JP2008293281A - Cache device, server, cache system, cache method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cache device, a server, a cache system, a cache method and a program, solving that cache efficiency is easy to deteriorate. <P>SOLUTION: This cache device stores a file by caching algorithm different according to the kind of the file. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cache device, a server, a cache system, a cache method, and a program, and more particularly, to a cache device, a server, a cache system, a cache method, and a program for storing a file with a different caching algorithm depending on the type of the file. .

  An example of a file transmission / reception system including a cache computer is described in Patent Document 1. The cache computer in this file transmission / reception system determines the type of the cache file. Then, the cache computer selects and deletes a predetermined number of cache files from the cache file based on the deletion order determined for each type of cache file.

JP 2000-357113 A

  The cache computer in the file transmission / reception system described above performs processing according to the type of cache file. However, there is a problem in that cache efficiency tends to be reduced in a situation where characteristics such as a required file size vary. The reason is that the cache computer described above uses a specific algorithm that determines the deletion order for each type of cache file, but does not use a different algorithm for each type of cache file.

  For example, the file transmission / reception system described in Patent Document 1 uses an algorithm that sets the deletion order of document files before the deletion order of image files. However, a caching algorithm for a document file and a caching algorithm for an image file are not separately provided.

  Here, for example, it is assumed that an algorithm having a large amount of calculation for determining the file deletion order (file replacement order) on the cache is used for both the document file and the image file. In this case, the algorithm is applied even when a small file such as a document file is frequently requested. As a result, the calculation for determining the file deletion order on the cache takes time, and the algorithm processing time in the cache may be longer than the download time of the document file.

  An object of the present invention is to provide a cache device, a server, a cache system, a cache method, and a program that solve the problem that the cache efficiency, which is a problem of the related art described above, is likely to decrease.

  The cache device according to the present invention stores a file with a different caching algorithm depending on the type of the file.

  The server of the present invention stores a file with a different caching algorithm depending on the type of the file.

  A cache system according to the present invention includes a Web server that stores a file, a client that requests the file on the Web server, and a proxy server that is connected to the client and connects to the Web server as a proxy for the client. And a network to which the Web server and the proxy server are connected, and the cache device stores the file with a different caching algorithm depending on the type of the file.

  The cache method of the present invention is characterized in that a file is stored with a different caching algorithm depending on the type of the file.

  The program according to the present invention causes a computer to store a file with a different caching algorithm depending on the type of the file.

  The present invention has an effect that cache efficiency can be improved. The reason is that the file is stored with a different caching algorithm depending on the file type.

  Next, a first embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a cache system 1001 in the first embodiment of the present invention. The cache system 1001 includes a client 100, a client 110, a client 120, a cache device 200, and the Internet 400. The cache system 1001 includes a World Wide Web server 500 (hereinafter referred to as the Web server 500), an image (still image or moving image) file 510, and a document file 520. The clients 100 to 120, the cache device 200, and the Web server 500 are information processing devices including a processor, and realize functions described later by executing a program stored in a program storage medium. The number of clients 100 to 120 is three as an example, but it may be more or less. Hereinafter, the client 100 will be described as a representative of the clients 100 to 120.

  The client 100 is a terminal that requests files such as an image file 510 and a document file 520 on the Web server 500 via a proxy server 210 and the Internet 400 described later.

  The Internet 400 is a network in which the cache device 200 including the proxy server 210 and the Web server 500 are connected.

  The Web server 500 is a server that stores and manages files such as an image file 510 and a document file 520. The Web server 500 provides these files via the Internet 400.

  The cache device 200 is a device connected to the clients 100 to 120 and the Internet 400. The cache device 200 includes a proxy server 210 and a plurality of caches (in this embodiment, cache disks 300 to 320 are shown as an example. The cache disks 300 to 320 are not limited to hard disks, and a cache made of semiconductor memory may be used. .). The number of cache disks 300 to 320 is three as an example, but it may be more or less.

  To the proxy server 210, clients 100 to 120 and cache disks 300 to 320 are connected. The proxy server 210 connects to the Web server 500 via the Internet 400 on behalf of the clients 100 to 120. When the cache disks 300 to 320 store a file requested by the client 100, the proxy server 210 transmits the file to the client 100. If the cache disks 300 to 320 do not store the file, the file is received from the Web server 500 and transferred to the client 100.

  The proxy server 210 includes a file type determination unit 211 and a cache disk distribution unit 212.

