Loom Grafana

Grafana and the LGTM Stack

Visualization, dashboards, alerting, and exploration. Scope: dashboards/panels, LogQL, TraceQL, data sources, templating, Grafana alerting. PromQL query semantics → loom-prometheus.

Overview

Collector: Grafana Alloy (OTel Collector distribution). Grafana Agent is EOL (2025-11-01) — migrate.

Dashboard Design

Hierarchy: Overview → Service → Component → Deep Dive. Signals: RED (Rate/Errors/Duration) for services, USE (Utilization/Saturation/Errors) for resources. Variable-driven, 24-column grid, < 15 panels/dashboard.

Panel types

Panel config

• Titles include the unit + dimension ("P95 Latency (s) by Endpoint", not "Latency"); add a description tooltip.
• Units: always set fieldConfig.defaults.unit (s, bytes, reqps, percentunit for 0–1 ratios, percent for 0–100). Wrong unit is the most common panel bug.
• Legends: {{label}} templating; hide for single series; sort by value for Top-N.
• Thresholds: green (normal) / yellow (warning) / red (critical); drive Stat/Gauge color and Time Series bands.
• Data links: drill Overview→Service→Component; link to logs/traces/runbooks.

Variables & Templating

{ "templating": { "list": [
  { "name": "datasource", "type": "datasource", "query": "prometheus" },
  { "name": "namespace", "type": "query", "datasource": "${datasource}",
    "query": "label_values(kube_pod_info, namespace)", "multi": true, "includeAll": true },
  { "name": "app", "type": "query", "datasource": "${datasource}",
    "query": "label_values(kube_pod_info{namespace=~\"$namespace\"}, app)",
    "multi": true, "includeAll": true },
  { "name": "interval", "type": "interval", "auto": true,
    "options": ["1m","5m","15m","1h","6h","1d"] }
] } }

Reference with $var / ${var}. Dependent chain: $datasource → $cluster → $namespace → $app → $pod, each query filtering on the previous. Regex-filter a variable's values with "regex": "/^$app-.*/".

⚠️ Multi-value / Include-All variables interpolate as a regex alternation — use =~, never =. With multi: true/includeAll, Grafana renders the selection as (prod|staging); the = matcher treats that whole string as a literal value and silently matches nothing (no error, blank panel). Both $namespace and $app above are multi: true → MUST use {namespace=~"$namespace"}. A Custom allValue like .* is injected verbatim (not escaped) — intentional, but a footgun in a query string.

⚠️ label_values() ignores the dashboard time range. It scans ALL series matching the metric — slow on high-series backends and returns stale values (pods gone months ago). For only entities active in the window use query_result(), which is time-aware:

query_result(count by (service) (rate(http_requests_total[$__range])))   # only services seen in window
# vs label_values(http_requests_total, service)  — all-time, slow, stale

Annotations

Event markers on time-series panels, from any data source:

{ "annotations": { "list": [
  { "name": "Deployments", "datasource": "Prometheus",
    "expr": "changes(kube_deployment_spec_replicas{namespace=\"$namespace\"}[5m])",
    "tagKeys": "deployment,namespace", "iconColor": "blue" },
  { "name": "Alerts", "datasource": "Loki",
    "expr": "{app=\"alertmanager\"} | json | alertname!=\"\"", "iconColor": "red" }
] } }

Dashboard as Code & Provisioning

Generate JSON from typed models; do not commit hand-edited UI exports. Grafana 12 ships the Foundation SDK (Go/TS/Python/Java/PHP) + the gcx CLI (REST push; Git Sync = bidirectional). Typed models prevent schema drift (deprecated panel types, wrong field names) that UI exports re-introduce. For production use Foundation SDK + gcx, or Terraform with the Grafana provider.

const dashboard = new DashboardBuilder("App Observability")
  .withPanel(new TimeseriesPanelBuilder().title("Request Rate").unit("reqps"));
// gcx push

⚠️ allowUiUpdates: true silently discards UI edits on the next sync. UI edits persist across refreshes but the next provisioning sync (updateIntervalSeconds, default 10s) overwrites the DB version with the file version, ignoring the DB version — no warning. Production: allowUiUpdates: false, editable: false, disableDeletion: true. To keep a UI edit, export the JSON back into the provisioning file.

