U.S. patent application number 12/908964 was filed with the patent office on 2012-04-26 for cache sharing among branch proxy servers via a master proxy server at a data center.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Erik J. Burckart, John P. Cammarata, Andrew J. Ivory, Aaron K. Shook.
Application Number | 20120102134 12/908964 |
Document ID | / |
Family ID | 45973897 |
Filed Date | 2012-04-26 |
United States Patent
Application |
20120102134 |
Kind Code |
A1 |
Burckart; Erik J. ; et
al. |
April 26, 2012 |
CACHE SHARING AMONG BRANCH PROXY SERVERS VIA A MASTER PROXY SERVER
AT A DATA CENTER
Abstract
A method, system and computer program product for cache sharing
among branch proxy servers. A branch proxy sever receives a request
for accessing a resource at a data center. The branch proxy server
creates a cache entry in its cache to store the requested resource
if the branch proxy server does not store the requested resource.
Upon creating the cache entry, the branch proxy server sends the
cache entry to a master proxy server at the data center to transfer
ownership of the cache entry if the master proxy server did not
store the resource in its cache. When the resource becomes invalid
or expired, the master proxy server informs the appropriate branch
proxy servers storing the resource to purge the cache entry
containing this resource. In this manner, the master proxy server
ensures that the cached resource is synchronized across the branch
proxy servers storing this resource.
Inventors: |
Burckart; Erik J.; (Raleigh,
NC) ; Cammarata; John P.; (Wake Forest, NC) ;
Ivory; Andrew J.; (Wake Forest, NC) ; Shook; Aaron
K.; (Raleigh, NC) |
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
45973897 |
Appl. No.: |
12/908964 |
Filed: |
October 21, 2010 |
Current U.S.
Class: |
709/213 ;
711/E12.025 |
Current CPC
Class: |
H04L 67/2842 20130101;
H04L 67/2852 20130101; H04L 67/2885 20130101; G06F 13/00 20130101;
G06F 16/00 20190101 |
Class at
Publication: |
709/213 ;
711/E12.025 |
International
Class: |
G06F 15/167 20060101
G06F015/167; G06F 12/08 20060101 G06F012/08 |
Claims
1. A method for cache sharing among branch proxy servers, the
method comprising: receiving a request by a first proxy server in a
branch office to access a resource at a data center; transmitting a
request to a second proxy server at said data center to determine
if said resource is located in a cache of said second proxy server
in response to said first proxy server not storing said resource in
its cache; creating a cache entry in said cache of said first proxy
server to store said resource in response to said second proxy
server not storing said resource in its cache; and sending said
cache entry to said second proxy server to transfer ownership of
said cache entry to said second proxy server.
2. The method as recited in claim 1 further comprising: fetching
said resource by said first proxy server in response to said second
proxy server not storing said resource in its cache.
3. The method as recited in claim 1 further comprising: receiving
said resource by said first proxy server from said second proxy
server in response to said second proxy server storing said
resource in its cache.
4. The method as recited in claim 1 further comprising: receiving
said cache entry by said second proxy server from said first proxy
server; and storing said cache entry in said cache of said second
proxy server.
5. The method as recited in claim 4 further comprising: informing
said first proxy server to purge said cache entry in response to
said resource at said cache entry being one of invalid and
expired.
6. The method as recited in claim 4 further comprising: informing
one or more proxy servers at one or more branch offices to purge a
cache entry storing said resource in response to said resource at
said cache entry being one of invalid and expired.
7. A computer program product embodied in a computer readable
storage medium for cache sharing among branch proxy servers, the
computer program product comprising the programming instructions
for: receiving a request by a first proxy server in a branch office
to access a resource at a data center; transmitting a request to a
second proxy server at said data center to determine if said
resource is located in a cache of said second proxy server in
response to said first proxy server not storing said resource in
its cache; creating a cache entry in said cache of said first proxy
server to store said resource in response to said second proxy
server not storing said resource in its cache; and sending said
cache entry to said second proxy server to transfer ownership of
said cache entry to said second proxy server.
8. The computer program product as recited in claim 7 further
comprising the programming instructions for: fetching said resource
by said first proxy server in response to said second proxy server
not storing said resource in its cache.
