lostluck commented on code in PR #17955: URL: https://github.com/apache/beam/pull/17955#discussion_r894809823
########## sdks/go/examples/native_wordcap/nativepubsubio/native.go: ########## @@ -0,0 +1,236 @@ +// Licensed to the Apache Software Foundation (ASF) under one or more +// contributor license agreements. See the NOTICE file distributed with +// this work for additional information regarding copyright ownership. +// The ASF licenses this file to You 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 nativepubsubio contains a Golang implementation of streaming reads +// and writes to PubSub. This is not as fully featured as the cross-language +// pubsubio package present in the Beam Go repository and should not be used +// in place of it. +package nativepubsubio + +import ( + "context" + "errors" + "fmt" + "time" + + "cloud.google.com/go/pubsub" + "github.com/apache/beam/sdks/v2/go/pkg/beam" + "github.com/apache/beam/sdks/v2/go/pkg/beam/core/sdf" + "github.com/apache/beam/sdks/v2/go/pkg/beam/log" + "github.com/apache/beam/sdks/v2/go/pkg/beam/register" + "github.com/apache/beam/sdks/v2/go/pkg/beam/util/pubsubx" +) + +func init() { + register.DoFn4x2[beam.BundleFinalization, *sdf.LockRTracker, []byte, func(beam.EventTime, []byte), sdf.ProcessContinuation, error](&PubSubRead{}) + register.DoFn1x1[[]byte, error](&PubSubWrite{}) + register.Emitter2[beam.EventTime, []byte]() +} + +// PubSubRead is a structural DoFn representing a read from a given subscription ID. +type PubSubRead struct { + ProjectID string + Subscription string + Client *pubsub.Client + ProcessedMessages []*pubsub.Message +} + +// NewPubSubRead inserts an unbounded read from a PubSub topic into the pipeline. If an existing subscription +// is provided, the DoFn will read using that subscription; otherwise, a new subscription to the topic +// will be created using the provided subscription name. +func NewPubSubRead(ctx context.Context, projectID, topic, subscription string) (*PubSubRead, error) { + if topic == "" { + return nil, errors.New("please provide either a topic to read from") + } + client, err := pubsub.NewClient(ctx, projectID) + if err != nil { + return nil, err + } + + top := client.Topic(topic) + if ok, err := top.Exists(ctx); !ok || err != nil { + return nil, fmt.Errorf("failed to get topic; exists: %v, error: %v", ok, err) + } + sub, err := pubsubx.EnsureSubscription(ctx, client, topic, subscription) + if err != nil { + return nil, err + } + return &PubSubRead{ProjectID: projectID, Subscription: sub.ID()}, nil +} + +// CreateInitialRestriction() establishes the PubSub subscription ID as the +// initial restriction +func (r *PubSubRead) CreateInitialRestriction(_ []byte) string { + return r.Subscription +} + +// CreateTracker wraps the PubSub subscription ID in a StaticRTracker +// and applies a mutex via LockRTracker. +func (r *PubSubRead) CreateTracker(rest string) *sdf.LockRTracker { + return sdf.NewLockRTracker(NewSubscriptionRTracker(rest)) +} + +// RestrictionSize always returns 1.0, as the restriction is always 1 subscription. +func (r *PubSubRead) RestrictionSize(_ []byte, rest string) float64 { + return 1.0 +} + +// SplitRestriction is a no-op as the restriction cannot be split. +func (r *PubSubRead) SplitRestriction(_ []byte, rest string) []string { + return []string{rest} +} + +// ProcessElement initializes a PubSub client if one has not been created already, reads from the PubSub subscription, +// and emits elements as it reads them. If no messages are available, the DoFn will schedule itself to resume processing +// later. If polling the subscription returns an error, the error will be logged and the DoFn will not reschedule itself. +func (r *PubSubRead) ProcessElement(bf beam.BundleFinalization, rt *sdf.LockRTracker, _ []byte, emit func(beam.EventTime, []byte)) (sdf.ProcessContinuation, error) { + // Register finalization callback + bf.RegisterCallback(5*time.Minute, func() error { + for _, m := range r.ProcessedMessages { + m.Ack() + } + r.ProcessedMessages = []*pubsub.Message{} + return nil + }) + + // Initialize PubSub client if one has not been created already + if r.Client == nil { + client, err := pubsub.NewClient(context.Background(), r.ProjectID) + if err != nil { + return sdf.StopProcessing(), err + } + r.Client = client + } + + for { + ok := rt.TryClaim(r.Subscription) + if !ok { + return sdf.ResumeProcessingIn(5 * time.Second), nil + } + sub := r.Client.Subscription(r.Subscription) + ctx, cFn := context.WithCancel(context.Background()) + + // Because emitters are not thread safe and synchronous Receive() behavior + // is deprecated, we have to collect messages in a goroutine and pipe them + // out through a channel. + messChan := make(chan *pubsub.Message, 1) + go func(sendch chan<- *pubsub.Message) { + err := sub.Receive(ctx, func(ctx context.Context, m *pubsub.Message) { + messChan <- m + }) + if (err != nil) && (err != context.Canceled) { + log.Errorf(ctx, "error reading from PubSub: %v, stopping processing", err) + cFn() + close(messChan) + } + }(messChan) + + // Give the goroutines time to start polling. + time.Sleep(5 * time.Second) Review Comment: Ah I see I forgot to remove my first Boolean suggestion, which I thought I cleaned up after reading timer.Reset's doc. -- This is an automated message from the Apache Git Service. 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