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R_Melissari_180's avatar
R_Melissari_180
Icon for Nimbostratus rankNimbostratus
Oct 07, 2015
Solved

Standby F5 runs external health monitor

I have an external health monitor that I have written to verify a webserver is displaying the correct information and down the node if not. When looking over the http logs of the webserver I noticed...
application delivery
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LTM
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  • Hannes_Rapp_162's avatar
    Hannes_Rapp_162
    Oct 07, 2015

    Hello, this behavior is as expected.

     

    One reason this is beneficial comes down to troubleshooting - if more than one F5 appliances report that the pool member went "DOWN", it's a better evidence to rule out any possible F5 appliance issues. If you want, you can disable the health-check on standby F5s by writing a conditional check in the external script which verifies the appliance active-standby status prior to sending the health-check request.

     

    If the volume of health-check requests is a problem, perhaps it will help you if you increase the health-check interval a little bit? As far as I'm aware, no easy solutions exist to stop health-checks on the standby appliances. Could be wrong in regards to v11.6 or 12.0 releases.

     

Hannes_Rapp_162's avatar
Hannes_Rapp_162
Icon for Nacreous rankNacreous
Oct 07, 2015

Hello, this behavior is as expected.

 

One reason this is beneficial comes down to troubleshooting - if more than one F5 appliances report that the pool member went "DOWN", it's a better evidence to rule out any possible F5 appliance issues. If you want, you can disable the health-check on standby F5s by writing a conditional check in the external script which verifies the appliance active-standby status prior to sending the health-check request.

 

If the volume of health-check requests is a problem, perhaps it will help you if you increase the health-check interval a little bit? As far as I'm aware, no easy solutions exist to stop health-checks on the standby appliances. Could be wrong in regards to v11.6 or 12.0 releases.

 

gsharri's avatar
gsharri
Icon for Altostratus rankAltostratus
Oct 07, 2015
Yes as Hannes says this is expected behavior. If the standby unit is not monitoring the nodes/members and some of them are down, then if called upon to go active it will send traffic to an unavailable server until it discovers that it is down. Some clients will experience failed connections for the duration of the monitor timeout.