mirror of
https://github.com/restic/restic.git
synced 2024-12-25 09:18:55 +00:00
520 lines
14 KiB
Go
520 lines
14 KiB
Go
// Copyright 2016 Google Inc. All Rights Reserved.
|
|
//
|
|
// 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 pubsub
|
|
|
|
import (
|
|
"log"
|
|
"sync"
|
|
"time"
|
|
|
|
"golang.org/x/net/context"
|
|
"google.golang.org/api/iterator"
|
|
"google.golang.org/api/support/bundler"
|
|
pb "google.golang.org/genproto/googleapis/pubsub/v1"
|
|
"google.golang.org/grpc"
|
|
"google.golang.org/grpc/codes"
|
|
)
|
|
|
|
type messageIterator struct {
|
|
impl interface {
|
|
next() (*Message, error)
|
|
stop()
|
|
}
|
|
}
|
|
|
|
type pollingMessageIterator struct {
|
|
// kaTicker controls how often we send an ack deadline extension request.
|
|
kaTicker *time.Ticker
|
|
// ackTicker controls how often we acknowledge a batch of messages.
|
|
ackTicker *time.Ticker
|
|
|
|
ka *keepAlive
|
|
acker *acker
|
|
nacker *bundler.Bundler
|
|
puller *puller
|
|
|
|
// mu ensures that cleanup only happens once, and concurrent Stop
|
|
// invocations block until cleanup completes.
|
|
mu sync.Mutex
|
|
|
|
// closed is used to signal that Stop has been called.
|
|
closed chan struct{}
|
|
}
|
|
|
|
var useStreamingPull = false
|
|
|
|
// newMessageIterator starts a new messageIterator. Stop must be called on the messageIterator
|
|
// when it is no longer needed.
|
|
// subName is the full name of the subscription to pull messages from.
|
|
// ctx is the context to use for acking messages and extending message deadlines.
|
|
func newMessageIterator(ctx context.Context, s service, subName string, po *pullOptions) *messageIterator {
|
|
if !useStreamingPull {
|
|
return &messageIterator{
|
|
impl: newPollingMessageIterator(ctx, s, subName, po),
|
|
}
|
|
}
|
|
sp := s.newStreamingPuller(ctx, subName, int32(po.ackDeadline.Seconds()))
|
|
err := sp.open()
|
|
if grpc.Code(err) == codes.Unimplemented {
|
|
log.Println("pubsub: streaming pull unimplemented; falling back to legacy pull")
|
|
return &messageIterator{
|
|
impl: newPollingMessageIterator(ctx, s, subName, po),
|
|
}
|
|
}
|
|
// TODO(jba): handle other non-nil error?
|
|
log.Println("using streaming pull")
|
|
return &messageIterator{
|
|
impl: newStreamingMessageIterator(ctx, sp, po),
|
|
}
|
|
}
|
|
|
|
func newPollingMessageIterator(ctx context.Context, s service, subName string, po *pullOptions) *pollingMessageIterator {
|
|
// TODO: make kaTicker frequency more configurable.
|
|
// (ackDeadline - 5s) is a reasonable default for now, because the minimum ack period is 10s. This gives us 5s grace.
|
|
keepAlivePeriod := po.ackDeadline - 5*time.Second
|
|
kaTicker := time.NewTicker(keepAlivePeriod) // Stopped in it.Stop
|
|
|
|
// Ack promptly so users don't lose work if client crashes.
|
|
ackTicker := time.NewTicker(100 * time.Millisecond) // Stopped in it.Stop
|
|
ka := &keepAlive{
|
|
s: s,
|
|
Ctx: ctx,
|
|
Sub: subName,
|
|
ExtensionTick: kaTicker.C,
|
|
Deadline: po.ackDeadline,
|
|
MaxExtension: po.maxExtension,
|
|
}
|
|
|
|
ack := &acker{
|
|
s: s,
|
|
Ctx: ctx,
|
|
Sub: subName,
|
|
AckTick: ackTicker.C,
|
|
Notify: ka.Remove,
|
|
}
|
|
|
|
nacker := bundler.NewBundler("", func(ackIDs interface{}) {
|
|
// NACK by setting the ack deadline to zero, to make the message
|
|
// immediately available for redelivery.
