varnish (edge) http_resp_hdr_len does not match pantheon's setting.

[apotek]

What is the problem?

Pantheon's setting for http_resp_hdr_len on the edge server (varnish) is 25k.
The default varnish setting is 8k. The lando pantheon recipe does not match since it uses the default.

How does it manifest?

If you are doing drupal development and setting cache keys and cache tags, you will likely have the http.response.debug_cacheability_headers setting set to true. These diagnostic http headers are enormous, swelling the response header size far past what a default edge server is going to accept, leading to a Page Unavailable response (from varnish) even though the appserver and nginx are returning the page.

Is there a workaround?

Yes, since the edge image is using gotpl to configure varnish during build, we can set an environment variable at build time to make sure varnish gets built with a different setting than default.

The workaround is putting this in .lando.local.yml:

  edge:
    overrides:
      environment:
        VARNISHD_PARAM_HTTP_RESP_HDR_LEN: 25k

and then destroying and rebuilding.

What is the real solution?

Since the goal of this recipe is to match (as far as possible) a pantheon environment, we shouldn't have to use a workaround or override in lando configs, but instead the edge container should be built with an http_resp_hdr_len that matches pantheon's by default.

To do so requires defining our desired value for the build to ensure the value is written into the varnish startup parameters. I will put up a PR to adjust the http_resp_hdr_len varnish config value to 25k instead of the default 8k.

[apotek]

PR is up and local testing shows it works.

[apotek]

@reynoldsalec Should I close this issue since you merged in our work? Or does this stay open until it is in the latest release?

[labboy0276]

This will be included in the 0.5.8 release of this plugin. We will include it in the 3.6.3 release of Lando.