check_mysql_plugin returns NULL value

[theace18]

I would like to run query checks on all of our MySQL servers. I am using the check_mysql_plugin. I want to run it from the Nagios server and NOT through NRPE.

Running the plugin through NRPE runs the plugin fine. Running the plugin manually on the server runs fie. However when I try to run it through the actual Nagios app, it returns a NULL value. Permissions for the plugin look fine too, especially since I can run them as both root and the nagios user.

The command is as follows in my commands.cfg file:

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# Added 'check_avgwebusers' Command
define command{
        command_name check_avgwebusers
        command_line $USER1$/check_mysql_query -q "SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions;" -H $HOSTNAME$ -P 3306 -d database -u XXXXX -p XXXXX -w 44 -c 52
        }

The service check is called in my services.cfg file:

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# check_avgwebusers
define service{
        use                     generic-service
        host_name               mysql
        service_description     Check Avg Web Server Users
        check_command           check_avgwebusers
        }

Any thoughts? I am TOTALLY stumped right now. Any help would be appreciated. Thanks!

- Philippe

[slansing]

Check the manpage here:

http://nagiosplugins.org/man/check_mysql_query

try swapping some flags around in your check to make it look more like:

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$USER1$/check_mysql_query -H $HOSTNAME$ -P 3306 -d database -u XXXXX -p XXXXX -q "SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions;" -w 44 -c 52

I'd recommend running this from the command line first, more than likely the command will be like so:

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/usr/local/nagios/libexec/check_mysql_query -H <hostaddress> -P 3306 -d database -u username -p pass -q "SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions;" -w 44 -c 52

I'd verify that those warning and critical values do work with the plugin "through the manpage" and that those are values that would be true when running the query you show.

[theace18]

I switched around the flags like you suggested, but Nagios still returns a null value.

This is the command I ran manually from the Nagios server itself, and the result I got:

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[root@nagios libexec]# su nagios
sh-4.1$ ./check_mysql_query -H <host address> -P 3306 -d <database> -u XXXXX -p XXXXX -q "SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions;" -w 44 -c 52

QUERY OK: 'SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions;' returned 30.285700

So as you can see, the plugin runs just fine. Just for some reason won't return a value to Nagios. However if I run it through NRPE, it returns the value (but this isn't what I want to do).

[theace18]

I rearranged them like you said, but I am still getting a NULL value. It's just not making any sense why it works if I run it manually, but not when Nagios runs it.

BTW, if I run this through NRPE, it works fine. However, I don't want to run it through NRPE. I want to be able to run it on the server and generate a custom notification based on its results.

[slansing]

Can you try swapping:

"SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions"

For:

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 'SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions'

Alternatively you can try leaving the command with the double quotes, but still removing the semicolon.

[scottwilkerson]

I noticed that in your command you have $HOSTNAME$ and in your test you list <host address>

Are these the same? I see in your service you have

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# check_avgwebusers
define service{
        use                     generic-service
        host_name               mysql
        service_description     Check Avg Web Server Users
        check_command           check_avgwebusers
        }

Which means this will execute

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./check_mysql_query -H mysql -P 3306 -d <database> -u XXXXX -p XXXXX -q "SELECT COUNT(*)/COUNT(DISTINCT(Server)) FROM WebSessions;" -w 44 -c 52

mysql may not be resolvable

[theace18]

Yeah mysql is a resolvable hostname. Still stumped

[theace18]

WOW! I must need some sleep or something.

So it turned out that on my service check I still had it doing a NRPE check.

Thank you everyone SO MUCH for your help. This falls under System Administrator error. DOH!

[slansing]

Great to hear it was that simple, we all make mistakes like this.