JP2010238144A - Node device, node processing program, and content data deletion method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content data deletion method for suppressing a load to be imposed on a storage means such as a hard disk by deleting preliminarily accumulation-instructed accumulation content data at a prescribed timing. <P>SOLUTION: The content distribution and storage system for distributing and storing a plurality of content data in a plurality of node devices includes; a content data request and acquisition means for obtaining content data from the other node devices; a storage means for storing content data available by the content distribution and storage system including the obtained content data and preliminarily accumulation-instructed accumulation content data from the server device or the other node devices which distribute the content data; and a determination means for, on the basis of a disclosure date shown by disclosure date information when the accumulation content data are disclosed among the content data stored in a first storage area, determining whether or not it is a timing to delete the accumulation content stored in the first storage area. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 (P2P network) is composed of a plurality of node devices. Data files of various contents are stored (arranged) in a distributed manner in a plurality of node devices as duplicate data (hereinafter referred to as “replicas”) of the plurality of data files. The data file is a data file of various contents such as movies 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.

  Then, when the above-mentioned node device acquires desired content, a message (query) for searching (discovering) 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 acquired replica as a cache in various storage means.

  For example, considering that a peer-to-peer communication system is applied to a communication karaoke system, there are contents that are regularly distributed every month and stored by a node device regardless of the use of the contents. In addition to regularly distributed content that is regularly distributed, there is content that is acquired and stored in the storage means every time it is used in response to a request from the user.

  By the way, the above-mentioned regularly distributed content is frequently used immediately after being distributed until it is stored in the node device. However, it is conceivable that the usage rate of the content data of the regularly distributed content of each node device gradually decreases with the passage of time. For this reason, it is not a good idea from the viewpoint of effectively using the storage resources of the node device to cache the content whose usage rate is low in the storage means indefinitely.

  The present invention has been made in view of the above points, etc., and by deleting stored content data instructed to be stored in advance, such as regularly distributed content, from stored content data at a predetermined timing, the present invention It is an object of the present invention to provide a node device, a node processing program, and a content data deletion method capable of suppressing a load on a storage unit.

  In order to solve the above problem, the invention according to claim 1 is 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 is distributed to a plurality of node devices. The content data is transmitted to the other node devices participating in the content distributed storage system in the content distributed storage system in which the content data is made available between the node devices. Content data request acquisition means for requesting transmission of content data, request content data acquired by the content data request acquisition means, and a storage instruction from a server device or other node device that distributes content data in advance Stored content data that has been stored. Content data stored in the first storage area, storage means including a first storage area for storing content data that can be used in the distributed content storage system, and a second storage area for storing the accumulated content data Content determining means for determining whether or not the content data has been instructed to be stored in advance by the server device or the other node device, and among the content data stored in the first storage area, the content determining means The first storage area is based on the publication date information acquisition means for obtaining the publication date information describing the publication date and time when the stored content data determined by the method is published, and the publication date and time indicated by the obtained publication date information. Determining means for determining whether it is time to delete the stored content data stored in And a deletion unit that deletes the stored content data out of the content data stored in the first storage area when it is determined by the disconnecting unit that the timing is to be deleted. It is.

  According to this invention, it is determined whether or not the accumulated content data stored in the first storage area of the storage means is to be deleted based on the release date and time, and if it is the timing to be deleted, the stored content data Therefore, it is possible to suppress the amount of content data stored in the storage unit, to prevent an increase in the load on the storage unit, and to improve the access processing speed (responsiveness) to the storage unit.

  In order to solve the above problem, the invention according to claim 2 is the node device according to claim 1, wherein the determination unit is configured to execute the server device or the other when a predetermined time has elapsed from the disclosure date and time. This node device is characterized in that it is determined that it is time to delete content data instructed to be stored in advance by the node device.

  According to the present invention, the stored content data can be deleted from the first storage area at a timing when the stored content data is distributed evenly to each node device in the content distributed storage system.

  In order to solve the above problem, according to a third aspect of the present invention, in the node device according to the first or second aspect, is the date and time when the content data stored in the first storage area is deleted? A date / time determination unit for determining whether or not the date / time determination unit determines that the date / time at which the content data is to be deleted is stored in advance by the server device or the other node device. It is a node device characterized by determining whether or not it is time to delete instructed content data.

