail. Here, the routing table will be described in detail with reference to FIGS.

  FIG. 2 is a diagram illustrating an example of a routing table held by the node N2, and FIG. 3 is a conceptual diagram illustrating an example of an ID space of DHT. 2 and 3, for convenience of explanation, the bit length of the node ID is 2 bits × 3 digits = 6 bits. Therefore, each digit is represented by a quaternary number (integer of 0 to 3) represented by 2 bits. A bit length longer than 2 bits may be used for the case digit. For example, each digit may be represented by 4 bits and represented by a hexadecimal number of 0 to f.

  FIG. 2 is a conceptual diagram showing a routing table of the node N2. As shown in FIG. 2, the routing table is composed of a plurality of levels from level 1 (first stage) to level 3 (third stage). Node information is registered in each area. As node information, the node ID, the IP address and port number of the node device Nn corresponding to the node ID, and the free recording capacity of the storage unit of the node device Nn indicated by the node ID are registered in association with each other.

  Each area at each level is an area determined by dividing the node ID space. FIG. 3 is a conceptual diagram in which each area is determined using a node ID. The node ID space is configured by a three-digit number in which each digit is represented by a quaternary number (an integer from 0 to 3). As shown in FIG. 3, as a level 1 area, the node ID space is divided into four (due to quaternary numbers). Specifically, the level 1 area is divided into an area of 0XX, an area of 1XX, an area of 2XX, and an area of 3XX. The area of 0XX is an area where node IDs “000” to “033” exist. The 1XX area is an area where node IDs “100” to “133” exist. The 2XX area is an area where node IDs “200” to “233” exist. The 3XX area is an area where node IDs “300” to “333” exist.

  In level 2, the level 1 area is further divided into four (due to quaternary numbers). That is, each area from 0XX to 3XX is further divided into four. Similarly, the 0XX area, the 1XX area, the 2XX area, and the 3XX area are each divided into four. For example, in the case of a 1XX area, an area where node IDs “100” to “103” exist is divided as a 10X area. Also, the area where the node IDs “110” to “113” exist is divided as an 11X area. An area where node IDs “120” to “123” exist is divided into 12 × areas. An area where node IDs “130” to “133” exist is divided as a 13X area.

  Hereinafter, a case where the node ID of the node N2 is “122” will be described as an example. As shown in FIG. 2, the area of 1XX in level 1 of the routing table is an area where the node ID of the node N2 exists. Therefore, the node ID of the node N2, the IP address or port number, and the free recording capacity of the storage unit are registered in the level 1 1XX area. In this embodiment, the node ID, IP address or port number, and free recording capacity of the node N2 itself are registered. However, since the IP address, port number, and free recording capacity are those of the node N2, the node N2 is not registered. Also good. In the area where the node ID of the node N2 does not exist, the node ID of another arbitrary node device Nn, the IP address or port number, the free recording capacity, and the like are registered. When the node ID of the node N2 is “122”, the areas where the node ID of the node N2 does not exist are the 0XX area, the 2XX area, and the 3XX area.

  Further, the 12X area in the level 2 of the routing table is an area where the node ID of the node N2 exists. Therefore, the node ID of the node N2, the IP address or the port number, and the free recording capacity of the storage unit are registered in the 12X area of level 2. In this embodiment, the node ID, IP address or port number, and free recording capacity of the node N2 itself are registered. However, since the IP address, port number, and free recording capacity are those of the node N2, the node N2 is not registered. Also good. In the area where the node ID of the node N2 does not exist, the node ID of the other arbitrary node device Nn, the IP address or port number, the free recording capacity, and the like are registered in the same manner as in the level 1.

  Further, in the level 3 of the routing table, as shown in FIG. 2, the node IDs are “120” to “122”. Therefore, the node ID of the node N2, the IP address or port number, and the free recording capacity of the storage unit are registered in the area of level 3 122. In this embodiment, the node ID, IP address or port number, and free recording capacity of the node N2 itself are registered. However, since the IP address, port number, and free recording capacity are those of the node N2, the node N2 is not registered. Also good.

  In the example of FIGS. 2 and 3, the bit length of the node ID is 3 digits × 2 bits. For example, when the bit length of the node ID is 16 digits × 4 bits, a table for 16 levels is required. As shown in FIGS. 2 and 3, in the routing table according to the present embodiment, the area becomes narrower as the numerical value of the level increases. Such a routing table is generated, for example, when a non-participating node participates in the content distribution storage system S. Here, with reference to FIG. 4, a procedure for generating a routing table when participating in the distributed content storage system S will be described in detail.

  FIG. 4 is a conceptual diagram showing an example of a routing table generation procedure at the time of participation in the distributed content storage system S. Hereinafter, description will be made using an example in which the non-participating node N8 participates in the content distribution storage system S. The node ID of the node N8 is “123”.

