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engine.go
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engine.go
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package alerting
import (
"context"
"fmt"
"time"
"github.com/opentracing/opentracing-go"
"github.com/opentracing/opentracing-go/ext"
tlog "github.com/opentracing/opentracing-go/log"
"github.com/benbjohnson/clock"
"github.com/grafana/grafana/pkg/log"
"golang.org/x/sync/errgroup"
)
type Engine struct {
execQueue chan *Job
//clock clock.Clock
ticker *Ticker
scheduler Scheduler
evalHandler EvalHandler
ruleReader RuleReader
log log.Logger
resultHandler ResultHandler
}
func NewEngine() *Engine {
e := &Engine{
ticker: NewTicker(time.Now(), time.Second*0, clock.New()),
execQueue: make(chan *Job, 1000),
scheduler: NewScheduler(),
evalHandler: NewEvalHandler(),
ruleReader: NewRuleReader(),
log: log.New("alerting.engine"),
resultHandler: NewResultHandler(),
}
return e
}
func (e *Engine) Run(ctx context.Context) error {
e.log.Info("Initializing Alerting")
alertGroup, ctx := errgroup.WithContext(ctx)
alertGroup.Go(func() error { return e.alertingTicker(ctx) })
alertGroup.Go(func() error { return e.runJobDispatcher(ctx) })
err := alertGroup.Wait()
e.log.Info("Stopped Alerting", "reason", err)
return err
}
func (e *Engine) alertingTicker(grafanaCtx context.Context) error {
defer func() {
if err := recover(); err != nil {
e.log.Error("Scheduler Panic: stopping alertingTicker", "error", err, "stack", log.Stack(1))
}
}()
tickIndex := 0
for {
select {
case <-grafanaCtx.Done():
return grafanaCtx.Err()
case tick := <-e.ticker.C:
// TEMP SOLUTION update rules ever tenth tick
if tickIndex%10 == 0 {
e.scheduler.Update(e.ruleReader.Fetch())
}
e.scheduler.Tick(tick, e.execQueue)
tickIndex++
}
}
}
func (e *Engine) runJobDispatcher(grafanaCtx context.Context) error {
dispatcherGroup, alertCtx := errgroup.WithContext(grafanaCtx)
for {
select {
case <-grafanaCtx.Done():
return dispatcherGroup.Wait()
case job := <-e.execQueue:
dispatcherGroup.Go(func() error { return e.processJobWithRetry(alertCtx, job) })
}
}
}
var (
unfinishedWorkTimeout time.Duration = time.Second * 5
// TODO: Make alertTimeout and alertMaxAttempts configurable in the config file.
alertTimeout time.Duration = time.Second * 30
alertMaxAttempts int = 3
)
func (e *Engine) processJobWithRetry(grafanaCtx context.Context, job *Job) error {
defer func() {
if err := recover(); err != nil {
e.log.Error("Alert Panic", "error", err, "stack", log.Stack(1))
}
}()
cancelChan := make(chan context.CancelFunc, alertMaxAttempts)
attemptChan := make(chan int, 1)
// Initialize with first attemptID=1
attemptChan <- 1
job.Running = true
for {
select {
case <-grafanaCtx.Done():
// In case grafana server context is cancel, let a chance to job processing
// to finish gracefully - by waiting a timeout duration - before forcing its end.
unfinishedWorkTimer := time.NewTimer(unfinishedWorkTimeout)
select {
case <-unfinishedWorkTimer.C:
return e.endJob(grafanaCtx.Err(), cancelChan, job)
case <-attemptChan:
return e.endJob(nil, cancelChan, job)
}
case attemptID, more := <-attemptChan:
if !more {
return e.endJob(nil, cancelChan, job)
}
go e.processJob(attemptID, attemptChan, cancelChan, job)
}
}
}
func (e *Engine) endJob(err error, cancelChan chan context.CancelFunc, job *Job) error {
job.Running = false
close(cancelChan)
for cancelFn := range cancelChan {
cancelFn()
}
return err
}
func (e *Engine) processJob(attemptID int, attemptChan chan int, cancelChan chan context.CancelFunc, job *Job) {
defer func() {
if err := recover(); err != nil {
e.log.Error("Alert Panic", "error", err, "stack", log.Stack(1))
}
}()
alertCtx, cancelFn := context.WithTimeout(context.Background(), alertTimeout)
cancelChan <- cancelFn
span := opentracing.StartSpan("alert execution")
alertCtx = opentracing.ContextWithSpan(alertCtx, span)
evalContext := NewEvalContext(alertCtx, job.Rule)
evalContext.Ctx = alertCtx
go func() {
defer func() {
if err := recover(); err != nil {
e.log.Error("Alert Panic", "error", err, "stack", log.Stack(1))
ext.Error.Set(span, true)
span.LogFields(
tlog.Error(fmt.Errorf("%v", err)),
tlog.String("message", "failed to execute alert rule. panic was recovered."),
)
span.Finish()
close(attemptChan)
}
}()
e.evalHandler.Eval(evalContext)
span.SetTag("alertId", evalContext.Rule.Id)
span.SetTag("dashboardId", evalContext.Rule.DashboardId)
span.SetTag("firing", evalContext.Firing)
span.SetTag("nodatapoints", evalContext.NoDataFound)
span.SetTag("attemptID", attemptID)
if evalContext.Error != nil {
ext.Error.Set(span, true)
span.LogFields(
tlog.Error(evalContext.Error),
tlog.String("message", "alerting execution attempt failed"),
)
if attemptID < alertMaxAttempts {
span.Finish()
e.log.Debug("Job Execution attempt triggered retry", "timeMs", evalContext.GetDurationMs(), "alertId", evalContext.Rule.Id, "name", evalContext.Rule.Name, "firing", evalContext.Firing, "attemptID", attemptID)
attemptChan <- (attemptID + 1)
return
}
}
evalContext.Rule.State = evalContext.GetNewState()
e.resultHandler.Handle(evalContext)
span.Finish()
e.log.Debug("Job Execution completed", "timeMs", evalContext.GetDurationMs(), "alertId", evalContext.Rule.Id, "name", evalContext.Rule.Name, "firing", evalContext.Firing, "attemptID", attemptID)
close(attemptChan)
}()
}