Routing checks

undefined-receiver

Level: error

A route references a receiver that is not defined in receivers:. Alerts matched by this route will be silently dropped.

BadFixed

route:
  receiver: default
  routes:
    - match: {team: infra}
      receiver: pager-team   # not defined below!
receivers:
  - name: default
    slack_configs: [...]

route:
  receiver: default
  routes:
    - match: {team: infra}
      receiver: pager-team
receivers:
  - name: default
    slack_configs: [...]
  - name: pager-team         # add the missing receiver
    pagerduty_configs: [...]

---

no-root-route

Level: error

The config has no root route at all. Alertmanager will refuse to start.

BadFixed

receivers:
  - name: default
    slack_configs: [...]

route:
  receiver: default
receivers:
  - name: default
    slack_configs: [...]

---

bad-regex

Level: error

A match_re or matchers entry contains a regex that fails to compile. The route will never match anything.

BadFixed

route:
  receiver: default
  routes:
    - match_re:
        service: "auth(["    # unclosed character class
      receiver: team

    - match_re:
        service: "auth(.*)"  # valid regex
      receiver: team

---

unreachable-route

Level: warn

A catch-all route (no match, match_re, or matchers) with continue: false appears before sibling routes. All subsequent siblings are unreachable — they will never receive alerts.

BadFixed

routes:
  - receiver: default          # catch-all, continue defaults to false
  - match: {severity: critical}
    receiver: pager            # unreachable!

routes:
  - match: {severity: critical}
    receiver: pager            # specific first
  - receiver: default          # catch-all last

---

groupby-ellipsis

Level: warn

group_by contains ... (group by all labels) alongside explicit labels. The explicit labels are redundant — ... already includes everything.

BadFixed

route:
  group_by: ['...', alertname, cluster]  # alertname and cluster are redundant

route:
  group_by: ['...']     # or list only the labels you want

---

useless-continue

Level: info

A route has continue: true but it is the last sibling — there are no subsequent routes to continue to, so the flag has no effect.

BadFixed

routes:
  - match: {env: prod}
    receiver: team
    continue: true     # last sibling, no effect

routes:
  - match: {env: prod}
    receiver: team
    # remove continue: true, or add a sibling after this route

---

route-match-collision

Level: warn

Two sibling routes have identical matchers. Alertmanager evaluates siblings in order and stops at the first match — the second route with the same matchers will never receive any alerts.

BadFixed — use continueFixed — distinct matchers

routes:
  - match: {team: infra, severity: critical}
    receiver: pager
  - match: {team: infra, severity: critical}   # identical — dead code
    receiver: slack-infra

routes:
  - match: {team: infra, severity: critical}
    receiver: pager
    continue: true          # pass to next sibling too
  - match: {team: infra, severity: critical}
    receiver: slack-infra

routes:
  - match: {team: infra, severity: critical}
    receiver: pager
  - match: {team: infra, severity: warning}    # different severity
    receiver: slack-infra

---

deep-nesting

Level: info

The routing tree is more than 5 levels deep. Very deeply nested configs are hard to read, debug, and maintain.

Tip

Consider flattening the routing tree using matchers with multiple conditions instead of nested routes.