Connection error detection in MySQL Exporter

[Peter Zaitsev]

Hi,

I noticed if MySQL exporter can't connect to the database it should monitor (ie invalid password) it just  returns very few metrics rather than throwing the error

and the error is just seen in the error log file,  which complicates troubleshooting

I wonder what is the intended mechanism for fatal error reporting from the exporter so for example Prometheus Target page would display proper error message ? 

For example reporting HTTP 500  with  error information as a text could do it

[Ben Kochie]

The exporter should be returning a `mysql_up` metric as 0 in the case of failures.  This way you can differentiate between the exporter being up, and the target behind the exporter being up.

An alert would look something like this:

ALERT MySQLDown

  IF mysql_up == 0 or up == 0

...

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[Peter Zaitsev]

Thanks Ben,

This makes sense.  If I understand correctly there is no way to see the error message on Why MySQL is down without looking at the logs right ? 

On Wed, Mar 29, 2017 at 6:08 PM, Ben Kochie <sup...@gmail.com> wrote:

The exporter should be returning a `mysql_up` metric as 0 in the case of failures.  This way you can differentiate between the exporter being up, and the target behind the exporter being up.

An alert would look something like this:

ALERT MySQLDown

  IF mysql_up == 0 or up == 0

...

On Thu, Mar 30, 2017 at 12:00 AM, Peter Zaitsev <p...@percona.com> wrote:

Hi,

I noticed if MySQL exporter can't connect to the database it should monitor (ie invalid password) it just  returns very few metrics rather than throwing the error

and the error is just seen in the error log file,  which complicates troubleshooting

I wonder what is the intended mechanism for fatal error reporting from the exporter so for example Prometheus Target page would display proper error message ? 

For example reporting HTTP 500  with  error information as a text could do it

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Peter Zaitsev, CEO, Percona
Tel: +1 888 401 3401 ext 7360   Skype:  peter_zaitsev

[Ben Kochie]

Not currently, and it would be possibly too messy to try and fit that into a metric.

Part of the idea with Prometheus alerts is that they signal you to go look at the logs. :-) The typical annotation we recommend for an alert like this would be a "runbook" URL to docs that point the user to look at the error logs, try "service mysql status", or similar.

[Peter Zaitsev]

Thank you,

I understand the idea.