# /etc/grafana/provisioning/dashboards/dashboards.yaml
apiVersion: 1
providers:
  - name: application
    orgId: 1
    folder: Applications
    type: file
    disableDeletion: true
    editable: false
    updateIntervalSeconds: 10
    options: { path: /var/lib/grafana/dashboards/application }

Folder addressing: folderId (numeric) was removed from API paths in Grafana 10 — use folderUid (string; omit/empty = default folder). overwrite: true always wins over the DB dashboard regardless of version.

K8s delivery: a ConfigMap with label grafana_dashboard: "1" (sidecar auto-import), or the Grafana Operator GrafanaDashboard CRD (spec.instanceSelector + inline json).

Data Sources

⚠️ Provisioned data sources need an explicit, stable uid. Without one Grafana generates a random UID each startup; dashboard panels embed that UID, so on redeploy/recreate every panel shows "Datasource not found" — silent at provision time (Grafana loads fine, panels broken). Declare a pinned human-readable uid and reference it from dashboards via the object form {type, uid}, not the legacy name string (name refs break on rename).

# datasources.yaml (apiVersion: 1)
datasources:
  - name: Mimir
    type: prometheus
    uid: prometheus_uid           # pinned, stable
    url: http://mimir:8080/prometheus
    jsonData:
      httpMethod: POST
      prometheusType: Mimir
      exemplarTraceIdDestinations: [{ datasourceUid: tempo_uid, name: trace_id }]
      cacheLevel: High

  - name: Loki
    type: loki
    uid: loki_uid
    url: http://loki:3100
    jsonData:
      maxLines: 1000
      derivedFields:             # link a log field to a trace
        - datasourceUid: tempo_uid
          matcherRegex: "trace_id=(\\w+)"
          name: TraceID
          url: "$${__value.raw}"

  - name: Tempo
    type: tempo
    uid: tempo_uid
    url: http://tempo:3200
    jsonData:
      # tracesToLogsV2 supersedes legacy tracesToLogs (tags/mappedTags); adds customQuery
      # with ${__tags}/${__span.traceId} interpolation.
      tracesToLogsV2:
        datasourceUid: loki_uid
        spanStartTimeShift: "-1h"
        spanEndTimeShift: "1h"
        customQuery: true
        query: '{${__tags}} |= "${__span.traceId}"'
      tracesToMetrics: { datasourceUid: prometheus_uid }
      serviceMap: { datasourceUid: prometheus_uid }
      nodeGraph: { enabled: true }

LogQL (Loki)

Pipeline order = stream selector → line filters → parsers → label filters. Loki evaluates left-to-right; ordering controls how many lines reach each expensive stage (documented perf rule). Line filters |=/!= (string, cheapest) before |~/!~ (regex) before parsers (json/logfmt/pattern/regexp, most expensive).

# Stream selection (indexed labels — keep low-cardinality)
{namespace="production", app=~"api|web", level!="debug"}

# Line filters
{app="api"} |= "error" != "timeout" |~ "(?i)fatal"

# Parse + label filter (filter cheaply FIRST, then parse)
{app="api"} |= "error" | json | level="error" | duration > 500ms
{app="api"} | logfmt level, caller, msg
{app="nginx"} | pattern `<ip> - - <_> "<method> <uri> <_>" <status> <_>` | status >= 400

# Metric queries
sum(rate({app="api"} |= "error" [$__rate_interval])) by (namespace)
sum(rate({app="api"} |= "error" [5m])) / sum(rate({app="api"}[5m]))       # error ratio
quantile_over_time(0.95, {app="api"} | logfmt | unwrap duration_seconds(duration) [5m]) by (endpoint)
topk(10, sum by (msg) (count_over_time({app="api"} | json | level="error" [1h])))

TraceQL (Tempo)

Use scoped attributes (span. / resource.) and prefer &&. Tempo stores traces in columnar Parquet; unscoped .attr checks multiple columns (slower). All-&& queries push filtering into Parquet (predicate pushdown — fastest path); || and structural operators bypass it.

{ span.http.status_code = 500 && resource.service.name = "api" && span.http.method = "POST" }  # fast
{ trace:rootService = "gateway" && trace:duration > 1s }                # end-to-end slow traces
{ .service.name = "frontend" } >> { .service.name = "backend" && status = error }   # structural

TraceQL metrics = RED metrics from traces, no metrics generator (Tempo 2.4+, query type traceql_metrics). Append rate/quantile_over_time/count_over_time/histogram_over_time/compare/topk to a span filter. Enables retroactive dimensional slicing Prometheus can't (p99 of DB spans by db.system). Avoid structural operators here — full trace processing, slow.

