Pulsar Go client

Pulsar Go client

提示：目前，CGo 客户端将被废弃，如果你想要了解更多关于 CGo 客户端的信息，请参阅 CGo 客户端文档

您可以使用 Pulsar Go 客户端来创建使用 Go 语言的 Pulsar 生产者（producer）、消费者（consumer）和 readers 。

API docs available as well
For standard API docs, consult the Godoc.

安装

安装 go 工具包

You can install the pulsar library locally using go get.

$ get -u "github.com/apache/pulsar-client-go/pulsar"

Once installed locally, you can import it into your project:

import "github.com/apache/pulsar-client-go/pulsar"

连接 URL

To connect to Pulsar using client libraries, you need to specify a Pulsar protocol URL.

Pulsar protocol URLs are assigned to specific clusters, use the pulsar scheme and have a default port of 6650. Here’s an example for localhost:

pulsar://localhost:6650

如果你有多个brokers，你可以使用下面的方法设置URl

pulsar://localhost:6550,localhost:6651,localhost:6652

A URL for a production Pulsar cluster may look something like this:

pulsar://pulsar.us-west.example.com:6650

If you’re using TLS authentication, the URL will look like something like this:

pulsar+ssl://pulsar.us-west.example.com:6651

创建客户端

In order to interact with Pulsar, you’ll first need a Client object. You can create a client object using the NewClient function, passing in a ClientOptions object (more on configuration below). 下面是一个示例：

import (
    "log"
    "time"
    "github.com/apache/pulsar-client-go/pulsar"
)
func main() {
    client, err := pulsar.NewClient(pulsar.ClientOptions{
        URL:               "pulsar://localhost:6650",
        OperationTimeout:  30 * time.Second,
        ConnectionTimeout: 30 * time.Second,
    })
    if err != nil {
        log.Fatalf("Could not instantiate Pulsar client: %v", err)
    }
    defer client.Close()
}

如果你有多个broker，你可以想这样初始化PulsarClient.

import (
    "log"
    "time"
    "github.com/apache/pulsar-client-go/pulsar"
)
func main() {
    client, err := pulsar.NewClient(pulsar.ClientOptions{
        URL: "pulsar://localhost:6650,localhost:6651,localhost:6652",
        OperationTimeout:  30 * time.Second,
        ConnectionTimeout: 30 * time.Second,
    })
    if err != nil {
        log.Fatalf("Could not instantiate Pulsar client: %v", err)
    }
    defer client.Close()
}

The following configurable parameters are available for Pulsar clients:

Name | Description | Default | :———— | :————— |:————— | | URL | Configure the service URL for the Pulsar service.

If you have multiple brokers, you can set multiple Pulsar cluster addresses for a client.

Producers

Pulsar producers publish messages to Pulsar topics. You can configure Go producers using a ProducerOptions object. 下面是一个示例：

producer, err := client.CreateProducer(pulsar.ProducerOptions{
    Topic: "my-topic",
})
if err != nil {
    log.Fatal(err)
}
_, err = producer.Send(context.Background(), &pulsar.ProducerMessage{
    Payload: []byte("hello"),
})
defer producer.Close()
if err != nil {
    fmt.Println("Failed to publish message", err)
}
fmt.Println("Published message")

Producer operations

Pulsar Go producers have the following methods available:

Method	说明	Return type
`Topic()`	Fetches the producer’s topic	`string`
`Name()`	Fetches the producer’s name	`string`
`Send(context.Context, ProducerMessage)`	Publishes a message to the producer’s topic. This call will block until the message is successfully acknowledged by the Pulsar broker, or an error will be thrown if the timeout set using the `SendTimeout` in the producer’s configuration is exceeded.	(MessageID, error)
`SendAsync(context.Context, ProducerMessage, func(MessageID, *ProducerMessage, error))`	Send a message, this call will be blocking until is successfully acknowledged by the Pulsar broker.
`LastSequenceID()`	Get the last sequence id that was published by this producer. his represent either the automatically assigned or custom sequence id (set on the ProducerMessage) that was published and acknowledged by the broker.	int64
`Flush()`	Flush all the messages buffered in the client and wait until all messages have been successfully persisted.	error
`Close()`	Closes the producer and releases all resources allocated to it. If `Close()` is called then no more messages will be accepted from the publisher. This method will block until all pending publish requests have been persisted by Pulsar. If an error is thrown, no pending writes will be retried.

