Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
feat(pubsublite): Committer implementation (#3198)
Commits desired offsets based on the ack prefix offset. Commits are batched.
- Loading branch information
Showing
4 changed files
with
570 additions
and
1 deletion.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,219 @@ | ||
// Copyright 2020 Google LLC | ||
// | ||
// 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 | ||
// | ||
// https://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 | ||
|
||
package wire | ||
|
||
import ( | ||
"context" | ||
"errors" | ||
"fmt" | ||
"reflect" | ||
"time" | ||
|
||
"google.golang.org/grpc" | ||
|
||
vkit "cloud.google.com/go/pubsublite/apiv1" | ||
pb "google.golang.org/genproto/googleapis/cloud/pubsublite/v1" | ||
) | ||
|
||
var ( | ||
errInvalidInitialCommitResponse = errors.New("pubsublite: first response from server was not an initial response for streaming commit") | ||
errInvalidCommitResponse = errors.New("pubsublite: received invalid commit response from server") | ||
) | ||
|
||
// The frequency of batched cursor commits. | ||
const commitCursorPeriod = 50 * time.Millisecond | ||
|
||
// committer wraps a commit cursor stream for a subscription and partition. | ||
// A background task periodically effectively reads the latest desired cursor | ||
// offset from the `ackTracker` and sends a commit request to the stream if the | ||
// cursor needs to be updated. The `commitCursorTracker` is used to manage | ||
// in-flight commit requests. | ||
type committer struct { | ||
// Immutable after creation. | ||
cursorClient *vkit.CursorClient | ||
initialReq *pb.StreamingCommitCursorRequest | ||
|
||
// Fields below must be guarded with mutex. | ||
stream *retryableStream | ||
acks *ackTracker | ||
cursorTracker *commitCursorTracker | ||
pollCommits *periodicTask | ||
|
||
abstractService | ||
} | ||
|
||
func newCommitter(ctx context.Context, cursor *vkit.CursorClient, settings ReceiveSettings, | ||
subscription subscriptionPartition, acks *ackTracker, disableTasks bool) *committer { | ||
|
||
c := &committer{ | ||
cursorClient: cursor, | ||
initialReq: &pb.StreamingCommitCursorRequest{ | ||
Request: &pb.StreamingCommitCursorRequest_Initial{ | ||
Initial: &pb.InitialCommitCursorRequest{ | ||
Subscription: subscription.Path, | ||
Partition: int64(subscription.Partition), | ||
}, | ||
}, | ||
}, | ||
acks: acks, | ||
cursorTracker: newCommitCursorTracker(acks), | ||
} | ||
c.stream = newRetryableStream(ctx, c, settings.Timeout, reflect.TypeOf(pb.StreamingCommitCursorResponse{})) | ||
|
||
backgroundTask := c.commitOffsetToStream | ||
if disableTasks { | ||
backgroundTask = func() {} | ||
} | ||
c.pollCommits = newPeriodicTask(commitCursorPeriod, backgroundTask) | ||
return c | ||
} | ||
|
||
// Start attempts to establish a streaming commit cursor connection. | ||
func (c *committer) Start() { | ||
c.mu.Lock() | ||
defer c.mu.Unlock() | ||
|
||
if c.unsafeUpdateStatus(serviceStarting, nil) { | ||
c.stream.Start() | ||
c.pollCommits.Start() | ||
} | ||
} | ||
|
||
// Stop initiates shutdown of the committer. The commit stream remains open to | ||
// process all outstanding acks and send the final commit offset. | ||
func (c *committer) Stop() { | ||
c.mu.Lock() | ||
defer c.mu.Unlock() | ||
c.unsafeInitiateShutdown(serviceTerminating, nil) | ||
} | ||
|
||
func (c *committer) newStream(ctx context.Context) (grpc.ClientStream, error) { | ||
return c.cursorClient.StreamingCommitCursor(ctx) | ||
} | ||
|
||