9. The computer program product as recited in claim 7 further
comprising the programming instructions for: receiving said
resource by said first proxy server from said second proxy server
in response to said second proxy server storing said resource in
its cache.
10. The computer program product as recited in claim 7 further
comprising the programming instructions for: receiving said cache
entry by said second proxy server from said first proxy server; and
storing said cache entry in said cache of said second proxy
server.
11. The computer program product as recited in claim 10 further
comprising the programming instructions for: informing said first
proxy server to purge said cache entry in response to said resource
at said cache entry being one of invalid and expired.
12. The computer program product as recited in claim 10 further
comprising the programming instructions for: informing one or more
proxy servers at one or more branch offices to purge a cache entry
storing said resource in response to said resource at said cache
entry being one of invalid and expired.
13. A system, comprising: a first proxy server in a branch office
connected to a data center, wherein said first proxy server
comprises: a memory unit for storing a computer program for cache
sharing among branch proxy servers; and a processor coupled to said
memory unit, wherein said processor, responsive to said computer
program, comprises circuitry for receiving a request to access a
resource at said data center; circuitry for transmitting a request
to a second proxy server at said data center to determine if said
resource is located in a cache of said second proxy server in
response to said first proxy server not storing said resource in
its cache; circuitry for creating a cache entry in said cache of
said first proxy server to store said resource in response to said
second proxy server not storing said resource in its cache; and
circuitry for sending said cache entry to said second proxy server
to transfer ownership of said cache entry to said second proxy
server.
14. The system as recited in claim 13, wherein said processor of
said first proxy server further comprises: circuitry for fetching
said resource in response to said second proxy server not storing
said resource in its cache.
15. The system as recited in claim 13, wherein said processor of
said first proxy server further comprises: circuitry for receiving
said resource from said second proxy server in response to said
second proxy server storing said resource in its cache.
16. The system as recited in claim 13 further comprising: said
second proxy server located at said data center, wherein said
second proxy server comprises: a memory unit for storing a computer
program for synchronizing cache data among branch proxy servers;
and a processor coupled to said memory unit, wherein said
processor, responsive to said computer program, comprises circuitry
for receiving said cache entry from said first proxy server; and
circuitry for storing said cache entry in said cache.
17. The system as recited in claim 16, wherein said processor of
said second proxy server further comprises: circuitry for informing
said first proxy server to purge said cache entry in response to
said resource at said cache entry being one of invalid and
expired.
18. The system as recited in claim 16, wherein said processor of
said second proxy server further comprises: circuitry for informing
one or more proxy servers at one or more branch offices to purge a
cache entry storing said resource in response to said resource at
said cache entry being one of invalid and expired.
Description
TECHNICAL FIELD
[0001] The present invention relates to data network configurations
in business environments, and more particularly to cache sharing
among branch proxy servers in branch offices via a master proxy
server at a data center.
BACKGROUND
[0002] A data network configuration implemented in business
environments typically involves centralizing data storage at a data
center and providing this data (e.g., via a server at the data
center) to a plurality of client computing devices over a wide area
network (e.g., Internet). These client computing devices
("clients") may be located at "branch offices" of the company, such
as in the retail, banking, and airline industry. In each branch
office, client computing devices may be interconnected to each
other using a local area network (LAN). Applications running on the
client devices may require data from the data center, such as
records, files, merchandising data, etc. However, the
interconnection between the branch office and the data center is
typically via a low bandwidth connection. Since these applications
may require large amount of data, the slow connection leads to poor
application performance.
[0003] As a result, companies may increase the bandwidth of the
interconnection between the branch office and the data center.
However, increasing the bandwidth of the interconnection is
costly.
[0004] Alternatively, companies may add a proxy server at each
branch office to serve as an intermediary for requests from clients
seeking resources (e.g., file, merchandising data) from other
servers at the data center. Once the proxy server has serviced the
client's request, it may cache the resource for future requests for
the resource. In this manner, when a client requests that resource,
the proxy server may directly provide that resource instead of
obtaining the resource from the data center. While this improves
the performance of the branch application, each branch proxy server
is independent of one another. That is, each branch proxy server is
independent of the other branch proxy servers at the other branch
offices. As a result, one branch proxy server may store a later
version of the resource than another branch proxy server. A branch
proxy server may even be storing an expired or invalid resource;
whereas, another branch proxy server is storing a valid version of
the same resource.