生产者示例

如何在生产者中使用消息路由器

client, err := NewClient(pulsar.ClientOptions{
    URL: serviceURL,
})
if err != nil {
    log.Fatal(err)
}
defer client.Close()
// Only subscribe on the specific partition
consumer, err := client.Subscribe(pulsar.ConsumerOptions{
    Topic:            "my-partitioned-topic-partition-2",
    SubscriptionName: "my-sub",
})
if err != nil {
    log.Fatal(err)
}
defer consumer.Close()
producer, err := client.CreateProducer(pulsar.ProducerOptions{
    Topic: "my-partitioned-topic",
    MessageRouter: func(msg *ProducerMessage, tm TopicMetadata) int {
        fmt.Println("Routing message ", msg, " -- Partitions: ", tm.NumPartitions())
        return 2
    },
})
if err != nil {
    log.Fatal(err)
}
defer producer.Close()

How to use schema interface in producer

type testJSON struct {
    ID   int    `json:"id"`
    Name string `json:"name"`
}

var (
    exampleSchemaDef = "{\"type\":\"record\",\"name\":\"Example\",\"namespace\":\"test\"," +
        "\"fields\":[{\"name\":\"ID\",\"type\":\"int\"},{\"name\":\"Name\",\"type\":\"string\"}]}"
)

client, err := NewClient(pulsar.ClientOptions{
    URL: "pulsar://localhost:6650",
})
if err != nil {
    log.Fatal(err)
}
defer client.Close()
properties := make(map[string]string)
properties["pulsar"] = "hello"
jsonSchemaWithProperties := NewJSONSchema(exampleSchemaDef, properties)
producer, err := client.CreateProducer(ProducerOptions{
    Topic:  "jsonTopic",
    Schema: jsonSchemaWithProperties,
})
assert.Nil(t, err)
_, err = producer.Send(context.Background(), &ProducerMessage{
    Value: &testJSON{
        ID:   100,
        Name: "pulsar",
    },
})
if err != nil {
    log.Fatal(err)
}
producer.Close()

如何在生产者中使用相应的延迟

client, err := NewClient(pulsar.ClientOptions{
    URL: "pulsar://localhost:6650",
})
if err != nil {
    log.Fatal(err)
}
defer client.Close()
topicName := newTopicName()
producer, err := client.CreateProducer(pulsar.ProducerOptions{
    Topic: topicName,
})
if err != nil {
    log.Fatal(err)
}
defer producer.Close()
consumer, err := client.Subscribe(pulsar.ConsumerOptions{
    Topic:            topicName,
    SubscriptionName: "subName",
    Type:             Shared,
})
if err != nil {
    log.Fatal(err)
}
defer consumer.Close()
ID, err := producer.Send(context.Background(), &pulsar.ProducerMessage{
    Payload:      []byte(fmt.Sprintf("test")),
    DeliverAfter: 3 * time.Second,
})
if err != nil {
    log.Fatal(err)
}
fmt.Println(ID)
ctx, canc := context.WithTimeout(context.Background(), 1*time.Second)
msg, err := consumer.Receive(ctx)
if err != nil {
    log.Fatal(err)
}
fmt.Println(msg.Payload())
canc()
ctx, canc = context.WithTimeout(context.Background(), 5*time.Second)
msg, err = consumer.Receive(ctx)
if err != nil {
    log.Fatal(err)
}
fmt.Println(msg.Payload())
canc()

Producer 配置

Consumers

Pulsar consumers subscribe to one or more Pulsar topics and listen for incoming messages produced on that topic/those topics. You can configure Go consumers using a ConsumerOptions object. Here’s a basic example that uses channels:

consumer, err := client.Subscribe(pulsar.ConsumerOptions{
    Topic:            "topic-1",
    SubscriptionName: "my-sub",
    Type:             pulsar.Shared,
})
if err != nil {
    log.Fatal(err)
}
defer consumer.Close()
for i := 0; i < 10; i++ {
    msg, err := consumer.Receive(context.Background())
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Received message msgId: %#v -- content: '%s'\n",
        msg.ID(), string(msg.Payload()))
    consumer.Ack(msg)
}
if err := consumer.Unsubscribe(); err != nil {
    log.Fatal(err)
}