|
|
//
|
|
// If the RPC fails, nothing we can do about it. In the worst case, the
|
|
// deadline for these messages will expire and they will still get
|
|
// redelivered.
|
|
_ = s.modifyAckDeadline(ctx, subName, 0, ackIDs.([]string))
|
|
})
|
|
nacker.DelayThreshold = 100 * time.Millisecond // nack promptly
|
|
nacker.BundleCountThreshold = 10
|
|
|
|
pull := newPuller(s, subName, ctx, po.maxPrefetch, ka.Add, ka.Remove)
|
|
|
|
ka.Start()
|
|
ack.Start()
|
|
return &pollingMessageIterator{
|
|
kaTicker: kaTicker,
|
|
ackTicker: ackTicker,
|
|
ka: ka,
|
|
acker: ack,
|
|
nacker: nacker,
|
|
puller: pull,
|
|
closed: make(chan struct{}),
|
|
}
|
|
}
|
|
|
|
// Next returns the next Message to be processed. The caller must call
|
|
// Message.Done when finished with it.
|
|
// Once Stop has been called, calls to Next will return iterator.Done.
|
|
func (it *messageIterator) Next() (*Message, error) {
|
|
return it.impl.next()
|
|
}
|
|
|
|
func (it *pollingMessageIterator) next() (*Message, error) {
|
|
m, err := it.puller.Next()
|
|
if err == nil {
|
|
m.doneFunc = it.done
|
|
return m, nil
|
|
}
|
|
|
|
select {
|
|
// If Stop has been called, we return Done regardless the value of err.
|
|
case <-it.closed:
|
|
return nil, iterator.Done
|
|
default:
|
|
return nil, err
|
|
}
|
|
}
|
|
|
|
// Client code must call Stop on a messageIterator when finished with it.
|
|
// Stop will block until Done has been called on all Messages that have been
|
|
// returned by Next, or until the context with which the messageIterator was created
|
|
// is cancelled or exceeds its deadline.
|
|
// Stop need only be called once, but may be called multiple times from
|
|
// multiple goroutines.
|
|
func (it *messageIterator) Stop() {
|
|
it.impl.stop()
|
|
}
|
|
|
|
func (it *pollingMessageIterator) stop() {
|
|
it.mu.Lock()
|
|
defer it.mu.Unlock()
|
|
|
|
select {
|
|
case <-it.closed:
|
|
// Cleanup has already been performed.
|
|
return
|
|
default:
|
|
}
|
|
|
|
// We close this channel before calling it.puller.Stop to ensure that we
|
|
// reliably return iterator.Done from Next.
|
|
close(it.closed)
|
|
|
|
// Stop the puller. Once this completes, no more messages will be added
|
|
// to it.ka.
|
|
it.puller.Stop()
|
|
|
|
// Start acking messages as they arrive, ignoring ackTicker. This will
|
|
// result in it.ka.Stop, below, returning as soon as possible.
|
|
it.acker.FastMode()
|
|
|
|
// This will block until
|
|
// (a) it.ka.Ctx is done, or
|
|
// (b) all messages have been removed from keepAlive.
|
|
// (b) will happen once all outstanding messages have been either ACKed or NACKed.
|
|
it.ka.Stop()
|
|
|
|
// There are no more live messages, so kill off the acker.
|
|
it.acker.Stop()
|
|
it.nacker.Flush()
|
|
it.kaTicker.Stop()
|
|
it.ackTicker.Stop()
|
|
}
|
|
|
|
func (it *pollingMessageIterator) done(ackID string, ack bool) {
|
|
if ack {
|
|
it.acker.Ack(ackID)
|
|
// There's no need to call it.ka.Remove here, as acker will
|
|
// call it via its Notify function.
