Oh, that lib won't help, sorry, forget about my pinger_program path
So do I have to recompile squid myself and than install the pinger as
described here:
https://wiki.squid-cache.org/SquidFaq/OperatingSquid#Using_ICMP_to_Measure_the_Network
?
On 09.02.21 16:03, Chris wrote:
Hi,
thank you Amos, this is bringing me into the right direction.
Now I know what I'll have to debug: the pinger.
Cache.log shows:
2021/02/09 14:49:27| pinger: Initialising ICMP pinger ...
2021/02/09 14:49:27| pinger: ICMP socket opened.
2021/02/09 14:49:27| pinger: ICMPv6 socket opened
2021/02/09 14:49:27| Pinger exiting.
and that last line "pinger exiting" looks like a problem here.
Squid is used as a package from ubuntu bionic, it's configured with
"--enable-icmp" as stated by squid -v.
Now I explicitly wrote a "pinger_enable on" and the pinger_program
path (in this case: "/usr/lib/squid/pinger" ) into the squid.conf (as
well as icmp_query on) and reconfigured but the cache.log still shows:
"Pinger exiting"
So I don't understand why the pinger is exiting. The pinger_program is
owned by root and has 0755 execution rights. Normal ping commands do
work and show the one originserver at ttl=53 and time=50 while the
other is at ttl=56 and time=155 - so a RTT comparison for
weighted-round-robin should work here.
Any hints on how I can find out why the pinger is exiting? Right now
I'm debuging with debug_options ALL,1 44,3 15,8 but don't see a reason
why the pinger exits.
The Originservers are defined by (with icp/htcp disabled):
cache_peer [ipv4_address_srv1] parent [http_port] 0 no-digest
no-netdb-exchange weighted-round-robin originserver name=srv1
forceddomain=[domainname]
cache_peer [ipv4_address_srv2] parent [http_port] 0 no-digest
no-netdb-exchange weighted-round-robin originserver name=srv2
forceddomain=[domainname]
Thank you for your help,
Chris
On 09.02.21 04:23, Amos Jeffries wrote:
On 9/02/21 3:40 am, Chris wrote:
Hi all,
I'm trying to figure out the best way to use squid (version 3.5.27)
in reverse proxy mode in regard to originserver health checks and
load balancing.
So far I had been using the round-robin originserver cache peer
selection algorithm while using weight to favor originservers with
closer proximity/lower latency.
Ok.
The problem: if one cache_peer is dead it takes ages for squid to
choose the second originserver. It does look as if (e.g. if one
originserver has a weight of 32, the other of 2) squid tries the
dead server several times before accessing the other one.
The DEAD check by default requires 10 failures in a row to trigger.
This is configurable with the connect-fail-limit=N option.
Now instead of using round-robin plus weight it would be best to use
weighted-round-robin. But as I understand it, this wouldn't work
with originserver if (as it's normally the case) the originserver
won't handle icp or htcp requests. Did I miss sth. here? Would
background-ping work?
Well, kind of.
ICP/HTCP is just a protocol. Most origin servers do not support them,
but some do. Especially if the server is not a true origin but a
reverse-proxy.
I tried weighted-round-robin and background-ping on originservers
but got only an evenly distributed request handling even if ones
originservers rtt would be less than half of the others. But then
again, those originservers won't handle icp requests.
RTT is retrieved from ICMP data primarily. Check your Squid is built
with --enable-icmp, the pinger helper is operational, and that ICMP
Echo traffic is working on all possible network routes between your
Squid and the peer server(s).
So what's the best solution to a) choose the originserver with the
lowest rtt and b) still have a fast switch if one of the
originservers switches into dead state?
Check whether the RTT is actually being measured properly by Squid
(debug_options ALL,1 44,3 15,8). If the peers are fast enough
responding or close enough in the network RTT could come out as a 0
value or some N value equal for both peer. ie. neither being "closer".
Amos
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