[squid-users] SMP and AUFS

[Eliezer Croitoru]

I believe that some admins do not have enough time to sit and find the documentation.
I have seen it more than once that an admin just don't want to read the docs since it's like the "ocean" or something similar.

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 Marcus Kool
Sent: Sunday, March 19, 2017 2:36 PM
To: squid-users at lists.squid-cache.org
Subject: Re: [squid-users] SMP and AUFS

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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