LogsVolumePanel: support filtering logs from the selected level

[matyax]

Closes #422

This PR adds support to apply level filters from the Logs Volume panel.

Demo.mov

[matyax]

There's one scenario that we need to consider: the user previously had applied a level filter.

Interacting with the Logs Volume panel adds detected_level filters. Options:

• Ignore: do nothing, add a detected_level filter
• Remove the level filter before adding detected_level
• Change the existing level filter

[matyax]

When the user is appending levels, we don't change the filters because we don't yet support filters with multiple values.

[cyriltovena]

LGTM

[matyax]

Thanks @cyriltovena ! What does @grafana/observability-logs / @zizzpudding this of this? How does this behavior feels to you?

[gtk-grafana]

@matyax what if we just ignored level/detected_level in the logs volume, although then we'd want to be able to set legend visibility when a level/detected_level filter is applied, but it looks like we can do that with series visibility overrides? 🤔

"matcher": {
          "id": "byNames",
          "options": {
            "mode": "exclude",
            "names": [
              "A-series1"
            ],
            "prefix": "All except:",
            "readOnly": true
          }
        },

[cyriltovena]

I haven't follow the tech side of it but I love this feature.

[matyax]

I've added a new variable, dedicated to hold the level, that is used everywhere but in the logs volume query. This should take this feature pretty much where we wanted.

[matyax]

Not having to refresh logs volume seems to produce a bit more of responsiveness in the app. And it's one less query that we need to run. 💡

[matyax]

@grafana/observability-logs Mind taking another look? Thanks!

[matyax]

It seems that we've been bitten by the buggy interpolation error we recently fixed, as the metric query it's producing for for fields and values is like: sum(count_over_time({service_name=tempo-distributor} | logfmt {service_name=\"tempo-distributor\"}| drop __error__ | namespace!=\"\" [$__auto])) by (namespace)

[matyax]

We either hold this PR until a new Grafana image is available, or we do something like this. Any suggestion will be much appreciated.

To reproduce, use the app with yarn server (as the e2e tests do), and browse labels.

[matyax]

We will wait for a new Grafana release before merging these changes.

[matyax]

Never stop believing.

[svennergr]

I think with that we should also upgrade the grafana versions in plugin.json and docker-compose.yaml, WDYT?

[matyax]

Definitely.