Reconcile duplication between "Hosts being rate limited" panel vs the "Federation rate limiter" section in Grafana

[MadLittleMods]

There is a Hosts being rate limited Grafana panel under the Requests section which covers the same base as the Federation rate limiter section I added below it, https://grafana.matrix.org/d/000000012/synapse?orgId=1&from=now-12h&to=now

I can't see any data from the Hosts being rate limited panel because of a Datasource ${DS_PROMETHEUS} was not found error there but would be good to consolidate those. Who worked on that one? (trying to find the person that cares about it)

---

The rate limit metrics were originally added in:

• Add metrics to track how the rate limiter is affecting requests (sleep/reject) #13534
• Track number of hosts affected by the rate limiter #13541
• Add metrics to track rate limiter queue timing #13544

[DMRobertson]

I think that was me when I was trying to confirm that #13649 worked as part of releaseing 1.66.0rc2. Feel free to remove it from grafana.

[MadLittleMods]

Removed 👍

Here is a backup in case we want to reference it:

Hosts being rate limited panel JSON

{
  "id": 225,
  "gridPos": {
    "h": 9,
    "w": 12,
    "x": 12,
    "y": 53
  },
  "type": "timeseries",
  "title": "Hosts being rate limited",
  "datasource": {
    "type": "prometheus",
    "uid": "${DS_PROMETHEUS}"
  },
  "description": "Average number of hosts being rate limited across each worker type.",
  "fieldConfig": {
    "defaults": {
      "custom": {
        "drawStyle": "line",
        "lineInterpolation": "linear",
        "barAlignment": 0,
        "lineWidth": 1,
        "fillOpacity": 0,
        "gradientMode": "none",
        "spanNulls": false,
        "showPoints": "auto",
        "pointSize": 5,
        "stacking": {
          "mode": "none",
          "group": "A"
        },
        "axisPlacement": "auto",
        "axisLabel": "",
        "axisColorMode": "text",
        "scaleDistribution": {
          "type": "linear"
        },
        "axisCenteredZero": false,
        "hideFrom": {
          "tooltip": false,
          "viz": false,
          "legend": false
        },
        "thresholdsStyle": {
          "mode": "off"
        }
      },
      "color": {
        "mode": "palette-classic"
      },
      "mappings": [],
      "thresholds": {
        "mode": "absolute",
        "steps": [
          {
            "color": "green",
            "value": null
          }
        ]
      },
      "unit": "none"
    },
    "overrides": []
  },
  "options": {
    "tooltip": {
      "mode": "single",
      "sort": "desc"
    },
    "legend": {
      "showLegend": true,
      "displayMode": "list",
      "placement": "bottom",
      "calcs": []
    }
  },
  "targets": [
    {
      "datasource": {
        "type": "prometheus",
        "uid": "${DS_PROMETHEUS}"
      },
      "editorMode": "builder",
      "expr": "avg by(job, rate_limiter_name) (synapse_rate_limit_sleep_affected_hosts{instance=\"$instance\", job=~\"$job\", index=~\"$index\"})",
      "hide": false,
      "legendFormat": "Slept by {{job}}:{{rate_limiter_name}}",
      "range": true,
      "refId": "B"
    },
    {
      "datasource": {
        "type": "prometheus",
        "uid": "${DS_PROMETHEUS}"
      },
      "editorMode": "builder",
      "expr": "avg by(job, rate_limiter_name) (synapse_rate_limit_reject_affected_hosts{instance=\"$instance\", job=~\"$job\", index=~\"$index\"})",
      "legendFormat": "Rejected by {{job}}:{{rate_limiter_name}}",
      "range": true,
      "refId": "A"
    }
  ]
}