[squid-users] SMP and AUFS

[Alex Rousskov]

On 03/16/2017 10:42 PM, senor wrote:

> I understand that AUFS is not SMP aware but if each worker has its own
> AUFS cache is there any problem other than the inefficiencies of
> duplicate cache?

Yes. Clients may get stale cached entries, possibly breaking advanced
HTTP transactions that rely on a more-or-less compliant proxy cache.

Also, I do not know exactly how local and shared cache indexes interact
when SMP-unaware store updates its local index without updating the
shared one. Most likely, such partial updates lead to bugs. You may
reduce bugs probability by not mixing shared and ufs-based stores in SMP
mode, but I doubt you can eliminate all problems that way.


> I'm pretty sure that AUFS is used with squid running in SMP mode a lot.

I can think of many examples where a lot of people do things they should
not be doing and do not do things they should be doing. Just because
many use X to solve some problem, does not make using X a good idea and
certainly does not make it the best solution available.


> The squid wiki even has a CARP configuration example for this combination.

I hope there are no official examples advertising SMP AUFS
configurations. If there are, they should be removed IMO.

Alex.