Google Pub / Sub消息订购不起作用或将延迟增加到10秒以上？

如何解决Google Pub / Sub消息订购不起作用或将延迟增加到10秒以上？

我正在尝试做一个简化的示例，演示Google Pub / Sub的消息排序功能（https://cloud.google.com/pubsub/docs/ordering）的使用。在这些文档中，为订阅启用消息排序后，

设置了消息订购属性之后，发布/订阅服务以与发布/订阅服务接收消息的顺序相同的订购密钥传递消息。例如，如果发布者使用相同的订购密钥发送两条消息，则发布/订阅服务将首先传递最早的消息。

我用它来编写以下示例：

A

首先，我尝试了该程序，但未在package main import ( "context" "log" "time" "cloud.google.com/go/pubsub" uuid "github.com/satori/go.uuid" ) func main() { client,err := pubsub.NewClient(context.Background(),"my-project") if err != nil { log.Fatalf("NewClient: %v",err) } topicID := "test-topic-" + uuid.NewV4().String() topic,err := client.CreateTopic(context.Background(),topicID) if err != nil { log.Fatalf("CreateTopic: %v",err) } defer topic.Delete(context.Background()) subID := "test-subscription-" + uuid.NewV4().String() sub,err := client.CreateSubscription(context.Background(),subID,pubsub.SubscriptionConfig{ Topic: topic,EnableMessageOrdering: true,}) if err != nil { log.Fatalf("CreateSubscription: %v",err) } defer sub.Delete(context.Background()) ctx,cancel := context.WithCancel(context.Background()) defer cancel() messageReceived := make(chan struct{}) go sub.Receive(ctx,func(ctx context.Context,msg *pubsub.Message) { log.Printf("Received message with ordering key %s: %s",msg.OrderingKey,msg.Data) msg.Ack() messageReceived <- struct{}{} }) topic.Publish(context.Background(),&pubsub.Message{Data: []byte("Dang1!"),OrderingKey: "foobar"}) topic.Publish(context.Background(),&pubsub.Message{Data: []byte("Dang2!"),OrderingKey: "foobar"}) for i := 0; i < 2; i++ { select { case <-messageReceived: case <-time.After(10 * time.Second): log.Fatal("Expected to receive a message,but timed out after 10 seconds.") } } } 调用中指定OrderingKey: "foobar"。这产生了以下输出：

topic.Publish()

换句话说，接收消息的顺序与发布时的顺序不同，在我的用例中，这是不可取的，我想通过指定> go run main.go 2020/08/10 21:40:34 Received message with ordering key : Dang2! 2020/08/10 21:40:34 Received message with ordering key : Dang1!

来防止

但是，一旦我在发布调用中添加了OrderingKey，该程序就会在等待接收发布/订阅消息10秒钟后超时：

OrderingKey

我希望现在首先收到消息> go run main.go 2020/08/10 21:44:36 Expected to receive a message,but timed out after 10 seconds. exit status 1 ，然后再收到Dang1!，但是我没有收到任何消息。知道为什么这种情况不会发生吗？

解决方法

发布失败，并出现以下错误：Failed to publish: Topic.EnableMessageOrdering=false,but an OrderingKey was set in Message. Please remove the OrderingKey or turn on Topic.EnableMessageOrdering。

如果您更改发布呼叫以检查错误，则可以看到此信息：

res1 := topic.Publish(context.Background(),&pubsub.Message{Data: []byte("Dang1!"),OrderingKey: "foobar"})
res2 := topic.Publish(context.Background(),&pubsub.Message{Data: []byte("Dang2!"),OrderingKey: "foobar"})

_,err = res1.Get(ctx)
if err != nil {
    fmt.Printf("Failed to publish: %v",err)
    return
}

_,err = res2.Get(ctx)
if err != nil {
    fmt.Printf("Failed to publish: %v",err)
    return
}

要修复此问题，请添加一行以启用您主题上的消息排序。您的主题创建如下：

topic,err := client.CreateTopic(context.Background(),topicID)
if err != nil {
    log.Fatalf("CreateTopic: %v",err)
}
topic.EnableMessageOrdering = true
defer topic.Delete(context.Background())

,

我独立地提出了与Kamal相同的解决方案，只是想分享完整的修订实施：

package main

import (
    "context"
    "flag"
    "log"
    "time"

    "cloud.google.com/go/pubsub"
    uuid "github.com/satori/go.uuid"
)

var enableMessageOrdering bool

func main() {
    flag.BoolVar(&enableMessageOrdering,"enableMessageOrdering",false,"Enable and use Pub/Sub message ordering")
    flag.Parse()

    client,err := pubsub.NewClient(context.Background(),"fleetsmith-dev")
    if err != nil {
        log.Fatalf("NewClient: %v",err)
    }

    topicID := "test-topic-" + uuid.NewV4().String()
    topic,topicID)
    if err != nil {
        log.Fatalf("CreateTopic: %v",err)
    }
    topic.EnableMessageOrdering = enableMessageOrdering
    defer topic.Delete(context.Background())

    subID := "test-subscription-" + uuid.NewV4().String()
    sub,err := client.CreateSubscription(context.Background(),subID,pubsub.SubscriptionConfig{
        Topic:                 topic,EnableMessageOrdering: enableMessageOrdering,})
    if err != nil {
        log.Fatalf("CreateSubscription: %v",err)
    }
    defer sub.Delete(context.Background())

    ctx,cancel := context.WithCancel(context.Background())
    defer cancel()

    messageReceived := make(chan struct{})
    go sub.Receive(ctx,func(ctx context.Context,msg *pubsub.Message) {
        log.Printf("Received message with ordering key %s: %s",msg.OrderingKey,msg.Data)
        msg.Ack()
        messageReceived <- struct{}{}
    })

    msg1,msg2 := &pubsub.Message{Data: []byte("Dang1!")},&pubsub.Message{Data: []byte("Dang2!")}
    if enableMessageOrdering {
        msg1.OrderingKey,msg2.OrderingKey = "foobar","foobar"
    }
    publishMessage(topic,msg1)
    publishMessage(topic,msg2)

    for i := 0; i < 2; i++ {
        select {
        case <-messageReceived:
        case <-time.After(10 * time.Second):
            log.Fatal("Expected to receive a message,but timed out after 10 seconds.")
        }
    }
}

func publishMessage(topic *pubsub.Topic,msg *pubsub.Message) {
    publishResult := topic.Publish(context.Background(),msg)
    messageID,err := publishResult.Get(context.Background())
    if err != nil {
        log.Fatalf("Get: %v",err)
    }
    log.Printf("Published message with ID %s",messageID)
}

在将enableMessageOrdering标志设置为true的情况下被调用时，我首先收到Dang1!，然后收到Dang2!：

> go run main.go --enableMessageOrdering
2020/08/11 05:38:07 Published message with ID 1420685949616723
2020/08/11 05:38:08 Published message with ID 1420726763302425
2020/08/11 05:38:09 Received message with ordering key foobar: Dang1!
2020/08/11 05:38:11 Received message with ordering key foobar: Dang2!

如果没有它，我会像以前一样以相反的顺序收到它们：

> go run main.go
2020/08/11 05:38:47 Published message with ID 1420687395091051
2020/08/11 05:38:47 Published message with ID 1420693737065665
2020/08/11 05:38:48 Received message with ordering key : Dang2!
2020/08/11 05:38:48 Received message with ordering key : Dang1!