Varnish unresponsive on our server

[Uday Kumar]

Hello all,

We are facing frequent issues of varnish unresponsiveness for sometime on
our production server.

During this time we have seen that pz_list is being increased to ~3000 and
recv_queue is increased to ~130
Also, varnish is responding with response code '0' for sometime, which
meant unresponsive.

This is causing multiple 5xx on front ends.

FYR:
User request count during this time is normal.

Note:
During this time, we have confirmed that our backend servers are healthy
without any issues.


May I know what could be the reason for this behaviour at varnish?

Please give me the direction on how to debug this issue.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.varnish-cache.org/lists/pipermail/varnish-misc/attachments/20240620/6d066946/attachment-0001.html>