  According to the present invention, stored content data can be automatically deleted at a predetermined date and time without receiving an instruction from the user.

  In order to solve the above-mentioned problem, according to a fourth aspect of the present invention, in the node device according to any one of the first to third aspects, the content data request acquisition unit transmits the content data. When requested, the determination unit determines whether or not it is time to delete content data instructed in advance by the server device or the other node device.

  According to the present invention, it is possible to prevent an increase in the load on the storage unit when acquiring new content data.

  In order to solve the above-mentioned problem, the invention according to claim 5 is the node device according to any one of claims 1 to 4, wherein the determination means generates random numbers. And only when the generated random number is within a predetermined range, it is determined that it is time to delete the content data instructed to be stored in advance by the server device or the other node device. It is a node device.

  According to the present invention, since the stored content data is deleted only when the generated random number is within the predetermined range, it is possible to prevent the stored content data from being deleted all at once in the deletion process performed in each node device. Content distributed storage system can be kept stable.

  In order to solve the above-mentioned problem, an invention according to claim 6 is a node processing program that causes a computer to function as the node device according to any one of claims 1 to 5.

  In order to solve the above problem, the invention according to claim 7 is 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 is distributed to a plurality of node devices. Content data deletion method in the node device of the distributed content storage system that enables the content data to be used between the respective node devices, and for other node devices participating in the distributed content storage system A content data request acquisition step for requesting transmission of the content data and acquiring the content data, the requested content data acquired by the content data request acquisition step, and a server device or other node that distributes the content data Storage container instructed in advance by the device Storing content data that can be used in the content distributed storage system including the data in the first storage area of the storage means, and storing the accumulated content data in the second storage area of the storage means, A content determination step of determining whether or not the content data stored in the first storage area is content data instructed in advance by the server device or the other node device; and storing in the first storage region Among the content data thus obtained, the disclosure date / time information acquisition step for acquiring the publication date / time information describing the publication date / time when the stored content data determined by the content determination step is disclosed, and the acquired publication date / time information indicate Delete the stored content data stored in the first storage area based on the release date A determination step for determining whether or not the timing should be, and deleting the stored content data among the content data stored in the first storage area when it is determined by the determination step that the timing is to be deleted A content data deletion method comprising: a step.

  According to the present invention, it is determined whether or not the accumulated content data stored in the first storage area of the storage means should be deleted based on the release date and time, and if it is the timing to delete, the stored content data Therefore, it is possible to suppress the amount of content data stored in the storage unit, to prevent an increase in the load on the storage unit, and to improve the access processing speed (responsiveness) to the storage unit.

It is a figure which shows an example of the connection aspect of each node apparatus in the data file distributed storage system S which concerns on this embodiment. It is an example of catalog information. It is a block diagram which shows the example of a schematic structure of the node Nn. It is an example of a cache list. It is a flowchart which shows the cache list update process of the control part 11 in the node Nn. It is a flowchart which shows the cache deletion process of the control part 11 in the node Nn.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. Configuration and Operation Overview of Content Distributed Storage System First, the configuration and operation overview of the content distributed storage system S according to the present embodiment will be described with reference to FIG.

  FIG. 1 is a diagram showing an example of a connection mode of each node device in the content distributed storage system S according to the present embodiment.

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

  A plurality of node devices (hereinafter referred to as “nodes”) Nn (n = 1, 2, 3,...) Are connected to such a network 8. Each node Nn is assigned a unique manufacturing number and an IP (Internet Protocol) address. The content distributed storage system S according to the present embodiment is a peer-to-peer network system formed by participation of any of a plurality of nodes Nn, as shown in the upper frame 100 of FIG. It has become.

  A network 9 shown in the upper frame 100 of FIG. 1 is an overlay network 9 (logical network) that forms a virtual link formed using the existing network 8. Such an overlay network 9 is realized by a specific algorithm, for example, an algorithm using DHT. Each node Nn participating in the content distributed storage system S (in other words, the overlay network 9) is assigned a node ID (an example of node device identification information) that is unique identification information having a predetermined number of digits. ing.

  The node ID is, for example, a value (for example, the bit length is 160 bits) obtained by hashing an IP address or a manufacturing number individually assigned to each node Nn with a common hash function (for example, SHA-1). Yes, it will be distributed in one ID space without any bias.