消费者操作

Pulsar Go consumers have the following methods available:

Method	说明	Return type
`Subscription()`	Returns the consumer’s subscription name	`string`
`Unsubcribe()`	Unsubscribes the consumer from the assigned topic. Throws an error if the unsubscribe operation is somehow unsuccessful.	`error`
`Receive(context.Context)`	Receives a single message from the topic. This method blocks until a message is available.	`(Message, error)`
`Chan()`	Chan returns a channel from which to consume messages.	`<-chan ConsumerMessage`
`Ack(Message)`	Acknowledges a message to the Pulsar broker
`AckID(MessageID)`	Acknowledges a message to the Pulsar broker by message ID
`ReconsumeLater(msg Message, delay time.Duration)`	ReconsumeLater mark a message for redelivery after custom delay
`Nack(Message)`	Acknowledge the failure to process a single message.
`NackID(MessageID)`	Acknowledge the failure to process a single message.
`Seek(msgID MessageID)`	Reset the subscription associated with this consumer to a specific message id. The message id can either be a specific message or represent the first or last messages in the topic.	`error`
`SeekByTime(time time.Time)`	Reset the subscription associated with this consumer to a specific message publish time.	`error`
`Close()`	Closes the consumer, disabling its ability to receive messages from the broker
`Name()`	Name returns the name of consumer	`string`

Receive example

How to use regex consumer

client, err := pulsar.NewClient(pulsar.ClientOptions{
    URL: "pulsar://localhost:6650",
})
defer client.Close()
p, err := client.CreateProducer(pulsar.ProducerOptions{
    Topic:           topicInRegex,
    DisableBatching: true,
})
if err != nil {
    log.Fatal(err)
}
defer p.Close()
topicsPattern := fmt.Sprintf("persistent://%s/foo.*", namespace)
opts := pulsar.ConsumerOptions{
    TopicsPattern:    topicsPattern,
    SubscriptionName: "regex-sub",
}
consumer, err := client.Subscribe(opts)
if err != nil {
    log.Fatal(err)
}
defer consumer.Close()

如何使用多topic 的Consumer

func newTopicName() string {
    return fmt.Sprintf("my-topic-%v", time.Now().Nanosecond())
}
topic1 := "topic-1"
topic2 := "topic-2"
client, err := NewClient(pulsar.ClientOptions{
    URL: "pulsar://localhost:6650",
})
if err != nil {
    log.Fatal(err)
}
topics := []string{topic1, topic2}
consumer, err := client.Subscribe(pulsar.ConsumerOptions{
    Topics:           topics,
    SubscriptionName: "multi-topic-sub",
})
if err != nil {
    log.Fatal(err)
}
defer consumer.Close()

如何使用消费监听器

import (
    "fmt"
    "log"
    "github.com/apache/pulsar-client-go/pulsar"
)
func main() {
    client, err := pulsar.NewClient(pulsar.ClientOptions{URL: "pulsar://localhost:6650"})
    if err != nil {
        log.Fatal(err)
    }
    defer client.Close()
    channel := make(chan pulsar.ConsumerMessage, 100)
    options := pulsar.ConsumerOptions{
        Topic:            "topic-1",
        SubscriptionName: "my-subscription",
        Type:             pulsar.Shared,
    }
    options.MessageChannel = channel
    consumer, err := client.Subscribe(options)
    if err != nil {
        log.Fatal(err)
    }
    defer consumer.Close()
    // Receive messages from channel. The channel returns a struct which contains message and the consumer from where
    // the message was received. It's not necessary here since we have 1 single consumer, but the channel could be
    // shared across multiple consumers as well
    for cm := range channel {
        msg := cm.Message
        fmt.Printf("Received message  msgId: %v -- content: '%s'\n",
            msg.ID(), string(msg.Payload()))
        consumer.Ack(msg)
    }
}