  As shown in FIG. 4, when a node N8 that has not participated participates in the content distribution storage system S, a participation message is transmitted to the contact node using the IP address of the contact node. The participation message includes node information of the node N8. It is assumed that the node device Nn knows in advance the IP address for transmitting a message to the contact node. For example, when downloading software necessary to participate in a P2P network, the IP address of the contact node is distributed. The contact node that has received the participation message refers to the routing table of the contact node. Specifically, the node information registered in the level 1 table in the routing table is referred to. The contact node returns a reply message including the node information registered in the level 1 table to the node N8. Furthermore, the contact node compares the node ID included in the received participation message with the node ID of another node Nn registered in the routing table. One node Nn is selected from the routing table based on the comparison result. For example, the node N35 that is the node ID closest to the node ID included in the participation message is selected. The closest node ID is an ID with a higher number of upper digits that match or an ID with the smallest difference from the compared node ID. A description will be given using an example in which the selected node device is the node device N2. At this time, the participation message includes information indicating the number of steps of the table to be returned next. In the above example, level 2 is included in the participation message.

  The node N35 that has received the participation message returns a reply message including node information registered in the level 2 table of the routing table of the node N35 to the node N8. Further, the node N35 transfers the participation message to the node N2 selected from the routing table. At this time, information indicating level 3 is included in the participation message as the number of steps of the table to be returned next.

  The node N2 that has received the participation message returns a reply message including node information registered in the level 3 table in the routing table of the node N2 to the node N8. As described above, the participation message is transferred based on the DHT routing using the node ID as a key. Therefore, the data is transferred to the node Nn having the node ID closest to the node ID of the non-participating node N8.

  Then, the node N8 generates a routing table using the node information included in the reply message received from each node Nn. Specifically, the node information transmitted from the contact node is registered in the table 1 of the routing table of the node N8. The node information transmitted from the node N35 is registered in the level 2 of the node N8 routing table. The node information transmitted from the node N2 is registered in the level 3 of the routing table of the node N8.

  Thus, the node N8 completes participation in the content distributed storage system S.

  In the present embodiment, the participation message as described above and various messages such as a query to be described later include the node information of the node device Nn that is the message transmission source or transfer source. Therefore, the node device Nn that has received the message registers and updates the node information included in the message in the routing table of the node device Nn.

  FIG. 5 is a conceptual diagram showing a state of a message transferred between the node devices Nn. Specifically, FIG. 5 is a conceptual diagram in which a participation message from the node N8 is transferred between the node N31, the node N35, and the node N2.

  The message transferred between the node devices Nn includes the node ID of the message transmission source, the content of the message, and the node information of the transmission source node Nn. The node ID of the message transmission source is the node ID of the node Nn of the transmission source that transmitted the message. The contents of the message are “participation”, “publish”, “query”, and the like indicating the purpose of the message. The node information of the transmission source node Nn is the node information of the transmission source or transmission source node Nn that has transmitted or transferred the message. Specifically, the node information includes the node ID of the source or transfer source node Nn, the IP address or port number, and the free recording capacity of the storage means. In the case of a participation message, the “message content” includes information indicating that a reply to registration information in the table is requested. In the case of a publish (registration) message or query, the content ID of the content to be published (registered) or queried (request) is included.

  In the example shown in FIG. 5, the node N35 receives the participation message from the node N31 of the contact node, and registers the node information of the transmission source or transfer source node N31 included in the participation message in the routing table of the node N35. . At this time, when the node information of the node N31 is already registered in the routing table of the node N35, the node information of the registered node N31 is updated based on the received node information.

   Similarly, the node N2 that has received the participation message from the node N35 registers or updates the node information of the transmission source or transfer source node N35 included in the participation message in the routing table of the node N2.

  According to the above procedure, the routing table registers or updates node information. Therefore, it is possible to acquire the free recording capacity of the storage unit of the node Nn registered in the routing table. Also, the free recording capacity of the routing table can always be kept up-to-date.

[Index Cache]
In the content distributed storage system S, various content replicas having different contents are distributed and stored in a plurality of node devices Nn in a predetermined file format. The content is a movie and a movie or music. A replica can be transmitted and received between the node devices Nn. For example, it is assumed that a replica of a movie content whose title is XXX is stored in the node N5. On the other hand, it is assumed that a replica of the movie content whose title is YYY is stored in the node device N3. As described above, the plurality of node devices Nn store replicated replicas. Hereinafter, the node device Nn that stores the content is referred to as a “content holding node”.

  Each of these content replicas is provided with information including a content name (title) and a content ID. The content name may be a content title. The content ID is content identification information unique to each content. For example, the content ID is generated by hashing the content name + arbitrary numerical value with a hash function common to that for obtaining the node ID. For this reason, the content ID is arranged in the same ID space as the node ID. Alternatively, the system administrator may give a unique ID value for each content. The ID value may have the same bit length as the node ID. A content catalog list in which the correspondence between content names and content IDs is written is distributed to all nodes Nn. In the content catalog list, the content name, the content ID, and the publication start date and time and the publication end date and time of the replica represented by the content ID are described in association with each other. Details of the content catalog list are described in Japanese Patent Application Laid-Open No. 2008-129694, and detailed description thereof is omitted.