BRIEF SUMMARY
[0005] In one embodiment of the present invention, a method for
cache sharing among branch proxy servers comprises receiving a
request by a first proxy server in a branch office to access a
resource at a data center. The method further comprises
transmitting a request to a second proxy server at the data center
to determine if the resource is located in a cache of the second
proxy server in response to the first proxy server not storing the
resource in its cache. Additionally, the method comprises creating
a cache entry in the cache of the first proxy server to store the
resource in response to the second proxy server not storing the
resource in its cache. In addition, the method comprises sending
the cache entry to the second proxy server to transfer ownership of
the cache entry to the second proxy server.
[0006] The foregoing has outlined rather generally the features and
technical advantages of one or more embodiments of the present
invention in order that the detailed description of the present
invention that follows may be better understood. Additional
features and advantages of the present invention will be described
hereinafter which may form the subject of the claims of the present
invention.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0007] A better understanding of the present invention can be
obtained when the following detailed description is considered in
conjunction with the following drawings, in which:
[0008] FIG. 1 illustrates a business computing environment in
accordance with an embodiment of the present invention;
[0009] FIG. 2 is a hardware configuration of a branch proxy server
and a master proxy server in accordance with an embodiment of the
present invention;
[0010] FIG. 3 is a flowchart of a method for cache sharing among
branch proxy servers in accordance with an embodiment of the
present invention;
[0011] FIG. 4 is a diagram illustrating cache sharing among branch
proxy servers in accordance with an embodiment of the present
invention; and
[0012] FIG. 5 is a flowchart of a method for synchronizing cache
data among branch proxy servers in accordance with an embodiment of
the present invention.
DETAILED DESCRIPTION
[0013] The present invention comprises a method, system and
computer program product for cache sharing among branch proxy
servers. In one embodiment of the present invention, a branch proxy
sever receives a request from a client in its branch office for
accessing a resource at a data center. The branch proxy server
transmits a request to a master proxy server at the data center to
determine if the resource is located in its cache if the branch
proxy server does not store the requested resource in its cache.
The branch proxy server creates a cache entry in its cache to store
the requested resource. Upon creating the cache entry, the branch
proxy server sends the cache entry to the master proxy server to
transfer ownership of the cache entry if the master proxy server
did not store the resource in its cache. When the resource becomes
invalid or expired, the master proxy server informs the appropriate
branch proxy servers storing the resource to purge the cache entry
containing this resource. The master proxy server may provide an
updated version of the resource to be stored in place of the prior
version thereby ensuring that all of the branch proxy servers
storing this resource are storing the correct version. In this
manner, the master proxy server ensures that the cached resource is
synchronized across the branch proxy servers storing this resource
thereby preventing the branch proxy servers from storing different
versions or even invalid or expired versions of the resource.
[0014] While the following discusses the present invention in
connection with a computing environment for business organizations
with branch offices (e.g., banking, airline and retail industries),
the principles of the present invention may be applied to other
environments where cache entries need to be synchronized among
proxy servers. A person of ordinary skill in the art would be
capable of applying the principles of the present invention to such
implementations. Further, embodiments applying the principles of
the present invention to such implementations would fall within the
scope of the present invention.
[0015] In the following description, numerous specific details are
set forth to provide a thorough understanding of the present
invention. However, it will be apparent to those skilled in the art
that the present invention may be practiced without such specific
details. In other instances, well-known circuits have been shown in
block diagram form in order not to obscure the present invention in
unnecessary detail. For the most part, details considering timing
considerations and the like have been omitted inasmuch as such
details are not necessary to obtain a complete understanding of the
present invention and are within the skills of persons of ordinary
skill in the relevant art.
[0016] Referring now to the Figures in detail, FIG. 1 illustrates a
suitable business computing environment 100 for practicing the
principles of the present invention in accordance with an
embodiment of the present invention. Computing environment 100
includes one or more branch offices 101A-101B. Branch offices
101A-101B may collectively or individually be referred to as branch
offices 101 or branch office 101, respectively. Each branch office
101 includes one or more client computing devices "clients." For
example, branch office 101A includes clients 102A-102C and branch
office 101B includes clients 102D-102F. Clients 102A-102F may
collectively or individually be referred to as clients 102 or
client 102, respectively.
