[squid-users] SMP and AUFS

[Marcus Kool]

The root cause of why admins configure SMP + [A]UFS is the lack of good documentation.
A few lines in the wiki and squid.conf.documented should be enough.

Marcus


On 19/03/17 06:11, Eliezer  Croitoru wrote:
> I think that some warning message like "WARNING: be sure you know that UFS\AUFS doesn't support SMP\MultiWorkers" should be added to the stderr or cache.log.
>
> Eliezer
>
> ----
> Eliezer Croitoru
> Linux System Administrator
> Mobile: +972-5-28704261
> Email: eliezer at ngtech.co.il
>
>
> -----Original Message-----
> From: squid-users [mailto:squid-users-bounces at lists.squid-cache.org] On Behalf Of senor
> Sent: Sunday, March 19, 2017 7:12 AM
> To: squid-users at lists.squid-cache.org
> Subject: Re: [squid-users] SMP and AUFS
>
> On 3/17/2017 7:45, Alex Rousskov wrote:
>> 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.
>>
> There are many references in the squid wiki, FAQ and Knowlegebase about
> SMP but I don't see any of them reflecting the concerns you have brought
> up. My point in mentioning that there are a lot of installations using
> SMP and AUFS is that something widely used but buggy tends to be brought
> up on this email list and I haven't seen it.
>
> I'm not trying to claim there are no problems. I'm just making sure my
> expectations are realistic. Your comments were the first I became aware
> anyone thought poorly about the combination of AUFS with SMP. Rock is of
> course preferred but it comes with more baggage than AUFS. My own
> experience has been pretty good. Maybe just lucky.
>
> Senor
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