  As described above, the location of replicas distributed and stored is managed by index information. The index information is composed of information obtained by combining the node information of the node device Nn in which the replica is stored and the content ID of the replica. The index information is stored by the node Nn that manages the location of the replica. A node that manages the location of the replica is defined as a “root node”. That is, the node information of the content holding node storing the content replica is managed by the root node so as to be provided in response to an inquiry from another node Nn.

  For example, the index information about the replica of the movie content whose title is XXX is managed by the node N4 which is the root node of the content ID of the replica. The index information about the replica of the movie content whose title is YYY is managed by the node N7 which is the root node of the content ID of the replica. For example, a node Nn having a node ID closest to the content ID is selected as such a root node. For example, “closest to the content ID” means that the upper digits match more or the difference between the comparison results is the smallest.

  FIG. 6 is a conceptual diagram illustrating an example of an index cache held by the node N2. The node N2 registers and manages the node information of the content holding node that stores the content 1, the content 2, the content 3,. The node N2 is a root node for content 1, content 2, content 3,. The node N2 receives a publish (registration) message described later from the content holding node Nn shown in FIG. Then, the node N2 registers the content ID and node information included in the publish message in the index cache as index information.

  When a user of a certain node device Nn wants to acquire a replica of the desired content, the node device Nn that desires to acquire the replica generates a content location inquiry message (query). A node device Nn that the user desires to acquire a replica is set as a user node. The query includes the content ID of the content and the IP address of the user node. The content ID included in the query is the content ID of the content selected from the content catalog list by the user.

  The user node transmits a query to another node Nn according to the routing table of the user node. That is, the user node transmits the query toward the root node. Thus, the query finally arrives at the root node by DHT routing using the content ID as a key. Since this DHT routing is known in Japanese Patent Laid-Open No. 2006-197400 and the like, detailed description thereof is omitted.

  Information selected by the user in each node device Nn is described in the content catalog list. In the content catalog list, the content name of the content, the content ID, and attribute information such as the release date and time are described. The content ID included in the query may be generated by the user node by hashing the content name with the common hash function.

  The root node that has received the query acquires index information corresponding to the content ID included in the query from the index cache. The acquired index information is returned to the user node that is the transmission source of the query. Thus, the user node that has acquired the index information can know the IP address of the content holding node from the acquired index information. Based on the acquired IP address of the content holding node, the user node transmits a content transmission request message. The user node can acquire (download) a replica of the content from the content holding node. When acquiring a replica, the content ID of the replica and the evaluation value of the replica are acquired together with the replica.

  Then, the user node stores the content replica acquired from the content holding node in a storage unit such as a hard disk. The user node storing the replica informs the root node that the replica has been stored. In order to notify that the replica has been saved, the user node generates a publish (registration) message including the content ID of the replica and the node information of the user node. The generated publish message is transmitted from the user node to the root node. By transmitting the publish message, the other node devices Nn participating in the distributed content storage system S can acquire (download) the replica from the user node that acquired the replica.

  According to the above-described method, the publish message arrives at the root node by DHT routing using the content ID as a key, like the query. The root node can register index information including a set of node information of the user node and a content ID of the replica included in the received publish message. In this way, the user node becomes a new content holding node that holds a replica of the content. Note that the index information that is a set of the node information of the user node device and the content ID included in the publish message is also registered in the node device Nn in the transfer path up to the root node.

  FIG. 7 is a conceptual diagram showing a state of a publish message transferred between the node devices Nn. FIG. 7 shows an example in which a publish message is transmitted from the node N1 storing a replica of an arbitrary content. The transmitted publish message is transferred between the node N7, the node N29, and the node N2. The publish message includes the node information of the source node device Nn that has transmitted the publish message, the content ID, and the node information of the transfer source node device Nn that has transferred the publish message. In the node device Nn on the publish message transfer path, the node information of the source node device Nn is registered in the index cache. The node information of the transfer source node Nn is registered in the routing table.

  In the case of the example shown in FIG. 7, the node N7 that has received the publish message from the node N1 that holds arbitrary content registers the node information of the source node N1 in the index cache of the node N7. At this time, when the node information of the node N1 is already registered in the index cache, the node N1 is updated based on the registered node information. The node N29 that has received the publish message from the node N7 registers or updates the node information of the transmission source node N1 included in the publish message in the index cache of the node N29.

  Further, the node N29 registers the node information of the transmission source node N7 included in the publish message in the routing table of the node N29. At this time, when the node information of the node N7 is already registered in the routing table, the registered node information is updated based on the received node information.

  Then, the node N2 that has received the publish message from the node N29 registers or updates the node information of the transmission source node N1 in the index cache of the node N2. The node information of the source node N29 is registered or updated in the routing table of the node N2.

  In the example shown in FIG. 6, the node N2 stores the free recording capacities of the nodes N1, N14, N21, and N11 that store the content 1 in the index cache. Further, the node N2 stores the free storage capacity of the node N35 that stores the content 2. Similarly, the node N2 stores free recording capacities of storage units of the nodes N32, N22, and N5 that store the content 3. Since the node information of the index cache is registered or updated according to the procedure described with reference to FIG. 7, the free recording capacity of the storage unit of the node Nn registered in the index cache can always be kept up-to-date. .

