> -----Message d'origine----- > De : Sandro Tosi [mailto:sandro.tosi@xxxxxxxxxxx] > Envoyé : mardi 2 février 2010 15:00 > À : users@xxxxxxxxxxxxxxxx > Objet : Apache is slow at accepting connections > > Hello, > we have a rather busy Apache web server (~200/300 contemporary > connections). There are time when Apache is really slow at letting > client connects to it. For example, with curl, I see: > > 02:05:17.885074 == Info: About to connect() to IP_ADDRESS port 80 (#0) > 02:05:17.885280 == Info: Trying IP_ADDRESS... 02:05:20.898748 == Info: > connected > 02:05:20.898785 == Info: Connected to IP_ADDRESS (IP_ADDRESS) port 80 (#0) > ... > 02:05:20.917068 == Info: Closing connection #0 > > and > > 02:06:53.098230 == Info: About to connect() to IP_ADDRESS port 80 (#0) > 02:06:53.099272 == Info: Trying IP_ADDRESS... 02:07:02.111596 == Info: > connected > 02:07:02.111636 == Info: Connected to IP_ADDRESS (IP_ADDRESS) port 80 (#0) > 02:07:02.111731 => Send header, 222 bytes (0xde) > ... > 02:07:02.422093 == Info: Closing connection #0 > > as you can see, we see a 3 seconds (first example) and a 9 seconds > (second example) delay between apache server contact and when the > connection is actually accepted. The delay is always either 3 or 9 > seconds, that's quite weird and it seems to indicate a sort of > retry+backoff (3 secs, 3x2 secs (9 secs total) and so on) implemented in > some Apache layers. > > Anyhow, once the client is able to connect to Apache, the request is > served very fast. Just to be sure it's nothing in the VirtualHosts we've > setup, we tried also with /server-status but even that page is slow at > connect. > > In addition, sometimes we also see: > > 02:10:40.651926 == Info: About to connect() to IP_ADDRESS port 80 (#0) > 02:10:40.652543 == Info: Trying IP_ADDRESS... 02:11:00.060879 == Info: > Connection refused > 02:11:00.060924 == Info: couldn't connect to host > 02:11:00.060942 == Info: Closing connection #0 > > as if the client was not able to be served by any Apache server. > > The MPM config we use is: > > StartServers 200 > MinSpareServers 150 > MaxSpareServers 300 > ServerLimit 2000 > MaxClients 2000 > MaxRequestsPerChild 100 > > KeepAlive off > > We tried everything that came to our minds to avoid that delay: > > - tune the parameters above (StartServer, Min/MaxSpareServer etc) > - only Listen on a single port (inferred from > http://httpd.apache.org/docs/2.2/misc/perf-tuning.html) > - change every possible AcceptMutex values: flock, fcntl, pthread, and > sysvsem (the default) > > but none of them helped. > > Does anyone know how to solve this problem? If there are other info > needed, just let me now and I'll provide them. > > Thanks in advance, > Sandro > Hi, Couldn't this latency come from dns lookups ? Are you using some directives such as 'UseCanonicalName DNS', 'HostnameLookups On|double' or even hostnames in some 'VirtualHost' entries ? Emmanuel --------------------------------------------------------------------- The official User-To-User support forum of the Apache HTTP Server Project. See <URL:http://httpd.apache.org/userslist.html> for more info. To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx
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