[0017] As further illustrated in FIG. 1, each branch office 101 may
also include a branch proxy server connected to a client 102 via a
local area network. For example, branch office 101A includes branch
proxy server 103A that is connected to clients 102A-102C via local
area network ("LAN") 104A. Similarly, branch office 101B includes
branch proxy server 103B that is connected to clients 102D-102F via
local area network 104B. Branch proxy servers 103A-103B may
collectively or individually be referred to as branch proxy servers
103 or branch proxy server 103, respectively. A detailed
description of the hardware configuration of branch proxy server
103 is provided further below in connection with FIG. 2.
Furthermore, local area networks 104A-104B may collectively or
individually be referred to as local area networks 104 or local
area network 104, respectively.
[0018] Computing environment 100 further includes a data center 105
which is interconnected to branch offices 101 via a wide area
network ("WAN") 106, such as the Internet. Data center 105 includes
a master proxy server 107 and a sever 108 for providing the
resources requested by clients 102. Master proxy server 107 is
interconnected between wide area network 106 and server 108. A
detailed description of the hardware configuration of master proxy
server 107 is provided further below in connection with FIG. 2.
[0019] In one embodiment, branch proxy server 103 serves as an
intermediary for requests from clients 102 seeking resources (e.g.,
file, merchandising data) from server 108 at data center 105.
Similarly, master proxy server 107 servers as an intermediary for
requests from branch proxy server 103 and server 108 at data center
105. Master proxy server 107 is configured to synchronize cache
data among branch proxy servers 103 as discussed below in further
detail.
[0020] Computing environment 100 is not to be limited in scope to
any one particular computer architecture. Computing environment 100
may include any number of branch offices 101, where each branch
office 101 may include any number of clients 102 interconnected
with a branch proxy server 103 via a local area network 104.
Furthermore, data center 105 may include any number of servers 108
providing resources requested by clients 102.
[0021] Referring to FIG. 2, FIG. 2 illustrates an embodiment of a
branch proxy server 103 (FIG. 1), master proxy server 107 (FIG. 1)
which is representative of a hardware environment for practicing
the present invention. Proxy servers 103, 107 may have a processor
201 coupled to various other components by system bus 202. An
operating system 203 may run on processor 201 and provide control
and coordinate the functions of the various components of FIG. 2.
An application 204 in accordance with the principles of the present
invention may run in conjunction with operating system 203 and
provide calls to operating system 203 where the calls implement the
various functions or services to be performed by application 204.
Application 204 for branch proxy server 103 may include, for
example, an application for cache sharing among branch proxy
servers 103 as discussed further below in association with FIGS.
3-4. Application 204 for master proxy server 107 may include, for
example, an application for synchronizing cache data among branch
proxy servers 103 as discussed further below in association with
FIGS. 4-5.
[0022] Referring again to FIG. 2, read-only memory ("ROM") 205 may
be coupled to system bus 202 and include a basic input/output
system ("BIOS") that controls certain basic functions of proxy
servers 103, 107. Random access memory ("RAM") 206 and disk adapter
207 may also be coupled to system bus 202. It should be noted that
software components including operating system 203 and application
204 may be loaded into RAM 206, which may be proxy servers 103, 107
main memory for execution. Disk adapter 207 may be an integrated
drive electronics ("IDE") adapter that communicates with a disk
unit 208, e.g., disk drive. It is noted that the program for cache
sharing among branch proxy servers 103 and for synchronizing cache
data among branch proxy servers 103 as discussed further below in
association with FIGS. 3-5, may reside in disk unit 208 or in
application 204.
[0023] Proxy servers 103, 107 may further include a communications
adapter 209 coupled to bus 202. Referring to FIG. 2, in conjunction
with FIG. 1, communications adapter 209 of proxy server 103 may
interconnect bus 202 with an outside network (not shown) thereby
allowing proxy server 103 to communicate with data center 105
(e.g., master proxy server 107) and clients 102. Communications
adaptor 209 of proxy server 107 may interconnect bus 202 with an
outside network (not shown) thereby allowing proxy server 107 to
communicate with server 108 as well as with branch proxy server
103.