  Each node Nn holds a routing table using DHT. This routing table defines the transfer destinations of various messages on the content distributed storage system S. Specifically, the node information (node ID, address information (IP address) of the node Nn that is moderately separated in the ID space. And port number etc.) are registered.

  By the way, in the distributed content storage system S, copy data (hereinafter referred to as “replica” or “content data”) of contents such as various movies, animations, and music having different contents are stored in a plurality of nodes in a predetermined file format. Nn is distributed and stored (stored), and the replica can be used between the nodes Nn. For example, the node N5 stores a replica of the movie content with the title XXX, while the node N3 stores a replica of the movie content with the title YYY. (Hereinafter referred to as “content holding nodes”).

  In addition, information such as a content name (title) and a content ID is added to each of these content replicas. The content ID is identification information unique to each content (an example of content identification information). This content ID is generated, for example, by hashing the content name + an arbitrary numerical value with a hash function common to the case of obtaining the node ID. It may be the first few bytes of the content. The content ID is arranged in the same ID space as the node ID. In addition, the system administrator may uniquely assign a content ID having the same bit length as the node ID for each content. The node ID and the content ID are configured to exist in the same ID space. The ID space is well known in Japanese Patent Application Laid-Open No. 2006-197400 and the like, and thus detailed description thereof is omitted.

  The location of the replica of the content that is distributed and stored in this way, that is, a set of node information (node ID, address information) of the node Nn that stores (also referred to as storage or cache) the replica and the content ID of the content, etc. Is stored by the node Nn (hereinafter referred to as “root node” or “root node of content (content ID)”) that manages the location of the replica of the content (stored in the index cache) , Has come to be managed.

  In such a distributed content storage system S, when downloading content data, a user node requesting content is first sent from a management server (an example of a server device) of an administrator who operates the distributed content storage system S. With reference to the catalog information distributed to each node Nn, the content ID of the content to be acquired is acquired.

  In the catalog information, content attribute information is described (stored). Examples of the attribute information include a content ID, publication date / time information indicating a content publication date, and content type information (described later) indicating a content type. Content search keyword, content evaluation value, content title (if the content is a movie, a movie title, if the content is a song, a song title, if the content is a broadcast program, a program title), a genre (if the content is In the case of movies, action, horror, comedy, love story, etc., if the content is music, rock, jazz, pop, classic, etc. If the content is a broadcast program, drama, sports, news, movie, music, anime, variety, etc. ), Artist name (content is sound Singer, group, etc.) in the case of, the cast of the case performer (the content of the film and broadcast programs), director name (if the content is of the movie), and the like.

  FIG. 2 is an example of catalog information.

  In the case of the catalog information shown in FIG. 2, content publication date / time information, content type information, content title, and content search keywords are described in association with content IDs. In the disclosure date and time information shown in the figure, for the sake of simplicity of explanation, the disclosure date and time information is information up to the publication date, and is not limited to the unit of date and time. In order to simplify the description, the content ID is 8 digits.

  Then, the user node generates a search message (query) including the acquired content ID in order to search for the location of the content storage node. Then, the generated query is transmitted to the root node according to the routing table, and the address information of the content storage node that stores the content data of the content is transmitted from the root node. Then, the content storage node is accessed according to the address information, a content transmission request message is transmitted, and the content data of the content is downloaded therefrom. Alternatively, the root node that has received the query from the user node transmits a content transmission request message including the address information of the user node to the content storage node, whereby the user node receives the content of the content from the content storage node. Data can also be downloaded.

  Note that the routing table using DHT and the message transfer (routing) between the nodes Nn using the routing table are known in Japanese Patent Application Laid-Open No. 2006-197400 and the like. Omitted.

2. Content type The content type distinguishes between content that is downloaded in response to a transmission (download) request from each node Nn and regularly distributed content that is periodically input from the management server of the administrator. .

  The content downloaded in response to the request is content acquired from the content holding node according to the routing using the DHT, for example, with the node Nn serving as the request node. The content is an example of the requested content data of the present invention, and will be referred to as “on demand type content” in the following description. In the example illustrated in FIG. 2, content with content ID “959b9c99” or “158432c3” is On Demand type content.

