Re: [squid-users] Q: http keepalives and time_wait sockets

Gaetano Giunta wrote:
> Q1: Reading the archives of this mailing list, I concluded that squid
> does not support using keep-alive in connections to source servers.
>
> I assume that setting keep-alive On on an Apache source server cached by
> squid would thus be harmless: since squid does not do keepalives, the
> connections would be terminated immediately - Apache would waste time
> keeping processes busy waiting on sockets after squid terminated its
> http/1.0 request.
>
> The advantage being that is the same apache server serves some other
> site beside the one cached by squid, or if squid is disabled
> temporarily, keepalives will be automatically in effect.
>
> Is this correct? Are there any advantages/drawbacks that are escaping me?

The conclusion that Squid does not support keepalive is incorrect. Note
the default config setting.
http://www.squid-cache.org/Doc/config/server_persistent_connections/

Also, HTTP/1.0 protocol assumes that keepalive is off unless explicitly
stated as provided. Thus Apache receiving HTTP/1.0 request without
keepalive permitted will result in the Apache will terminate the
connection or send back a reply explicitly requesting the proxy to do
keepalive.

When Squid closes any connection the far-end always receives a FIN or
RST TCP message. They are not left hanging waiting for data.

>
> Q2: Using squid as reverse proxy, I have seen that a lot of sockets (200
> to 300) are always listed on the origin server, coming from the squid
> server, in TIME_WAIT status.
> Using netstat on the squid server itself at the same time, I see about
> 10 open sockets, none of which in TIME_WAIT.
> Is this normal? Is it a sign of some misconfiguration? (note: there is
> probably a firewall currently sitting between the two servers). Can it
> be related somehow to keepalives?

Maybe yes, maybe no. More likely related to unknown-length objects with
the server closing the connection after each send to signal end-of-object.

TIME_WAIT only means that the sockets were previously used (even if
closed properly) and are waiting the TCP timeout before safe re-use.

Amos

-- 
Please be using
   Current Stable Squid 2.7.STABLE9 or 3.1.1