[Outline of content input server CS]
Next, the content input server CS will be described.

  The content input server CS instructs the arbitrary node Nn of the content distributed storage system S to store the replica. The replica storage instruction is an instruction including the storage capacity of the replica to be stored. The node Nn that has received the save instruction repeatedly issues the save instruction to the other node devices Nn. By repeating, the replica is pre-stored in the content storage / distribution system S.

  In the present embodiment, when the content input server CS instructs the storage of the content replica, the content replica is transmitted together with the storage instruction to the storage destination node device Nn. So-called “push-type” content storage is performed.

  The content input server CS may be configured to instruct storage of a replica to an arbitrary number of nodes Nn selected at random. An arbitrary number of node devices Nn are randomly selected from the node devices Nn participating in the content distributed storage system S. The method for determining the node Nn to which the replica storage instruction is transmitted is not particularly limited to the above method.

  The replica transmitted from the content input server CS is stored in a predetermined node device Nn. The content pre-holding node that stores the replica instructs other nodes Nn to store the replica based on the routing table of the content holding node.

[Electric configuration of node equipment]
Next, the electrical configuration of the node Nn will be described with reference to FIG.

  FIG. 8 is a block diagram showing an electrical configuration of the node device Nn of this embodiment. As shown in FIG. 8, the node device Nn according to the first embodiment includes a CPU 11 that controls the node device Nn. A RAM 12, an HDD 13, a decoder unit 14, a communication unit 19, and an input unit 20 are electrically connected to the CPU 11, respectively. The storage means such as the RAM 12 and the HDD 13 and the CPU 11 constitute a computer of the node device Nn. The computer controls the operation of the node device Nn.

  The RAM 12 includes various message temporary storage areas 121. The various message temporary storage area 121 temporarily stores various messages received by the node device Nn. For example, a participation message or a query.

  The HDD 13 includes a program storage area 131, a replica storage area 133, an index cache storage area 134, a routing table storage area 135, and a content catalog list storage area. The program storage area 131 includes a main operation program storage area 132. The main operation program storage area 132 stores program information for controlling the node device Nn. The replica storage area 133 stores a replica transmitted from the content input server CS or another node device Nn. The replica storage area 133 stores the evaluation value of the stored replica in association with the replica. The index cache storage area 134 stores the above-described index cache. The routing table storage area 135 stores the above-described DHT routing table. The content catalog list storage area 136 stores the content catalog list described above. The replica storage area 133 is an example of storage means of the present invention. The index cache storage area 134 and the routing table storage area 135 of this embodiment are an example of node information acquisition means of the present invention.

  The decoder unit 14 decodes video information and audio information. Decoding in this embodiment is data expansion or decoding of encoded video information and audio information. Video information and audio information are included in a replica of content data.

  The video processing unit 15 performs a predetermined drawing process on the decoded video information and outputs a video signal.

  The display 16 displays a video based on the video signal output from the video processing unit 15. The display 16 is configured by a CRT display or a liquid crystal display.

  The audio processing unit 17 performs D (Digital) / A (Analog) conversion of the decoded audio information into an analog audio signal.

  The speaker 18 amplifies the changed analog audio signal by an amplifier and outputs it.

  The communication unit 19 connects the node device Nn to the Internet. The communication unit 19 transmits / receives information to / from another node device Nn or the content input server CS via the network 8.

  The input unit 20 receives an instruction from the user. The input unit 20 includes a keyboard, a mouse, an operation panel, or the like. As the node device Nn, a personal computer, an STB (Set Top Box), a TV receiver, or the like is applicable.

  Further, when the content distributed storage system S includes a contact node that is an access destination when participating in the content distributed storage system S, the IP address or port number of the contact node is stored in the HDD 13 of each node device Nn. Has been. The program stored in the HDD 13 may be downloaded from a predetermined server on the network 8, for example. Further, the program may be recorded on a recording medium such as a CD-ROM and read via a drive of the recording medium.

  When transmitting or transferring various messages to another node Nn, the CPU 11 acquires the free recording capacity of the HDD 13. For example, the total capacity of the storage area of the hard disk used for the replica storage area 133 of the HDD 13 and the used capacity already used are required. The available recording capacity is obtained by subtracting the used capacity from the total capacity (free recording capacity = total capacity−used capacity). Further, as a free recording capacity, a ratio between the total capacity and the used capacity may be used without subtraction as described above. The storage capacity of the replica storage area 133 may be used as the above-described total capacity or usage.

[Main processing operation of node device Nn]
The operation and action of the node device Nn of the present embodiment having the above-described configuration will be described with reference to the accompanying drawings. FIG. 9 is a flowchart illustrating a processing procedure of an operation in the node device Nn. The main processing operation of the node device Nn is performed by the CPU 11 executing the main processing operation program after the above-described participation process to the P2P network is completed. The processing shown below is processed by the CPU 11. The node device Nn on which the process of joining the P2P network is executed acquires a content catalog list from another node device or the content input server CS. The acquired content catalog list is stored in the content catalog list storage area 136.