  On the other hand, the regularly distributed content is an example of the accumulated content data of the present invention, and the content of the new song in January, the content of the new song in February, etc. are periodically instructed from the management server and distributed. Content. The management server transmits (uploads) the content data of the regularly distributed content to the node Nn in the content distributed storage system S when the time for distributing the regularly distributed content comes. The regularly distributed content is referred to as “Push-type content” in the following description. In the example shown in FIG. 2, contents with content IDs “2e02f64c” and “15436bce” are Push type contents.

  Note that the node Nn included in the content distributed storage system S may function as the management server. In this case, push-type content is instructed and distributed in advance from the node Nn functioning as the management server. It will be.

  By the way, when using (reproducing) content, the node Nn may request and acquire content data of an On Demand type content via a network. The On Demand type content acquired at the time of reproduction is stored in a request storage area, which is an example of a first storage area, so that it can be shared among the nodes Nn in the content distributed storage system S.

  On the other hand, the Push type content is not related to the use of the content, that is, the Push type content periodically distributed from the management server regardless of whether or not the node Nn reproduces (uses) the content. . In this case, Push type content is stored in the request storage area. Since Push type content is instructed to be stored in advance, the Push type content is further stored in a storage area different from the request storage area. The storage area is an example of the second storage area of the present invention. The storage area may be provided in a storage unit in the node Nn or may be provided in an external video server. The content stored regardless of the use of the content is, for example, content that is regularly distributed. In other words, the request storage area is a storage area for storing content data necessary for operating the P2P network, and the content data is acquired from the request storage area in response to a request.

  Of the content data stored in the request storage area described above, the Push-type content data is frequently downloaded between the nodes Nn participating in the content distributed storage system S immediately after being distributed from the management server.

  Accordingly, as the Push type content data is reproduced at each node Nn and stored in the storage storage area, the Push type content data stored in the request storage area of each node Nn gradually increases with time. It is conceivable that the utilization rate will decline.

  For this reason, it is not a good idea to cache the content data of the content whose usage rate is low in the request storage area from the viewpoint of effectively using the storage resources of the request storage area of the node Nn.

  Therefore, the content data of the Push type content is deleted at a predetermined timing among the content data cached in the request storage area by the node Nn.

3. Configuration and Function of Node Nn Next, the configuration and function of the node Nn will be described with reference to FIG.

  FIG. 3 is a block diagram illustrating a schematic configuration example of the node Nn.

  Each node Nn includes a control unit 11, a storage unit 12, a buffer memory 13, a decoder unit 14, a video processing unit 15, a display unit 16, an audio processing unit 17, a speaker 18, and a communication unit 20. , And an input unit 21. The control unit 11, the storage unit 12, the buffer memory 13, the decoder unit 14, the communication unit 20, and the input unit 21 are connected to each other via a bus 22.

  The control unit 11 includes a CPU having a calculation function, a working RAM, a ROM that stores various data and programs, and the like. The control unit 11 functions as a computer of this embodiment. The storage unit 12 includes a hard disk or the like for storing various data, various programs, and the like for storing (storing). For example, the storage unit 12 stores content data and a routing table. The buffer memory 13 temporarily stores received content data and the like. The decoder unit 14 decodes (data expansion, decoding, etc.) encoded video data (video information), audio data (audio information), and the like. When the content includes video and audio, the decoder unit 14 decodes encoded video data, audio data, and the like included in the content replica. The video processing unit 15 performs a predetermined drawing process on the decoded video data or the like and outputs it as a video signal. The display unit 16 is a CRT, a liquid crystal display, or the like that displays an image based on the video signal output from the image processing unit 15. The sound processing unit 17 performs D (Digital) / A (Analog) conversion of the decoded audio data into an analog audio signal, and then amplifies the signal by an amplifier and outputs the amplified signal. The communication unit 20 that outputs the audio signal output from the sound processing unit 17 as a sound wave performs communication control of information between other nodes Nn and the like through the network 8. The input unit 21 receives an instruction from the user and communicates an instruction signal corresponding to the instruction to the control unit 11. The input unit 21 is, for example, a keyboard, a mouse, or an operation panel.

  The control unit 11, the storage unit 12, the buffer memory 13, the decoder unit 14, the communication unit 20, and the input unit 21 are connected to each other via a bus 22.

  As the node Nn, a personal computer, an STB (Set Top Box), a communication karaoke apparatus, a TV receiver, or the like can be applied.

