Limits in xkey module usage ?

Carlos Abalde carlos.abalde at
Mon Sep 24 16:11:50 UTC 2018

Hi Oliver,

I'll let the creators of the VMOD talk here, but I think the only limit is the space needed in order to keep the in-memory data structure indexing the cached contents.

If you link an object to a lot of keys you might hit varnishd limits like max number of headers or the max length of a header. On the other hand, if you link a huge number of objects to the same key, that's not a problem at all, but you might experience some thread contention during invalidations of that key due to the associated locking required by the VMOD.


Carlos Abalde

> On 24 Sep 2018, at 18:00, Olivier Hanesse <olivier.hanesse at> wrote:
> Hello, 
> I'm in the process of testing xkey module, and I didn't find any "limits" in the documentation.
> Is there a limit of setting the same key on a very large number of objects ?
> Is there a limit on the number of key an object can be linked to ?
> I think, it is mainly a memory / pointer size issue, are those limits tunable ?
> Regards
> Olivier
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