  In step S101, it is determined whether or not there is a new node device to participate. Whether or not a new node device has joined is determined by whether or not a join message has been received. The participation message is stored in various message temporary storage areas 121. If it is determined that there is a new participating node, step S116 is executed. If it is determined that there is no new participating node, step S102 is executed. The computer of the present invention and step S101 are examples of the participation means of the present invention.

  In step S102, it is determined whether the node device Nn has received a replica storage instruction from another node device Nn different from the node device Nn or the content input server CS. The replica storage instruction includes the storage capacity of the replica to be stored. If it is determined that the replica storage instruction has been received, step S103 is executed. If it is not determined that the replica storage instruction has been received, step S106 is executed.

  In step S103, it is determined whether there is a storage capacity capable of storing the replica. The storage capacity included in the save instruction received in step S102 is compared with the free recording capacity of the node device Nn. As a result of the comparison, if it is determined that the free recording capacity of the node device Nn is larger than the storage capacity included in the save instruction, step S104 is executed. If it is not determined that the free recording capacity of the node device Nn is larger than the storage capacity included in the save instruction, step S111 is executed.

  In step S104, the replica instructed to save in step S102 is stored in the replica storage area 133.

  In step S105, the node Nn that stores the replica in step S104 transmits a publish message based on the DHT routing table. Each node device Nn that has received the publish message registers or updates the index cache stored in the index cache storage area 134 based on the publish message.

  In step S <b> 106, it is determined whether a predetermined instruction is input from the input unit 20 by the user of the node device Nn. If it is determined that there is a predetermined instruction by the user, step S107 is executed. If it is determined that there is no predetermined instruction by the user, step S111 is executed.

  In step S107, it is determined whether or not the predetermined instruction from the user is a predetermined replica download instruction. If it is determined that the instruction is to download a predetermined replica, step S108 is executed. If it is not determined that the instruction is to download a predetermined replica, step S110 is executed.

  In step S108, a content location inquiry message (query) of the predetermined replica designated in step S107 is transmitted. The content location inquiry message (query) is a message for inquiring about the location of the replica described above.

  In step S109, the predetermined replica instructed in step S107 is downloaded based on the query transmitted in step S108.

  In step S110, other instructions are executed. The other instructions are instructions different from the download instruction in step S107. Other instructions are input by the user of the node device Nn through the input unit 20 as with the download instruction.

  In step S111, it is determined whether or not the HDD 12 of the node device Nn has a free recording capacity greater than a predetermined capacity. If it is determined that there is a free recording capacity equal to or greater than the predetermined capacity, step S119 is executed. If it is determined that there is no free recording capacity equal to or greater than the predetermined capacity, step S112 is executed.

  In step S112, a replica to be deleted is determined from a plurality of replicas stored in the replica storage area 133. Among the replicas stored in the replica storage area 133, the replica whose release date has passed is deleted. In addition, among the replicas stored in the replica storage area 133, replicas with bad evaluation values are deleted. In step S112, only the replica whose publication date has passed may be deleted. Also, only replicas with bad evaluation values may be deleted. In addition, both a replica whose publication date has passed and a replica with a bad evaluation value may be deleted. The number of replicas to be deleted may be one or plural. Whether or not the replica has been published is determined by the publication end date and time of the content catalog list stored in the content catalog list storage area 136. Whether or not the evaluation value is bad is determined based on the evaluation value of the replica stored in the replica storage area 133. The computer of this embodiment and step S112 are an example of the disclosure time determination means of the present invention.

  In step S113, it is determined whether there is a node device whose free recording capacity is equal to or larger than a predetermined value among the node devices Nn described in the routing table or the index cache. When it is determined that there is a node device whose free recording capacity of each node device Nn shown in FIG. 2 or 6 is greater than or equal to a predetermined value, step S114 is executed. If it is determined that there is no node device having a free recording capacity equal to or greater than the predetermined value, step S115 is executed. Specifically, it is determined whether or not there is a node device having a free recording capacity larger than the storage capacity of the replica determined to be deleted in step S112. From the routing table shown in FIG. 2 or the index cache shown in FIG. 6, a node device Nn having a free recording capacity equal to or larger than a predetermined value is determined. In step S113, only the routing table shown in FIG. 2 may be referred to. In step S113, only the index cache shown in FIG. 6 may be referred to. Both the routing table shown in FIG. 2 and the index cache shown in FIG. 6 may be referred to. The process of referring to the computer of this embodiment and the routing table and index cache stored in the HDD 13 in step S113 is an example of the node information acquisition unit of the present invention. The process of referring to the routing table and index cache stored in the HDD 13 in step S113 is an example of the node information acquisition step of the present invention. The computer of this embodiment and step S113 are an example of the determination means of this invention. Moreover, step S113 of this embodiment is an example of the determination step of the present invention.

