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PK76363: IMPROVE MOD_MPMSTATS LOGGING IN IHS 6.0.X TO DISPLAY HANGING MODULES IN POST_READ_REQUEST HOOK

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APAR status

  • Closed as program error.

Error description

  • IHSDiag, The MustGather for IHS, contains a diagnostic
    module (mod_mpmstats) that traces the number of threads in
    various states as well as aggregating how many threads are
    busy in specific Apache modules. This latter form of tracking
    is enabled only when the TrackModules directive is set to "on".
    
    One particular phase of Apache processing, the
    "post_read_request" hook, has not been instrumented to provide
    the data required to identify the currently busy Apache module
    via "TrackModules on".
    
    If a module is hanging in this phase of processing,
    mod_mpmstats can only count it against the total of "reading"
    threads, but cannot count the thread towards the total
    number of threads busy in a particular modules.
    
    We have observed a number of incidents where third-party Apache
    modules hang in the post_read_request phase of processing, and
    mod_mpmstats is the best way to identify them.
    
    More info on mod_mpmstats is available at the following URL:
    http://publib.boulder.ibm.com/httpserv/ihsdiag/
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: Users debugging a hang with mod_mpmstats,    *
    * using the TrackModules feature, who see large numbers of     *
    * threads in the "rd" state but no particular modules listed   *
    * accounting for the "rd" threads.                             *
    ****************************************************************
    * PROBLEM DESCRIPTION: post_read_request hook not instrumented *
    * of mod_mpmstats, and many third-party modules can hang in    *
    * this phase.                                                  *
    ****************************************************************
    * RECOMMENDATION: Apply this fix, and use mod_mpmstats with    *
    * "TrackModules on", to debug webserver hangs                  *
    ****************************************************************
    
    The phases of Apache Processing need to be explicitly
    instrumented to identify the name of the module being run
    to mod_mpmstats. The post_read_request hook was not
    instrumented in previous releases of IHS.
    

Problem conclusion

  • The post_read_request hook was instrumented in the same
    fashion as several other existing phases of Apache processing.
    
    This fix is targeted for:
    Fix pack 6.0.2.35
    Fix pack 6.1.0.23
    (n/a for 7.0 release)
    

Temporary fix

Comments

APAR Information

  • APAR number

    PK76363

  • Reported component name

    WEBS APP SERV N

  • Reported component ID

    5724H8800

  • Reported release

    60A

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2008-11-24

  • Closed date

    2008-12-05

  • Last modified date

    2008-12-05

  • 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

    WEBS APP SERV N

  • Fixed component ID

    5724H8800

Applicable component levels

  • R60A PSN

       UP

  • R60H PSN

       UP

  • R60I PSN

       UP

  • R60P PSN

       UP

  • R60S PSN

       UP

  • R60W PSN

       UP

  • R61A PSN

       UP

  • R61H PSN

       UP

  • R61I PSN

       UP

  • R61P PSN

       UP

  • R61S PSN

       UP

  • R61W PSN

       UP

  • R61Z PSN

       UP

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Document Information

Modified date:
10 February 2022