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drupalwxt / docker-scaffold

Docker Scaffold for Drupal WxT
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Set Varnish http_resp_hdr_len to 64k to prevent 503 error #42

Closed smulvih2 closed 2 months ago

smulvih2 commented 3 months ago

On a project using the appsvc image in Prod, there was an issue reported where the second page of search results was giving a 503 error:

Error 503 Backend fetch failed
Backend fetch failed

Guru Meditation:
XID: 8881713

Varnish cache server

Using varnishlog to look at the output from the 503, I see this:

BogoHeader Header too long: Cache-Tags: config:b

This indicates that one of the headers, specifically Cache-Tags, exceeded the allowed length. Varnish is very strict about header sizes, and if a header is too long, it can lead to issues. So our search page, which lists a bunch of nodes, has too many cache tags and therefore kills Varnish.

If I run this in my environment, varnishadm param.show http_resp_hdr_len, I can see the default of 8kb is being used. Increasing this to a larger limit, varnishadm param.set http_resp_hdr_len 64k, resolves the issue.

This PR sets the http_resp_hdr_len value to 64k in the supervisord.ini file. I have tested this and it resolved the 503 error.

sylus commented 2 months ago

Oh wow thats a fun find! Amazing work @smulvih2 !!! :)

Merged!