Support for scraping multiple mysqld hosts.

[samitpal]

Discussion at https://github.com/prometheus/mysqld_exporter/issues/452#issuecomment-701893399

Short summary: This adds a new flag called export-multi-hosts and allows for passing a yaml file which contains the config related to this mode. Note that this change does not make any changes to the way mysqld_exporter works and as a result it would continue to use the ini format config when working in the non export-multi-hosts mode.

[SuperQ]

My only question is, because mysql users are used to the INI style of my.cnf, maybe we should stick to INI parsing. I would prefer to implement one kind of config for the exporter. Having multiple ways to configure gets confusing for users.

I also think port should come from the target URL param, not the config.

I'm thinking a config something along the lines of:

clients:
  default:
    user: foo
    password: foo123
  other_server:
    user: bar
    password: bar123

Or in INI style

[client]
user = foo
password = foo123
[client.other_server]
user = bar
password = bar123

[samitpal]

Makes sense. Given that the currently supported format is INI, I will try to modify my change to use INI instead of yaml.

[SuperQ]

It looks like some of the commits are missing DCO.

[RichiH]

YAML would have the advantage of being well-established in Prometheus-land; the question is if users are more likely to be DBAs exposing data or Prometheus people grabbing data from a lot of different places. I would suspect the latter, but don't have data, of course.

[SuperQ]

@RichiH Supporting the MySQL-style INI file was an often, and now implemented, requested feature. I think we want to stick with it.

[SuperQ]

Here's a proposal on how the final config (one config to rule them all) would look like.

[client]
user = foo
password = foo123
target = hostname:3306
[client.module1]
user = bar
password = bar123

The target key is only allowed in the default case and is ignored/rejected by additional modules.

• /metrics URL would be a backwards equivalent of /mysql?module=default.
• /mysql?module=default&target=some-remote:3306 would use the default user/password but override the target.
• /mysql?module=module1 is invalid, as it doesn't contain a target.
• /mysql?module=module1&target=some-remote:3306 is a typical scrape of a remote.

I'm also thinking about an option to make /metrics not return mysql data, just exporter data. This would make it easier to separate exporter data from target data. Easier to monitor the health of just the exporter.

[piotr1212]

Any progress on this? Would be very nice to have this.

[yum-dev]

When is this being merged? We are waiting for this too.

[rpsadarangani]

Hi, When this will get merge, we are also waiting for this.

[samitpal]

For our internal use case my implementation is sufficient. I won't be able to work on the proposal as outlined at #504 (comment). If any one else wants to take this forward, please feel free to go ahead.

[SuperQ]

Alright, if I can find some help to work on this, we could merge it and build on it. But as-is, this needs work before it could be released.

[Dims-lab]

Is it possible to use prometheus exporter when mysql is running on a different port then 3306? When i change the /etc/.mysqld_exporter.cnf file for looking at another port. it still tries to connect with port 3306. changes i have made are.

[client] user=mysqld_exporter password=apassword host=localhost:portnumber

exporter service is running with error level=error msg="Error pinging mysqld: dial tcp: lookup localhost:45654:3306:

[ning1875]

I have an improved version here, transformed into a probe, which supports http incoming parameters like blackbox_exporter . https://github.com/ning1875/mysqld_exporter/releases/tag/v0.12.1

[HerrTamm]

Is there a plan to finalize this PR?

[SuperQ]

This was completed in #651