  The file type determination unit 211 determines the Content-Type of HyperText Transfer Protocol (hereinafter referred to as HTTP protocol) corresponding to the file extension. The file type determination unit 211 includes an extension-Content-Type correspondence table 2111. FIG. 2 is a diagram illustrating an example of the extension-Content-Type correspondence table 2111. Assume that general correspondence has already been registered in the initial state.

  The cache disk distribution unit 212 includes a Content-Type-cache disk number correspondence table 2121 and a cache disk number-Expires field correspondence table 2122.

  The cache disk distribution unit 212 refers to the Content-Type-cache disk number correspondence table 2121 and determines a cache disk having a cache disk number corresponding to the Content-Type of the file requested from the client 100. For example, it is assumed that the cache disk 300 (cache disk with the cache disk number 1) corresponds to the Content-Type of the file requested from the client 100. The cache disk distribution unit 212 refers to the cache disk number-Expires field correspondence table 2122 to determine whether the cache disk 300 is set to use the expiration date set for the file.

  FIG. 3 shows a Content-Type-cache disk number correspondence table 2121, and FIG. 4 shows a cache disk number-Expires field correspondence table 2122. In this embodiment, the cache disk numbers 1, 2, and 3 correspond to the cache disks 300, 310, and 320, respectively. The cache disk number-Expires field correspondence table 2122 is a flag indicating whether or not each cache disk 300 to 320 (the cache disk number) is set to use an expiration date, corresponding to each cache disk 300 to 320. (Use Expires field? Yes / No).

  Also, the cache disk number-Expires field correspondence table 2122 stores the algorithm numbers used by the respective cache disks 300 to 320. The extension-Content-Type correspondence table 2111, the Content-Type-cache disk number correspondence table 2121, and the cache disk number-Expires field correspondence table 2122 can be set by the proxy server administrator.

  The cache disks 300 to 320 store files with different caching algorithms (cache replacement algorithms) according to the cache disk number-Expires field correspondence table 2122. For example, the cache disk 300 and the cache disk 310 store files using an LRU (Least Recently Used) algorithm, and the cache disk 320 stores files using a Landlord Algorithm. In addition, the cache disks 300 to 320 include the file name of each file to be stored, the Expires parameter of each file, the value parameter (value parameter in the aforementioned LRU, Landlord Algorithm, etc.), the Expires parameter, an address indicating the storage area, A correspondence table with the URL of the Web server 500 is provided (not shown).

  Next, the operation of the first embodiment of the present invention will be described in detail with reference to the flowcharts of FIGS.

  FIG. 5 is a flowchart showing the operation of the cache device 200 when a request for acquiring a file in the Web server 500 is received from the client 100.

  First, referring to the flowchart of FIG. 5, the client 100 requests an image file 510 or a document file 520 in the Web server 500 (step 100). Here, as an example, it is assumed that the client 100 requests the document file 520. The request from the client 100 includes a Uniform Resource Locator (URL) where the document file 520 exists. The proxy server 210 refers to the extension attached to the file name of this URL, and determines the extension of the document file 520 (step 101). Then, the proxy server 210 refers to the extension-Content-Type correspondence table 2111 of the file type determination unit 211 and determines whether the extension of the document file 520 is registered in the extension-Content-Type correspondence table 2111. (Step 102).

  When the extension of the document file 520 is registered in the extension-Content-Type correspondence table 2111 (Yes at Step 102), the Content-Type in the HTTP protocol corresponding to the document file 520 is determined (Step 103). .

  The cache disk distribution unit 212 includes a Content-Type-cache disk number correspondence table 2121. The proxy server 210 refers to the Content-Type-cache disk number correspondence table 2121 and determines a cache disk corresponding to the Content-Type based on the Content-Type (Step 104). Here, it is assumed that the cache disk 310 is a cache disk corresponding to the Content-Type. The proxy server 210 searches the cache disk 310 for the document file 520 (step 105). That is, in the correspondence table provided in the cache disk 310, the proxy server 210 performs a search using the file name of the document file 520 and the URL of the Web server 500 as keys. The proxy server 210 searches for the URL of the Web server 500 in parallel in case there are a plurality of the same file names, and calculates the product of the search results.