|
|
} else {
|
|
it.ka.Remove(ackID)
|
|
_ = it.nacker.Add(ackID, len(ackID)) // ignore error; this is just an optimization
|
|
}
|
|
}
|
|
|
|
type streamingMessageIterator struct {
|
|
ctx context.Context
|
|
po *pullOptions
|
|
sp *streamingPuller
|
|
kaTicker *time.Ticker // keep-alive (deadline extensions)
|
|
ackTicker *time.Ticker // message acks
|
|
nackTicker *time.Ticker // message nacks (more frequent than acks)
|
|
failed chan struct{} // closed on stream error
|
|
stopped chan struct{} // closed when Stop is called
|
|
drained chan struct{} // closed when stopped && no more pending messages
|
|
msgc chan *Message
|
|
wg sync.WaitGroup
|
|
|
|
mu sync.Mutex
|
|
keepAliveDeadlines map[string]time.Time
|
|
pendingReq *pb.StreamingPullRequest
|
|
err error // error from stream failure
|
|
}
|
|
|
|
func newStreamingMessageIterator(ctx context.Context, sp *streamingPuller, po *pullOptions) *streamingMessageIterator {
|
|
// TODO: make kaTicker frequency more configurable. (ackDeadline - 5s) is a
|
|
// reasonable default for now, because the minimum ack period is 10s. This
|
|
// gives us 5s grace.
|
|
keepAlivePeriod := po.ackDeadline - 5*time.Second
|
|
kaTicker := time.NewTicker(keepAlivePeriod)
|
|
|
|
// Ack promptly so users don't lose work if client crashes.
|
|
ackTicker := time.NewTicker(100 * time.Millisecond)
|
|
nackTicker := time.NewTicker(100 * time.Millisecond)
|
|
it := &streamingMessageIterator{
|
|
ctx: ctx,
|
|
sp: sp,
|
|
po: po,
|
|
kaTicker: kaTicker,
|
|
ackTicker: ackTicker,
|
|
nackTicker: nackTicker,
|
|
failed: make(chan struct{}),
|
|
stopped: make(chan struct{}),
|
|
drained: make(chan struct{}),
|
|
// use maxPrefetch as the channel's buffer size.
|
|
msgc: make(chan *Message, po.maxPrefetch),
|
|
keepAliveDeadlines: map[string]time.Time{},
|
|
pendingReq: &pb.StreamingPullRequest{},
|
|
}
|
|
it.wg.Add(2)
|
|
go it.receiver()
|
|
go it.sender()
|
|
return it
|
|
}
|
|
|
|
func (it *streamingMessageIterator) next() (*Message, error) {
|
|
// If ctx has been cancelled or the iterator is done, return straight
|
|
// away (even if there are buffered messages available).
|
|
select {
|
|
case <-it.ctx.Done():
|
|
return nil, it.ctx.Err()
|
|
|
|
case <-it.failed:
|
|
break
|
|
|
|
case <-it.stopped:
|
|
break
|
|
|
|
default:
|
|
// Wait for a message, but also for one of the above conditions.
|
|
select {
|
|
case msg := <-it.msgc:
|
|
// Since active select cases are chosen at random, this can return
|
|
// nil (from the channel close) even if it.failed or it.stopped is
|
|
// closed.
|
|
if msg == nil {
|
|
break
|
|
}
|
|
msg.doneFunc = it.done
|
|
return msg, nil
|
|
|
|
case <-it.ctx.Done():
|
|
return nil, it.ctx.Err()
|
|
|
|
case <-it.failed:
|
|
break
|
|
|
|
case <-it.stopped:
|
|
break
|
|
}
|
|
}
|
|
// Here if the iterator is done.
