CODEWITHSUNDEEP
varnishvarnish-vclvarnish-4
Or Guz
Or Guz

Reputation: 1018

Varnish 4.1 - Call a restart according to the backend response

Prior to Varnish 4, One could call a restart from vcl_fetch to start another flow reaching vcl_recv.

In version 4, logic was separated to client and backend, I need to be able to call a restart according to the backend response. One direction I thought might be possible is using vcl_synth as a middleware between backend and client but the backend can't send a specific error code or msg only standard 503 error.

Any ideas?

Upvotes: 1

Views: 449

Answers (1)

Carlos Abalde
Carlos Abalde

Reputation: 1087

You cannot restart a request during vcl_backend_* in Varnish 4.x.

You could return (abandon) during vcl_backend_* and then restart the request in vcl_synth if resp.status == 503, but you cannot transport any information from vcl_backend_* to vcl_synth in order to implement a smarter conditional.

As an alternative, you could execute the restart during vcl_deliver based on whatever was returned by the backend side.

Upvotes: 1

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