如何使用消费者接收超时器

client, err := NewClient(pulsar.ClientOptions{
    URL: "pulsar://localhost:6650",
})
if err != nil {
    log.Fatal(err)
}
defer client.Close()
topic := "test-topic-with-no-messages"
ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
defer cancel()
// create consumer
consumer, err := client.Subscribe(pulsar.ConsumerOptions{
    Topic:            topic,
    SubscriptionName: "my-sub1",
    Type:             Shared,
})
if err != nil {
    log.Fatal(err)
}
defer consumer.Close()
msg, err := consumer.Receive(ctx)
fmt.Println(msg.Payload())
if err != nil {
    log.Fatal(err)
}

How to use schema in consumer

type testJSON struct {
    ID   int    `json:"id"`
    Name string `json:"name"`
}

var (
    exampleSchemaDef = "{\"type\":\"record\",\"name\":\"Example\",\"namespace\":\"test\"," +
        "\"fields\":[{\"name\":\"ID\",\"type\":\"int\"},{\"name\":\"Name\",\"type\":\"string\"}]}"
)

client, err := NewClient(pulsar.ClientOptions{
    URL: "pulsar://localhost:6650",
})
if err != nil {
    log.Fatal(err)
}
defer client.Close()
var s testJSON
consumerJS := NewJSONSchema(exampleSchemaDef, nil)
consumer, err := client.Subscribe(ConsumerOptions{
    Topic:                       "jsonTopic",
    SubscriptionName:            "sub-1",
    Schema:                      consumerJS,
    SubscriptionInitialPosition: SubscriptionPositionEarliest,
})
assert.Nil(t, err)
msg, err := consumer.Receive(context.Background())
assert.Nil(t, err)
err = msg.GetSchemaValue(&s)
if err != nil {
    log.Fatal(err)
}
defer consumer.Close()

Consumer configuration

Reader

Pulsar readers process messages from Pulsar topics. Readers are different from consumers because with readers you need to explicitly specify which message in the stream you want to begin with (consumers, on the other hand, automatically begin with the most recent unacked message). You can configure Go readers using a ReaderOptions object. 下面是一个示例：

reader, err := client.CreateReader(pulsar.ReaderOptions{
    Topic:          "topic-1",
    StartMessageID: pulsar.EarliestMessageID(),
})
if err != nil {
    log.Fatal(err)
}
defer reader.Close()

Reader operations

Pulsar Go readers have the following methods available:

Method	说明	Return type
`Topic()`	Returns the reader’s topic	`string`
`Next(context.Context)`	Receives the next message on the topic (analogous to the `Receive` method for consumers). This method blocks until a message is available.	`(Message, error)`
`HasNext()`	Check if there is any message available to read from the current position	(bool, error)
`Close()`	Closes the reader, disabling its ability to receive messages from the broker	`error`
`Seek(MessageID)`	Reset the subscription associated with this reader to a specific message ID	`error`
`SeekByTime(time time.Time)`	Reset the subscription associated with this reader to a specific message publish time	`error`

Reader 示例

如何使用阅读器读取“下一个”消息

Here’s an example usage of a Go reader that uses the Next() method to process incoming messages:

import (
    "context"
    "fmt"
    "log"
    "github.com/apache/pulsar-client-go/pulsar"
)
func main() {
    client, err := pulsar.NewClient(pulsar.ClientOptions{URL: "pulsar://localhost:6650"})
    if err != nil {
        log.Fatal(err)
    }
    defer client.Close()
    reader, err := client.CreateReader(pulsar.ReaderOptions{
        Topic:          "topic-1",
        StartMessageID: pulsar.EarliestMessageID(),
    })
    if err != nil {
        log.Fatal(err)
    }
    defer reader.Close()
    for reader.HasNext() {
        msg, err := reader.Next(context.Background())
        if err != nil {
            log.Fatal(err)
        }
        fmt.Printf("Received message msgId: %#v -- content: '%s'\n",
            msg.ID(), string(msg.Payload()))
    }
}

In the example above, the reader begins reading from the earliest available message (specified by pulsar.EarliestMessage). The reader can also begin reading from the latest message (pulsar.LatestMessage) or some other message ID specified by bytes using the DeserializeMessageID function, which takes a byte array and returns a MessageID object. 下面是一个示例：

lastSavedId := // Read last saved message id from external store as byte[]
reader, err := client.CreateReader(pulsar.ReaderOptions{
    Topic:          "my-golang-topic",
    StartMessageID: pulsar.DeserializeMessageID(lastSavedId),
})