[0024] Additionally, proxy servers 103, 107 may include a cache
210, such as a level-1 cache, to store resources as discussed
further below in connection with FIGS. 3-5. While cache 210 is
shown to be internal within processor 201, cache 210 may be located
external to processor. Cache 210 may be any type of cache (e.g.,
physically indexed, physically tagged; virtually indexed, virtually
tagged; virtually indexed, physically tagged).
[0025] As will be appreciated by one skilled in the art, aspects of
the present invention may be embodied as a system, method or
computer program product. Accordingly, aspects of the present
invention may take the form of an entirely hardware embodiment, an
entirely software embodiment (including firmware, resident
software, micro-code, etc.) or an embodiment combining software and
hardware aspects that may all generally be referred to herein as a
"circuit," `module" or "system." Furthermore, aspects of the
present invention may take the form of a computer program product
embodied in one or more computer readable medium(s) having computer
readable program code embodied thereon.
[0026] Any combination of one or more computer readable medium(s)
may be utilized. The computer readable medium may be a computer
readable signal medium or a computer readable storage medium. A
computer readable storage medium may be, for example, but not
limited to, an electronic, magnetic, optical, electromagnetic,
infrared, or semiconductor system, apparatus, or device, or any
suitable combination of the foregoing. More specific examples (a
non-exhaustive list) of the computer readable storage medium would
include the following: an electrical connection having one or more
wires, a portable computer diskette, a hard disk, a random access
memory (RAM), a read-only memory (ROM), an erasable programmable
read-only memory (EPROM or flash memory), a portable compact disc
read-only memory (CD-ROM), an optical storage device, a magnetic
storage device, or any suitable combination of the foregoing. In
the context of this document, a computer readable storage medium
may be any tangible medium that can contain, or store a program for
use by or in connection with an instruction execution system,
apparatus, or device.
[0027] A computer readable signal medium may include a propagated
data signal with computer readable program code embodied therein,
for example, in baseband or as part of a carrier wave. Such a
propagated signal may take any of a variety of forms, including,
but not limited to, electro-magnetic, optical, or any suitable
combination thereof A computer readable signal medium may be any
computer readable medium that is not a computer readable storage
medium and that can communicate, propagate, or transport a program
for use by or in connection with an instruction execution system,
apparatus or device.
[0028] Program code embodied on a computer readable medium may be
transmitted using any appropriate medium, including but not limited
to wireless, wireline, optical fiber cable, RF, etc., or any
suitable combination of the foregoing.
[0029] Computer program code for carrying out operations for
aspects of the present invention may be written in any combination
of one or more programming languages, including an object oriented
programming language such as Java, Smalltalk, C++ or the like and
conventional procedural programming languages, such as the C
programming language or similar programming languages. The program
code may execute entirely on the user's computer, partly on the
user's computer, as a stand-alone software package, partly on the
user's computer and partly on a remote computer or entirely on the
remote computer or server. In the latter scenario, the remote
computer may be connected to the user's computer through any type
of network, including a local area network (LAN) or a wide area
network (WAN), or the connection may be made to an external
computer (for example, through the Internet using an Internet
Service Provider).
[0030] Aspects of the present invention are described below with
reference to flowchart illustrations and/or block diagrams of
methods, apparatus (systems) and computer program products
according to embodiments of the present invention. It will be
understood that each block of the flowchart illustrations and/or
block diagrams, and combinations of blocks in the flowchart
illustrations and/or block diagrams, can be implemented by computer
program instructions. These computer program instructions may be
provided to a processor of a general purpose computer, special
purpose computer, or other programmable data processing apparatus
to product a machine, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the function/acts
specified in the flowchart and/or block diagram block or
blocks.
[0031] These computer program instructions may also be stored in a
computer readable medium that can direct a computer, other
programmable data processing apparatus, or other devices to
function in a particular manner, such that the instructions stored
in the computer readable medium produce an article of manufacture
including instructions which implement the function/act specified
in the flowchart and/or block diagram block or blocks.
[0032] The computer program instructions may also be loaded onto a
computer, other programmable data processing apparatus, or other
devices to cause a series of operational steps to be performed on
the computer, other programmable apparatus or other devices to
produce a computer implemented process such that the instructions
which execute on the computer or other programmable apparatus
provide processes for implementing the function/acts specified in
the flowchart and/or block diagram block or blocks.
