prometheus/rules/alerting.go

270 lines
8.0 KiB
Go

// Copyright 2013 The Prometheus Authors
// 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 rules
import (
"fmt"
"html/template"
"reflect"
"sync"
"time"
clientmodel "github.com/prometheus/client_golang/model"
"github.com/prometheus/prometheus/promql"
"github.com/prometheus/prometheus/utility"
)
const (
// AlertMetricName is the metric name for synthetic alert timeseries.
AlertMetricName clientmodel.LabelValue = "ALERTS"
// AlertNameLabel is the label name indicating the name of an alert.
AlertNameLabel clientmodel.LabelName = "alertname"
// AlertStateLabel is the label name indicating the state of an alert.
AlertStateLabel clientmodel.LabelName = "alertstate"
)
// AlertState denotes the state of an active alert.
type AlertState int
func (s AlertState) String() string {
switch s {
case Inactive:
return "inactive"
case Pending:
return "pending"
case Firing:
return "firing"
default:
panic("undefined")
}
}
const (
// Inactive alerts are neither firing nor pending.
Inactive AlertState = iota
// Pending alerts have been active for less than the configured
// threshold duration.
Pending
// Firing alerts have been active for longer than the configured
// threshold duration.
Firing
)
// Alert is used to track active (pending/firing) alerts over time.
type Alert struct {
// The name of the alert.
Name string
// The vector element labelset triggering this alert.
Labels clientmodel.LabelSet
// The state of the alert (Pending or Firing).
State AlertState
// The time when the alert first transitioned into Pending state.
ActiveSince clientmodel.Timestamp
// The value of the alert expression for this vector element.
Value clientmodel.SampleValue
}
// sample returns a Sample suitable for recording the alert.
func (a Alert) sample(timestamp clientmodel.Timestamp, value clientmodel.SampleValue) *promql.Sample {
recordedMetric := clientmodel.Metric{}
for label, value := range a.Labels {
recordedMetric[label] = value
}
recordedMetric[clientmodel.MetricNameLabel] = AlertMetricName
recordedMetric[AlertNameLabel] = clientmodel.LabelValue(a.Name)
recordedMetric[AlertStateLabel] = clientmodel.LabelValue(a.State.String())
return &promql.Sample{
Metric: clientmodel.COWMetric{
Metric: recordedMetric,
Copied: true,
},
Value: value,
Timestamp: timestamp,
}
}
// An AlertingRule generates alerts from its vector expression.
type AlertingRule struct {
// The name of the alert.
name string
// The vector expression from which to generate alerts.
Vector promql.Expr
// The duration for which a labelset needs to persist in the expression
// output vector before an alert transitions from Pending to Firing state.
holdDuration time.Duration
// Extra labels to attach to the resulting alert sample vectors.
Labels clientmodel.LabelSet
// Short alert summary, suitable for email subjects.
Summary string
// More detailed alert description.
Description string
// Protects the below.
mutex sync.Mutex
// A map of alerts which are currently active (Pending or Firing), keyed by
// the fingerprint of the labelset they correspond to.
activeAlerts map[clientmodel.Fingerprint]*Alert
}
// Name returns the name of the alert.
func (rule *AlertingRule) Name() string {
return rule.name
}
// EvalRaw returns the raw value of the rule expression, without creating alerts.
func (rule *AlertingRule) EvalRaw(timestamp clientmodel.Timestamp, engine *promql.Engine) (promql.Vector, error) {
query, err := engine.NewInstantQuery(rule.Vector.String(), timestamp)
if err != nil {
return nil, err
}
return query.Exec().Vector()
}
// Eval evaluates the rule expression and then creates pending alerts and fires
// or removes previously pending alerts accordingly.
func (rule *AlertingRule) Eval(timestamp clientmodel.Timestamp, engine *promql.Engine) (promql.Vector, error) {
exprResult, err := rule.EvalRaw(timestamp, engine)
if err != nil {
return nil, err
}
rule.mutex.Lock()
defer rule.mutex.Unlock()
// Create pending alerts for any new vector elements in the alert expression
// or update the expression value for existing elements.