  Assume that the document file 520 exists in the cache disk 310 (step 106, Yes). The cache disk distribution unit 212 checks whether the cache disk 310 is set to use the Expires field with reference to the cache disk number-Expires field correspondence table 2122 (step 107). Assume that the cache disk 310 is set to use the Expires field (step 107, Yes). Then, the cache disk distribution unit 212 acquires the Expires parameter of the document file 520. That is, the cache disk 310 that has received the Expires parameter acquisition request from the cache disk distribution unit 212 refers to the correspondence table between the file name of each file stored in the cache disk 310 and the Expires parameter of each file. Then, the cache disk 310 transfers the Expires parameter corresponding to the document file 520 to the cache disk distribution unit 212 (step 108).

  When the current time exceeds the value of the Expires parameter of the document file 520 (step 109, Yes), the cache disk distribution unit 212 deletes the document file 520 in the cache disk 310 (step 112), and step A ( Go to step 200) in FIG. If the extension of the document file 520 is not registered in the extension-Content-Type correspondence table 2111 (No at Step 102), the process proceeds to Step A (Step 200 in FIG. 6). Even when the document file 520 does not exist in the cache disks 300 to 320 (step 106, No), the process proceeds to step A (step 200 in FIG. 6).

  Assume that the cache disk 300 is not set to use the Expires field (step 107, No), or the current time does not exceed the value of the Expires parameter of the document file 520 (step 109, No). The cache disk 310 increases the value parameter in the cache disk 310 of the document file 520 in the cache disk 310 using an algorithm set for the cache disk 310 (step 110). For example, the cache disk 310 sets the document file 520 as the most recently used file in the value parameter column of the correspondence table provided in the cache disk 310 in the LRU algorithm. The proxy server 210 transfers the document file 520 from the cache disk 310 to the client 100 (step 111).

  FIG. 6 is a flowchart showing the operation of the cache device 200 when the cache disk 310 does not have the document file 520 requested by the client 100 and the original document file 520 is downloaded from the Web server 500 in the flowchart of FIG. is there. Alternatively, FIG. 6 is a flowchart showing the operation of the cache device 200 when the current time exceeds the value of the Expires parameter of the document file 520.

  The proxy server 210 accesses the Web server 500 (Step 200). The proxy server 210 makes a request for acquiring only the http header information of the document file 520 to the Web server 500 before making a request for actually acquiring the document file 520. Then, the proxy server 210 acquires the http header of the document file 520 requested by the client 100 from the Web server 500 (step 201). The proxy server 210 acquires the Content-Type of the document file 520 from the http header acquired in Step 200 (Step 202).

  It is assumed that the correspondence between the Content-Type of the document file 520 obtained in Step 201 and the extension of the document file 520 does not exist in the extension-Content-Type correspondence table 2111 held by the file type determination unit 211 (Step 203). , No). The file type determination unit 211 registers the new correspondence in the extension-Content-Type correspondence table 2111 (step 204).

  Assume that the correspondence between the Content-Type of the document file 520 obtained in step 201 and the extension of the document file 520 exists in the extension-Content-Type correspondence table 2111 held by the file type determination unit 211 (step 203, Yes). Alternatively, it is assumed that a new correspondence is registered in the extension-Content-Type correspondence table 2111 (step 204). In both cases, the cache disk distribution unit 212 determines the cache disk 310 of the cache disk number corresponding to the Content-Type from the Content-Type obtained in Step 202 (Step 205). Here, as an example, the cache disk 310 is assumed to be applicable.

  Then, the proxy server 210 actually acquires the document file 520 from the Web server 500 (step 206). The proxy server 210 transfers the document file 520 to the client 100 (step 207). The proxy server 210 transfers the document file 520 to the cache disk 310, and sets the value parameter of the document file 520 based on the algorithm set in the cache disk 310 (step 208). For example, in the LRU algorithm, the document file 520 is set in the cache disk 310 as the most recently used file. Assume that the cache disk 300 is set to use the Expires field (step 209, Yes). The proxy server 210 sets the value (Expires parameter) of the Expires field of the http header of the document file 520 acquired in step 200 in the Expires parameter in the cache disk 300 (step 210). The operation according to the first embodiment of the present invention is thus completed.

  In the first embodiment of the present invention described above, the proxy server 210 includes the file type determination unit 211 and the cache disk distribution unit 212. However, only the file type determination and cache disk distribution functions are transferred to another server. It is good. FIG. 7 shows a modification of the configuration of the cache system 1001. Compared to FIG. 1, the proxy server 210 is different from the proxy server 210 and the cache server 220.

  As a difference in operation, in the flowchart shown in FIG. 5, a step of transferring the requested document file 520 information from the proxy server 210 to the cache server 220 is inserted between step 101 and step 102. In the flowchart shown in FIG. 6, Step 206 is changed, and the cache server 220 acquires the document file 520 from the Web server 500 via the proxy server 210.

