Routing Tree#

Alertmanager receives alerts from Prometheus and decides where to send them based on a routing tree. Every alert enters at the root route and travels down the tree until it matches a child route. If no child matches, the root route’s receiver handles it.

# alertmanager.yml
global:
  resolve_timeout: 5m
  slack_api_url: "https://hooks.slack.com/services/T00/B00/xxx"
  pagerduty_url: "https://events.pagerduty.com/v2/enqueue"

route:
  receiver: "default-slack"
  group_by: ["alertname", "namespace"]
  group_wait: 30s
  group_interval: 5m
  repeat_interval: 4h
  routes:
    - match:
        severity: critical
      receiver: "pagerduty-oncall"
      group_wait: 10s
      repeat_interval: 1h
      routes:
        - match:
            team: database
          receiver: "pagerduty-dba"
    - match:
        severity: warning
      receiver: "team-slack"
      repeat_interval: 12h
    - match_re:
        namespace: "staging|dev"
      receiver: "dev-slack"
      repeat_interval: 24h

Timing parameters matter. group_wait is how long Alertmanager waits after receiving the first alert in a new group before sending the notification – this lets it batch related alerts together. group_interval is the minimum time before sending updates about a group that already fired. repeat_interval controls how often an unchanged active alert is re-sent.

ArgoCD Notifications#

ArgoCD Notifications is a built-in component (since ArgoCD 2.5) that monitors applications and sends alerts when specific events occur – sync succeeded, sync failed, health degraded, new version deployed. Before notifications existed, teams polled the ArgoCD UI or built custom watchers. Notifications eliminates that.

Architecture#

ArgoCD Notifications runs as a controller alongside the ArgoCD application controller. It watches Application resources for state changes and matches them against triggers. When a trigger fires, it renders a template and sends it through a configured service (Slack, Teams, webhook, email, etc.).