JP2001168921A - Data relay method by gateway device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proxy server, which relays a data transfer request from a terminal belonging to one network to other network, relays the data received from the other network to the terminal and is provided with a disk cache to store and reuse the received data, that can enhance increase in a response time, due to increase in the access frequency from the terminal. SOLUTION: When a proxy relay section 44 of a proxy server 40 receives a data transfer request from a terminal 30, in the case that no desired data is present in a memory cache 41, the proxy server 40 compares an estimated access time to a disk cache 42 with an estimated response time of a network 20 to a server 10 and decides whether the proxy server 40 makes a data transfer request to the server 10 or retrieves data on the disk cache 42, depending on whether the former is larger than the latter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data relay method using a gateway device interposed between networks, and more particularly to a data relay method for efficiently using a data cache provided in a gateway device.

[0002]

2. Description of the Related Art When a terminal device belonging to a company network accesses a server device belonging to a wide area network such as the Internet, a gateway device is interposed between the wide area network and the company network.
A system in which the terminal device accesses the wide area network via the gateway device is configured. The gateway device relays a data transfer request from the terminal device to a server device on the wide area network, and relays data received from the server device to the terminal device. JP-A-4-31
According to Japanese Patent No. 3126, a disk cache is provided in such a gateway computer, data received from a server device is stored in the disk cache, and data on the disk cache is used when there is a transfer request of the same data. This avoids communication with the wide area network and shortens the data access time. Such a gateway computer is called a proxy server.

[0003]

In the above proxy server, when the access frequency from the terminal device increases and the load becomes high, the access frequency to the disk cache increases and the disk access time becomes a bottleneck. ,
There is a problem that the response time is extremely deteriorated.

An object of the present invention is to improve the response time for a gateway device having the above-described data cache.

[0005]

According to the present invention, a data transfer request from a terminal device belonging to a first network is relayed to a device belonging to a second network, and data transmitted from a device belonging to the second network is relayed. Relays to the requesting terminal belonging to the first network, and if there is requested data in the data cache, transmits the data in the data cache to the requesting terminal to communicate with the second network. In the data relay method by a gateway device to be avoided, when the time required to acquire data via the second network is smaller than the time required to acquire data from the data cache, the data transfer request is transmitted to the device belonging to the second network. The method is characterized by a data relay method by a gateway device relaying to a gateway.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a system according to the present embodiment. The system is network 20, network 50
And proxy server device 40 interposed between both networks
Consists of The network 20 is a wide area network such as the Internet, and includes many server devices 10 such as WWW servers. Network 5
Reference numeral 0 denotes an in-company network, and terminal devices 30 belonging to this network are client terminals that issue data transfer requests to the server device 10. The proxy server device 40 includes the network 20 and the network 50
And a gateway device that relays the data transfer request of the terminal device 30 to the target server device 10 belonging to the network 20 and relays data such as a home page sent from the server device 10 to the requesting terminal device 30. is there.

The proxy server device 40 is a server computer and has a memory, that is, a storage area of a memory cache 41 on a main storage device (semiconductor storage device), and a storage area of a disk cache 42 on a connected disk device. Is provided. The communication control unit 47 includes the network 5
0 is a hardware / software that establishes a connection with the terminal device 30 via the communication device 0 and controls communication between the terminal device 30 and the proxy server device 40. The communication control unit 48 establishes a connection with the target server device 10 via the network 20 and
Hardware / software for controlling communication between the proxy server device 40 and the proxy server device 40.

The proxy relay unit 44 receives a data transfer request from the terminal device 30 via the communication control unit 47 and is stored in the memory of the proxy server device 40.
8 to the server device 10 and the server device 1
0 is a program for relaying data sent from the terminal 0 to the terminal device 30. However, the target data is the memory cache 4
If the data exists in 1, the data is sent to the terminal device 30, and communication with the server device 10 is avoided. If the waiting time for accessing the disk cache 42 is short and the target data exists in the disk cache 42, the data is sent to the terminal device 30 and the server device 10
Avoid communication for data acquisition between and. Further, the proxy relay unit 44 controls to store the data received from the server device 10 in the memory cache 41. The proxy relay unit 44 operates according to a process started for each data transfer request from the terminal device 30.