  The storage unit 12 stores address information of the node Nn itself.

  In addition, after participating in the distributed content storage system S, the storage unit 12 stores the node ID, routing table, and catalog information (see FIG. 2) of the node Nn itself, and further manages its location. For example, index information including a set of node information of the node Nn that is a content holding node that is the root node and the content ID of the content is stored as an index cache.

  Furthermore, the storage unit 12 includes a request storage area and a storage area.

  Content data of On Demand type and Push type content is stored in the request storage area, and content data of Push type content is stored in the storage area.

  Furthermore, the storage unit 12 stores information on content data stored (cached) in the request storage area of the storage unit 12 as a cache list.

  FIG. 4 is an example of a cache list.

  When three content data whose content IDs are “2e02f64c”, “959b9c99” and “e28672c3” are stored in the request storage area, the content ID, publication date / time information, and content type information are registered as information related to these content data Has been.

  When the control unit 11 acquires content data from another node Nn or the management server, a “cache list update process” to be described later is executed based on the control of the control unit 11, and content related to new content data in the cache list ID, release date information, and content type information are added. Then, in a “cache deletion process” to be described later, the cache list is referred to, and when the content type is a push type content, the content data is deleted from the request storage area.

  In such a configuration, the control unit 11 performs overall control by reading and executing a program stored in the storage unit 12 or the like by the CPU, and the above-described user nodes by participating in the content distributed storage system S, Processing as at least one of a relay node, a root node, and a content holding node is performed.

  Further, the control unit 11 executes the node processing program of the present invention, so that the storage unit, the content data request acquisition unit, the storage unit, the content determination unit, the disclosure date / time information acquisition unit, the determination unit, the deletion unit in the present invention, Functions as a date / time determination unit, a random number generation unit, and the like. The node processing program may be downloaded from a predetermined server on the network 8, for example, or recorded on a recording medium such as a CD-ROM and read via the drive of the recording medium. You may make it.

4). Processing in the node Nn at the processing node Nn will be described in detail with reference to the drawings.

4-1. Cache List Update Process FIG. 5 is a flowchart showing the cache list update process of the control unit 11 in the node Nn. The push type content newly distributed from the management server (or via another node Nn) is shown. A process that is started based on control by the control unit 11 when content data is acquired or when content data of On Demand type content is newly acquired from the content holding node when the node Nn becomes a user node. is there. The cache list update process is a part of the node processing program of the present invention.

  First, the control unit 11 stores (caches) the acquired content data in the request storage area of the storage unit 12 (step S10).

  Next, the control unit 11 extracts the publication date information and the content type information corresponding to the content ID of the content data stored in step S10 from the catalog information in the storage unit 12 (step S11), and the cache list in the storage unit 12 Is registered (added) (step S12), and the process is terminated.

  In addition, after performing the process of step S11 and S12 previously, you may perform the process of step S10. That is, for the acquired content data, after extracting the publication date information and content type information corresponding to the content ID of the content data from the catalog information and registering it in the cache list, the acquired content data is stored in the request storage area of the storage unit 12. You may comprise so that it may memorize | store.

4-2. Cache Deletion Processing FIG. 6 is a flowchart showing the cache deletion processing of the control unit 11 in the node Nn, and is processing that starts after joining the content distributed storage system S. The cache deletion process is a part of the node processing program of the present invention.

  First, the control unit 11 determines whether or not the power of the node Nn itself is turned off (step S20), and when the power is turned off (step S20: Yes), the process is terminated and the power is turned off. If it is not turned off (step S20: No), it is determined whether or not it is a predetermined deletion date (step S21).

  As a result of the determination, if it is the deletion date and time (step S21: Yes), deletion processing is performed on all content data stored in the request storage area of the storage unit 12 (step S22 to step S29). This process is a process that is performed based on a cache list in which all content data stored in the request storage area is registered, and is a process that is sequentially performed on all contents registered in the cache list.

  First, the control unit 11 determines whether or not the power of the node Nn itself is turned off (step S23), and when the power is turned off (step S23: Yes), the process ends and the power is turned off. If not turned off (step S23: No), the content type information of the first content in the cache list (for example, the content type registered first in the cache list shown in FIG. 4) is acquired, and the content type It is determined whether or not the content type indicated by the information is Push type (step S24).

