argoproj/argo-cd

Notifications

Argo CD's notifications subsystem reacts to Application state changes and sends messages over Slack, email, webhooks, and many other channels.

Components

graph LR
    AppCh[Application changes] --> Watcher[notification_controller]
    Watcher --> Eval[Evaluate triggers - util/notification/expression]
    Eval --> Subs[Read subscriptions - argocd-cm + app annotations]
    Subs --> Tmpl[Render template]
    Tmpl --> Engine[notifications-engine services]
    Engine --> Slack[Slack/Teams/Email/...]

Path	Purpose
`notification_controller/`	The controller binary's runtime.
`util/notification/argocd/`	Glue that maps Argo CD types into the engine.
`util/notification/expression/`	Trigger expression evaluator (CEL/expr based).
`util/notification/k8s/`	Loaders for ConfigMap/Secret-backed configuration.
`util/notification/settings/`	Parsing of triggers/templates from settings.
`notifications_catalog/`	Out-of-the-box trigger/template YAML.

Triggers

A trigger is a CEL/expr predicate that evaluates against the Application object. Built-in triggers (in notifications_catalog/triggers/) include:

on-sync-succeeded, on-sync-failed, on-sync-status-unknown.
on-deployed (sync succeeded and healthy).
on-health-degraded, on-app-health-progressing.
on-created, on-deleted.

Custom triggers can be added by extending argocd-notifications-cm.

A template renders the matched event into a payload. Built-ins live in notifications_catalog/templates/. They cover the same set of triggers but produce service-specific payloads (Slack JSON, email HTML, Teams adaptive cards, …).

Subscriptions

Subscriptions can live in two places:

Cluster-wide in argocd-notifications-cm:

subscriptions: |
  - recipients:
      - slack:my-team
    triggers: [on-sync-failed]

Per-Application as annotations on the Application:

metadata:
  annotations:
    notifications.argoproj.io/subscribe.on-sync-succeeded.slack: my-team

The latter is gated by the --self-service-notification-enabled flag on the controller.

Services

Service implementations come from the upstream argoproj/notifications-engine library. Configured services live under service.<name> keys in the ConfigMap, with credentials in argocd-notifications-secret. Common services: slack, email, webhook, teams, mattermost, rocketchat, telegram, opsgenie, pagerduty, github, gitlab, googlechat.

Observability

Per-app notification state is persisted on the Application as the annotation notified.notifications.argoproj.io. This is also referenced from applicationset/controllers/applicationset_controller.go so that the AppSet controller can preserve the annotation across template renders.

CLI

argocd admin notifications (cmd/argocd/commands/admin/notifications.go) lets operators dry-run triggers/templates against a running cluster, which is the recommended way to debug a misconfigured subscription.