mass purge causes high load?

Dag-Erling Smørgrav des at
Mon Apr 14 13:43:11 CEST 2008

[resent to varnish-misc]

Sascha Ottolski <ottolski at> writes:
> Dag-Erling Smørgrav <des at> writes:
> > If you know the exact URL to purge, use an HTTP PURGE (see VCL code
> > examples in the vcl man page)
> I'm aware of this, but had expected that the semantic of both method
> would be identical. Especially as I did not pass regular expresssions,
> but the complete URLs. Well, at least that's what I thought :-)

No, the semantics are completely different.  With HTTP PURGE, you do a
direct cache lookup, and set the object's TTL to 0 if it exists.  With
url.purge, you add an entry to a ban list, and every time an object is
looked up in the cache, it is checked against all ban list entries that
have arrived since the last time.  This is the only way to implement
regexp purging efficiently.

Dag-Erling Smørgrav
Senior Software Developer
Linpro AS -

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