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Chris_Phillips's avatar
Chris_Phillips
Icon for Nimbostratus rankNimbostratus
Jan 31, 2012

pool reselect tries - "user-specified interval"?

From the v10.2.0 LTM guide:

 

 

 

====

 

Specifying the number of reselect tries

 

 

 

The Reselect Tries setting specifies the number of times that the system

 

tries to contact a new pool member after a passive failure. A passive failure

 

consists of a server-connect failure or a failure to receive a data response

 

within a user-specified interval. The default value of 0 indicates no reselects.

 

====

 

 

 

What is this "user-specified interval" I see no other reference to it whatsoever. The closest I can see is the TCP profiles Idle timeout, but that just totally reset the connection, and doesn't reselect. The way this is worded suggests that it should be able to handle an HTTP request that is left waiting for a response for too long... does it?

 

 

 

Thanks

 

 

 

Chris

 

config
design

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  • nitass's avatar
    nitass
    Icon for Employee rankEmployee
    Jan 31, 2012
    according to statement in sol10640 below, i guess it depends on maximum syn retransmissions option in tcp profile.

     

     

    However, beginning in BIG-IP version 10.x it is possible to cause a reselection by using the Reselect Tries advanced pool feature. This feature is equivalent to the LB::reselect iRule command. Once a connection attempt to a pool member is considered failed (equivalent to the LB_FAILED iRule event), the BIG-IP system selects a new pool member. Should that pool member also fail, the system repeats the reselection until it reaches the limit configured for this option. Only at this point is the client connection reset.

     

     

    sol10640: Pool member reselection options

     

    http://support.f5.com/kb/en-us/solutions/public/10000/600/sol10640.html

     

     

    LB_FAILED wiki

     

    http://devcentral.f5.com/wiki/iRules.LB_FAILED.ashx
  • Chris_Phillips's avatar
    Chris_Phillips
    Icon for Nimbostratus rankNimbostratus
    Jan 31, 2012
    the max syn transmissions are surely covered in the connection failure part of the description. The wording seems to very clearly point towards a higher level lack of response than TCP.

     

     

    TBH this mostly looks like sloppy manual writing, but i'm hoping that some more light can be shed on this.

     

  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Feb 01, 2012
    Hi Chris,

     

     

    I'm not sure where the logic is for retry interval. It would be great if you could open a case with F5 Support to confirm this and reply back with what you find.

     

     

    Aaron