The disk access queue 43 is a control table provided on the memory and queuing an access request to the disk cache 42. The disk search unit 45 is started by a disk search request from a process of the proxy relay unit 44, searches the disk cache 42 in the search request order of the disk access queue 43,
If there is target data, the program passes the data to the request source process of the proxy relay unit 44. The data migration unit 46 moves old data in the memory cache 41 to the disk cache 42, and stores data acquired from the server device 10 and data accessed in the disk cache 42 in the memory cache 41.

At least a program of the proxy relay unit 44 is stored in a storage medium and read into a memory of the proxy server device 40 via a drive device connected to the proxy server device 40, or a drive device connected to another computer. Can be transmitted to the proxy server device 40 via another computer and a network, and can be executed by the proxy server device 40.

The memory cache 41 comprises a directory storage area and a data storage area. The directory storage area stores, as directories, a server name / file name of a data page requested from the terminal device 30 and a memory address of a storage location for storing the corresponding data page, and stores a list of these directories. The directories are arranged in the order of access, and are stored by wrapping around from the end of the directory storage area to the beginning. The data storage area stores the requested data page. The data pages are arranged in the order of access, and are stored by wrapping around from the end of the data storage area to the beginning. When searching the memory cache 41, first, a directory is searched, and a target server name /
If the file name exists, the data page in the corresponding data storage area is accessed.

The disk cache 42 also includes a directory storage area and a data storage area. The directory storage area stores, as directories, a server name / file name and a logical block address on a disk for storing a corresponding data page, and stores a list of these directories. The directories are arranged in the order of access, and are stored by wrapping around from the end of the directory storage area to the beginning. The data pages in the data storage area are arranged in the order of access, and are stored by wrapping around from the end of the data storage area to the beginning. When searching the disk cache 42, similarly to the case of the memory cache 41, a directory is searched first, and if a target server name / file name exists, a data page in the corresponding data storage area is accessed.

FIGS. 2A and 2B show the proxy relay unit 44.
3 is a flowchart showing the flow of the processing of FIG. The proxy relay unit 44 is connected to the network 50 via the communication control unit 47.
When a data transfer request is received from the terminal device 30 above (step 61), first, the memory cache 41 is searched (step 62). If there is data on the memory cache 41 (step 63 YES), the data page is transferred to the terminal device 30 (step 64). That is, it is assumed that access to the memory cache 41 is performed at high speed, and if there is data in the memory cache 41, it is used unconditionally.

If there is no data on the memory cache 41 (step 63 NO), the disk access queue 43
To obtain the current number of disk access queues (step 65). Further, the current expected response time on the network 20 is obtained (step 66). Here, the response time is the time from when the proxy server device 40 transmits a data transfer request to the server device 10 until when the requested data is received. Since the traffic to the server device 10, that is, the number of accesses per unit time is considered to change periodically like a daily cycle,
By storing in advance the statistical data of the traffic change due to the time on the storage device, the approximate traffic expected from the current time can be obtained. Since the response time is a function related to traffic, an expected response time at the current time can be estimated by setting a function form in advance.

Next, the current effective disk access time is compared with the obtained expected response time (step 67). Here, the effective disk access time is
(Disk access queue number + 1) × average disk access time / data, and average disk access time / data = average directory read time + data page read time + data migration overhead. The data migration overhead is the contribution of the overhead time when moving old data pages in the memory cache 41 to the disk cache 42 to the average disk access time / data. Note that the disk access time is assumed to be 1 when the read / write multiplicity of the disk cache 42 is 1. Therefore, when the multiplicity is 2 or more, it may be divided by the multiplicity.

The disk access time thus obtained is compared with the expected response time, and if the disk access time> the expected response time (step 67).
YES), establish a connection with the target server device 10 on the network 20 via the communication control unit 48,
A data transfer request is transmitted to receive a data page (step 68). Next, the data received via the communication control unit 47 is transferred to the requesting terminal device 30 on the network 50 (step 69).

