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inhibit.go
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inhibit.go
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// Copyright 2015 Prometheus Team
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package inhibit
import (
"context"
"fmt"
"sync"
"time"
"github.com/go-kit/kit/log"
"github.com/go-kit/kit/log/level"
"github.com/oklog/oklog/pkg/group"
"github.com/prometheus/common/model"
"github.com/prometheus/alertmanager/config"
"github.com/prometheus/alertmanager/provider"
"github.com/prometheus/alertmanager/types"
)
// An Inhibitor determines whether a given label set is muted
// based on the currently active alerts and a set of inhibition rules.
type Inhibitor struct {
alerts provider.Alerts
rules []*InhibitRule
marker types.Marker
logger log.Logger
mtx sync.RWMutex
cancel func()
}
// NewInhibitor returns a new Inhibitor.
func NewInhibitor(ap provider.Alerts, rs []*config.InhibitRule, mk types.Marker, logger log.Logger) *Inhibitor {
ih := &Inhibitor{
alerts: ap,
marker: mk,
logger: logger,
}
for _, cr := range rs {
r := NewInhibitRule(cr)
ih.rules = append(ih.rules, r)
}
return ih
}
func (ih *Inhibitor) runGC(ctx context.Context) {
for {
select {
case <-time.After(15 * time.Minute):
for _, r := range ih.rules {
r.gc()
}
case <-ctx.Done():
return
}
}
}
func (ih *Inhibitor) run(ctx context.Context) {
it := ih.alerts.Subscribe()
defer it.Close()
for {
select {
case <-ctx.Done():
return
case a := <-it.Next():
if err := it.Err(); err != nil {
level.Error(ih.logger).Log("msg", "Error iterating alerts", "err", err)
continue
}
if a.Resolved() {
// As alerts can also time out without an update, we never
// handle new resolved alerts but invalidate the cache on read.
continue
}
// Populate the inhibition rules' cache.
for _, r := range ih.rules {
if r.SourceMatchers.Match(a.Labels) {
r.set(a)
}
}
}
}
}
// Run the Inihibitor's background processing.
func (ih *Inhibitor) Run() {
var (
g group.Group
ctx context.Context
)
ih.mtx.Lock()
ctx, ih.cancel = context.WithCancel(context.Background())
ih.mtx.Unlock()
gcCtx, gcCancel := context.WithCancel(ctx)
runCtx, runCancel := context.WithCancel(ctx)
g.Add(func() error {
ih.runGC(gcCtx)
return nil
}, func(err error) {
gcCancel()
})
g.Add(func() error {
ih.run(runCtx)
return nil
}, func(err error) {
runCancel()
})
g.Run()
}
// Stop the Inhibitor's background processing.
func (ih *Inhibitor) Stop() {
if ih == nil {
return
}
ih.mtx.RLock()
defer ih.mtx.RUnlock()
if ih.cancel != nil {
ih.cancel()
}
}
// Mutes returns true iff the given label set is muted.
func (ih *Inhibitor) Mutes(lset model.LabelSet) bool {
fp := lset.Fingerprint()
for _, r := range ih.rules {
// Only inhibit if target matchers match but source matchers don't.
if inhibitedByFP, eq := r.hasEqual(lset); !r.SourceMatchers.Match(lset) && r.TargetMatchers.Match(lset) && eq {
ih.marker.SetInhibited(fp, fmt.Sprintf("%d", inhibitedByFP))
return true
}
}
ih.marker.SetInhibited(fp)
return false
}
// An InhibitRule specifies that a class of (source) alerts should inhibit
// notifications for another class of (target) alerts if all specified matching
// labels are equal between the two alerts. This may be used to inhibit alerts
// from sending notifications if their meaning is logically a subset of a
// higher-level alert.
type InhibitRule struct {
// The set of Filters which define the group of source alerts (which inhibit
// the target alerts).
SourceMatchers types.Matchers
// The set of Filters which define the group of target alerts (which are
// inhibited by the source alerts).
TargetMatchers types.Matchers
// A set of label names whose label values need to be identical in source and
// target alerts in order for the inhibition to take effect.
Equal map[model.LabelName]struct{}
mtx sync.RWMutex
// Cache of alerts matching source labels.
scache map[model.Fingerprint]*types.Alert
}
// NewInhibitRule returns a new InihibtRule based on a configuration definition.
func NewInhibitRule(cr *config.InhibitRule) *InhibitRule {
var (
sourcem types.Matchers
targetm types.Matchers
)
for ln, lv := range cr.SourceMatch {
sourcem = append(sourcem, types.NewMatcher(model.LabelName(ln), lv))
}
for ln, lv := range cr.SourceMatchRE {
sourcem = append(sourcem, types.NewRegexMatcher(model.LabelName(ln), lv.Regexp))
}
for ln, lv := range cr.TargetMatch {
targetm = append(targetm, types.NewMatcher(model.LabelName(ln), lv))
}
for ln, lv := range cr.TargetMatchRE {
targetm = append(targetm, types.NewRegexMatcher(model.LabelName(ln), lv.Regexp))
}
equal := map[model.LabelName]struct{}{}
for _, ln := range cr.Equal {
equal[ln] = struct{}{}
}
return &InhibitRule{
SourceMatchers: sourcem,
TargetMatchers: targetm,
Equal: equal,
scache: map[model.Fingerprint]*types.Alert{},
}
}
// set the alert in the source cache.
func (r *InhibitRule) set(a *types.Alert) {
r.mtx.Lock()
defer r.mtx.Unlock()
r.scache[a.Fingerprint()] = a
}
// hasEqual checks whether the source cache contains alerts matching
// the equal labels for the given label set.
func (r *InhibitRule) hasEqual(lset model.LabelSet) (model.Fingerprint, bool) {
r.mtx.RLock()
defer r.mtx.RUnlock()
Outer:
for fp, a := range r.scache {
// The cache might be stale and contain resolved alerts.
if a.Resolved() {
continue
}
for n := range r.Equal {
if a.Labels[n] != lset[n] {
continue Outer
}
}
return fp, true
}
return model.Fingerprint(0), false
}
// gc clears out resolved alerts from the source cache.
func (r *InhibitRule) gc() {
r.mtx.Lock()
defer r.mtx.Unlock()
for fp, a := range r.scache {
if a.Resolved() {
delete(r.scache, fp)
}
}
}