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pipeline_ack.go
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pipeline_ack.go
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package pipeline
import (
"errors"
"github.com/elastic/beats/libbeat/publisher/beat"
)
type ackBuilder interface {
createPipelineACKer(canDrop bool, sema *sema) acker
createCountACKer(canDrop bool, sema *sema, fn func(int)) acker
createEventACKer(canDrop bool, sema *sema, fn func([]beat.Event)) acker
}
type pipelineEmptyACK struct {
pipeline *Pipeline
}
func (b *pipelineEmptyACK) createPipelineACKer(canDrop bool, sema *sema) acker {
return nilACKer
}
func (b *pipelineEmptyACK) createCountACKer(canDrop bool, sema *sema, fn func(int)) acker {
return buildClientCountACK(b.pipeline, canDrop, sema, func(guard *clientACKer) func(int, int) {
return func(total, acked int) {
if guard.Active() {
fn(total)
}
}
})
}
func (b *pipelineEmptyACK) createEventACKer(
canDrop bool,
sema *sema,
fn func([]beat.Event),
) acker {
return buildClientEventACK(b.pipeline, canDrop, sema, func(guard *clientACKer) func([]beat.Event, int) {
return func(events []beat.Event, acked int) {
if guard.Active() {
fn(events)
}
}
})
}
type pipelineCountACK struct {
pipeline *Pipeline
cb func(int, int)
}
func (b *pipelineCountACK) createPipelineACKer(canDrop bool, sema *sema) acker {
return makeCountACK(b.pipeline, canDrop, sema, b.cb)
}
func (b *pipelineCountACK) createCountACKer(canDrop bool, sema *sema, fn func(int)) acker {
return buildClientCountACK(b.pipeline, canDrop, sema, func(guard *clientACKer) func(int, int) {
return func(total, acked int) {
b.cb(total, acked)
if guard.Active() {
fn(total)
}
}
})
}
func (b *pipelineCountACK) createEventACKer(
canDrop bool,
sema *sema,
fn func([]beat.Event),
) acker {
return buildClientEventACK(b.pipeline, canDrop, sema, func(guard *clientACKer) func([]beat.Event, int) {
return func(events []beat.Event, acked int) {
b.cb(len(events), acked)
if guard.Active() {
fn(events)
}
}
})
}
type pipelineEventsACK struct {
pipeline *Pipeline
cb func([]beat.Event, int)
}
func (b *pipelineEventsACK) createPipelineACKer(canDrop bool, sema *sema) acker {
return newEventACK(b.pipeline, canDrop, sema, b.cb)
}
func (b *pipelineEventsACK) createCountACKer(canDrop bool, sema *sema, fn func(int)) acker {
return buildClientEventACK(b.pipeline, canDrop, sema, func(guard *clientACKer) func([]beat.Event, int) {
return func(events []beat.Event, acked int) {
b.cb(events, acked)
if guard.Active() {
fn(len(events))
}
}
})
}
func (b *pipelineEventsACK) createEventACKer(canDrop bool, sema *sema, fn func([]beat.Event)) acker {
return buildClientEventACK(b.pipeline, canDrop, sema, func(guard *clientACKer) func([]beat.Event, int) {
return func(events []beat.Event, acked int) {
b.cb(events, acked)
if guard.Active() {
fn(events)
}
}
})
}
// pipelineEventCB internally handles active ACKs in the pipeline.
// It receives ACK events from the broker and the individual clients.
// Once the broker returns an ACK to the pipelineEventCB, the worker loop will collect
// events from all clients having published events in the last batch of events
// being ACKed.