如何使用阅读器读取特定消息

client, err := NewClient(pulsar.ClientOptions{
    URL: lookupURL,
})
if err != nil {
    log.Fatal(err)
}
defer client.Close()
topic := "topic-1"
ctx := context.Background()
// create producer
producer, err := client.CreateProducer(pulsar.ProducerOptions{
    Topic:           topic,
    DisableBatching: true,
})
if err != nil {
    log.Fatal(err)
}
defer producer.Close()
// send 10 messages
msgIDs := [10]MessageID{}
for i := 0; i < 10; i++ {
    msgID, err := producer.Send(ctx, &pulsar.ProducerMessage{
        Payload: []byte(fmt.Sprintf("hello-%d", i)),
    })
    assert.NoError(t, err)
    assert.NotNil(t, msgID)
    msgIDs[i] = msgID
}
// create reader on 5th message (not included)
reader, err := client.CreateReader(pulsar.ReaderOptions{
    Topic:          topic,
    StartMessageID: msgIDs[4],
})
if err != nil {
    log.Fatal(err)
}
defer reader.Close()
// receive the remaining 5 messages
for i := 5; i < 10; i++ {
    msg, err := reader.Next(context.Background())
    if err != nil {
    log.Fatal(err)
}
// create reader on 5th message (included)
readerInclusive, err := client.CreateReader(pulsar.ReaderOptions{
    Topic:                   topic,
    StartMessageID:          msgIDs[4],
    StartMessageIDInclusive: true,
})
if err != nil {
    log.Fatal(err)
}
defer readerInclusive.Close()

Reader configuration

消息

The Pulsar Go client provides a ProducerMessage interface that you can use to construct messages to producer on Pulsar topics. Here’s an example message:

msg := pulsar.ProducerMessage{
    Payload: []byte("Here is some message data"),
    Key: "message-key",
    Properties: map[string]string{
        "foo": "bar",
    },
    EventTime: time.Now(),
    ReplicationClusters: []string{"cluster1", "cluster3"},
}
if _, err := producer.send(msg); err != nil {
    log.Fatalf("Could not publish message due to: %v", err)
}

The following methods parameters are available for ProducerMessage objects:

参数名	说明
`Payload`	The actual data payload of the message
`Value`	Value and payload is mutually exclusive, `Value interface{}` for schema message.
`Key`	The optional key associated with the message (particularly useful for things like topic compaction)
`OrderingKey`	OrderingKey sets the ordering key of the message.
`属性`	A key-value map (both keys and values must be strings) for any application-specific metadata attached to the message
`EventTime`	The timestamp associated with the message
`ReplicationClusters`	The clusters to which this message will be replicated. Pulsar brokers handle message replication automatically; you should only change this setting if you want to override the broker default.
`SequenceID`	Set the sequence id to assign to the current message
`DeliverAfter`	仅在特定的相对延迟后才请求传递消息
`DeliverAt`	仅在特定的绝对时间戳或(在特定的绝对时间戳)之后传递消息

TLS 加密和身份验证

In order to use TLS encryption, you’ll need to configure your client to do so:

使用 pulsar+ssl URL 类型
设置 TLSTrustCertCertsFilePath 到你的客户端和 Pulsar broker 使用的 TLS 证书路径
配置 认证 选项

下面是一个示例：

opts := pulsar.ClientOptions{
    URL: "pulsar+ssl://my-cluster.com:6651",
    TLSTrustCertsFilePath: "/path/to/certs/my-cert.csr",
    Authentication: NewAuthenticationTLS("my-cert.pem", "my-key.pem"),
}

OAuth2 身份验证

To use OAuth2 authentication, you’ll need to configure your client to perform the following operations. This example shows how to configure OAuth2 authentication.

oauth := pulsar.NewAuthenticationOAuth2(map[string]string{
        "type":       "client_credentials",
        "issuerUrl":  "https://dev-kt-aa9ne.us.auth0.com",
        "audience":   "https://dev-kt-aa9ne.us.auth0.com/api/v2/",
        "privateKey": "/path/to/privateKey",
        "clientId":   "0Xx...Yyxeny",
    })
client, err := pulsar.NewClient(pulsar.ClientOptions{
        URL:              "pulsar://my-cluster:6650",
        Authentication:   oauth,
})