{ span:name = "GET /:endpoint" } | quantile_over_time(duration, .99) by (span.http.target)
{ status = error } | rate() by (resource.service.name)

Grafana Alerting

Unified alerting: multi-datasource rules, provisioned as YAML. Alert expressions use PromQL/LogQL (see loom-prometheus / LogQL above); the structure is Grafana-specific.

# /etc/grafana/provisioning/alerting/rules.yaml (apiVersion: 1)
groups:
  - name: application_alerts
    interval: 1m
    rules:
      - uid: error_rate_high
        title: High Error Rate
        condition: A
        data:
          - refId: A
            relativeTimeRange: { from: 300, to: 0 }
            datasourceUid: prometheus_uid
            model:
              expr: |
                sum(rate(http_requests_total{status=~"5.."}[5m]))
                / sum(rate(http_requests_total[5m])) > 0.05
        for: 5m                 # pending period before firing
        keep_firing_for: 2m     # anti-flap on exit
        noDataState: NoData
        execErrState: Error
        labels: { severity: critical, team: platform }
        annotations:
          description: 'Error rate {{ printf "%.2f" $values.A.Value }}%'
          runbook_url: https://wiki.company.com/runbooks/high-error-rate

# Loki-backed rule: model.expr = sum(rate({app="api"} | json | level="error" [5m])) > 10

Contact points + notification policies (routing tree, matchers, grouping):

# contactpoints.yaml / policies
contactPoints:
  - orgId: 1
    name: pagerduty-oncall
    receivers: [{ uid: pd, type: pagerduty, settings: { integrationKey: KEY, severity: critical } }]
notificationPolicies:
  - orgId: 1
    receiver: slack-critical
    group_by: [alertname, namespace]
    group_wait: 30s
    group_interval: 5m
    repeat_interval: 4h
    routes:
      - receiver: pagerduty-oncall
        matchers: [severity = critical, page = true]
        group_wait: 10s
        continue: true

Complete Dashboard Example

RED dashboard: request rate, P95 latency, error ratio, error logs. Note $__rate_interval with rate(), percentunit on the 0–1 ratio, {type, uid} datasource refs, and Explore data links.

{
  "dashboard": {
    "title": "Application Observability - ${app}",
    "tags": ["observability"], "graphTooltip": 1, "refresh": "30s",
    "time": { "from": "now-1h", "to": "now" },
    "templating": { "list": [
      { "name": "datasource", "type": "datasource", "query": "prometheus" },
      { "name": "app", "type": "query", "datasource": {"type":"prometheus","uid":"${datasource}"},
        "query": "label_values(up, app)" },
      { "name": "namespace", "type": "query", "datasource": {"type":"prometheus","uid":"${datasource}"},
        "query": "label_values(up{app=\"$app\"}, namespace)", "multi": true, "includeAll": true }
    ] },
    "panels": [
      { "id": 1, "title": "Request Rate", "type": "timeseries",
        "datasource": {"type":"prometheus","uid":"${datasource}"},
        "gridPos": {"h":8,"w":12,"x":0,"y":0},
        "fieldConfig": {"defaults": {"unit": "reqps"}},
        "targets": [{ "expr": "sum(rate(http_requests_total{app=\"$app\", namespace=~\"$namespace\"}[$__rate_interval])) by (method, status)",
          "legendFormat": "{{method}} - {{status}}" }] },
      { "id": 2, "title": "P95 Latency", "type": "timeseries",
        "datasource": {"type":"prometheus","uid":"${datasource}"},
        "gridPos": {"h":8,"w":12,"x":12,"y":0},
        "fieldConfig": {"defaults": {"unit": "s",
          "thresholds": {"mode":"absolute","steps":[{"color":"green","value":null},{"color":"red","value":1}]}}},
        "targets": [{ "expr": "histogram_quantile(0.95, sum(rate(http_request_duration_seconds_bucket{app=\"$app\", namespace=~\"$namespace\"}[$__rate_interval])) by (le, endpoint))",
          "legendFormat": "{{endpoint}}" }] },
      { "id": 3, "title": "Error Rate", "type": "timeseries",
        "datasource": {"type":"prometheus","uid":"${datasource}"},
        "gridPos": {"h":8,"w":12,"x":0,"y":8},
        "fieldConfig": {"defaults": {"unit": "percentunit", "min": 0, "max": 1}},
        "targets": [{ "expr": "sum(rate(http_requests_total{app=\"$app\", namespace=~\"$namespace\", status=~\"5..\"}[$__rate_interval])) / sum(rate(http_requests_total{app=\"$app\", namespace=~\"$namespace\"}[$__rate_interval]))",
          "legendFormat": "Error %" }] },
      { "id": 4, "title": "Recent Error Logs", "type": "logs",
        "datasource": {"type":"loki","uid":"loki_uid"},
        "gridPos": {"h":8,"w":12,"x":12,"y":8},
        "options": {"showTime": true, "wrapLogMessage": true, "enableLogDetails": true},
        "targets": [{ "expr": "{app=\"$app\", namespace=~\"$namespace\"} | json | level=\"error\"", "refId": "A" }] }
    ],
    "links": [
      { "title": "Explore Traces", "type": "link", "icon": "gf-traces",
        "url": "/explore?left={\"datasource\":\"Tempo\",\"queries\":[{\"query\":\"{resource.service.name=\\\"$app\\\"}\",\"queryType\":\"traceql\"}]}" }
    ]
  },
  "overwrite": true, "folderUid": null
}

