package memberlist
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import (
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"sync"
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"time"
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"github.com/armon/go-metrics"
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)
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// awareness manages a simple metric for tracking the estimated health of the
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// local node. Health is primary the node's ability to respond in the soft
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// real-time manner required for correct health checking of other nodes in the
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// cluster.
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type awareness struct {
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sync.RWMutex
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// max is the upper threshold for the timeout scale (the score will be
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// constrained to be from 0 <= score < max).
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max int
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// score is the current awareness score. Lower values are healthier and
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// zero is the minimum value.
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score int
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}
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// newAwareness returns a new awareness object.
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func newAwareness(max int) *awareness {
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return &awareness{
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max: max,
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score: 0,
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}
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}
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// ApplyDelta takes the given delta and applies it to the score in a thread-safe
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// manner. It also enforces a floor of zero and a max of max, so deltas may not
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// change the overall score if it's railed at one of the extremes.
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func (a *awareness) ApplyDelta(delta int) {
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a.Lock()
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initial := a.score
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a.score += delta
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if a.score < 0 {
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a.score = 0
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} else if a.score > (a.max - 1) {
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a.score = (a.max - 1)
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}
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final := a.score
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a.Unlock()
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if initial != final {
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metrics.SetGauge([]string{"memberlist", "health", "score"}, float32(final))
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}
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}
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// GetHealthScore returns the raw health score.
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func (a *awareness) GetHealthScore() int {
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a.RLock()
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score := a.score
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a.RUnlock()
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return score
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}
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// ScaleTimeout takes the given duration and scales it based on the current
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// score. Less healthyness will lead to longer timeouts.
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func (a *awareness) ScaleTimeout(timeout time.Duration) time.Duration {
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a.RLock()
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score := a.score
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a.RUnlock()
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return timeout * (time.Duration(score) + 1)
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}
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