[erlang-questions] HTTP requests and the meaning of eaddrinuse
Fri Jan 30 19:21:16 CET 2009
Sverker Eriksson wrote:
> Johnny Billquist wrote:
>> Sverker Eriksson wrote:
>>> Johnny Billquist wrote:
>>>> [...] you will most probably hit the limit of the number of open
>>>> file descriptors long before you exhaust all the local port numbers.
>>>> By default on on my mac, the max file descriptors is 256 (per
>>>> process). There is also a limit on the total number of file
>>>> descriptors in the OS. Nowhere near the theoretical limit of 65536
>>>> ports in tcp. So that should give you enfile or emfile.
>>> The internal TIME_WAIT state of the TCP protocol may cause exhaustion
>>> of port numbers even though the file descriptor limit is much lower
>>> than 65536. Use the netstat command tool to view lingering
>>> connections in TIME_WAIT state.
>> True, if the connections aren't closed properly.
> Actually, kind of the opposite. The peer that actively closes the
> connection by calling close() will cause its "socket" into TIME_WAIT.
> It's like a quarantine to avoid late arriving packets of the old
> connection from being confused with a new connection using the same
> port. A major flaw of TCP if you ask me.
And I case of put, the inets HTTP client will close the connection after
the response is received, since it is mixing up pipelining and keep
alive . We have seen this during load tests of our systems, in which
case we implemented interface pools to get around the problem.
>> But yes, that could be it. I wonder if eaddrinuse really is returned
>> in that case. [...]
> I experienced this some time ago writing a benchmark on Linux. I'm quite
> sure it was eaddrinuse that I got when the port numbers where exhausted.
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