Nagios 'could not connect' to MySQL database

[Richard.Luys at vanderlet.nl]

Hello Again Werner!

> -----Original Message-----
> From: nagios-users-admin at lists.sourceforge.net 
> [mailto:nagios-users-admin at lists.sourceforge.net] On Behalf 
> Of Werner Flamme
> Sent: Tuesday, August 16, 2005 4:03 PM
> To: nagios-users at lists.sourceforge.net
> Subject: Re: [Nagios-users] Nagios 'could not connect' to 
> MySQL database
> 
> Richard.Luys at vanderlet.nl schrieb am 16.08.2005 14:24:
> > Werner,
> >  
> > 
> > 
> >>---snip---
> >>
> >>>When I check the nagios.log I get the following errors:
> >>>[1123752497] Finished daemonizing... (New PID=26747) [1123752497]
> >>>Error: Could not connect to MySQL database 'nagios' on host 
> >>>'localhost' using username 'nagios' and password 
> 'removed'.  Status 
> >>>data will not be saved!
> 
> Hmmm... when I look at my self-compiled nagios 1.2 on SLES 8, 
> I see that there are 2 files you have to maintain for mysql. 
> Did you look at cgi.cfg?

My bad. I typed nagios.cfg when I meant cgi.cfg. The other is the
resource.cfg. It's strange indeed that you have to put a lot of this
identical information in two different config-files. But these files are
both correctly configured.

> 
> If yes - I don't know what may be the cause then. I remember 
> I made the entries in one of those and forgot the other. And 
> I had quite similar errors...

I think I do. Here's what I found:

Googling on the internet reminded me of the 'check_nagios_db.pl' script;
which is used for checking if Nagios is running when you use a database
for the logging etc. I ran the script, and got the same error. So I
focussed a bit on the Perl::DBI driver, and came across a very basic
script to test if it works correctly. I ran that script, and received an
error like 'Client does not support authentication protocol requested by
server...'. That was more descriptive than 'could not connect...'! So I
took the part that is responsible for showing this error( $DBI::errstr),
and put it in the error-comment of the check_nagios_db.pl script. And
voila! I got the same message there!

In other words, it looks like there is an incompatibility issue in how
Perl::DBI and Nagios try to authenticate with the database. I checked
the MySQL-site and found this very same error in the documentation pages
( http://dev.mysql.com/doc/mysql/en/old-client.html ). I will look
further into it, and post my findings; maybe it helps somebody with the
same problem.

I learned a very important lesson here: When you write a script, develop
a program, or whatever, make sure you give sufficient feedback! When the
errors in the logging stated why they 'could not connect' instead of
just that message, the problem was probably fixed a week ago! I had to
stumble across a perl-statement for showing the real error, to find out
what is really the problem...

> 
> HTH now ;-)
> Werner
> 
> --
> Werner Flamme, Abt. WKDV
> UFZ Umweltforschungszentrum Leipzig-Halle GmbH, Permoserstr. 
> 15, 04318 Leipzig - http://www.ufz.de
> eMail: werner.flamme at ufz.de, Tel.: (0341) 235-2500
> 
> 
> 
> 
> 
> 
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