  In step S114, the replica determined to be deleted in step S112 is transmitted to the node device Nn determined in step S113. Specifically, when the number of replicas to be deleted in step S112 is one, the replica to be deleted is transmitted from the node devices determined in step S113 to the node device having the largest available recording capacity. . If the number of replicas to be deleted in step S112 is plural, replicas are transmitted in order from the node device determined in step S113 in order from the node device with the largest free recording capacity. The computer of this embodiment and step S114 are an example of the content transmission means of this invention. Moreover, step S114 of this embodiment is an example of the content transmission step of this invention.

  In step S115, the replica determined to be deleted in step S112 is deleted from the replica storage area 133. The computer of this embodiment and step S115 are an example of the deletion unit of the present invention. Step S115 is an example of the deletion step of the present invention.

  In step S116, the replica to be deleted is determined by the same method as in step S112.

  In step S117, it is determined whether or not the new node device has a free recording capacity equal to or larger than a predetermined capacity. Specifically, it is determined whether or not the free recording capacity included in the participation message is greater than or equal to a predetermined free capacity. The free recording capacity included in the participation message is stored in various message temporary storage areas 121 together with the participation message. If it is determined that the new node device has a free recording capacity equal to or greater than the predetermined capacity, step S118 is executed. If it is determined that the new node device has no free recording capacity equal to or greater than the predetermined capacity, step S119 is executed. Specifically, it is determined whether or not the recording capacity is larger than the storage capacity of the replica determined to be deleted in step S116.

  In step S118, the content determined to be deleted in step S116 is transmitted to the new node device.

  In step S119, it is determined whether the power OFF button provided in the node device Nn has been operated. When the power OFF button is operated, the main processing operation is terminated. If not operated, step S101 is executed again. In step S119, the determination may be made by an instruction to leave from the P2P network 9 instead of operating the power OFF button. The leave instruction is input by the user of the node device Nn. In addition, the leave instruction may be automatically generated from the node device Nn. When there is a withdrawal instruction, the main processing operation is terminated. If there is no withdrawal instruction, step S101 is executed again.

(Modification 1)
Modification 1 of step S113 of the main processing operation of the present embodiment will be described. In the present embodiment, a node device having a free recording capacity is determined based on the routing table or the index cache. In the first modification, instead of using the routing table or the index cache, the node devices Nn participating in the P2P network 9 may transmit / receive the free recording capacity to / from each other at a predetermined timing. In this case, each node device Nn stores the received free recording capacity in association with the node ID of the transmission source from which the free recording capacity has been sent. Further, the free recording capacity may be transmitted / received from all the node devices Nn participating in the P2P network. The empty recording capacity may be transmitted / received from some node devices Nn participating in the P2P network.

(Modification 2)
A second modification of the RAM 12 and the HDD 13 according to the present embodiment will be described. In the present embodiment, a replica storage area 133, an index cache storage area 134, a routing table storage area 135, and a content catalog list storage area 136 are stored in the HDD 13. In the second modification, the replica storage area 133, the index cache storage area 134, the routing table storage area 135, and the content catalog list storage area 136 may be stored in the RAM. The replica storage area 133, the index cache storage area 134, the routing table storage area 135, and the content catalog list storage area 136 may be stored in either the HDD or the RAM. Similarly, the various message temporary storage areas 121 of the RAM 12 may be stored in either the RAM or the HDD.

(Modification 3)
A modification 3 of step S112 of the main processing operation of the present embodiment will be described. In the third modification, when there are a plurality of replicas determined to be deleted in step S112, in step S113, is there a node device having a free recording capacity larger than the total storage capacity of the plurality of replicas determined to be deleted. It may be determined whether or not. In addition, it may be determined whether or not there are a plurality of node devices each having a determined free recording capacity for each of the determined plurality of replicas. For example, when the number of replicas deleted in step S112 is larger than the number of node devices determined in step S113, the replicas corresponding to the number of node devices are sequentially deleted from the deleted replicas in descending order of the storage capacity. Is selected. The selected replica may be transmitted to each node device determined in step S113. In this case, the replica determined in step S113 and transmitted to each node device is deleted from the replica storage area. Replicas that have not been sent are not deleted from the replica storage area.

(Modification 4)
A modification 4 of step S113 of the main processing operation of the present embodiment will be described. In the present embodiment, a node device having a free recording capacity is determined based on the routing table or the index cache. In the modified example 4, instead of using the routing table or the index cache, a message for searching whether each node device Nn has a free recording capacity is transmitted to each node device Nn participating in the P2P network 9 by multicast. good. In this case, each node device Nn that has received the recording capacity search message determines whether or not there is a predetermined free recording capacity. As a result of the determination, the node device Nn determined to have free recording capacity may acquire or download the content to be deleted in step S112 of the main operation. Further, as a result of the determination, the node device Nn determined to have free recording capacity may transmit a message indicating that there is free recording capacity to the node device that has transmitted the search message. In this case, the node device that is the transmission source of the search message may transmit the content to be deleted to the node device that has transmitted the message indicating that there is a free recording capacity.