If the disk access time ≦ the expected response time (step 67 NO), the process moves to FIG. 2B, where an access request is registered in the disk access queue 43 and the number of queues is increased by one (step 70). And issues a data search request to the disk search unit 45 (step 71). The disk search unit 45
The data in the disk cache 42 is searched in the registration order of the disk access queue 43, and the result is returned to the request source process of the proxy relay unit 44. If there is data requested to be accessed, the directory corresponding to the data is deleted from the disk cache 42. The requesting process of the proxy relay unit 44 is the disk access queue 4
3 is deleted, and the number of queues is reduced by one (step 72). If the target data page exists on the disk cache 42 (step 73YES),
The data page is transferred to the requesting terminal device 30 (step 74). Then, go to step 77.

If there is no target data page on the disk cache 42 (step 73 NO), the communication control unit 4
A connection is established with the target server device 10 on the network 20 via the network 8, a data transfer request is transmitted, and a data page is received (step 75). Next, the data received via the communication control unit 47 is transmitted to the network 50.
Transfer to the above requesting terminal device 30 (step 7)
6).

Next, the proxy relay unit 44 transmits the received data page or the disk cache 4 to the data transfer unit 46.
Then, the data page extracted from 2 is passed along with the server name / file name to request storage in the memory cache 41. If the data migration unit 46 is full and wrapped around to the end of the directory storage area and data storage area of the memory cache 41, the oldest directory and data page pointed to by the pointer for both storage areas are respectively stored in the directory of the disk cache 42. The storage area and the data storage area are moved to the next storage location indicated by the pointer (step 77), and the latter pointer is updated. Next, with respect to the directory storage area and the data storage area of the memory cache 41, the directory and the data page including the received server name / file name are stored in the storage locations indicated by the respective pointers (step 78), and the pointer is updated. If the storage area of the memory cache 41 is not full, the directory and the data page including the received server name / file name are simply stored in the storage location indicated by the pointer, and the pointer is simply updated.

[0021]

As described above, according to the present invention, whether or not to use the data cache is controlled according to the access frequency from the terminal device, so that the response time of data acquisition as seen from the terminal can be improved. Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a system according to an embodiment.

FIG. 2A is a flowchart illustrating a processing flow of a proxy relay unit 44 of the embodiment.

FIG. 2B is a flowchart (continued) showing a processing flow of the proxy relay unit 44 of the embodiment.

[Explanation of symbols]

10: server device, 20: network, 30: terminal device, 40: proxy server device, 41: memory cache, 42: disk cache, 43: disk access queue, 44: proxy relay unit, 45: disk search unit, 46: Data migration unit, 50: Network

Claims (4)

[Claims] 1. A data transfer request from a terminal device belonging to a first network is relayed to a device belonging to a second network, and data sent from a device belonging to the second network is a request source belonging to the first network. Data relay by a gateway device which relays data to the terminal device of the data cache and, if there is requested data in the data cache, transmits the data in the data cache to the requesting terminal device to avoid communication with the second network. In the method, the second
A response time required to acquire data via the network is compared with a data access time required to acquire data in the data cache. If the response time is smaller than the data access time, a data transfer request is made. Relaying data to a device belonging to a second network. 2. The data access time according to claim 1, wherein the data access time depends on the number of queues of data access requests.
A data relay method using the gateway device described in the above. 3. A data transfer request from a terminal device belonging to a first network is relayed to a device belonging to a second network, and data sent from a device belonging to the second network is a request source belonging to the first network. Data relay by a gateway device which relays data to the terminal device of the data cache and, if there is requested data in the data cache, transmits the data in the data cache to the requesting terminal device to avoid communication with the second network. In the method, the second
Relaying a data transfer request to a device belonging to a second network when the time required to obtain data via the network is smaller than the time required to obtain data from the data cache. Data relay method. 4. A storage medium for storing a computer-readable program, said program relaying a data transfer request from a terminal device belonging to a first network to a device belonging to a second network, and Relays the data sent from the device belonging to the first network to the requesting terminal device belonging to the first network, and if there is requested data in the data cache, sends the data in the data cache to the requesting terminal device A storage medium for storing a program which is transmitted and controlled to avoid communication with the second network, and which has the following functions: Response required until data is acquired via the second network Compare time with data access time required to get data in data cache That function, and if the response time is less than the data access time function of relaying the devices belonging to the data transfer request to the second network.