resultFingerprints := utility.Set{}
for _, sample := range exprResult {
fp := sample.Metric.Metric.Fingerprint()
resultFingerprints.Add(fp)
if alert, ok := rule.activeAlerts[fp]; !ok {
labels := clientmodel.LabelSet{}
labels.MergeFromMetric(sample.Metric.Metric)
labels = labels.Merge(rule.Labels)
if _, ok := labels[clientmodel.MetricNameLabel]; ok {
delete(labels, clientmodel.MetricNameLabel)
}
rule.activeAlerts[fp] = &Alert{
Name: rule.name,
Labels: labels,
State: Pending,
ActiveSince: timestamp,
Value: sample.Value,
}
} else {
alert.Value = sample.Value
}
}
vector := promql.Vector{}
// Check if any pending alerts should be removed or fire now. Write out alert timeseries.
for fp, activeAlert := range rule.activeAlerts {
if !resultFingerprints.Has(fp) {
vector = append(vector, activeAlert.sample(timestamp, 0))
delete(rule.activeAlerts, fp)
continue
}
if activeAlert.State == Pending && timestamp.Sub(activeAlert.ActiveSince) >= rule.holdDuration {
vector = append(vector, activeAlert.sample(timestamp, 0))
activeAlert.State = Firing
}
vector = append(vector, activeAlert.sample(timestamp, 1))
}
return vector, nil
}
// DotGraph returns the text representation of a dot graph.
func (rule *AlertingRule) DotGraph() string {
graph := fmt.Sprintf(
`digraph "Rules" {
%#p[shape="box",label="ALERT %s IF FOR %s"];
%#p -> %x;
%s
}`,
&rule, rule.name, utility.DurationToString(rule.holdDuration),
&rule, reflect.ValueOf(rule.Vector).Pointer(),
rule.Vector.DotGraph(),
)
return graph
}
func (rule *AlertingRule) String() string {
return fmt.Sprintf("ALERT %s IF %s FOR %s WITH %s", rule.name, rule.Vector, utility.DurationToString(rule.holdDuration), rule.Labels)
}
// HTMLSnippet returns an HTML snippet representing this alerting rule.
func (rule *AlertingRule) HTMLSnippet(pathPrefix string) template.HTML {
alertMetric := clientmodel.Metric{
clientmodel.MetricNameLabel: AlertMetricName,
AlertNameLabel: clientmodel.LabelValue(rule.name),
}
return template.HTML(fmt.Sprintf(
`ALERT <a href="%s">%s</a> IF <a href="%s">%s</a> FOR %s WITH %s`,
pathPrefix+utility.GraphLinkForExpression(alertMetric.String()),
rule.name,
pathPrefix+utility.GraphLinkForExpression(rule.Vector.String()),
rule.Vector,
utility.DurationToString(rule.holdDuration),
rule.Labels))
}
// State returns the "maximum" state: firing > pending > inactive.
func (rule *AlertingRule) State() AlertState {
rule.mutex.Lock()
defer rule.mutex.Unlock()
maxState := Inactive
for _, activeAlert := range rule.activeAlerts {
if activeAlert.State > maxState {
maxState = activeAlert.State
}
}
return maxState
}
// ActiveAlerts returns a slice of active alerts.
func (rule *AlertingRule) ActiveAlerts() []Alert {
rule.mutex.Lock()
defer rule.mutex.Unlock()
alerts := make([]Alert, 0, len(rule.activeAlerts))
for _, alert := range rule.activeAlerts {
alerts = append(alerts, *alert)
}
return alerts
}
// NewAlertingRule constructs a new AlertingRule.
func NewAlertingRule(name string, vector promql.Expr, holdDuration time.Duration, labels clientmodel.LabelSet, summary string, description string) *AlertingRule {
return &AlertingRule{
name: name,
Vector: vector,
holdDuration: holdDuration,
Labels: labels,
Summary: summary,
Description: description,
activeAlerts: map[clientmodel.Fingerprint]*Alert{},
}
}