(Modification 5)
Modification 5 of step S113 of the main processing operation of the present embodiment will be described. In step S113, it is determined whether there is a node device whose free recording capacity is greater than or equal to a predetermined value among the node devices described in the routing table or the index cache. In the modified example 5, instead of using the routing table or the index cache, a management server for managing the free recording capacity of each node device Nn may be installed in the P2P network 9. When the content to be deleted is determined in step S112 of the main processing operation, the free recording capacity of each node device Nn managed by the management server is searched in order to search for a node device having a predetermined free recording capacity. Reference may be made. The management server stores the free recording capacity of the storage means of each node device Nn as a log. Each node device Nn transmits the above-described free recording capacity of the storage unit as a log to the management server at predetermined intervals. Further, instead of the free recording capacity of the storage means, the total operating time of the node device may be used as the free recording capacity.

(Modification 6)
A modification 6 of step S113 of the main processing operation of the present embodiment will be described. In step S113, it is determined whether there is a node device whose free recording capacity is greater than or equal to a predetermined value among the node devices described in the routing table or the index cache. In the sixth modification, a message for inquiring whether each node device Nn has a predetermined free recording capacity may be transmitted using a routing table or an index cache. In this case, the free recording capacity of the node device is not stored in the routing table or the index cache. The node device that has received the message asking whether there is a predetermined free recording capacity determines whether there is a predetermined free recording capacity. As a result of the determination, the node device that has been determined to have free recording capacity may acquire or download the content to be deleted in step S112 of the main operation. In addition, as a result of the determination, a node device that has been determined to have free recording capacity may transmit a message that there is free recording capacity to the node device that has transmitted the search message. In this case, the node device that is the transmission source of the search message may transmit the content to be deleted to the node device that has transmitted the message indicating that there is a free recording capacity.

(Modification 7)
Modification 7 of step S113 of the main processing operation of the present embodiment will be described. In step S113, it is determined whether there is a node device whose free recording capacity is greater than or equal to a predetermined value among the node devices described in the routing table or the index cache. In the modified example 7, instead of using the routing table or the index cache, a message for searching whether each node device has a free recording capacity may be randomly transmitted to the node devices participating in the P2P network 9. In this case, the node device selected at random and receiving the recording capacity search message determines whether or not there is a predetermined free recording capacity. As a result of the determination, the node device that has been determined to have free recording capacity may acquire or download the content to be deleted in step S112 of the main operation. In addition, as a result of the determination, a node device that has been determined to have free recording capacity may transmit a message that there is free recording capacity to the node device that has transmitted the search message. In this case, the node device that is the transmission source of the search message may transmit the content to be deleted to the node device that has transmitted the message indicating that there is a free recording capacity. Until a node device having a free recording capacity is found, the node device may be selected repeatedly at random.

(Modification 8)
Modification 8 of the present embodiment will be described. In this embodiment, the free recording capacity of the storage unit of each node device Nn is used as the free recording capacity. In the modification 8, the participation time when the node device participates in the P2P network 9 may be used as the free recording capacity instead of the free recording capacity of the storage unit of each node device Nn. In this case, it is presumed that a large number of replicas are stored in the storage unit because the node device with the earlier participation time participates in the P2P network 9. In addition, it is estimated that the node device with a late participation time participates in the P2P network 9, but many replicas are not yet stored in the storage means. A management server for managing the participation time as the free recording capacity may be installed in the P2P network 9. In step S113 of the main processing operation of this embodiment, an inquiry may be made to the above-described management server instead of referring to the routing table or the index cache. Further, the participation time may be described in the routing table or the index cache.

(Modification 9)
In the present embodiment, a routing table using DHT is used as the routing table. In Modification 9, a routing table other than DHT is used.

3 IX
4a, 4b ISP
5a, 5b DSL line operator device 6 FTTH line carrier device 7 Line speed 8 Network 9 P2P network (overlay network)
11 CPU
12 RAM
13 HDD
14 Decoder unit 15 Video processing unit 16 Display 17 Audio processing unit 18 Speaker 19 Communication unit 20 Input unit 121 Various message storage temporary storage area 131 Program storage area 132 Main operation program storage area 133 Replica storage area 134 Index cache storage area 135 Routing table Storage area
136 Content catalog list storage area S Content distributed storage system Nn node CS Content input server

Claims (10)