LGTM Backend Config

# loki.yaml — new installs: schema v13 + store tsdb (required for structured metadata, OTLP, bloom)
schema_config:
  configs:
    - from: 2024-01-01
      store: tsdb
      object_store: s3
      schema: v13
      index: { prefix: index_, period: 24h }
compactor:
  retention_enabled: true
  delete_request_store: s3     # REQUIRED in Loki 3.0 when retention_enabled
limits_config:
  retention_period: 744h
# ⚠ shared_store was REMOVED in Loki 3.0 (boltdb_shipper/tsdb_shipper/compactor). Storage is
#   selected per-period via object_store above; a lingering shared_store fails to start.
#   Existing cluster: add a NEW period_config with a future from:, don't mutate the old one.

# tempo.yaml — OTLP + metrics generator remote_write to Mimir
distributor:
  receivers: { otlp: { protocols: { http: {}, grpc: {} } } }
metrics_generator:
  storage: { path: /var/tempo/generator/wal,
    remote_write: [{ url: http://mimir:9009/api/v1/push, send_exemplars: true }] }
storage:
  trace: { backend: s3, s3: { bucket: tempo-traces, region: us-east-1 }, wal: { path: /var/tempo/wal } }

Expert Practices: Idioms, Anti-Patterns & Gotchas

Mechanism-level rules. Many are silent — no error, just wrong or empty panels.

Query Idioms

Use $__rate_interval (never $__interval or fixed [5m]) with rate()/increase(). These need ≥2 samples in the range vector. $__interval is the display step and shrinks below the scrape interval on zoom → empty/NaN gaps. $__rate_interval = max($__interval + scrape_interval, 4 * scrape_interval), always ≥4× scrape. Reserve $__interval for avg_over_time-style aggregations. Silent correctness bug at narrow zoom.

Order Grafana transformations: normalize → combine(join) → filter → reduce. A pipeline; each step feeds the next. Classic mistake: Reduce (collapses each series to one value) before a Join destroys the shared Time field the join keys on → nothing matches. Correct: convert types; Outer join on Time (or Merge); filter; reduce last only if a scalar is needed. Merge joins on ALL matching fields — queries sharing more fields than intended multiply rows; use Outer join on Time explicitly. The transformation debug icon shows each step's output shape.

LogQL Gotchas (silent wrong/empty data)

Parsers add an __error__ label rather than dropping lines. A failed json/logfmt/pattern line is NOT filtered — it gets __error__ and still counts, inflating aggregations. Filter | __error__="". Also: bare | json silently skips array values (| json first="servers[0]"); an extracted label colliding with a stream label is suffixed _extracted — reconcile with | label_format level=level_extracted.

{app="api"} | json | __error__="" | level="error"   # excludes parse failures
{app="api"} | json | level="error"                  # silently includes failed-parse lines

unwrap defaults to raw float64 — use duration_seconds() / bytes(). 150ms or 5 MiB fails raw conversion; instead of erroring, the line gets __error__ and drops out, so quantile_over_time/avg_over_time compute over only the parseable subset — silently. duration_seconds() expects Go format (1s,100ms); a field holding integer 1000 (ms) must be unwrapped raw and divided by 1000.

