parent peer timeout

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parent peer timeout

Ignacio Freyre
Hi guys, i have a simple configuration that i'm testing with 2 parent proxys for a specific domain, if parent proxy 192.168.1.1 fails, failover to 192.168.1.2 proxy.
I have a couple of questions:
1)Having configured "connect-timeout=3" and "connect-fail-limit=2", failover takes about 2 minutes, how can I reduce failover time?
2)If I enable cache_peer_access statements, failover never happens because the peers dont get detected as dead

#CONFIGURATION START
#hostname
visible_hostname testing

#parent proxy's
cache_peer 192.168.1.1 parent 3128 0 no-query no-digest connect-timeout=3 connect-fail-limit=2
cache_peer 192.168.1.2 parent 3128 0 no-query no-digest connect-timeout=3 connect-fail-limit=2

#send traffic to peers
acl foo_url url_regex site\.domain\.com
never_direct allow foo_url

#peer access
cache_peer_access 192.168.1.1 deny !foo_url
cache_peer_access 192.168.1.2 deny !foo_url

#allow all for testing purposes
http_access allow all

# Squid normally listens to port 3128
http_port 3128

# Leave coredumps in the first cache dir
coredump_dir /var/spool/squid

# Add any of your own refresh_pattern entries above these.
refresh_pattern ^ftp:           1440    20%     10080
refresh_pattern ^gopher:        1440    0%      1440
refresh_pattern -i (/cgi-bin/|\?) 0     0%      0
refresh_pattern .               0       20%     4320
#CONFIGURATION END

LOGS that I see when peer is detected as dead
2017/11/20 22:55:02| Ready to serve requests.
2017/11/20 22:55:03| storeLateRelease: released 0 objects
2017/11/20 22:56:55| TCP connection to 192.168.1.1/3128 failed
2017/11/20 22:56:55| TCP connection to 192.168.1.1/3128 failed
2017/11/20 22:56:55| Detected DEAD Parent: 192.168.1.1

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Re: parent peer timeout

Amos Jeffries
Administrator
On 21/11/17 14:09, Ignacio Freyre wrote:
> Hi guys, i have a simple configuration that i'm testing with 2 parent proxys for a specific domain, if parent proxy 192.168.1.1 fails, failover to 192.168.1.2 proxy.
> I have a couple of questions:
> 1)Having configured "connect-timeout=3" and "connect-fail-limit=2", failover takes about 2 minutes, how can I reduce failover time?

Are you actually terminating the peer, or just simulating it some other way?

The behaviour you are seeing is what will happen for the particular
error you cause to happen. I suspect you are only simulating a firewall
rule table overload (ie firewall suddenly stops allowing *new*
connections) instead of actual peer machine disconnect or shutdown.

The connect-timeout=3 is to make *new* TCP connections signal failure if
the SYN+ACK takes more than 3 seconds to return. Otherwise it is a
successful connect.

Added to that Squid is HTTP/1.1 software these days. Which means it uses
multiplexing and pipeline features to reduce new TCP connections being
needed at all. So that type of network failure may have zero effect on
the proxy<->peer communications. Exactly as intended by the HTTP/1.1 design.


> 2)If I enable cache_peer_access statements, failover never happens because the peers dont get detected as dead


You disabled the features used as primary methods of detecting dead
peers (no-query no-digest).

Additionally restricting traffic with cache_peer_access removes
additional hints from HTTP and TCP traffic.


It is hard to say how those two things are impacting your proxies peer
selection logic, since it is also complicated by the things mentioned
above about #1.


>
> #CONFIGURATION START
> #hostname
> visible_hostname testing
>
> #parent proxy's
> cache_peer 192.168.1.1 parent 3128 0 no-query no-digest connect-timeout=3 connect-fail-limit=2
> cache_peer 192.168.1.2 parent 3128 0 no-query no-digest connect-timeout=3 connect-fail-limit=2
>
> #send traffic to peers
> acl foo_url url_regex site\.domain\.com
> never_direct allow foo_url

regex is the second slowest ACL type around, generally to match domain
use dstdomain ACL type.


>
> #peer access
> cache_peer_access 192.168.1.1 deny !foo_url
> cache_peer_access 192.168.1.2 deny !foo_url
>
> #allow all for testing purposes
> http_access allow all
>

Not a good idea even for testing purposes. If there is a problem with
your intended http_access rules that needs solving before anything else
can be properly investigated since what is allowed to be handled by the
proxy impacts on what can happen for outbound attempts.


> # Squid normally listens to port 3128
> http_port 3128
>
> # Leave coredumps in the first cache dir
> coredump_dir /var/spool/squid
>
> # Add any of your own refresh_pattern entries above these.
> refresh_pattern ^ftp:           1440    20%     10080
> refresh_pattern ^gopher:        1440    0%      1440
> refresh_pattern -i (/cgi-bin/|\?) 0     0%      0
> refresh_pattern .               0       20%     4320
> #CONFIGURATION END
>
> LOGS that I see when peer is detected as dead
> 2017/11/20 22:55:02| Ready to serve requests.
> 2017/11/20 22:55:03| storeLateRelease: released 0 objects
> 2017/11/20 22:56:55| TCP connection to 192.168.1.1/3128 failed
> 2017/11/20 22:56:55| TCP connection to 192.168.1.1/3128 failed
> 2017/11/20 22:56:55| Detected DEAD Parent: 192.168.1.1
>

Configure "debug_options 28,3" to see the peer selection results.


Amos
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