// the PipelineACKHandler will be notified, once all events being ACKed
// (including dropped events) have been collected. Only one ACK-event is handled
// at a time. The pipeline global and clients ACK handler will be blocked for the time
// an ACK event is being processed.
type pipelineEventCB struct {
done chan struct{}
acks chan int
events chan eventsMsg
droppedEvents chan eventsMsg
mode pipelineACKMode
handler beat.PipelineACKHandler
}
type eventsMsg struct {
events []beat.Event
total, acked int
sig chan struct{}
}
type pipelineACKMode uint8
const (
noACKMode pipelineACKMode = iota
countACKMode
eventsACKMode
lastEventsACKMode
)
func newPipelineEventCB(handler beat.PipelineACKHandler) (*pipelineEventCB, error) {
mode := noACKMode
if handler.ACKCount != nil {
mode = countACKMode
}
if handler.ACKEvents != nil {
if mode != noACKMode {
return nil, errors.New("only one callback can be set")
}
mode = eventsACKMode
}
if handler.ACKLastEvents != nil {
if mode != noACKMode {
return nil, errors.New("only one callback can be set")
}
mode = lastEventsACKMode
}
// yay, no work
if mode == noACKMode {
return nil, nil
}
cb := &pipelineEventCB{
acks: make(chan int),
mode: mode,
handler: handler,
events: make(chan eventsMsg),
droppedEvents: make(chan eventsMsg),
}
go cb.worker()
return cb, nil
}
func (p *pipelineEventCB) close() {
close(p.done)
}
// reportEvents sends a batch of ACKed events to the ACKer.
// The events array contains send and dropped events. The `acked` counters
// indicates the total number of events acked by the pipeline.
// That is, the number of dropped events is given by `len(events) - acked`.
// A client can report events with acked=0, iff the client has no waiting events
// in the pipeline (ACK ordering requirements)
//
// Note: the call blocks, until the ACK handler has collected all active events
// from all clients. This ensure an ACK event being fully 'captured'
// by the pipeline, before receiving/processing another ACK event.
// In the meantime the broker has the chance of batching-up more ACK events,
// such that only one ACK event is being reported to the pipeline handler
func (p *pipelineEventCB) onEvents(events []beat.Event, acked int) {
p.pushMsg(eventsMsg{events: events, total: len(events), acked: acked})
}
func (p *pipelineEventCB) onCounts(total, acked int) {
p.pushMsg(eventsMsg{total: total, acked: acked})
}
func (p *pipelineEventCB) pushMsg(msg eventsMsg) {
if msg.acked == 0 {
p.droppedEvents <- msg
} else {
msg.sig = make(chan struct{})
p.events <- msg
<-msg.sig
}
}
// Starts a new ACKed event.
func (p *pipelineEventCB) reportBrokerACK(acked int) {
p.acks <- acked
}
func (p *pipelineEventCB) worker() {
defer close(p.acks)
defer close(p.events)
defer close(p.droppedEvents)
for {
select {
case count := <-p.acks:
exit := p.collect(count)
if exit {
return
}
// short circuite dropped events, but have client block until all events
// have been processed by pipeline ack handler
case msg := <-p.droppedEvents:
p.reportEvents(msg.events, msg.total)
if msg.sig != nil {
close(msg.sig)
}
case <-p.done:
return
}
}
}
func (p *pipelineEventCB) collect(count int) (exit bool) {
var (
signalers []chan struct{}
events []beat.Event
acked int
total int
)
for acked < count {
var msg eventsMsg
select {
case msg = <-p.events:
case msg = <-p.droppedEvents:
case <-p.done:
exit = true
return
}
if msg.sig != nil {
signalers = append(signalers, msg.sig)
}
total += msg.total
acked += msg.acked
if count-acked < 0 {
panic("ack count mismatch")
}
switch p.mode {
case eventsACKMode:
events = append(events, msg.events...)
case lastEventsACKMode:
if L := len(msg.events); L > 0 {
events = append(events, msg.events[L-1])
}
}
}
// signal clients we processed all active ACKs, as reported by broker
for _, sig := range signalers {
close(sig)
}
p.reportEvents(events, total)
return
}
func (p *pipelineEventCB) reportEvents(events []beat.Event, total int) {
// report ACK back to the beat
switch p.mode {
case countACKMode:
p.handler.ACKCount(total)
case eventsACKMode:
p.handler.ACKEvents(events)
case lastEventsACKMode:
p.handler.ACKLastEvents(events)
}
}