A distributed content storage system comprising a plurality of node devices that can communicate with each other via a network, wherein a plurality of content data is distributed and stored in the plurality of node devices, and the content data is used between the node devices The node device in the distributed content storage system that is enabled,
Node information acquisition for acquiring node information in which location information indicating the location of a node device participating in the distributed content storage system is associated with capacity information for specifying the free storage capacity of the node device indicated by the location information Means,
Storage means for storing the content data usable in the content distributed storage system;
Deleting means for deleting content data based on a predetermined condition among the content data stored in the storage means;
Determining means for determining whether or not there is a node device having the free storage capacity equal to or larger than a predetermined capacity based on the node information when the content data is deleted by the deleting means;
When the determination unit determines that there is a node capacity when there is the free capacity, content that transmits the content data deleted by the deletion unit to the node device indicated by the node device identification information determined to have the free capacity A transmission means;
A node device comprising:   The node device according to claim 1, wherein the content transmission unit transmits the content deleted by the deletion unit to the node device having the largest available capacity. A routing table acquisition means for acquiring a routing table including the location information of the node device capable of transmitting a message including content for processing a predetermined request from the node device;
Search message transmitting means for transmitting a search message for searching for the capacity information of the node device indicated by the location information described in the routing table according to the routing table when the content data is deleted by the deleting means; ,
With
The node information acquisition means acquires the node information in which the location information and the capacity information are associated from the node device that has received the search message,
2. The determination unit according to claim 1, wherein the determination unit determines whether there is a node device having the free storage capacity of a predetermined capacity or more based on the node information acquired by the node information acquisition unit. 2. The node device according to 2. The node information acquisition unit stores the location information and the free capacity in association with each other in a routing table including the location information of the node device capable of transmitting a message including content for processing a predetermined request from the node device. ,
The determination unit determines whether the free capacity of the node device described in the routing table is equal to or greater than a predetermined capacity,
The content transmission means transmits the deleted content to a node device described in the routing table and having free capacity when the determination means determines that the free capacity is available. The node device according to claim 1 or 2. The storage means stores publication time information describing a publication time for publishing the content data,
Based on the publication time information, comprising a publication time determination means for judging whether or not the publication time of the content data stored in the storage means has ended,
When the publication time determination means determines that the publication time has ended, the deletion means deletes the content data, and the determination means does not make a determination, or the content transmission means is deleted. 5. The node device according to claim 1, wherein content is not transmitted. The storage means stores the content data stored in the storage means in association with an evaluation value indicating an evaluation of the content data,
The deletion unit is configured to delete, from the storage unit, the content having the evaluation value lower than a predetermined value in the content data stored in the storage unit as the predetermined condition. The node device according to claim 4. Participation process determination means for determining whether or not a new node device participates in the content distributed storage system;
When it is determined by the participation process determination unit that a new node device participates in the distributed content storage system, the determination unit determines whether the new node device has the free storage capacity equal to or larger than a predetermined capacity. ,
7. The content transmitting unit transmits the deleted content to the new node when the determining unit determines that the new node has the free storage capacity. The node device according to any one of the above. A distributed content storage system comprising a plurality of node devices that can communicate with each other via a network, wherein a plurality of content data is distributed and stored in the plurality of node devices, and the content data is used between the node devices In the computer of the node device in the content distributed storage system made possible,
Node information acquisition for acquiring node information in which location information indicating the location of a node device participating in the distributed content storage system is associated with capacity information for specifying the free storage capacity of the node device indicated by the location information Steps,
A deletion step of deleting content data based on a predetermined condition among the content data stored in the storage means for storing the content data usable in the content distributed storage system;
A determination step of determining whether or not there is a node device having the free storage capacity of a predetermined capacity or more based on the node information when the content data is deleted by the deletion step;
When the determination step determines that there is a free space, it is determined that there is a node device, and content that transmits the content data deleted by the deletion step to the node device indicated by the node device identification information determined to have free space Sending step;
A program characterized by being executed by a computer . A distributed content storage system comprising a plurality of node devices that can communicate with each other via a network, wherein a plurality of content data is distributed and stored in a plurality of node devices, and the content data can be used between the respective node devices The content distributed storage system
Node information acquisition for acquiring node information in which location information indicating the location of a node device participating in the distributed content storage system is associated with capacity information for specifying the free storage capacity of the node device indicated by the location information Means,
Storage means for storing the content data usable in the content distributed storage system;
Deleting means for deleting content data based on a predetermined condition among the content data stored in the storage means;
Determining means for determining whether or not there is a node device having the free storage capacity equal to or larger than a predetermined capacity based on the node information when the content data is deleted by the deleting means;
Content in which the node device indicated by the node device identification information determined to have free space acquires content data to be deleted by the deleting device when the determination unit determines that there is a node device if there is free space Acquisition means;
A content distributed storage system comprising: A distributed content storage system comprising a plurality of node devices that can communicate with each other via a network, wherein a plurality of content data is distributed and stored in the plurality of node devices, and the content data is used between the node devices A content storage method in a distributed content storage system,
Node information acquisition for acquiring node information in which location information indicating the location of a node device participating in the distributed content storage system is associated with capacity information for specifying the free storage capacity of the node device indicated by the location information Steps,
A deletion step of deleting content data based on a predetermined condition among the content data stored in the storage means for storing the content data usable in the content distributed storage system;
A determination step of determining whether or not a node device has a free storage capacity of a predetermined capacity or more based on the node information when the content data is deleted by the deletion step;
When the determination step determines that there is a node device having the free capacity, the node device indicated by the node device identification information determined to have the free capacity acquires content data to be deleted by the deletion step Steps,
A content storage method comprising: