Workspace exhaustion with Varnish 4 under load

[Geoff Simmons]

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On 05/28/2015 08:25 PM, Geoff Simmons wrote:
> 
> We're getting our first experience with testing Varnish 4 under
> load (v4.0.3), and we're having severe problems with workspace
> exhaustion

To follow this up, in case someone finds it in an archive search
someday -- it turns out that this was a problem entirely of our own
making, due to a bug in our VCL.

We had VCL code to replace req.url in vcl_recv() under certain
circumstances, but it should have been done only at ESI level 0, and
it was happening at every ESI level. The result was massive ESI
expansion in both depth and breadth that was enough to explode
workspaces. The trac ticket (#1743) explains in a little more detail
how that happened.

After we fixed the VCL bug so that the req.url replacement only
happens at ESI level 0, the tests ran successfully. So let it be said
that our load tests do *not* indicate a problem with workspace
management on the part of varnishd.

The ticket will be closed, thanks again to phk for helping out.


Best,
Geoff
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