[0033] As stated in the Background section, companies may add a
proxy server at each branch office to serve as an intermediary for
requests from clients seeking resources (e.g., file, merchandising
data) from other servers at the data center. Once the proxy server
has serviced the client's request, it may cache the resource for
future requests for the resource. In this manner, when a client
requests that resource, the proxy server may directly provide that
resource instead of obtaining the resource from the data center.
While this improves the performance of the branch application, each
branch proxy server is independent of one another. That is, each
branch proxy server is independent of the other branch proxy
servers at the other branch offices. As a result, one branch proxy
server may store a later version of the resource than another
branch proxy server. A branch proxy server may even be storing an
expired or invalid resource; whereas, another branch proxy server
is storing a valid version of the same resource.
[0034] The principles of the present invention enable the cached
resources to be synchronized across the branch proxy servers
thereby ensuring that the client branch applications obtain the
correct data while improving the performance of the client branch
applications as discussed below in connection with FIGS. 3-5. FIG.
3 is a flowchart of a method for cache sharing among branch proxy
servers 103 (FIG. 1). FIG. 4 is a diagram illustrating cache
sharing among branch proxy servers 103. FIG. 5 is a flowchart of a
method for synchronizing cache data among branch proxy servers
103.
[0035] Referring to FIG. 3, FIG. 3 is a flowchart of a method 300
for cache sharing among branch proxy servers 103 (FIG. 3) in
accordance with an embodiment of the present invention.
[0036] Method 300 will be discussed in conjunction with FIG. 4,
which is a diagram illustrating cache sharing among branch proxy
servers 103 as well as illustrating the synchronization of cache
data among branch proxy servers 103 in accordance with an
embodiment of the present invention.
[0037] Referring again to FIG. 3, in conjunction with FIGS. 1-2 and
4, in step 301, branch proxy server 103 receives a request from
client 102 to access a resource from data center 105 (e.g., server
108).
[0038] In step 302, a determination is made by branch proxy server
103 as to whether the requested resource is stored in its local
cache 210.
[0039] If the requested resource is stored in its local cache 210,
then, in step 303, branch proxy sever 103 accesses the resource and
sends it to the requesting client 102.
[0040] If, however, the requested resource is not stored in its
local cache 210, then, in step 304, branch proxy server 103
transmits a request to master proxy server 107 to determine if the
resource is located in its local cache 210. As illustrated in FIG.
4, a business may have multiple branch proxy servers 103 (e.g.,
branch proxy server 103A, branch proxy server 103B) in various
locations that are connected to master proxy server 107 at a data
center 105. One of the branch proxy servers 103 (e.g., branch proxy
server 103A) may request master proxy server 107 for the requested
cached resource (in the example illustrated in FIG. 4, the
requested resource is identified by "/foo") as identified by step
401 if the branch proxy server 103A does not store the requested
resource locally in its cache 210.
[0041] Returning to FIG. 3, in conjunction with FIGS. 1-2 and 4, in
step 305, branch proxy server 103 receives the response from master
proxy sever 107 as to whether master proxy server 107 has the
requested resource in its local cache 210. A determination is made
by branch proxy server 103 in step 306 as to whether master proxy
server 107 has the requested resource cached.
[0042] If master proxy server 107 has the requested resource
cached, then, in step 307, branch proxy server 103 receives the
requested resource from master proxy server 107 and caches it in
its local cache 210 for future client requests.
[0043] If, however, master proxy server 107 does not have the
requested resource cached, as illustrated in step 402 in FIG. 4,
then, in step 308, branch proxy server 103 fetches the requested
resource from data center 105 (e.g., server 108). Alternatively,
branch proxy server 103 may request master proxy server 107 to
fetch the requested resource from data center 105 (e.g., server
108) on its behalf.
[0044] In step 309, branch proxy server 103 creates a cache entry
in its local cache 210 to store the fetched resource. Referring to
FIG. 4, upon master proxy server 107 informing branch proxy server
103A that the requested resource is not cached in its local cache
210, branch proxy server 103A creates a cache entry in its local
cache 210 and caches the requested resource in step 404.
