Show if pod is currently a master/replica on pod details

[gricey432]

Describe the enhancement you are proposing:

When looking at Pod details to debug performance issues the first thing I usually need to figure out is which pod is the write master.

Looks like there's a metric coming in pg_replication_is_replica which would make this easy to figure out at a glance. I'm assuming that if it's not a replica then it must be the write master, though I'm not sure if that's true in all setups.

I've added this panel myself through the Grafana UI but I just don't know enough about Grafana to make it into a PR; if I just copy out the dashboard json there's hundreds of seemingly unrelated changes.

My panel json looks like

{
  "id": 17,
  "gridPos": {
    "x": 0,
    "y": 0,
    "w": 24,
    "h": 2
  },
  "type": "stat",
  "title": "Pod Type",
  "targets": [
    {
      "refId": "A",
      "datasource": {
        "type": "prometheus",
        "uid": "kOjrg6AVk"
      },
      "editorMode": "code",
      "expr": "pg_replication_is_replica{pod=\"[[pod]]\", pg_cluster=\"[[cluster]]\"}",
      "legendFormat": "__auto",
      "range": false,
      "instant": true,
      "exemplar": false,
      "format": "table"
    }
  ],
  "options": {
    "reduceOptions": {
      "values": false,
      "calcs": [
        "lastNotNull"
      ],
      "fields": ""
    },
    "orientation": "auto",
    "textMode": "auto",
    "colorMode": "none",
    "graphMode": "none",
    "justifyMode": "auto",
    "text": {
      "valueSize": 30
    }
  },
  "fieldConfig": {
    "defaults": {
      "mappings": [
        {
          "type": "value",
          "options": {
            "0": {
              "text": "Master",
              "index": 0
            },
            "1": {
              "text": "Standby",
              "index": 1
            }
          }
        }
      ],
      "thresholds": {
        "mode": "absolute",
        "steps": [
          {
            "color": "green",
            "value": null
          }
        ]
      },
      "color": {
        "mode": "thresholds"
      }
    },
    "overrides": []
  },
  "datasource": {
    "uid": "kOjrg6AVk",
    "type": "prometheus"
  },
  "pluginVersion": "9.2.20",
  "description": ""
}

[gricey432]

Also unsure on the best labels to use for consistency.

• Patroni seems to use Leader and Replica
• The exporter uses master and replica for labels in prometheus
• Postgres docs use primary and standby

I'm not sure which pair would be best to show here

[keithf4]

That is the correct metric. There are only two possible valid values so if it's not one it's the other

I would go with Primary/Replica as the labels. That's generally what we've been using.

As for adding a new panel, the easiest way would be exporting out the entire dashboard. The other changes are likely to do with the version of Grafana you're doing the export from. I'm not sure what version of Grafana the latest container dashboards were exported from, but the main ones for pgMonitor are from Grafana 9.2. If you want to stick with the other dashboard versions, you'll have to install that version of Grafana to do your changes and export from there. Otherwise you're pretty much making that the new minimum version of Grafana supported once you export from a newer version.