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Ben_Lamb_227759's avatar
Ben_Lamb_227759
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May 03, 2016
Solved

Persistence causing problems with redirection iRule?

I have a slightly strange case on website where I am seeing traffic being redirected strangely, and I believe it may be down to my persistence. I was wondering if anyone could advise on if what I am ...
application delivery
cookie persistence
iRules
LTM
  • Hannes_Rapp_162's avatar
    Hannes_Rapp_162
    May 03, 2016

    You're missing a else-clause (default action) in your iRule. In other words, once a request lands in your test pool, there's no way to return to default pool (since the balancing decision is already locked in).

    when HTTP_REQUEST {
   Save the name of default pool (as configured in VS Resources Tab) as a variable, before it can be modified by conditional actions below
  set poolDefault [LB::server pool]

  if { "[HTTP::host][HTTP::uri]" starts_with "www.website.com/test" } {
    pool test_pool
  } else {
    pool $poolDefault
  }
}

    Similar problem here: https://devcentral.f5.com/questions/incorrect-load-balancing-when-disabling-oneconnect

Hannes_Rapp's avatar
Hannes_Rapp
Icon for Nimbostratus rankNimbostratus
May 03, 2016

You're missing a else-clause (default action) in your iRule. In other words, once a request lands in your test pool, there's no way to return to default pool (since the balancing decision is already locked in).

when HTTP_REQUEST {
   Save the name of default pool (as configured in VS Resources Tab) as a variable, before it can be modified by conditional actions below
  set poolDefault [LB::server pool]

  if { "[HTTP::host][HTTP::uri]" starts_with "www.website.com/test" } {
    pool test_pool
  } else {
    pool $poolDefault
  }
}

Similar problem here: https://devcentral.f5.com/questions/incorrect-load-balancing-when-disabling-oneconnect

  • Ben_Lamb_227759's avatar
    Ben_Lamb_227759
    Icon for Nimbostratus rankNimbostratus
    May 03, 2016
    Thanks for that. I don't really understand why that is necessary though. The VS has a default pool set up, which works in the majority of cases. If the HTTP request comes in and doesn't match the 'if' clause, should it not default to the default pool selection specified in the VS? This is what happens for 99% of the traffic directed at www.website.com. The default pool is selected and used. I don't understand what's happening differently in the other 1% of cases, and why this change would have any impact.
  • Ben_Lamb_227759's avatar
    Ben_Lamb_227759
    Icon for Nimbostratus rankNimbostratus
    May 03, 2016
    Thanks :) I'll give it a go and report back.
  • Ben_Lamb_227759's avatar
    Ben_Lamb_227759
    Icon for Nimbostratus rankNimbostratus
    May 09, 2016
    This fixed it, thanks!