Check apache-httpd-status

Overview

This check „allows a server administrator to find out how well their server is performing“. For the check plugin to work you have to enable mod_status and set ExtendedStatus to On. Have a look at https://httpd.apache.org/docs/2.4/mod/mod_status.html.

Busy workers (workers serving requests) are:

C: Closing connection
D: DNS Lookup
G: Gracefully finishing
I: Idle cleanup of worker
K: Keepalive (read)
L: Logging
R: Reading Request
S: Starting up
W: Sending Reply

Idle workers are:

_: Waiting for Connection

Free workers are:

.: Open slot with no current process

Load the Apache module:

LoadModule status_module modules/mod_status.so

If you want to configure /server-status in your main Apache config file:

<IfModule status_module>
    # the alias prevents the processing of .htaccess files, which could contain RewriteRules
    # that interfere with server-status
    Alias /server-status /dev/null
    ExtendedStatus On
    <Location /server-status>
        SetHandler server-status
        Require local
    </Location>
</IfModule>

If you want to configure /server-status in a virtual host:

<IfModule status_module>
    ExtendedStatus On
</IfModule>

<VirtualHost *:80>
    ServerName localhost
    <IfModule status_module>
        # the alias prevents the processing of .htaccess files, which could contain RewriteRules
        # that interfere with server-status
        Alias /server-status /dev/null
        <Location /server-status>
            SetHandler server-status
            Require local
        </Location>
    </IfModule>
</VirtualHost>

Fact Sheet

Check Plugin Download	https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/apache-httpd-status
Check Interval Recommendation	Once a minute
Can be called without parameters	Yes
Compiled for	Linux, Windows
Requirements	Enable `mod_status` and set `ExtendedStatus` to `On`
Uses SQLite DBs	`$TEMP/linuxfabrik-monitoring-plugins-apache-httpd-status.db`

Help

usage: apache-httpd-status [-h] [-V] [--always-ok] [-c CRIT] [-u URL]
                            [-w WARN]

Checks how well an Apache httpd server is performing.

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  --always-ok           Always returns OK.
  -c CRIT, --critical CRIT
                        Set the CRIT threshold for the number of workers
                        processing requests in percent. Default: >= 95
  -u URL, --url URL     Apache Server Status URL. Default: http://localhost
                        /server-status
  -w WARN, --warning WARN
                        Set the WARN threshold for the number of workers
                        processing requests in percent. Default: >= 80

Usage Examples

./apache-httpd-status --url http://apache-httpd/server-status --warning 80 --critical 90

Output:

192.168.122.97: 2/400 workers busy (0.5%; 0 "G"), 98 idle, 300 free; 54.0 accesses, 122.0KiB traffic; Up 1W 1D

Key                            ! Value
-------------------------------+-----------------------------------------------------
Current Time                   ! Wednesday, 28-Jul-2021 14:40:48 CEST
Restart Time                   ! Monday, 19-Jul-2021 20:17:11 CEST
Check Interval                 ! 3m 52s
Uptime                         ! 1W 1D
Requests                       ! 54.0
Bytes                          ! 122.0KiB
Request Duration               ! 10s 28ms
Load1                          ! 0.08
Load5                          ! 0.06
Load15                         ! 0.01
Workers Total                  ! 400
  Busy                         ! 2
  Idle                         ! 98
  Usage (%)                    ! 0.5
Parent Server ConfigGeneration ! 19
Parent Server MPMGeneration    ! 18
Server Name                    ! 192.168.122.97
Server MPM                     ! worker
Server Version                 ! Apache/2.4.48 (Fedora) OpenSSL/1.1.1k mod_qos/11.66
Server Built                   ! Jun  2 2021 00:00:00

States

WARN or CRIT if more than 80% or 95% busy workers compared to the total possible number of workers found.

Perfdata / Metrics

Name	Type	Description
Accesses	Number	A total number of accesses and byte count served
BusyWorkers	Number	workers_closing + workers_dns + workers_idle + workers_keepalive + workers_logging + workers_reading + workers_replying + workers_starting
Bytes	Number	Bytes sent
ConnsAsyncClosing	Number
ConnsAsyncKeepAlive	Number
ConnsAsyncWriting	Number
ConnsTotal	Number
CPULoad	Number
IdleWorkers	Number	workers_finishing + workers_waiting
Load1	Number
Load15	Number
Load5	Number
ParentServerConfigGeneration	Number
ParentServerMPMGeneration	Number
Processes	Number
Stopping	Number
Total Duration	Seconds
TotalWorkers	Number
Uptime	Seconds	The time the server has been running for
WorkerUsagePercentage	Percentage
workers_closing	Number	BusyWorkers; Closing connection, ‚C‘ in Apache Scoreboard (SERVER_CLOSING)
workers_dns	Number	BusyWorkers; DNS Lookup,‘D‘ in Apache Scoreboard (SERVER_BUSY_DNS)
workers_finishing	Number	IdleWorkers; Gracefully finishing, ‚G‘ in Apache Scoreboard (SERVER_GRACEFUL)
workers_free	Number	Open slot with no current process, ‚.‘ in Apache Scoreboard (SERVER_DEAD)
workers_idle	Number	BusyWorkers; Idle cleanup of worker, ‚I‘ in Apache Scoreboard (SERVER_IDLE_KILL)
workers_keepalive	Number	BusyWorkers; Keepalive (read), ‚K‘ in Apache Scoreboard (SERVER_BUSY_KEEPALIVE)
workers_logging	Number	BusyWorkers; Logging, ‚L‘ in Apache Scoreboard (SERVER_BUSY_LOG)
workers_reading	Number	BusyWorkers; Reading Request, ‚R‘ in Apache Scoreboard (SERVER_BUSY_READ)
workers_replying	Number	BusyWorkers; Sending Reply, ‚W‘ in Apache Scoreboard (SERVER_BUSY_WRITE)
workers_starting	Number	BusyWorkers; Starting up, ‚S‘ in Apache Scoreboard (SERVER_STARTING)
workers_waiting	Number	IdleWorkers; Waiting for Connection, ‚_‘ in Apache Scoreboard (SERVER_READY)

Troubleshooting

From https://httpd.apache.org/docs/2.4/mod/mod_status.html#troubleshoot:

The check may be used as a starting place for troubleshooting a situation where your server is consuming all available resources (CPU or memory), and you wish to identify which requests or clients are causing the problem.

First, ensure that you have ExtendedStatus set on, so that you can see the full request and client information for each child or thread.

Now look in your process list (using top, or similar process viewing utility) to identify the specific processes that are the main culprits. Order the output of top by CPU usage, or memory usage, depending on what problem you’re trying to address.

Reload the server-status page, and look for those process ids, and you’ll be able to see what request is being served by that process, for what client. Requests are transient, so you may need to try several times before you catch it in the act, so to speak.

This process should give you some idea what client, or what type of requests, are primarily responsible for your load problems. Often you will identify a particular web application that is misbehaving, or a particular client that is attacking your site.

Credits, License

Authors: Linuxfabrik GmbH, Zurich
License: The Unlicense, see LICENSE file.