HTTP Trailers

Rainer Canavan rainer.canavan+varnish at
Tue Oct 23 15:13:57 UTC 2018


I would like to log the content of a HTTP Trailer sent to Varnish in a
response from a server within our own infrastructure. Since the data I
want to log requires the entire body to be available, we don't want to
send it in a header for performance reasons.

Logging the header field as such works as expected. Announcing it as a
Trailer and sending it as such leaves the log field empty.

As far as I can see, I'm generating the trailers correctly, e.g. I can
see the infos I stuck into the Server-Timing Trailer in the Firefox
console in window.performance.getEntries().

In addition to all that, I would also like to pass the Server-Timing
Trailer to the client.  However, both the TE: Trailers request header
field as well the the Trailer: response-header and the trailers
themselves are removed with our current varnish setup using  Varnish
5.2 or 6.1.

Are Trailers supported at all in any Varnish version, and if so, do I
have to take special measures to (1) transparently handle them when
passing a response or (2) log their values?



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