Implementing a message queuing interface (MQI) indexed queue support that adds a key to the index on put commit

• US 7,035,852 B2
• Filed: 07/20/2001
• Issued: 04/25/2006
• Est. Priority Date: 07/21/2000
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kettley, Paul, Nick, Jeffrey M., Siddall, Peter, Hopewell, Paul, Warnes, James H.
• Primary Examiner(s): Choules, Jack M.
• Application Number:
  US09/909,538
• Publication Number:
  US 20020087507A1
• Time in Patent Office: 1,740 Days
• Field of Search: 707/1, 707/8, 707/2
• US Class Current: 1/1
• CPC Class Codes: G06F 2209/547 Messaging middleware
• CPC Class Codes: G06F 2209/548 Queue
• CPC Class Codes: G06F 9/546 Message passing systems or structures, e.g. queues
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

Provided are a method, computer program product and system for providing indexed queue support for efficient retrieval of messages from a queue. An index key for expediting message retrieval is assigned to a message when the operation of placing the message on a queue is committed. The index key assigned at commit time comprises an attribute (such as a message ID or correlation ID) specified by the sending application program, which placed the message on the queue. This deferred assignment of an index key until commit time means that the index key can be used to search for messages having the particular attribute without any possibility of identifying messages for retrieval before the messages have been committed. This maintains transactional requirements of a transaction-oriented messaging system which requires a message to only be made available for retrieval by receiver application programs after the sender application'"'"'s put operation has committed.

Claims

1. A method of managing retrieval of messages from a shared queue, where a plurality of receiver applications retrieve messages from the same shared queue, where a PUT operation by a sender application is used to place a message onto the shared queue, and where a message on the queue is not to be retrieved until a subsequent commit of the PUT operation occurs, the method comprising:

assigning an index key to a message in response to a commit of the PUT operation, wherein the assigned index key comprises an attribute value of the message which was specified by the sender application when the message was placed on the queue, so that the assignment of the index key is deferred until a commit occurs of the PUT operation; and

in response to a receiver application requesting retrieval of messages from the queue and specifying a request attribute value, monitoring the availability of messages in the queue with reference to said assigned index key to identify a match,

whereby the index key being assigned to the message in response to said commit is usable for identifying committed messages having an attribute value matching the request attribute value.

2. A method according to claim 1 wherein the receiver application specifies other criteria for a match, said method further including the step of:

in response to the monitoring step identifying the availability of a committed message in the queue which has the assigned index key, determining whether the message matches other criteria of the retrieval request; and

in response to a positive match, sending a response to the receiver application which issued the request.

3. A method according to claim 2, wherein the monitoring step identifies to the requester application the the message corresponding to the match.

4. A method according to claim 1, wherein the attribute value included in the assigned index key is a message identifier or a correlation identifier.

5. A method according to claim 1, wherein receiver application programs are able to issue retrieval requests with a wait attribute, and wherein the method includes:

responsive to identifying no messages which match the requested attribute value, triggering a monitoring process to repeatedly perform the monitoring step for the request attribute value.

6. A method according to claim 1, wherein the queue is a shared queue held in a list structure of a Coupling Facility to which a plurality of resource managers can connect to put messages on the queue and to retrieve messages from the shared queue on behalf of respective sender and receiver applications.

7. A method according to claim 6, wherein the step of assigning an index key at commit time comprises a resource manager which put the message on the shared queue providing the attribute value to the Coupling Facility in response to committing the put operation, the Coupling Facility then building the index key and storing it in association with the enqueued message.

8. A method according to claim 6, wherein the assigned index value for each message is held in a predefined control data area of the Coupling Facility list structure which holds the shared queue.

9. A method according to claim 8, wherein the predefined control data area of the Coupling Facility list structure is a Coupling Facility list entry control data area, and the predefined control data area holds a message identifier and a correlation identifier for the message, the assigned index key comprising one of said message identifier or correlation identifier.

10. A method according to claim 6, wherein the monitoring step is performed by a monitoring process within the Coupling Facility in response to receipt of a retrieval request which specifies the request attribute value, the monitoring process including:

means for determining whether an identified available message matches all criteria of the received retrieval request; and

means, responsive to a positive match, for sending a response to the application program which issued the request.

11. A method according to claim 10, wherein the monitoring process is adapted to invoke said means for determining a match for all identified messages in said queue which have said assigned index value corresponding to the request attribute value.

12. A program product comprising program code including executable program instructions recorded on a machine-readable recording medium, for controlling the performance of operations of a data processing apparatus on which it executes relating to storage and retrieval of messages on a shared queue where a PUT operation is used to place a message on the queue but access is not intended until a subsequent commit action is taken, the program code including:

program code for postponing the assigning an index key to a message to be in response to such commit of the PUT operation, wherein the assigned index key comprises an attribute value of the message which was specified when the message was sent; and

program code, responsive to a receiver application program requesting retrieval of messages from the queue and specifying a request attribute value, for monitoring the availability of messages in the queue with reference to said assigned index key, whereby the index key assigned to the message in response to said commit provides an index which is usable for identifying only committed messages having the attribute value that matches the requested attribute value.

13. A resource manager component for a data processing apparatus, for storing messages within a queue and storing index keys in association with the enqueued messages for use in retrieval of the messages from the queue, the resource manager component including:

means for assigning an index key to a message after a delay to be in response to commit of the operation of putting the message on the queue, wherein the assigned index key comprises an attribute value of the message which was specified by the sending application when the message was sent; and

means, responsive to a receiver application program requesting retrieval of messages from the queue and specifying a request attribute value, for monitoring the availability of messages in the queue with reference to said assigned index key, whereby the index key assigned to the message in response to said commit provides an index which is usable for identifying only committed messages having the particular the request attribute value.

14. A data processing apparatus including:

storage means;

a data processor;

a resource manager component for storing messages within a queue and storing index keys in association with the enqueued messages for use in retrieval of the messages from the queue, the resource manager component including;

means for assigning an index key to a message after a delay to be in response to commit of the operation of putting the message on the queue, wherein the assigned index key comprises an attribute value of the message which was specified by the sending application when the message was sent; and

means, responsive to a receiver application program requesting retrieval of messages from the queue and specifying a request attribute value, for monitoring the availability of messages in the queue with reference to said assigned index key, whereby the index key assigned to the message in response to said commit provides an index which is usable for identifying only committed messages having the request attribute value.