Varnish 3.0 slow backend fetches

Andreas Plesner apj at
Mon Aug 31 08:37:34 CEST 2015

On Sun, Aug 30, 2015 at 12:48:42AM +0200, Christian Hartlage wrote:
> Testing these requests with curl showed that it takes nginx/php-fpm about
> 0.2sec for a single response. For us it seems like varnish can do only 1
> fetch at once, so that the backend request are blocking. Is that possible?

Sounds like you're doing return(hit_for_pass) in vcl_fetch without setting a
TTL, thus effectively serializing all requests with the same hash.

If you set a TTL, varnish will cache that it can't cache that particular URL
and not attempt to coalesce requests in the future.


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