LogQL label-filter boolean precedence is strictly left-to-right, NOT AND-before-OR. | duration >= 20ms or method="GET" and size <= 20KB parses as ((duration>=20ms or method="GET") and size<=20KB). Always parenthesize multi-predicate filters.

Loki labels are streams — keep high-cardinality fields in structured metadata, not labels. Each unique label set is a separate stream with its own chunks; high-card labels (trace_id, request_id, pod, user_id) explode the index and force tiny-chunk write amplification. Loki 3.0 (v13+TSDB) adds structured metadata: per-line KV, not indexed but queryable; the OTLP endpoint maps non-default OTel attributes there. Critical: structured metadata CANNOT go in the {} selector — it's a pipeline filter (| trace_id="...") with no index pre-filter. Keep dynamic labels to single-/low-tens cardinality.

{namespace="prod", app="api"} | trace_id="0242ac12" | pod="svc-abc"   # low-card labels, rest filtered
{namespace="prod", app="api", trace_id="0242ac12", pod="svc-abc"}     # stream explosion

TraceQL Gotcha

Structural operators return the RIGHT-side spans; span:duration ≠ trace:duration. { .service.name="gateway" } >> { status=error } returns the error descendant spans, not the gateway parent. span:duration is one span's end-start; trace:duration is whole-request wall time (max(end)-min(start)) and trace-level intrinsics are far more performant — use trace:duration for end-to-end latency.

Alerting Gotchas

NoData / Error create synthetic DatasourceNoData / DatasourceError instances that bypass existing silences. They carry different labels (alertname=DatasourceNoData, plus datasource_uid, rulename) from the parent, so silences/mute-timings/policies keyed to the parent do NOT apply — the #1 surprise-page source. Options: Set NoData (default), Set Alerting, Set Normal, Keep last state; for applies (Normal→Pending→NoData); grafana_state_reason explains divergence. To suppress: silence/route on the synthetic labels, or noDataState: KeepLast for transient hiccups.

Symptom-based alerting + for/keep_firing_for — page on user-visible latency/errors/availability, not causes (see loom-prometheus for the SRE rationale). Grafana-specific: pair for (pending) with keep_firing_for (anti-flap on exit).

Currency: removed mechanisms (Grafana 12 / Loki 3.0 / Tempo 2.4+)

Graph (old) panel and in-panel alert blocks are gone. AngularJS was removed in Grafana 12; "type": "graph" (with yaxes[] + root-level thresholds) is force-migrated to timeseries on load, dropping that config — emit "type": "timeseries" with fieldConfig.defaults. The panel-level "alert" block was removed with legacy alerting in Grafana 11 — completely inert (no rule, no firing). Define alerts under /etc/grafana/provisioning/alerting/.

Prometheus native histograms are GA. histogram_quantile() works on the native metric directly — no _bucket, no by(le) (details → loom-prometheus). Grafana caveat: the Time Series panel can't render a native histogram; use Histogram or Heatmap.

Verification Checklist

• Every rate()/increase() in a panel/alert uses [$__rate_interval], not [$__interval] or a fixed window
• Multi-value / Include-All variables are matched with =~ (never =)
• Panels reference data sources by {type, uid}; provisioned data sources have a pinned uid
• Every panel sets an explicit unit (percentunit for 0–1 ratios); titles include units
• "type": "timeseries" (no "graph"); no in-panel "alert" blocks
• LogQL pipeline is selector → line filter → parser → label filter; parsers followed by | __error__=""; unwrap uses duration_seconds()/bytes()
• TraceQL uses scoped span./resource. attributes and trace:duration for end-to-end latency
• Loki: schema v13 + tsdb; no shared_store; delete_request_store set when retention enabled
• Alert rules account for NoData/Error routing on synthetic labels
• Provisioning: production dashboards allowUiUpdates: false; generated from typed models, not UI exports

Resources

• Grafana: https://grafana.com/docs/grafana/latest/ · LogQL: /docs/loki/latest/query/
• Tempo/TraceQL: https://grafana.com/docs/tempo/latest/traceql/
• Foundation SDK + gcx, Terraform Grafana provider, Grafana Operator