Apache error codes are three-digit numbers returned by the Apache web server when something goes wrong during the processing of HTTP requests.

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Earlier, we created a script to restart the Apache web server HERE. Today we are going to add this to Cron so it restart every day a 3:00AM.

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Today, we are installing certbot on Debian 11 with Apache2 (Apache/2.4.54 (Debian). This article assumes you have Apache installed. If not, see How To Install LAMP (Linux, Apache, MySql-Maria, PHP) On Debian 11.

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How to test apache.

Create 2 files:
testload.php
test.php

Create a php file testload.php that checks the existence of another file named test.php in the same directory of two CentOS 7 servers with the same hardware characteristics and load but with different MPM. One of them will use event and the other one will use prefork.

<!--?php $filename = 'test.php'; if (file_exists($filename)) { echo "The file $filename exists"; } else { echo "The file $filename does not exist"; } ?-->

With ab, we will sent 50 (-c 50) concurrent requests at the same time and repeat the test 1000000 times

# ab -c 50 -n 100000 http://localhost/testload.php

200 simultaneous requests until 2000 requests are completed:

# ab -k -c 100 -n 2000 localhost/testload.php

Another test to localhost
PREFORK

]# ab -c 50 -n 100000 http://localhost/index.html
This is ApacheBench, Version 2.3 <$Revision: 1430300 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking localhost (be patient)
Completed 10000 requests
Completed 20000 requests
Completed 30000 requests
^C

Server Software:        Apache/2.4.6
Server Hostname:        localhost
Server Port:            80

Document Path:          /index.html
Document Length:        15167 bytes

Concurrency Level:      50
Time taken for tests:   3596.808 seconds
Complete requests:      34570
Failed requests:        0
Write errors:           0
Non-2xx responses:      34571
Total transferred:      537122767 bytes
HTML transferred:       524331497 bytes
Requests per second:    9.61 [#/sec] (mean)
Time per request:       5202.210 [ms] (mean)
Time per request:       104.044 [ms] (mean, across all concurrent requests)
Transfer rate:          145.83 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       3
Processing:   213 5198 241.5   5203   10154
Waiting:      174 4428 227.6   4435    9302
Total:        214 5198 241.5   5203   10154

Percentage of the requests served within a certain time (ms)
  50%   5203
  66%   5264
  75%   5302
  80%   5327
  90%   5391
  95%   5449
  98%   5532
  99%   5617
 100%  10154 (longest request)

The Apache mod_status module is something that can be very useful when troubleshooting high CPU or Memory usage with Apache.

Taken it directly from the Apache documentation:

– The number of worker serving requests.
– The number of idle worker.
– The status of each worker, the number of requests that worker has performed and the total number of bytes served by the worker.
– A total number of accesses and byte count served.
– The time the server was started/restarted and the time it has been running for.
– Averages giving the number of requests per second, the number of bytes served per second and the average number of bytes per request.
– The current percentage CPU used by each worker and in total by all workers combined.
– The current hosts and requests being processed.

Setting it up is simple.

# CentOS 6 / CentOS 7
[root@web01 ~]# vim /etc/httpd/conf.d/status.conf

# Ubuntu 12.04
[root@web01 ~]# vim /etc/apache2/conf.d/status.conf

# Ubuntu 14.04
[root@web01 ~]# vim /etc/apache2/conf-available/status.conf

Using the correct location for your distro use the following configuration to enable mod_status. Update the AuthUserFile line accordingly for your distro:

<IfModule mod_status.c>
#
# ExtendedStatus controls whether Apache will generate "full" status
# information (ExtendedStatus On) or just basic information (ExtendedStatus
# Off) when the "server-status" handler is called. The default is Off.
#
ExtendedStatus On

# Allow server status reports generated by mod_status,
# with the URL of http://servername/server-status
# Uncomment and change the ".example.com" to allow
# access from other hosts.
#
<Location /server-status>
     SetHandler server-status
     Order deny,allow
     Deny from all
     Allow from localhost ip6-localhost
     <IfModule mod_rewrite.c>
          RewriteEngine off
     </IfModule>
     Allow from 127.0.0.1

# On CentOS / RedHat systems, uncomment the following line
     AuthUserFile /etc/httpd/status-htpasswd

# On Debian / Ubuntu systems, uncomment the following line
#     AuthUserFile /etc/apache2/status-htpasswd

     AuthName "Password protected"
     AuthType Basic
     Require valid-user

     # Allow password-less access for allowed IPs
     Satisfy any
</Location>

</IfModule>

Once you have the configuration in place, you can secure it with a username and password:

# CentOS 6 / CentOS 7
[root@web01 ~]# htpasswd -c /etc/httpd/status-htpasswd serverinfo
[root@web01 ~]# service httpd restart

# Ubuntu 12.04
[root@web01 ~]# htpasswd -c /etc/apache2/status-htpasswd serverinfo
[root@web01 ~]# service apache2 restart

# Ubuntu 14.04
[root@web01 ~]# htpasswd -c /etc/apache2/status-htpasswd serverinfo
[root@web01 ~]# a2enconf status.conf
[root@web01 ~]# service apache2 restart

Now go to:

http://serverip/server-status

You can have the /server-status page refresh automatically by using the following in the URL:

http://serverip/server-status?refresh=2

It may give you some idea of what client, or what types of requests, are causing the resource contention issues. Usually it is a specific web application misbehaving, or a specific client is attacking a site.

How to Install mod_cloudflare.so, file_cache_module.so and mod_mem_cache.so on CentOS 6

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