|
|
it.mu.Lock()
|
|
defer it.mu.Unlock()
|
|
return nil, it.err
|
|
}
|
|
|
|
func (it *streamingMessageIterator) stop() {
|
|
it.mu.Lock()
|
|
select {
|
|
case <-it.stopped:
|
|
it.mu.Unlock()
|
|
it.wg.Wait()
|
|
return
|
|
default:
|
|
close(it.stopped)
|
|
}
|
|
if it.err == nil {
|
|
it.err = iterator.Done
|
|
}
|
|
// Before reading from the channel, see if we're already drained.
|
|
it.checkDrained()
|
|
it.mu.Unlock()
|
|
// Nack all the pending messages.
|
|
// Grab the lock separately for each message to allow the receiver
|
|
// and sender goroutines to make progress.
|
|
// Why this will eventually terminate:
|
|
// - If the receiver is not blocked on a stream Recv, then
|
|
// it will write all the messages it has received to the channel,
|
|
// then exit, closing the channel.
|
|
// - If the receiver is blocked, then this loop will eventually
|
|
// nack all the messages in the channel. Once done is called
|
|
// on the remaining messages, the iterator will be marked as drained,
|
|
// which will trigger the sender to terminate. When it does, it
|
|
// performs a CloseSend on the stream, which will result in the blocked
|
|
// stream Recv returning.
|
|
for m := range it.msgc {
|
|
it.mu.Lock()
|
|
delete(it.keepAliveDeadlines, m.ackID)
|
|
it.addDeadlineMod(m.ackID, 0)
|
|
it.checkDrained()
|
|
it.mu.Unlock()
|
|
}
|
|
it.wg.Wait()
|
|
}
|
|
|
|
// checkDrained closes the drained channel if the iterator has been stopped and all
|
|
// pending messages have either been n/acked or expired.
|
|
//
|
|
// Called with the lock held.
|
|
func (it *streamingMessageIterator) checkDrained() {
|
|
select {
|
|
case <-it.drained:
|
|
return
|
|
default:
|
|
}
|
|
select {
|
|
case <-it.stopped:
|
|
if len(it.keepAliveDeadlines) == 0 {
|
|
close(it.drained)
|
|
}
|
|
default:
|
|
}
|
|
}
|
|
|
|
// Called when a message is acked/nacked.
|
|
func (it *streamingMessageIterator) done(ackID string, ack bool) {
|
|
it.mu.Lock()
|
|
defer it.mu.Unlock()
|
|
delete(it.keepAliveDeadlines, ackID)
|
|
if ack {
|
|
it.pendingReq.AckIds = append(it.pendingReq.AckIds, ackID)
|
|
} else {
|
|
it.addDeadlineMod(ackID, 0) // Nack indicated by modifying the deadline to zero.
|
|
}
|
|
it.checkDrained()
|
|
}
|
|
|
|
// addDeadlineMod adds the ack ID to the pending request with the given deadline.
|
|
//
|
|
// Called with the lock held.
|
|
func (it *streamingMessageIterator) addDeadlineMod(ackID string, deadlineSecs int32) {
|
|
pr := it.pendingReq
|
|
pr.ModifyDeadlineAckIds = append(pr.ModifyDeadlineAckIds, ackID)
|
|
pr.ModifyDeadlineSeconds = append(pr.ModifyDeadlineSeconds, deadlineSecs)
|
|
}
|
|
|
|
// fail is called when a stream method returns a permanent error.
|
|
func (it *streamingMessageIterator) fail(err error) {
|
|
it.mu.Lock()
|
|
if it.err == nil {
|
|
it.err = err
|
|
close(it.failed)
|
|
}
|
|
it.mu.Unlock()
|
|
}
|
|
|
|
// receiver runs in a goroutine and handles all receives from the stream.
|
|
func (it *streamingMessageIterator) receiver() {
|
|
defer it.wg.Done()
|
|
defer close(it.msgc)
|
|
for {
|
|
// Stop retrieving messages if the context is done, the stream
|
|
// failed, or the iterator's Stop method was called.
