Varnish 5.2 started reporting "500 Internal Server Error"

Question

I have been running Varnish for some time and about 6 months ago I added a Varnish 5.2 server that has been running perfectly.

A couple of weeks ago we have started to see odd "500 Internal Server Error" and when looking at older reports they suggest its the server running out of internal memory.

There was a suggestion to tune the parameters (which I have tried) but I am still getting the errors any suggestions on where to look?

Alan

PS The sugested tuning I saw was:

         -p workspace_client=160k \
         -p workspace_backend=160k \

The up the workspace elements from the default 64k, I tried 128k and then 160k but no change in the reported occasional issues.

Answer 1

You can control the "maximum number of HTTP header lines" varnish allows via the http_max_hdr option. The default is 64 and, in my case, setting it to 128 or 256 solved my problem. Note that, for some reason, the value needs to be set in power of two, so setting it to 100 or 150 will not allow varnish to restart.

https://varnish-cache.org/docs/4.1/reference/varnishd.html#http-max-hdr