IBM Support

PH41417: LOAD BALANCER INCORRECTLY MARKS SERVER AS COLLOCATED

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APAR status

  • Closed as program error.

Error description

  • Collocated is set to yes when a 'server set' command is issued
    to multiple servers and one of the servers is collocated.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:  IBM WebSphere Application Server Edge Load  *
    *                  Balancer for IPv4 and IPv6 users            *
    ****************************************************************
    * PROBLEM DESCRIPTION: LB may not forward to a server. LB      *
    *                      reports indicate packets forwarded to   *
    *                      the server.                             *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    If you have a collocated server and issue a 'server set'
    command with the collocated server and another server at the
    same time, LB incorrectly flags both servers as collocated.
    When the non-collocated server is selected to receive traffic,
    LB forwards the packet to the collocated server instead of the
    selected server.
    Example problematic 'server set' commands (assume 1.2.3.4 is a
    collocated server):
    dscontrol server set cluster@port@1.2.3.4+1.1.1.1 weight 5
    dscontrol server set @@ weight 5
    

Problem conclusion

  • Internal code for the 'server set' command checked if the
    address of the server existed on the local LB machine. If the
    address was found, the code set the collocated flag to true.
    This causes LB to forward the packet as if the server is
    collocated so the traffic is not sent to the selected server.
    
    Code corrected to eliminate setting collocated flag on
    non-collocated servers.
    
    Fix levels:
       8.5.5.21
       9.0.5.10
    

Temporary fix

  • Two workarounds are available to prevent this problem:
    
    1) Do not issue compound 'server set' commands when using a
    collocated servers. For example, instead of "dscontrol server
    set cluster@port@1.2.3.4+1.1.1.1 weight 5", issue the commands
    separately: "dscontrol server set cluster@port@1.2.3.4 weight
    5" and "dscontrol server set cluster@port@1.1.1.1 weight 5"
    
    2) After setting server values, issue additional commands to
    ensure collocated flag set correctly. For example:
    dscontrol server set cluster@port@1.2.3.4 collocated yes
    dscontrol server set cluster@port@1.1.1.1 collocated no
    

Comments

APAR Information

  • APAR number

    PH41417

  • Reported component name

    WS EDGE LB IPV4

  • Reported component ID

    5724H8812

  • Reported release

    900

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2021-10-19

  • Closed date

    2021-10-19

  • Last modified date

    2021-10-19

  • 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

    WS EDGE LB IPV4

  • Fixed component ID

    5724H8812

Applicable component levels

[{"Line of Business":{"code":"LOB45","label":"Automation"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"900"}]

Document Information

Modified date:
20 October 2021