Patent Application
20110153563
This invention is related generally to the fields of networking, computing, and databases, and specifically to the replication of filtered database update modifications wherein multiple database entries are to be replicated . . . . The disclosure uses LDAP (Lightweight Directory Access Protocol) as an example. However, the principles of the specification can be extended in general to any database. The disclosed, illustrative embodiment is designed to execute on a computer such as a desktop, a workstation, a laptop or general-purpose mainframe, although alternative embodiments such as special-purpose electronics are possible. LDAP is an open industry standard defining a method for accessing and updating information in a directory. A directory server is an implementation of the LDAP protocol. It is basically a read-centric repository, wherein users can store any kind of data such as names and addresses, applications, files, printers, network resources etc. Data is stored in the directory servers in the form of tree entries. LDAP replications of multiple entries that are changed using query filters presently require a separate replication message for every changed entry.
A first embodiment of the invention is a method of replicating a database update operation. Responsive to an update request received at a supplier server that affects more than one database entry at the supplier server, a single replication request is built that contains an expression identifying the affected database entries to be replicated and the respective values of the attributes to be replicated. The single replication request is transmitted to the consumer server.
A second embodiment is a computer program product containing computer program code for replicating a database update operation. The computer program product has computer usable program code embodied therewith. The computer usable program code is configured to build a single replication request containing an expression identifying the affected database entries to be replicated to a consumer server and the respective values of the attributes to be updated. The supplier server also contains computer usable program code configured to transmit the single replication request to the consumer server.
A third embodiment is an update database server. The database server contains computer program code responsive to an update request received at the supplier server that affects more than one database entry at the supplier server for building a single replication request. The single replication request contains an expression identifying the affected database entries at a consumer server to be replicated and the respective values of the attributes to be replicated. The supplier server also contains computer program code for transmitting the single replication request to the consumer server.
In the drawings:
As will be appreciated by one skilled in the art, the present invention may be embodied as a method, system, or computer program product. Accordingly, 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, the present invention may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium.
Any suitable computer usable or computer readable medium may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. In many environments, there can be computer storage or propagation media at both server and client, and software at the server that embodies the invention can be downloaded to a client for execution. More specific examples (a non-exhaustive list) of the computer-readable 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), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-usable medium may include a propagated data signal with the computer-usable program code embodied therewith, either in baseband or as part of a carrier wave. The computer usable program code may be transmitted using any appropriate medium, including but not limited to the Internet, wireline, optical fiber cable, RF, etc.
Computer program code for carrying out operations of the present invention may be written in an object oriented programming language such as Java, Smalltalk, C++ or the like. However, the computer program code for carrying out operations of the present invention may also be written in conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the designer's computer, partly on the designer's computer, as a stand-alone software package, partly on the designer'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 designer's computer through 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).
The present invention is described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the 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 produce 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 functions/acts specified in the flowchart and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
With reference now to
At server 100 (the supplier), database update requests 102 arrive at server 100 and are entered into a request processing thread 104. In this illustrative embodiment of the invention, request processing thread 104 processes a modification request normally according to the LDAP protocols described in IETF RFCs 4511 et seq and updates the main database 107. If a filtered modification is performed at server 100 according to a query operation that affects multiple entries in the main database 107, the processing thread 104 builds a single replicate request and places the request in a replication update table 108. If the replication request affects only one entry at server 106, replication proceeds conventionally by placing that single entry request into replication update table 108. Periodically a replication thread 110 at server 100 fetches replication requests from table 108 and uploads the requests to the consumer server 106. These replication requests are inputted to the request processing thread 112 at server 106 via a separate link shown at 116 of
As an example, the following shows an update request from a client to change the Department numbers of all employees at the Delhi, India office to “DEPT1”.
idsldapmodify-p<port>-D<adminDN>-w<password>
dn: o=Delhi,c=India
filter: objectclass=person
changetype: modify
replace: dept
dept: DEPT1
Step 302 analyzes the request, builds an update stricture at step 302, request and executes the request locally at server 100. The following is a local update request that might be built by server 100 in response to the client request above.
Base DN: o=Delhi,c=India
Filter: objectclass=person
Modify type: replace
Attribute: dept
Value: DEPT1
Step 304 of
The following is an illustrative example of a replicate request, using the above example.