  The invention in the first embodiment has an effect that, for example, the cache efficiency can be improved. The reason is that the file is stored with a different caching algorithm depending on the file type. There are various types of files such as images, moving images, and documents in the Internet 400, and differences in characteristics such as file size, download time, required frequency, and update frequency are recognized depending on the type. The present invention discriminates the file type and saves it with a different caching algorithm depending on the file type. As a result, for example, there is an effect that the average download waiting time is reduced by increasing the cache effect. In addition, for example, an increase in the cash effect has the effect of reducing communication charges.

  In addition, it is possible to set whether or not the cache disks 300 to 320 use the expiration date set in the file (for example, set whether or not to use the value of the Expires field included in the http header). This is one of the reasons why it can be improved.

  For example, since document files are generally updated frequently, the cache needs to discard document files that are not fresh that exceed the value of the Expires field included in the http header. However, the value of the Expires field is often unimportant because video and audio files generally do not change after being uploaded. By not using the Expires field value for video and audio files, files that have expired but do not actually need to be discarded can be left in the cache, improving cache efficiency. .

  Next, a second embodiment of the present invention will be described with reference to the drawings. In the second embodiment of the present invention, only the extension is used for determining the file type, not the Content-Type.

  First, the configuration of the second embodiment of the present invention will be described. FIG. 8 is a diagram showing the configuration of the cache system 1001 in the second embodiment of the present invention. Compared with the cache system 1001 in the first embodiment of the present invention shown in FIG. 1, the difference is that the file type determination unit 211 does not exist. Further, a difference is that an extension-cache disk number correspondence table 2123 is provided instead of the Content-Type-cache disk number correspondence table 2121 in the cache disk distribution unit 212.

  Next, the operation in the second embodiment of the present invention will be described. Changes from FIG. 5 and FIG. 6, which are flowcharts showing operations in the first embodiment, will be described.

  In the flowchart shown in FIG. 5, the processing of steps 102, 103, and 104 is changed, and processing for determining the cache disks 300 to 320 having the cache disk number corresponding to the file extension is performed. In the flowchart shown in FIG. 6, the processing of steps 202, 203, and 204 is not necessary. Further, the processing in step 205 is changed, and the cache disks 300 to 320 having the cache disk number corresponding to the file extension are determined.

  The invention according to the second embodiment has an effect that it is possible to increase the speed in distributing the files to the cache disks 300 to 320. This is because, for example, the correspondence between the extension and the Content-Type is not checked. This is because, by looking at the extension of the requested file name, the cache disks 300 to 320 to be searched or the cache disks 300 to 320 to be cached can be determined directly from the extension.

  The present invention can be applied to, for example, a proxy server between a local network of a company or a school and the Internet. The present invention can also be applied to applications such as proxy servers that connect to the Internet on behalf of users at Internet service providers.

It is a figure which shows the structure of the cache system 1001 in 1st Example of this invention. It is a figure which shows an example of the extension-Content-Type correspondence table 2111. This is a Content-Type-cache disk number correspondence table 2121. This is a cache disk number-Expires field correspondence table 2122. 5 is a flowchart illustrating an operation of the cache device 200 when a file acquisition request in the Web server 500 is received from the client 100. 6 is a flowchart showing the operation of the cache device 200 when there is no file requested by the client 100 on the cache disk 300 and the original file is downloaded from the Web server 500 in the flowchart of FIG. This is a modification of the configuration of the cache system 1001. It is a figure which shows the structure of the cache system 1001 in 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Client 110 Client 120 Client 1001 Cache system 200 Cache device 210 Proxy server 211 File type determination unit 2111 Extension-Content-Type correspondence table 212 Cache disk distribution unit 2121 Content-Type-Cache disk number correspondence table 2122 Cache disk number-Expires Field correspondence table 2123 Extension-cache disk number correspondence table 300 Cache disk 310 Cache disk 320 Cache disk 400 Internet 500 Web server 510 Image file 520 Document file

Claims (21)

