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Xhuxhu's avatar
Xhuxhu
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Jan 12, 2021

Zero downtime deployment with f5 GTM+LTM

We have a GTM+LTM set up for our application which is running on 12 servers. This servers are separated in 4 LTMs with 3 servers each with monitoring set to a static page and "Action on service down"...
application delivery
BIG-IP
LTM
  • jaikumar_f5's avatar
    jaikumar_f5
    Jan 15, 2021

    GTM does also play a role here, I'd say before you mark down the respective ltm's servers, mark the GTM Pool member as disabled too. In that way the DNS resolution goes to other VIP's. Also how's your GTM setup configured here, RR ? How many GTM pools ? etc etc.

     

    Also before you mark start your deploy, always check if there's any existing connections coming to the VIP.

    Because they have to tcp time out before you start you deploy. Else when the subsequent request comes to the pool member, its obvious it would get dropped & you'll see client impact.

     

    Hope these helps.

Xhuxhu's avatar
Xhuxhu
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Thanks a lot for the answer. The setup is one GTM pool with 4 ltms, and yes it is RR. We do wait 5 min before deploying and after marking them as down. I believe the issue here might be with the TCP timeout or the DNS resolver cache. That would explain the connection dropping since they would still go to the same LTM even after marking all the servers inside as down. I'll try to always keep at least one server in the LTM pool as up and see if it fixes it.

jaikumar_f5's avatar
jaikumar_f5
Icon for MVP rankMVP
Jan 20, 2021

If I were you, I'll be disabling the VIP's on the GTM pool 1st.

Then I'll just disable the pool members or even force disable them in the respective 2 LTM's. Watch for the connections to get timed out. Because any existing connections would still go through, thereby no outage is caused. Once all traffic is drained, will let the deployment team to start deploying their code.

 

Once code is deployed, then enable them back on the LTM, have the servers tested though this VIP directly to see everything is working fine. Then turn it on the GTM pool, so its customer facing.

 

The practice to follow traffic drain depends from application to application. Some application could be heavily used, so traffic drain takes even hours.

 

Hope this helps too.