checkfleet

NATS JetStream check

nats — NATS JetStream

Cluster health from /varz and /jsz — meta-leader present, offline or lagging peers, ghost peers, mixed versions.

checkfleet check nats --config checkfleet.yml

Preflight/health of a NATS JetStream cluster, read from each node’s HTTP monitoring port (/varz and /jsz?meta=1) — the read-only endpoints only, it never mutates the cluster. It encodes the operational signals from the ops runbook:

  • Reachability + version per node (OK with server_name, version, conns, uptime; ERROR if the monitoring port doesn’t answer).
  • Mixed versions across the cluster → WARN (e.g. mid-upgrade skew).
  • Meta-leader: BAD if no meta-leader is elected (quorum lost), WARN if the elected leader disagrees across nodes, or if it isn’t the expect_meta_leader you configured.
  • Peer health (from the meta raft group): BAD if a peer is OFFLINE, WARN if not current.
  • Peer lag: WARN/BAD when a peer’s raft lag crosses lag_warn/lag_crit.
  • Ghost / missing peers: with expect_peers set, an unexpected member is a WARN (ghost), an expected member absent from the cluster is BAD.

See Configuration → checks.nats.

See the full module reference for every check, or configuration for the config keys.