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Prometheus Alertmanager

INFRA · APIS
Velocity6.3

Alert routing, grouping, silencing and notification dispatcher for Prometheus

prometheus.io/docs/alerting/latest/alertmanager ↗

Alertmanager 0.35 adds a gRPC API and a new UI, and breaks event recorder configs

alertingprometheusobservabilitybreaking-changesgrpcapi
◆Current state
Alertmanager handles deduplication, grouping, silencing and routing of Prometheus alerts. 0.35.0 (November 9) is the largest release in the feed: an experimental ConnectRPC API (Connect, gRPC and gRPC-Web) beside api/v2, a new Mantine UI at /ui/, Slack thread replies for alert updates, and breaking changes that require named event recorder outputs, move its output to an events/v2 schema and promote auto-gomemlimit to a plain flag. It follows 0.34.2, which turned CORS off by default.
◆Where it's heading
The project is replacing its interfaces in parallel rather than in place: a new API generation and a new UI now run alongside the old ones. The event recorder introduced in 0.33 is being reshaped with breaking schema changes, so anything consuming it is tracking a moving target.
◆Prediction
Expect 0.35.x patch releases fixing fallout from the breaking changes, and further services added to the ConnectRPC API beyond the initial status service.

◆Recent moves

  1. 4d ago

    0.35.0: gRPC API, new UI, Slack threads, breaking recorder changes

    ⚡ SPARK

    The biggest release since the 0.33 marker rework: a second API generation over Connect and gRPC, a new UI served alongside the old one, and breaking changes to the event recorder that 0.33 introduced. It sets up a migration path rather than forcing one, except for event recorder users.

    View source ↗
  2. 16d ago

    0.34.2: CORS off by default, eMudhra CAs distrusted

    A security patch with a breaking default: browser tools calling api/v2 cross-origin now need the new --web.cors.origin flag. The Go rebuild picks up the eMudhra CA distrust.

    View source ↗
  3. 1mo ago

    0.34.1: inhibition fixes stop alerts being wrongly un-muted

    Fixes several inhibition bugs that could un-mute alerts that should have stayed silent. A correctness fix in a core path.

    View source ↗
  4. 2mo ago

    Notification failure reasons split; templatable route labels added

    Splits authError and rateLimited out of clientError on alertmanager_notifications_failed_total, which silently changes what existing dashboards match — the release notes flag it as requiring updates. Adds templatable labels on alert routes, server-side active, expired and pending filters on the silences API, SNS external_id support, and toDate template functions.

    View source ↗
  5. 4mo ago

    Silence snapshot legacy matchers field restored

    Three bug fixes, the notable one restoring the legacy matchers field in silence snapshots so older Alertmanager versions can read newer snapshots again. A compatibility repair on the 0.33 line.

    View source ↗
  6. 5mo ago

    Per-group alert markers replace the global one; event recorder lands

    ⚡ SPARK

    Replaces the global alert marker with per-aggregation-group AlertMarkers, removing the alertmanager_marked_alerts metric and relocating marker types out of the public types package. The structured event recorder also arrives behind a feature flag with file, webhook and kafka outputs — the foundation the next release keeps building on.

    View source ↗