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Apache Monitoring using mod_status (server-status)

The mod_status Apache module provides out-of-the-box functionality for monitoring the performance of Apache installations.

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Setup

The mod_status Apache module should be loaded by default in any modern version of Apache. You can see this by checking for the following line in the "/etc/httpd/conf/httpd.conf" file.

LoadModule status_module modules/mod_status.so

Assuming that is in place already, you just need to enable to "server-status" page by making two amendments to the "/etc/httpd/conf/httpd.conf".

If you want additional status information, you can set the ExtendedStatus option to "On". The default is "Off".

ExtendedStatus On

Uncomment the "server-status" location, amending the "Allow from" line to include any domains or IP addresses that you want to have access to the status page. It is a good idea to lock this down as much as possible.

<Location /server-status>
    SetHandler server-status
    Order deny,allow
    Deny from all
    Allow from localhost 192.168.0.4
</Location>

Reload or restart Apache.

# service httpd reload
# # OR
# service httpd restart

The server status page should now be visible from the following type of URL. The "refresh=15" parameter means the page will refresh every 15 seconds.

http://localhost/server-status

http://localhost/server-status?refresh=15

Reading the server-status Page

The status page is made up of several distinct sections. The header contains basic information about the Apache installation.

Apache Server Status for localhost

Server Version: Apache/2.2.15 (Unix) DAV/2
Server Built: Aug 13 2013 10:51:17 

There is a status summary containing basic status information.

Current Time: Tuesday, 18-Mar-2014 10:12:23 GMT
Restart Time: Tuesday, 18-Mar-2014 10:08:10 GMT
Parent Server Generation: 0
Server uptime: 4 minutes 13 seconds
Total accesses: 6 - Total Traffic: 19 kB
CPU Usage: u0 s0 cu0 cs0
.0237 requests/sec - 76 B/second - 3242 B/request
1 requests currently being processed, 7 idle workers 

The scoreboard gives a visual display of how the available slots are being used.

_W______........................................................
................................................................
................................................................
................................................................

Scoreboard Key:
"_" Waiting for Connection, "S" Starting up, "R" Reading Request,
"W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup,
"C" Closing connection, "L" Logging, "G" Gracefully finishing,
"I" Idle cleanup of worker, "." Open slot with no current process

We have 8 servers spawned, with 7 of them idle (_). In total, there are 256 slots. If we look at the configuration in the "httpd.conf" file, we can see this is what we should expect.

<IfModule prefork.c>
StartServers       8
MinSpareServers    5
MaxSpareServers   20
ServerLimit      256
MaxClients       256
MaxRequestsPerChild  4000
</IfModule>

The bottom of the status page contains information about current requests.

Srv	PID	Acc	M	CPU 	SS	Req	Conn	Child	Slot	Client	VHost	Request
0-0	31705	0/13/13	W 	0.00	0	0	0.0	0.05	0.05 	::1	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1
1-0	31706	0/13/13	_ 	0.00	75	0	0.0	0.05	0.05 	localhost	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1
2-0	31707	0/13/13	_ 	0.00	105	0	0.0	0.05	0.05 	localhost	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1
3-0	31708	0/13/13	_ 	0.00	90	0	0.0	0.05	0.05 	localhost	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1
4-0	31709	0/13/13	_ 	0.00	60	0	0.0	0.05	0.05 	localhost	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1
5-0	31710	0/13/13	_ 	0.00	45	0	0.0	0.06	0.06 	localhost	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1
6-0	31711	0/13/13	_ 	0.00	30	1	0.0	0.06	0.06 	localhost	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1
7-0	31712	0/13/13	_ 	0.00	15	0	0.0	0.06	0.06 	localhost	ol6-mysql.localdomain	GET /server-status?refresh=15 HTTP/1.1

Srv	Child Server number - generation
PID	OS process ID
Acc	Number of accesses this connection / this child / this slot
M	Mode of operation
CPU	CPU usage, number of seconds
SS	Seconds since beginning of most recent request
Req	Milliseconds required to process most recent request
Conn	Kilobytes transferred this connection
Child	Megabytes transferred this child
Slot	Total megabytes transferred this slot

During periods of high activity, you can now monitor the status of the Apache server to see if your configuration needs adjusting.

For more information see:

Hope this helps. Regards Tim...

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