Passing Backend App Errors to End Users

Andreas Plesner apj at
Wed Jul 20 09:32:18 CEST 2016

On Tue, Jul 19, 2016 at 04:00:16PM +0000, Kelvin Loke wrote:
> I have a tough time digging this and none of my tries would work.
> The error messages from my backend contains useful details such as:
> HTTP 400 Bad Request
> Body: Missing required parameter: queueList
> The messages is very useful for the end users to know what was wrong with
> their request.
> I was trying hard to figure how Varnish could pass the backend app error to
> end users, not the Varnish's wrapped error message (Guru Mediation...)

Varnish will do that by default. If you get a 503 from Varnish, it is because your VCL returns that or because your backend violates the HTTP protocol.

As always: Show us varnishlog and we will be able to tell.


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