On 9/15/22 10:29, Hildegard Meier wrote:
we have two Squid servers (Linux hosts) and each shall have the very same config file /etc/squid/squid.conf
which is versioned and deployed from a central deployment server.
So each host shall have deployed the same files.
Each of the two shall have the other configured as sibling cache peer.
So node1 shall have
cache_peer node2.examlpe.com sibling 3128 3130
and node2 shalle have
cache_peer node1.examlpe.com sibling 3128 3130
I guess it is not so nice to have both configured with both lines together, no?
cache_peer node1.examlpe.com sibling 3128 3130
cache_peer node2.examlpe.com sibling 3128 3130
> I find that ugly.
I agree.
Squid does not support being its own peer (yet?): Upon startup, Squid
validates connectivity to peers. If that validation happens before Squid
starts listening for requests, the validation will (silently) fail.
There are several race conditions here, but that failure is likely in a
self-peering case.
In your particular use case, such self-peering also does not reflect
reality. You do not want to lie to Squid about it being its own peer
because Squid will try to use both configured peers, creating problems
that you do not want to solve. It also duplicates peer configurations.
Does squif offer a hostname conditional if clause ?
Not yet. Squid currently only supports three kinds of conditions: true,
false, and integer equality comparison (as documented).
The only build-in macro that always yields an integer is the
${process_number} macro.
Depending on your setup, you may also be able to use the ${service_name}
macro if your service name is an integer, but that is kind of hacky, and
I have not tested it.
For now, your best option is probably to post-process the versioned
configuration to substitute your own custom macro(s). For example, your
Squid startup (or deployment) stript can substitute a
${mynamespace:PeerName} macro in squid.conf.template with either true or
false, depending on the node, producing squid.conf that Squid can use:
cache_peer ${mynamespace:PeerName} sibling 3128 3130
If you need to hard-code peer names or substantially different
configurations for individual cache peers, then you can do something
like this in the template configuration file:
if ${mynamespace:AtNode1()}
cache_peer node2.example.com sibling 3128 3130
endif
if ${mynamespace:AtNode2()}
cache_peer node1.example.com sibling 3128 3130
endif
FWIW, quality PRs introducing the following related features should be
welcomed IMO:
* a macro function evaluating a named environment variable
* a macro function evaluating a given shell command
* string comparison in squid.conf conditionals
HTH,
Alex.
I think about something like this:
if $MY_HOSTNAME == 'node1' then
cache_peer node2.examlpe.com sibling 3128 3130
fi
if $MY_HOSTNAME == 'node2' then
cache_peer node1.examlpe.com sibling 3128 3130
fi
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