  As a result of the determination, if it is not the Push type (Step S24: No), the process proceeds to Step S29. If it is the Push type (Step S24: Yes), the publication date / time information of the content is acquired from the cache list. Based on the release date and time indicated by the release date and time information, it is determined whether or not it is time to delete the content. Here, it is determined whether or not a predetermined time (for example, one month) has elapsed since the release date (step S25), and if the predetermined time has not elapsed (step S25: No), it should be deleted. It is determined that it is not the timing, and the process proceeds to step S29.

  On the other hand, if the predetermined time has elapsed (step S25: Yes), it is determined that it is time to delete, a random number is generated (step S26), and whether or not the generated random number is within a predetermined range. Determination is made (step S27). The predetermined range in step S26 is, for example, “random number is even number”, “random number is a multiple of 3”, “the last digit of the random number is the same as the last digit of the content ID of the content to be deleted”, etc. .

  As a result of the determination, if the generated random number is not within the predetermined range (step S27: No), the process proceeds to step S29. If it is within the predetermined range (step S27: Yes), the content data of the content is requested. Delete from the storage area (step S28).

  And after performing the process of step S23-step S28 with respect to all the contents registered into the cache list (step S29), it transfers to the process of step S20 and a power supply is turned off (step S20: Yes). The above process is repeated until.

  On the other hand, if the result of determination in step S21 is not a predetermined deletion date and time (step S21: No), the process proceeds to step S30, and other processing as the node Nn participating in the content distributed storage system S (described above) The “cache list update process”, other user node, relay node, root node, and content holding node processes) are performed (step S30), and the process proceeds to step S20.

  As described above, the node Nn determines whether or not the content data stored in the request storage area should be deleted based on the release date for the push-type content data. If the timing is reached, the content data is deleted from the request storage area. Therefore, by deleting only the Push-type content data and suppressing the amount of content data stored in the request storage area, It is possible to prevent the load on the storage area from increasing and improve the access processing speed (responsiveness) to the requested storage area.

  Furthermore, in the present embodiment, since it is determined whether or not it is time to delete the content data based on whether or not a predetermined time has elapsed since the date and time when the content was published, the content data is stored in a distributed content storage system. The content data is requested when an appropriate period has passed since it was used in S (for example, one month), that is, at a timing when the content is distributed uniformly and uniformly in each node Nn. It can be deleted from the storage area.

  As the amount of content data increases, it takes more time for transmission / reception between the nodes Nn. Therefore, it can be predicted that the time until the nodes Nn are spread evenly becomes longer. The predetermined time may be appropriately determined according to the data amount of the content data. In this case, information on a predetermined time from the publication date calculated in advance from the data amount of the content data is also described in the catalog information in association with the content ID, and the above-described “cache list update processing” performs the cache list. Information for a predetermined time from the publication date is also registered, and based on the publication date of the content and the information for the predetermined time, it is determined whether or not it is time to delete the content data. .

  The data amount of the content data may be described in the catalog information, and each node Nn may be configured to calculate a predetermined time from the release date according to the data amount. In this case, the calculation method may be stored in the storage unit 12 or described in the catalog information.

  Further, when it is determined that the deletion date / time is determined in step S21, the deletion process (steps S22 to S29) is performed. For example, 5:00 AM every day, midnight every Monday, etc. are set as the deletion date and time. By determining in advance, the content data deletion process can be automatically executed without receiving an instruction from the user.

  The node Nn may be configured to perform the deletion process (steps S22 to S29) when requesting acquisition of new content. When the node Nn acquires (downloads) the desired content, the node Nn becomes a user node, sends a query including the content ID of the content desired to be acquired to the root node, and from the root node Instructing the address information of the content holding node that holds the replica of the content to acquire it by sending a content transmission request message from the user node to the content holding node, and when the root node sends the address information of the user node to the content holding node In some cases, the content holding node sends content data to the user node when the content holding request message is sent to the user node. In the former case, the content holding request message is sent to the content holding node. The query When transmitted toward the root node, it is sufficient to perform the deletion process.