func (c *committer) initialRequest() (req interface{}, needsResp bool) { | ||
req = c.initialReq | ||
needsResp = true | ||
return | ||
} | ||
|
||
func (c *committer) validateInitialResponse(response interface{}) error { | ||
commitResponse, _ := response.(*pb.StreamingCommitCursorResponse) | ||
if commitResponse.GetInitial() == nil { | ||
return errInvalidInitialCommitResponse | ||
} | ||
return nil | ||
} | ||
|
||
func (c *committer) onStreamStatusChange(status streamStatus) { | ||
c.mu.Lock() | ||
defer c.mu.Unlock() | ||
|
||
switch status { | ||
case streamConnected: | ||
c.unsafeUpdateStatus(serviceActive, nil) | ||
// Once the stream connects, clear unconfirmed commits and immediately send | ||
// the latest desired commit offset. | ||
c.cursorTracker.ClearPending() | ||
c.unsafeCommitOffsetToStream() | ||
c.pollCommits.Start() | ||
|
||
case streamReconnecting: | ||
c.pollCommits.Stop() | ||
|
||
case streamTerminated: | ||
c.unsafeInitiateShutdown(serviceTerminated, c.stream.Error()) | ||
} | ||
} | ||
|
||
func (c *committer) onResponse(response interface{}) { | ||
c.mu.Lock() | ||
defer c.mu.Unlock() | ||
|
||
// If an inconsistency is detected in the server's responses, immediately | ||
// terminate the committer, as correct processing of commits cannot be | ||
// guaranteed. | ||
processResponse := func() error { | ||
commitResponse, _ := response.(*pb.StreamingCommitCursorResponse) | ||
if commitResponse.GetCommit() == nil { | ||
return errInvalidCommitResponse | ||
} | ||
numAcked := commitResponse.GetCommit().GetAcknowledgedCommits() | ||
if numAcked <= 0 { | ||
return fmt.Errorf("pubsublite: server acknowledged an invalid commit count: %d", numAcked) | ||
} | ||
if err := c.cursorTracker.ConfirmOffsets(numAcked); err != nil { | ||
return err | ||
} | ||
c.unsafeCheckDone() | ||
return nil | ||
} | ||
if err := processResponse(); err != nil { | ||
c.unsafeInitiateShutdown(serviceTerminated, err) | ||
} | ||
} | ||
|
||
// commitOffsetToStream is called by the periodic background task. | ||
func (c *committer) commitOffsetToStream() { | ||
c.mu.Lock() | ||
defer c.mu.Unlock() | ||
c.unsafeCommitOffsetToStream() | ||
} | ||
|
||
func (c *committer) unsafeCommitOffsetToStream() { | ||
nextOffset := c.cursorTracker.NextOffset() | ||
if nextOffset == nilCursorOffset { | ||
return | ||
} | ||
|
||
req := &pb.StreamingCommitCursorRequest{ | ||
Request: &pb.StreamingCommitCursorRequest_Commit{ | ||
Commit: &pb.SequencedCommitCursorRequest{ | ||
Cursor: &pb.Cursor{Offset: nextOffset}, | ||
}, | ||
}, | ||
} | ||
if c.stream.Send(req) { | ||
c.cursorTracker.AddPending(nextOffset) | ||
} | ||
} | ||
|
||
func (c *committer) unsafeInitiateShutdown(targetStatus serviceStatus, err error) { | ||
if !c.unsafeUpdateStatus(targetStatus, err) { | ||
return | ||
} | ||
|
||
// If it's a graceful shutdown, expedite sending final commits to the stream. | ||
if targetStatus == serviceTerminating { | ||
c.unsafeCommitOffsetToStream() | ||
c.unsafeCheckDone() | ||
return | ||
} | ||
// Otherwise immediately terminate the stream. | ||
c.unsafeTerminate() | ||
} | ||
|
||
func (c *committer) unsafeCheckDone() { | ||
// If the user stops the subscriber, they will no longer receive messages, but | ||
// the commit stream remains open to process acks for outstanding messages. | ||
if c.status == serviceTerminating && c.cursorTracker.Done() && c.acks.Empty() { | ||
c.unsafeTerminate() | ||
} | ||
} | ||
|
||
func (c *committer) unsafeTerminate() { | ||
c.acks.Release() | ||
c.pollCommits.Stop() | ||
c.stream.Stop() | ||
} |
Oops, something went wrong.