Ubuntu – keepAlive in Apache causing apache to reach its max_clients

apache-2.2keep-alivekeepaliveUbuntuweb-server

I have an Apache 2.2 running on ubuntu 11.4 with 16Gb RAM, for image hosting from mobile phones through GPRS,since connection is slow i have enabled keepalive and set time out to 6,**based on average loading time.But usually even with 10-20 users apache is reaching its max_clients of 300 and preventing further connections.But the interesting thing is even **with keepalive turned OFF Apache is reaching its maxcients and refuses to accept new connection

**KeepAlive ON /tried Off also

MaxKeepAliveRequests 100

keepalivetimeout to 6 (since lot of dynamic images and slow connection)

StartServers 100

MinSpareServers 100

MaxSpareServers 150

ServerLimit 300

MaxClients 300

MaxRequestsPerChild 3000**

What should i do,to improve performance without hitting max_clients.Caching and deflate module is also enabled.Is to ok to set maxrequestperchild to 10 to prevent reaching max-clients.

Best Answer

You're running apache 2.2 with the prefork MPM; this is notoriously unsuited to serve large numbers of concurrent connections.

Consider either switching to the worker MPM, or upgrading to apache 2.4.

Even apache 2.2 using the worker MPM can serve thousands of concurrent requests with 16GB of memory.

Especially on mobile devices, setting KeepAliveTimeout too low will hurt you; consider increasing it to at least 30 seconds.

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Linux – Fine tunning of Apache 2 MPM Prefork module parameters

You are going to run out of ram before you will be able to server a Million requests. How large are you apache client processes? I bet over 10MB (probably 25MB). You server could probably only handle 250 clients if the clients were only 10MB.

Might try lighttpd with fast-cgi.

To answer you question you would need to edit the mpm.conf files /etc/apache2/modules.d/00_mpm.conf for me, but im on gentoo so it will be a bit diffrent depending on the distro of linux you are using. But in that config there is a secion for prefork

Here is mine for a server with 12Gb of ram. (and we load balance the sites of 20 identical servers)

<IfModule mpm_prefork_module>
        StartServers            100
        MinSpareServers          5
        MaxSpareServers         200
        ServerLimit             375
        MaxClients              375
        MaxRequestsPerChild      0
</IfModule>

Why are processes increasing continuously on the apache web server

This looks like you have some requests that never terminate, forcing Apache to spawn new processes until the configured maximum is reached. After that, Apache has no option to create new processes for new requests and appears dead.

It's impossible to tell what might cause this with the few data you give us.

Do you see any hints in the log files? What kind of pages to you serve to the clients? Static HTML, PHP, CGI or something else? On what OS?

Best Answer

Related Solutions

Linux – Fine tunning of Apache 2 MPM Prefork module parameters

Why are processes increasing continuously on the apache web server

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