Base DN: o=Delhi,c=India
Filter: objectclass=person
Modify type: replace
Attribute: dept
Value: DEPT1
Timestamp: <op timestamp>
Transaction Flag: true
Step 306 determines if the Transaction flag is true in a replicate request. If Transaction Flag is True, then step 308 sets a marker to begin the processing of the transaction and then step 310 is executed. If Transaction Flag is False, then step 310 is entered without marking a transaction. In both cases, a single replication request message is placed in the replication update table 108 at step 310. Server 100 then executes the request locally at step 312. At step 316, if the Transaction Flag is true, and assuming no failures have occurred, then step 314 commits the transaction and this operation is ended at 312. In the meantime, the replication thread 110 of the server 100 pushes this single replication request message into the request processing thread 112 of consumer server 106.
On receiving the single replication request message, consumer server 106 performs an update operation using the details in the single replication request message in the same manner as that of the server 100. Server 106 also applies the same timestamp that is received in the single replicate request message to each entry being modified at consumer server 106. This ensures that the timestamp of all the modified entries will be same on both server 100 and the consumer server 106. This avoids replication conflicts arising out of timestamp mismatches. Note that if the transaction flag indicates that the operation was performed on the server 100 server as a transaction, consumer server 106 will also perform it as a transaction.
There are two special cases to be handled:
If the operation to be performed by the supplier server 100 affects only entries that are not under the replication context, then the operation will not be replicated to the replication server 106. If the update request from a client contains a null DN, which means that the operation is to be performed on all the trees in the server 100, then the replication is performed for only those suffixes that are defined to be within replication contexts. In this case, the server 100 will place as many replication request messages in the replication update table 108 as there are replication contexts.
Here is an example of the second special case. Remember that supplier server 100 hosts three trees—“O=ACME,C=INDIA”, “O=ACME,C=USA”, “CN=ACMEPOLICIES”. Also assume that replication is setup between server 100 and consumer server 106 for “O=ACME,C=INDIA” and “CN=ACMEPOLICIES”. Now assume that a filtered update operation is received by server 100 with the following parameters:
Base DN: ″″
Filter:Objectclass=person
Modify type: replace
Attribute:DepartmentNumber
Value: DEPT1
On the server 100 side, this operation would be performed on all the three trees. Since the replication is setup for only “O=ACME,C=IN” and “CN=ACMEPOLICIES”, it cannot be performed on NULL DN in consumer server 106. So supplier server 100 sends the following two messages to consumer server 106 for replication:
Base DN: o=acme,c=india
Filter: objectclass=person
Modify type: replace
Attribute: departmentNumber
Value: DEPT1
Timestamp: <op timestamp>
TransactionFlag: true
Base DN: cn=ACMEPolicies
Filter: objectclass=person
Modify type: replace
Attribute: departmentNumber
Value: DEPT1
Timestamp: <op timestamp>
TransactionFlag: true
On consumer server 106, two different filtered update operations are performed—one on “O=IBM, C=INDIA” and other on “CN=IBMPOLICIES”.
There are two error scenarios to consider:
1. Operation is performed as a transaction: If a filtered update is being performed as a transaction, then the sequence of steps to be followed would be:
Begin the database transaction.
Put the replication entry in the replication update table.
Perform the filtered modification op.
Commit the database transaction.
Replication thread 110 of the server 100 is able to select the replication request from table 108 only after the transaction is committed. Now assume that there is an error while performing the update operation. In this case the entire operation is rolled back. So nothing is replicated to the replication server 106.
2. The operation is not performed as a transaction: An option can be given to users to specify the maximum number of errors that can be tolerated while the operation is being performed. If errors are encountered, server would ignore them until the maximum number of errors is reached. There are two scenarios to be considered:
a) If the user has specified NumMaxErrors, then the server 100 would first put the replication update request in the replication update table 108. NumMaxErrors would be part the of the replication request. If there are any errors while server 100 is performing the update, it will continue until the NumMaxErrors is reached. Since the replication request was put in the table 108 in advance, replication server 106 would perform the update in parallel. Server 106 would adopt the same strategy as that of the server 100 while tolerating the errors. Synchronization of data in the two servers would not be ensured.
b) If the user has not specified NumMaxErrors, this means that the user wants to stop the processing at the first error. The replication request is put in the table 108 and the update is performed. If an error is encountered, processing is stopped. This will be true for both supplier server 100 as well as consumer server 106.
The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
Having thus described the invention of the present application in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
