Documentation
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Overview ¶
Package nodehealth holds the pure node-liveness decision types shared by the gossip failure detector (internal/daemon/mesh) and the liveness monitor (internal/daemon/api). It is a dependency-free leaf so both can import it without a cycle (the mesh package's tests import api, so api must not import mesh).
Index ¶
Constants ¶
const GossipDownStaleThreshold = 10 * time.Second
GossipDownStaleThreshold is the flap guard: gossip may only push a node to DOWN once its heartbeat has ALSO been stale at least this long. It is well under the 30s heartbeat deadline, so gossip still accelerates detection, but a transient gossip false-positive alone cannot demote a still-heart-beating node.
Variables ¶
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Functions ¶
This section is empty.
Types ¶
type GossipLiveness ¶
type GossipLiveness struct {
Alive bool
// Since is when this alive/dead state was first observed.
Since time.Time
}
GossipLiveness is the gossip layer's view of one node.
type LivenessInputs ¶
type LivenessInputs struct {
// GossipKnown is false when gossip has no opinion (single-node, gossip down,
// or a node it has never seen).
GossipKnown bool
GossipAlive bool
// HeartbeatReceived is whether livestate holds any heartbeat for the node;
// HeartbeatStaleFor is the age of that heartbeat when it does.
HeartbeatReceived bool
HeartbeatStaleFor time.Duration
}
LivenessInputs combines the two detectors for one node.
type Verdict ¶
type Verdict int
Verdict is the durable status the combined signals imply for a node.
func Decide ¶
func Decide(in LivenessInputs) Verdict
Decide applies the flap guard (T-56) at the gossip time scale (GossipDownStaleThreshold, ~10s — well under the 30s heartbeat deadline):
- ALIVE if EITHER signal is fresh — a heartbeat within the threshold, or gossip reporting the node up.
- DOWN only when gossip reports the node dead AND its heartbeat is stale past the threshold (or never arrived). This is what lets gossip demote a failed node in seconds instead of waiting the full heartbeat deadline.
- NoChange otherwise — notably when gossip has no opinion and the heartbeat is merely stale: the caller falls back to the heartbeat-only deadline.
Because DOWN needs both detectors to agree, neither can flap a node alone.
Source Files