|
|
select {
|
|
case <-it.ctx.Done():
|
|
return
|
|
case <-it.failed:
|
|
return
|
|
case <-it.stopped:
|
|
return
|
|
default:
|
|
}
|
|
// Receive messages from stream. This may block indefinitely.
|
|
msgs, err := it.sp.fetchMessages()
|
|
|
|
// The streamingPuller handles retries, so any error here
|
|
// is fatal to the iterator.
|
|
if err != nil {
|
|
it.fail(err)
|
|
return
|
|
}
|
|
// We received some messages. Remember them so we can
|
|
// keep them alive.
|
|
deadline := time.Now().Add(it.po.maxExtension)
|
|
it.mu.Lock()
|
|
for _, m := range msgs {
|
|
it.keepAliveDeadlines[m.ackID] = deadline
|
|
}
|
|
it.mu.Unlock()
|
|
// Deliver the messages to the channel.
|
|
for _, m := range msgs {
|
|
select {
|
|
case <-it.ctx.Done():
|
|
return
|
|
case <-it.failed:
|
|
return
|
|
// Don't return if stopped. We want to send the remaining
|
|
// messages on the channel, where they will be nacked.
|
|
case it.msgc <- m:
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// sender runs in a goroutine and handles all sends to the stream.
|
|
func (it *streamingMessageIterator) sender() {
|
|
defer it.wg.Done()
|
|
defer it.kaTicker.Stop()
|
|
defer it.ackTicker.Stop()
|
|
defer it.nackTicker.Stop()
|
|
defer it.sp.closeSend()
|
|
|
|
done := false
|
|
for !done {
|
|
send := false
|
|
select {
|
|
case <-it.ctx.Done():
|
|
// Context canceled or timed out: stop immediately, without
|
|
// another RPC.
|
|
return
|
|
|
|
case <-it.failed:
|
|
// Stream failed: nothing to do, so stop immediately.
|
|
return
|
|
|
|
case <-it.drained:
|
|
// All outstanding messages have been marked done:
|
|
// nothing left to do except send the final request.
|
|
it.mu.Lock()
|
|
send = (len(it.pendingReq.AckIds) > 0 || len(it.pendingReq.ModifyDeadlineAckIds) > 0)
|
|
done = true
|
|
|
|
case <-it.kaTicker.C:
|
|
it.mu.Lock()
|
|
send = it.handleKeepAlives()
|
|
|
|
case <-it.nackTicker.C:
|
|
it.mu.Lock()
|
|
send = (len(it.pendingReq.ModifyDeadlineAckIds) > 0)
|
|
|
|
case <-it.ackTicker.C:
|
|
it.mu.Lock()
|
|
send = (len(it.pendingReq.AckIds) > 0)
|
|
|
|
}
|
|
// Lock is held here.
|
|
if send {
|
|
req := it.pendingReq
|
|
it.pendingReq = &pb.StreamingPullRequest{}
|
|
it.mu.Unlock()
|
|
err := it.sp.send(req)
|
|
if err != nil {
|
|
// The streamingPuller handles retries, so any error here
|
|
// is fatal to the iterator.
|
|
it.fail(err)
|
|
return
|
|
}
|
|
} else {
|
|
it.mu.Unlock()
|
|
}
|
|
}
|
|
}
|
|
|
|
// handleKeepAlives modifies the pending request to include deadline extensions
|
|
// for live messages. It also purges expired messages. It reports whether
|
|
// there were any live messages.
|
|
//
|
|
// Called with the lock held.
|
|
func (it *streamingMessageIterator) handleKeepAlives() bool {
|
|
live, expired := getKeepAliveAckIDs(it.keepAliveDeadlines)
|
|
for _, e := range expired {
|
|
delete(it.keepAliveDeadlines, e)
|
|
}
|
|
dl := trunc32(int64(it.po.ackDeadline.Seconds()))
|
|
for _, m := range live {
|
|
it.addDeadlineMod(m, dl)
|
|
}
|
|
it.checkDrained()
|
|
return len(live) > 0
|
|
}
|