  A cache device, wherein a file is stored with a different caching algorithm depending on the type of the file. The cache apparatus according to claim 1, further comprising: a cache distribution unit that determines a cache for searching or storing the file according to a type of the file. The cache device according to claim 2, further comprising: a plurality of caches that store the files with different caching algorithms according to types of the files. The file distribution unit
The cache apparatus according to claim 3, further comprising: a correspondence table between the file type and the cache. A web server for storing the file;
A client requesting the file on the web server;
A proxy server to which the client is connected and connects to a Web server as a proxy for the client;
In a cache system comprising a network to which the Web server and the proxy server are connected,
The cache device according to claim 4, wherein the cache device includes the proxy server. The proxy server is
If the cache stores the file, send the file to the client;
The cache device according to claim 5, wherein when the cache does not store the file, the file is received from the Web server and transferred to the client. Transmission of the file from the Web server to the proxy server is performed by HTTP protocol,
The proxy server is
A file type determination unit for determining the HTTP protocol Content-Type corresponding to the extension of the file;
The cache device according to claim 6, further comprising: The file type determination unit
The cache device according to claim 7, further comprising a correspondence table between extensions and Content-Type. The correspondence table between the file type and the cache is as follows:
Including correspondence table of Content-Type and cache number,
The cash distribution unit
Determine the cache of the cache number corresponding to the Content-Type of the file,
The cache device according to claim 8, wherein the cache is searched for the existence of the file. The cache device according to any one of claims 2 to 9, wherein the cache distribution unit determines whether the cache is set to use an expiration date set in the file. The cash distribution unit
The cache device according to claim 10, further comprising: a correspondence table between the cache and a flag indicating whether the cache is set to use an expiration date. The flag indicating whether or not the cache is set to use an expiration date is a flag indicating whether or not the cache is set to use the value of the Expires field in the HTTP protocol of the file received from the Web server. The cache device according to claim 11, characterized in that: A server that stores a file with a different caching algorithm depending on the type of the file. A web server for storing the file;
A client requesting the file on the web server;
A cache device comprising a proxy server to which the client is connected and which connects to a Web server as a proxy for the client;
A network to which the web server and the proxy server are connected;
The cache device is:
A cache system, wherein the file is stored with a different caching algorithm depending on the type of the file. A caching method, wherein a file is stored with a different caching algorithm depending on the type of the file. The cache method according to claim 15, wherein the cache for searching or storing the file is determined according to the type of the file. A client requests the file on the web server;
Determine the extension of the file from the extension attached to the file name of the URL (Uniform Resource Locator) where the file exists,
Determine whether the extension of the file is registered in the extension-Content-Type correspondence table,
If the extension of the file is registered in the extension-Content-Type correspondence table, determine the HTTP protocol Content-Type corresponding to the extension of the file,
Determine the cache of the cache number corresponding to the Content-Type,
The cache device according to claim 16, wherein the file is searched for whether the file exists in the cache. The cache method according to claim 17, wherein it is determined whether the cache is set to use an expiration date set in the file. If the file exists in the determined cache, determine whether the cache is configured to use the value of the Expires field;
If the cache is set to use the value of the Expires field, obtain the Expires parameter of the file, determine whether the current time exceeds the value of the Expires parameter of the file,
If the cache is not configured to use the value of the Expires field, or if the current time does not exceed the value of the Expires parameter of the file,
Increase the value parameter in the cache of the file in the cache according to an algorithm set in the cache;
The cache method according to claim 18, wherein the file is transferred from the cache to the client. If the extension of the file is not registered in the extension-Content-Type correspondence table, if the file does not exist in the determined cache, or if the file exists in the determined cache, When the cache is configured to use the value of the Expires field, and the current time exceeds the value of the Expires parameter of the file, and the file in the cache is deleted,
Access the web server,
Get the http header of the file on the web server,
Get Content-Type from the http header,
Determine whether the Content-Type is registered in the extension and Content-Type correspondence table,
When the Content-Type is registered in the correspondence table between the extension and Content-Type, the cache of the cache number corresponding to the Content-Type of the file is determined from the correspondence table of the Content-Type and the cache number,
If the Content-Type is not registered in the extension-Content-Type correspondence table, the Content-Type and the cache number are registered after the Content-Type is registered in the extension-Content-Type correspondence table. Determine the cache of the cache number corresponding to the Content-Type of the file from the correspondence table of
Obtaining the file from the web server;
Transfer the file to the client;
Transferring the file to the determined cache;
Set the value parameter in the cache of the file according to the algorithm set in the cache;
The cache method according to claim 19, wherein when the cache is configured to use an Expires field value, the Expires field value of the http header is set in an Expires parameter in the cache. On the computer,
A program for causing a file to be stored with a different caching algorithm depending on the type of the file.

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