[0045] Returning to FIG. 3, in conjunction with FIGS. 1-2 and 4, in
step 310, branch proxy server 103 sends the cache entry created in
step 309 that stores the requested resource to master proxy server
107 to transfer ownership of the cache entry to master proxy server
107 as illustrated in step 404 of FIG. 4.
[0046] Once master proxy server 107 acquires ownership of the cache
entry that stores the requested resource, which involves caching
the resource in its local cache 210 as discussed further below in
connection with FIG. 5, master proxy server 107 will be able to
provide the resource upon it being requested by other branch proxy
servers 103. For example, as illustrated in FIG. 4, branch proxy
server 103B may request for the resource identified in FIG. 4 as
"/foo" in step 405 after master proxy server 107 has taken
ownership of the cache entry for the resource "/foo" in step
404.
[0047] Upon receiving the request for the resource "/foo," master
proxy server 107 sends the requested resource to branch proxy
server 103A in step 406. Branch proxy server 103A then caches the
resource in its local cache 210 in step 407 (similarly discussed in
step 307 of FIG. 3).
[0048] In some implementations, method 300 may include other and/or
additional steps that, for clarity, are not depicted. Further, in
some implementations, method 300 may be executed in a different
order presented and that the order presented in the discussion of
FIGS. 3 and 4 is illustrative. Additionally, in some
implementations, certain steps in method 300 may be executed in a
substantially simultaneous manner or may be omitted.
[0049] As discussed above, ownership of the cache entry created by
branch proxy server 103 is transferred to master proxy server 107
in step 310 of FIG. 3. Once master proxy server 107 has ownership
of the cache entry for the resource, master proxy server 107
ensures that the cached resource is synchronized across branch
proxy servers 103 in various branch offices 101 using the process
described in FIG. 5. That is, master proxy server 107 ensures that
the resource that is cached in multiple branch proxy servers 103
are all the same version and up-to-date using the process described
in FIG. 5.
[0050] FIG. 5 is a flowchart of a method 500 for synchronizing
cache data among branch proxy servers 103 (FIG. 1) in accordance
with an embodiment of the present invention.
[0051] Referring to FIG. 5, in conjunction with FIGS. 1-4, in step
501, master proxy server 107 receives the cache entry that branch
proxy server 103 created in step 309 that stores the resource
requested by client 102 in order to transfer ownership of the cache
entry to master proxy server 107.
[0052] In step 502, master proxy server 107 stores the received
cache entry in its local cache 210.
[0053] In step 503, a determination is made by master proxy server
107 as to whether the resource at the cache entry is invalid or
expired.
[0054] If the resource at the cache entry is valid and not expired,
then master proxy server 107 repeats the determination step of 503
after a duration of time.
[0055] If, however, the resource at the cache entry is invalid or
expired, then, in step 504, master proxy server 107 informs the
appropriate branch proxy servers 103 (those branch proxy servers
103 storing this cached resource) to purge the cache entry
containing the resource. Master proxy server 107 may provide an
updated version of the resource to be stored in place of the prior
version thereby ensuring that all of the branch proxy servers 103
storing this resource are storing the correct version. In this
manner, master proxy server 107 ensures that the cached resource is
synchronized across branch proxy servers 103 storing this resource
thereby preventing branch proxy servers 103 from storing different
versions or even invalid or expired versions of the resource.
[0056] An illustration of step 504 is provided in FIG. 4. Referring
to FIG. 4, if branch proxy servers 103A, 103B both have cached the
resource "/foo" which needs to be purged for being invalid or
expired, then master proxy server 107 informs branch proxy servers
103 A, 103B in steps 408, 409, respectively, to purge the cache
entry "/foo" which can be replaced with an updated version of the
resource "/foo."
[0057] In some implementations, method 500 may include other and/or
additional steps that, for clarity, are not depicted. Further, in
some implementations, method 500 may be executed in a different
order presented and that the order presented in the discussion of
FIGS. 4 and 5 is illustrative. Additionally, in some
implementations, certain steps in method 500 may be executed in a
substantially simultaneous manner or may be omitted.
[0058] Although the method, system and computer program product are
described in connection with several embodiments, it is not
intended to be limited to the specific forms set forth herein, but
on the contrary, it is intended to cover such alternatives,
modifications and equivalents, as can be reasonably included within
the spirit and scope of the invention as defined by the appended
claims.
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