From: | Craig James <craig_james(at)emolecules(dot)com> |
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To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: pg_connect takes 3.0 seconds |
Date: | 2010-01-06 18:31:12 |
Message-ID: | 4B44D6F0.3090107@emolecules.com |
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Lists: | pgsql-performance |
Dave Crooke wrote:
> The fact that the delays are clustered at (3 + 0.2 n) seconds, rather
> than a distributed range, strongly indicates a timeout and not
> (directly) a resource issue.
>
> 3 seconds is too fast for a timeout on almost any DNS operation, unless
> it has been modified, so I'd suspect it's the TCP layer, e.g. perhaps
> the SYN packet goes awol and it has to retry.
>
> I'd second the vote for investigation with a packet sniffing tool
> (Wireshark, tcpdump, etc)
If you have a PC (Windows), pingplotter is a remarkable and simple tool to use that quickly identifies problems, and gives results that are convincing when you show them to your network admin. Wireshark and tcpdump have a pretty steep learning curve and are overkill if your problem is simple.
Craig
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