[nginx] Better process status output for good metric names

[zippolyte]

What does this PR do?

With this PR, the output of the status page is better processed so that streams and slabs metrics are correctly named and tagged. Also update the metadata.csv file to add all the missing metrics.

Motivation

What inspired you to submit this pull request?

Testing Guidelines

An overview on testing
is available in our contribution guidelines.

Versioning

• Bumped the check version in manifest.json
• Bumped the check version in datadog_checks/{integration}/__init__.py
• Updated CHANGELOG.md. Please use Unreleased as the date in the title
  for the new section.
• If PR impacts documentation, docs team has been notified or an issue has been opened on the documentation repo

Additional Notes

This is a major version change and is breaking for orgs that use the badly named metrics in dashboards or monitor since the names will change with this PR and the old names won't be sent anymore. We need to notify them.

[ofek]

Can you please explain further exactly what metrics are are being deprecated/removed? Are you saying metrics were previously being sent with tags inside them?

[ofek]

You can just put return cls._flatten_json(metric_base, parsed, tags).

[ofek]

I'd say instead tags.append('%s:%s' % (TAGGED_KEYS[key], tag_val)).

[zippolyte]

After seeing the tests fail miserably, I remembered why it was like this. I can't append to the tags list because I am in a for loop, and tags is a reference to the list. So I have to do like this to avoid having the tags of a metric being sent with the metrics of all the subsequent loops.

[ofek]

Based on the above change, just pass tags.

[zippolyte]

The metrics that are deprecated are the metrics prefixed with nginx.slabs and nginx.stream. The payload returned by the NGINX API changed since the check was first written, and the added metrics were then incorrectly named. Indeed, some parts of the metric names should be sent as tags instead.

e.g. there was a metric for stream that was being named
nginx.stream.server_zones.<user defined name>.connections, where the user defined name is a name defined in the NGINX configuration of the user.
Thus resulting in several distinct metrics nginx.stream.server_zones.*.connections, not really usable in the interface of the app.
Instead, the user defined name is now sent as a tag, and the metric is named nginx.stream.server_zones.connections, and the user can use the tags to slice and dice in Datadog.

I hope I am being clear.

[ofek]

Thanks for explaining!