Debugging check_http

This plugin tests the HTTP service on the specified host. It can test normal (HTTP) and secure (HTTPS) servers, follow redirects, search for strings and regular expressions, check connection times, and report on certificate expiration times.

Debugging

Debugging with curl

If you have trouble using check_http, you can start to query the URL with curl:

curl -x myproxyip:proxy_port https://www.google.com/ --verbose

Execute the active Check manually

There are several ways to access the command. One way is described here: Check Email (check_mail)

One other way is with cmk -N:

OMD[mysite]:~/lib/nagios/plugins$ cmk -N |grep http
  check_command                 check_mk_active-http!'-u' 'https://www.google.com/' '--ssl' '--onredirect=follow' '-j' 'CONNECT' '--sni' '-p' 'proxy_port' 'myproxyip' 'www.google.com'
  command_line                  /omd/sites/mysite/lib/nagios/plugins/check_http $ARG1$
  command_name                  check_mk_active-http

cmk -N will show you the nagios config. Active Checks in Checkmk are based on nagios.

A second way to access the command is via livestatus:

OMD[mysite]:~/lib/nagios/plugins$ lq "GET services\nColumns:host_name description check_command_expanded\nFilter: host_name = localhost\nFilter: description = HTTPS HTTPS"
localhost;HTTPS HTTPS;check_mk_active-http!'-u' 'https://www.google.com/' '--ssl' '--onredirect=follow' '-j' 'CONNECT' '--sni' '-p' 'proxy_port' 'myproxyip' 'www.google.com'

In both cases: Copy the parameters after the '!' for executing the command later.

Now you need to run the check_http and paste the copied parameters:

OMD[mysite]:~/lib/nagios/plugins$ ./check_http '-u' 'https://www.google.com/' '--ssl' '--onredirect=follow' '-j' 'CONNECT' '--sni' '-p' 'proxy_port' 'myproxyip' 'www.google.com'

For a detailed log, you can use --verbose at the end of the command:

OMD[mysite]:~/lib/nagios/plugins$ ./check_http '-u' 'https://www.google.com/' '--ssl' '--onredirect=follow' '-j' 'CONNECT' '--sni' '-p' 'proxy_port' 'myproxyip' 'www.google.com' --verbose

For more information, you can use --help command flag.

OMD[mysite]:~/lib/nagios/plugins$ ./check_http --help

Debugging Regular Expressions (Regex)

In the following example, we are using regular expressions on status.cloud.google.com to gather Access Content Manager information. 

The service check returns OK

Running the command by hand can help debug issues as well.

OMD[mysite]:~/lib/nagios/plugins$ ./check_http -u /regional/americas --ssl -l -R 'Access Context Manager' --sni -I status.cloud.google.com -H status.cloud.google.com 
HTTP OK: HTTP/1.1 200 OK - 584329 bytes in 4.511 second response time |time=4.511160s;;;0.000000;10.000000 size=584329B;;;0;

Some important options

• • Address (name / IP or Proxy)  → If you need a proxy to access the domain
  • Virtual host → is necessary if you have multiple domains and one host running
  • How to handle redirect → How to handle redirected pages
  • Regular Expression to expect in content → 
  • HTTP Method → Set to CONNECT if you're using a proxy

  • Disable SSL/TLS hostname extension support (SNI) →
    
    

Useful Links

Related articles

• Page:
  Changing a CA SSL certificate for the Agent Bakery
• Page:
  Debugging check_http