  In addition, since the random number is generated in step S26 and the content data is deleted only when the random number generated in step S27 is within the predetermined range, when the predetermined time elapses from the publication date and time In addition, in the cache deletion process performed at each node Nn, it is possible to prevent the simultaneous deletion and to keep the content distributed storage system S stable. Note that the node Nn whose generated random number is out of the predetermined range can try to delete the content data again at the next deletion date and time. In step S26 and step S27 of the present embodiment, it is determined whether or not the content data can be deleted based on the generated random number. The determination process of whether or not deletion is possible in step S26 and step S27 may or may not be performed.

  The content distributed storage system S has been described on the assumption that it is formed by an algorithm using DHT, but the present invention is not limited to this.

  In this embodiment, the example of the content periodically distributed from the management server as Push type content was described. In the present embodiment, when the content data of the Push type content has not been distributed to all the nodes Nn, the content data requested and acquired when using (playing back) is not only the On Demand type content but also Push. Type content may be used. In this case, Push-type content data requested and acquired when used (reproduced) is temporarily stored in the request storage area, and then stored in a storage area different from the request storage area. The present invention can also be applied to Push-type content that is requested and acquired during use (reproduction) and stored in the request storage area.

3 IX
4a, 4b ISP
5a, 5b DSL line company 6 FTTH line company 7 Communication line 8 Network 9 Overlay network (P2P network)
11 Control Unit 12 Storage Unit 13 Buffer Memory 14 Decoder Unit 15 Video Processing Unit 16 Display Unit 17 Audio Processing Unit 18 Speaker 20 Communication Unit 21 Input Unit 22 Bus Nn Node

Claims (7)

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,
Content data request acquisition means for requesting other node devices participating in the content distributed storage system to transmit the content data and acquiring the content data;
Available in the content distributed storage system including requested content data acquired by the content data request acquisition means and stored content data instructed in advance by a server device or other node device that distributes the content data Storage means including a first storage area for storing content data and a second storage area for storing the accumulated content data;
Content determination means for determining whether or not the content data stored in the first storage area is content data instructed in advance by the server device or the other node device;
A disclosure date and time information acquisition unit for acquiring disclosure date and time information describing a disclosure date and time when the stored content data determined by the content determination unit is disclosed among the content data stored in the first storage area;
Determining means for determining whether or not it is time to delete the stored content data stored in the first storage area, based on the publication date and time indicated by the obtained publication date and time information;
A deletion unit that deletes the stored content data among the content data stored in the first storage area when it is determined by the determination unit that the timing should be deleted;
A node device comprising: The node device according to claim 1,
The determination unit determines that it is time to delete content data instructed in advance by the server device or the other node device when a predetermined time has elapsed from the disclosure date and time. apparatus. In the node device according to claim 1 or 2,
A date and time determination means for determining whether or not it is a date and time for deleting the content data stored in the first storage area;
When it is determined by the date determination unit that the content data is to be deleted, the determination unit is a timing at which the content data instructed to be stored in advance by the server device or the other node device should be deleted. A node device characterized by determining whether or not. In the node apparatus as described in any one of Claims 1-3,
When the content data request acquisition unit requests transmission of the content data, the determination unit determines whether it is time to delete content data instructed in advance by the server device or the other node device. A node device characterized by determining whether or not. The node device according to any one of claims 1 to 4, wherein
The determination unit includes a random number generation unit that generates a random number, and deletes content data instructed in advance by the server device or the other node device only when the generated random number is within a predetermined range. A node device, characterized in that it is determined to be a timing to be performed.   A node processing program for causing a computer to function as the node device according to any one of claims 1 to 5. 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 A content data deletion method in the node device of the content distributed storage system,
A content data request acquisition step of requesting transmission of the content data to other node devices participating in the content distributed storage system and acquiring the content data;
Available in the content distributed storage system including requested content data acquired by the content data request acquisition step and stored content data instructed in advance by a server device or other node device that distributes the content data Storing the content data in the first storage area of the storage means;
Storing the stored content data in a second storage area of the storage means;
A content determination step of determining whether the content data stored in the first storage area is content data instructed in advance by the server device or the other node device;
A publication date / time information acquisition step for obtaining publication date / time information describing a publication date / time when the stored content data determined by the content determination step is disclosed among the content data stored in the first storage area;
A determination step of determining whether it is time to delete the stored content data stored in the first storage area, based on a disclosure date and time indicated by the acquired disclosure date and time information;
A step of deleting the stored content data from the content data stored in the first storage area when it is determined by the determination step that the timing is to be deleted;
A content data deleting method comprising:

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