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async.go
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async.go
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package publisher
import (
"sync"
"sync/atomic"
"time"
"github.com/elastic/beats/filebeat/input"
"github.com/elastic/beats/libbeat/logp"
"github.com/elastic/beats/libbeat/publisher"
)
type asyncLogPublisher struct {
pub publisher.Publisher
client publisher.Client
in chan []*input.Event
out SuccessLogger
// list of in-flight batches
active batchList
stopping bool
done chan struct{}
wg sync.WaitGroup
}
// eventsBatch is used to store sorted list of actively published log lines.
// Implements `outputs.Signalerr` interface for marking batch as finished
type eventsBatch struct {
next *eventsBatch
flag int32
events []*input.Event
}
type batchList struct {
head, tail *eventsBatch
}
type batchStatus int32
const (
defaultGCTimeout = 1 * time.Second
)
const (
batchInProgress batchStatus = iota
batchSuccess
batchFailed
batchCanceled
)
func newAsyncLogPublisher(
in chan []*input.Event,
out SuccessLogger,
pub publisher.Publisher,
) *asyncLogPublisher {
return &asyncLogPublisher{
in: in,
out: out,
pub: pub,
done: make(chan struct{}),
}
}
func (p *asyncLogPublisher) Start() {
p.client = p.pub.Connect()
p.wg.Add(1)
go func() {
defer p.wg.Done()
logp.Info("Start sending events to output")
// short gc timer, in case no logs are received from spooler the queued
// bulkEvents can still be cleaned up and forwarded to the registrar
ticker := time.NewTicker(defaultGCTimeout)
for {
select {
case <-p.done:
return
case events := <-p.in:
batch := &eventsBatch{
flag: 0,
events: events,
}
p.client.PublishEvents(
getDataEvents(events),
publisher.Signal(batch),
publisher.Guaranteed)
p.active.append(batch)
case <-ticker.C:
}
p.collect()
}
}()
}
func (p *asyncLogPublisher) Stop() {
p.client.Close()
close(p.done)
p.wg.Wait()
}
// collect collects finished bulk-Events in order and forward processed batches
// to registrar. Reports to registrar are guaranteed to be in same order
// as bulk-Events have been received by the spooler
func (p *asyncLogPublisher) collect() bool {
for batch := p.active.head; batch != nil; batch = batch.next {
state := batchStatus(atomic.LoadInt32(&batch.flag))
if state == batchInProgress && !p.stopping {
break
}
if state == batchFailed {
// with guaranteed enabled this must must not happen.
msg := "Failed to process batch"
logp.Critical(msg)
panic(msg)
}
// remove batch from active list
p.active.head = batch.next
if batch.next == nil {
p.active.tail = nil
}
// Batches get marked as canceled, if publisher pipeline is shutting down
// In this case we do not want to send any more batches to the registrar
if state == batchCanceled {
p.stopping = true
}
if p.stopping {
logp.Info("Shutting down - No registrar update for potentially published batch.")
// if in failing state keep cleaning up queue
continue
}
// Tell the registrar that we've successfully publish the last batch events.
// If registrar queue is blocking (quite unlikely), but stop signal has been
// received in the meantime (by closing p.done), we do not wait for
// registrar picking up the current batch. Instead prefer to shut-down and
// resend the last published batch on next restart, basically taking advantage
// of send-at-last-once semantics in order to speed up cleanup on shutdown.
ok := p.out.Published(batch.events)
if !ok {
logp.Info("Shutting down - No registrar update for successfully published batch.")
return false
}
}
return true
}
func (b *eventsBatch) Completed() {
atomic.StoreInt32(&b.flag, int32(batchSuccess))
}
func (b *eventsBatch) Failed() {
logp.Err("Failed to publish batch. Stop updating registrar.")
atomic.StoreInt32(&b.flag, int32(batchFailed))
}
func (b *eventsBatch) Canceled() {
logp.Info("In-flight batch has been canceled during shutdown")
atomic.StoreInt32(&b.flag, int32(batchCanceled))
}
func (l *batchList) append(b *eventsBatch) {
if l.head == nil {
l.head = b
} else {
l.tail.next = b
}
b.next = nil
l.tail = b
}