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IT27849: MQ async consume client may hang during MQDISC

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APAR status

  • Closed as program error.

Error description

  • The MQ asynchronous client thread can hang during an MQDISC if
    MQAPI calls are made in the callback function.
    
    A captured MQ trace will show following sequence of calls for
    the hanging thread.
    
    06:32:50.405760   5268.1      RSESS:000011 !! - MQDISC >>
    06:32:50.405762   5268.1      RSESS:000011 !! - Hconn:
    06:32:50.405770   5268.1      RSESS:000011 !! - MQI:MQDISC
    HConn=01000019
    06:32:50.405772   5268.1      RSESS:000011 (03)----{  rpqMQCTL
    ..
    06:32:50.405789   5268.1      RSESS:000011 (04)-----{
    reqReleaseConn
    06:32:50.405791   5268.1      RSESS:000011 (04)-----}
    reqReleaseConn (rc=OK)
    06:32:50.405793   5268.1      RSESS:000011 (04)-----{
    xcsPostThreadEvent
    06:32:50.405797   5268.1      RSESS:000011 (04)-----}
    xcsPostThreadEvent (rc=OK)
    06:32:50.405799   5268.1      RSESS:000011 (04)-----{
    xcsWaitThreadEvent
    
    Before the hang, a communication error happens on the dispatch
    thread.
    
    06:31:30.174188   5268.19     RSESS:000011 --------{  MQCMIT
    06:31:30.174193   5268.19     RSESS:000011 ---------{
    reqGetConn
    06:31:30.174195   5268.19     RSESS:000011 ----------{
    zutLookupGet
    06:31:30.174199   5268.19     RSESS:000011 hLook=6B9223F0
    Flags=0x00000001 Identifier=0x01000019 pUseCount=0B19F47C
    phEntry=0B19F524
    06:31:30.174203   5268.19     RSESS:000011 Data: 0x01000019
    ..
    06:31:30.174962   5268.19     RSESS:000011 (10)-----------}
    ccxSend
    (rc=OK)
    06:31:30.174974   5268.19     RSESS:000011 (10)-----------{
    ccxReceive
    06:31:46.156463   5268.19     RSESS:000011 (11)------------}!
    ccxReceiveAsync (rc=rrcE_COMMUNICATIONS_ERROR)
    06:31:46.156469   5268.19     RSESS:000011 (10)-----------}!
    ccxReceive
    (rc=rrcE_COMMUNICATIONS_ERROR)
    

Local fix

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    Users using the MQ client with asynchronous consume and call the
    MQAPI in its callback function.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    If the MQ async consume application calls the MQAPI in its
    callback function and receives a communication error, then some
    of the connection resources are freed too early. When an MQDISC
    is run from the main thread this hangs while it attempts to
    cleanup the associated dispatcher thread which performed the
    callback actions.
    

Problem conclusion

  • The code causing the hang has been corrected to fix the issue.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v9.0 LTS   9.0.0.7
    v9.1 CD    9.1.3
    v9.1 LTS   9.1.0.3
    
    The latest available maintenance can be obtained from
    'WebSphere MQ Recommended Fixes'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
    
    If the maintenance level is not yet available information on
    its planned availability can be found in 'WebSphere MQ
    Planned Maintenance Release Dates'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
    ---------------------------------------------------------------
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT27849

  • Reported component name

    IBM MQ BASE M/P

  • Reported component ID

    5724H7261

  • Reported release

    900

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2019-01-22

  • Closed date

    2019-04-08

  • Last modified date

    2019-04-08

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    IBM MQ BASE M/P

  • Fixed component ID

    5724H7261

Applicable component levels

[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"9.0","Edition":"","Line of Business":{"code":"LOB36","label":"IBM Automation"}}]

Document Information

Modified date:
08 April 2019