Re: [squid-users] Some queries about cache_peer

bijayant kumar wrote:
>
> Bijayant Kumar
>
>
> --- On Thu, 31/7/08, Amos Jeffries <squid3_at_treenet.co.nz> wrote:
>
>> From: Amos Jeffries <squid3_at_treenet.co.nz>
>> Subject: Re: [squid-users] Some queries about cache_peer
>> To: bijayant4u_at_yahoo.com
>> Cc: "squid users" <squid-users_at_squid-cache.org>
>> Date: Thursday, 31 July, 2008, 5:09 PM
>> bijayant kumar wrote:
>>>> From: Amos Jeffries <squid3_at_treenet.co.nz>
>>>> Subject: Re: [squid-users] Some queries about
>> cache_peer
>>>> To: bijayant4u_at_yahoo.com
>>>> Cc: "squid users"
>> <squid-users_at_squid-cache.org>
>>>> Date: Thursday, 31 July, 2008, 9:31 AM
>>>>> Hello list,
>>>>>
>>>>> I tried to set up cache_peer, but i could not
>>>> understand that it has setup
>>>>> or not. Please give some inputs.
>>>>>
>>>>> Scenario:-
>>>>>
>>>>> I have setup three proxy-servers.squid 3.0.7
>> Stable
>>>>> proxy1 192.168.99.134
>>>>> proxy2 192.168.99.135
>>>>> proxy3 192.168.99.121
>>>>>
>>>>> Lan Computer 192.168.99.23.
>>>>>
>>>>> On my Lan Computer, i have configured proxy in
>> my
>>>> browser as
>>>>> 192.168.99.134 ie proxy1. All request first go
>> to
>>>> proxy1.
>>>>> In Proxy1 squid.conf:-
>>>>> cache_peer 192.168.99.135 parent 3128
>> 3130
>>>> proxy-only default
>>>>> cache_peer 192.168.99.121 parent 3128
>> 3130
>>>> proxy-only
>>>>> cache_peer_domain 192.168.99.135 .com
>>>>> cache_peer_domain 192.168.99.121 .net
>>>>>
>>>>> In proxy2 and proxy3 no cache_peer is
>> configured.
>>>>> I can browse the web. But i didnt understand
>> the
>>>> working. I have some
>>>>> queries regarding this scenario:
>>>>> If the page is not in any of the proxy server,
>> then
>>>> which proxy server
>>>>> will go to internet and fetch for the user. I
>> mean if
>>>> user access any
>>>>> ".net" domain then the request will
>> come to
>>>> the proxy1 first, it will
>>>>> query to the proxy3, if its there it will be
>> delivered
>>>> else the page will
>>>>> be fetched from the internet ,Same is for the
>>>> ".com" domain right?
>>>>
>>>> Usually. If netdb/icmp has been enabled squid will
>> keep
>>>> records of
>>>> response times and go to whichever of peer/web
>> responds
>>>> fastest. thinking
>>>> fastest available service is usually best to use.
>>>>
>>>> Check your access.log for info on which is being
>> selected
>>>> for each request.
>>>>
>>>>> Then my question is,
>>>>> 1) which server will query to the internet for
>> the
>>>> page which is not in
>>>>> the cache ie ".net" dedicated server
>> or the
>>>> main proxy1 server?
>>>>
>>>> Under only cache_peer_domain, maybe both. Use
>>>> 'never_direct' to force
>>>> requests to go via peers.
>>>>
>>> If i use 'never_direct' option then if parent
>> cache servers will go down then no body will be able to
>> browse the web. And if i will not use 'never_direct'
>> option then fetching of object will be done by proxy1,if
>> object not found in any cache(proxy2/proxy3), am i right?
>>
>> Yes.
>
>>>>> 2) The new page will be written to the which
>> cache,
>>>> proxy1 or
>>>>> proxy2/proxy3
>>>> 'proxy-only' prevents caching at proxy1 if
>> request
>>>> came from peer. If
>>>> request came from web DIRECT then it can be cached
>> at
>>>> proxy1 and used
>>>> later.
>>> In my configuration, proxy1 will query to the internet
>> for new objects and hence the cache will be populated of
>> proxy1 only, no matter it is of ".net" domain or
>> of ".com" domain. Then the new entry of
>> ".net" and ".com" domain will never be
>> written to the cache of the dedicated caching server for the
>> same.
>>> If i am right in my analogy then can you please
>> suggest me to how to avoid this situation. I mean that
>> ".net" cache will be written to ".net"
>> dedicated server(proxy3) and ".com" cache will be
>> written to the proxy2.
>>
>> In squid you only have a choice of peers vs DIRECT.
>>
>> Your config earlier was workable, in which case squid will
>> make that
>> choice every request. Usually going peers, but sometimes
>> going DIRECT.
>>
>> Or you can force a choice yourself with never_direct
>> (opposite is
>> always_direct, but its clear to me you don't want
>> that).
>>
>> It's up to you.
>>
>> To decide if a cache of 100% .com traffic is worth the
>> small risk of no
>> access to .com at all when proxy2 goes down. Which is only
>> 2x the same
>> risk of proxy1 going down by itself anyway.
>>
>> Keeping in mind that a quick admin reconfigure of proxy1
>> (commenting out
>> the proxy2 lines) can restore access while proxy2 is
>> debugged about why
>> it went down.
>>
> It means that this configuration will not serve my purpose of using cache_peer. I also can not afford of any down time also.
> I wanted to use proxy servers in my network which are 2 to 3 in numbers, share their cache among them. To achieve this setting shall i use DNS round robin or squid round robin along with the cache_peer settings in all the three server's squid.conf ? Can you give me some input to achieve this, it would be great help.

To mesh 2-3 squid together with high reliability and efficiency the best
option is probably 'carp'. AFAIK, thats the only thing you need to add
on the cache_peer line for it to work. Dropping the 'proxy-only' option
to share caches lets the highest usage objects be in the proxy closest
to the client.

That will then query all peers and the local cache for an object then go
direct.

You can then set DNS up to have one name configured in all clients and
point at 2-3 IP addresses for reasonable failover if any break.

Amos

-- 
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