Retrying a different application server after receiving error 503

Question

We use F5 Big-IP load-balancer (LB) with 2 application servers, A1 and A2.

When sending 10 requests to the LB, 5 of them are being sent to A1, and 5 to A2.

However, if 10 request are sent while A1 returns HTTP code 503 Service Unavailable, A2 still gets only 5 requests. The expected behavior would be that when the LB gets a 503 response, it will try to send the same request to A2, and eventually A2 will handle 10 requests.

What should be done to achieve it?

jonwest1_uk · Answer

You need an http monitor looking for 200 as response. When the Application server returns 503 to the BigIP, the BigIP will mark this server as down and send any subsequent requests to the other server. The interval of the monitor is important here as the 10 requests may be sent before the BigIP has a chance to mark it down.

jg · Answer

Please see: "HTTP::retry", where there is some example code.

jaikumar_f5 · Answer

Can you share your pool &amp; monitor configuration details,tmsh list ltm pool &lt;pool name&gt;tmsh list ltm monitor &lt;monitor type&gt; &lt;monitor name&gt;

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Retrying a different application server after receiving error 503

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