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kafka-node

Client for Apache Kafka v0.8+

Kafka-node

Kafka-node is a Node.js client with Zookeeper integration for Apache Kafka 0.8.1 and later.

Table of Contents

Features

  • Consumer and High Level Consumer
  • Producer and High Level Producer
  • Manage topic Offsets
  • SSL connections to brokers (Kafka 0.9+)

Install Kafka

Follow the instructions on the Kafka wiki to build Kafka 0.8 and get a test broker up and running.

API

  • connectionString: Zookeeper connection string, default localhost:2181/
  • clientId: This is a user-supplied identifier for the client application, default kafka-node-client
  • zkOptions: Object, Zookeeper options, see node-zookeeper-client
  • noAckBatchOptions: Object, when requireAcks is disabled on Producer side we can define the batch properties, 'noAckBatchSize' in bytes and 'noAckBatchAge' in milliseconds. The default value is { noAckBatchSize: null, noAckBatchAge: null } and it acts as if there was no batch
  • sslOptions: Object, options to be passed to the tls broker sockets, ex. { rejectUnauthorized: false } (Kafka +0.9)

Closes the connection to Zookeeper and the brokers so that the node process can exit gracefully.

  • cb: Function, the callback
  • client: client which keeps a connection with the Kafka server.
  • options: options for producer,
{
    // Configuration for when to consider a message as acknowledged, default 1 
    requireAcks: 1,
    // The amount of time in milliseconds to wait for all acks before considered, default 100ms 
    ackTimeoutMs: 100,
    // Partitioner type (default = 0, random = 1, cyclic = 2, keyed = 3), default 0 
    partitionerType: 2
}
var kafka = require('kafka-node'),
    Producer = kafka.Producer,
    client = new kafka.Client(),
    producer = new Producer(client);
  • ready: this event is emitted when producer is ready to send messages.
  • error: this is the error event propagates from internal client, producer should always listen it.
  • payloads: Array,array of ProduceRequest, ProduceRequest is a JSON object like:
{
   topic: 'topicName',
   messages: ['message body'], // multi messages should be a array, single message can be just a string or a KeyedMessage instance 
   key: 'theKey', // only needed when using keyed partitioner 
   partition: 0, // default 0 
   attributes: 2 // default: 0 
}
  • cb: Function, the callback

attributes controls compression of the message set. It supports the following values:

  • 0: No compression
  • 1: Compress using GZip
  • 2: Compress using snappy

Example:

var kafka = require('kafka-node'),
    Producer = kafka.Producer,
    KeyedMessage = kafka.KeyedMessage,
    client = new kafka.Client(),
    producer = new Producer(client),
    km = new KeyedMessage('key', 'message'),
    payloads = [
        { topic: 'topic1', messages: 'hi', partition: 0 },
        { topic: 'topic2', messages: ['hello', 'world', km] }
    ];
producer.on('ready', function () {
    producer.send(payloads, function (err, data) {
        console.log(data);
    });
});
 
producer.on('error', function (err) {})

⚠️WARNING: Batch multiple messages of the same topic/partition together as an array on the messages attribute otherwise you may lose messages!

This method is used to create topics on the Kafka server. It only works when auto.create.topics.enable, on the Kafka server, is set to true. Our client simply sends a metadata request to the server which will auto create topics. When async is set to false, this method does not return until all topics are created, otherwise it returns immediately.

  • topics: Array, array of topics
  • async: Boolean, async or sync
  • cb: Function, the callback

Example:

var kafka = require('kafka-node'),
    Producer = kafka.Producer,
    client = new kafka.Client(),
    producer = new Producer(client);
// Create topics sync 
producer.createTopics(['t','t1'], false, function (err, data) {
    console.log(data);
});
// Create topics async 
producer.createTopics(['t'], true, function (err, data) {});
producer.createTopics(['t'], function (err, data) {});// Simply omit 2nd arg 
  • client: client which keeps a connection with the Kafka server. Round-robins produce requests to the available topic partitions
  • options: options for producer,
{
    // Configuration for when to consider a message as acknowledged, default 1 
    requireAcks: 1,
    // The amount of time in milliseconds to wait for all acks before considered, default 100ms 
    ackTimeoutMs: 100,
    // Partitioner type (default = 0, random = 1, cyclic = 2, keyed = 3), default 2 
    partitionerType: 3
}
var kafka = require('kafka-node'),
    HighLevelProducer = kafka.HighLevelProducer,
    client = new kafka.Client(),
    producer = new HighLevelProducer(client);
  • ready: this event is emitted when producer is ready to send messages.
  • error: this is the error event propagates from internal client, producer should always listen it.
  • payloads: Array,array of ProduceRequest, ProduceRequest is a JSON object like:
{
   topic: 'topicName',
   messages: ['message body'], // multi messages should be a array, single message can be just a string, 
   key: 'theKey', // only needed when using keyed partitioner 
   attributes: 1
}
  • cb: Function, the callback

Example:

var kafka = require('kafka-node'),
    HighLevelProducer = kafka.HighLevelProducer,
    client = new kafka.Client(),
    producer = new HighLevelProducer(client),
    payloads = [
        { topic: 'topic1', messages: 'hi' },
        { topic: 'topic2', messages: ['hello', 'world'] }
    ];
producer.on('ready', function () {
    producer.send(payloads, function (err, data) {
        console.log(data);
    });
});

⚠️WARNING: Batch multiple messages of the same topic/partition together as an array on the messages attribute otherwise you may lose messages!

This method is used to create topics on the Kafka server. It only work when auto.create.topics.enable, on the Kafka server, is set to true. Our client simply sends a metadata request to the server which will auto create topics. When async is set to false, this method does not return until all topics are created, otherwise it returns immediately.

  • topics: Array,array of topics
  • async: Boolean,async or sync
  • cb: Function,the callback

Example:

var kafka = require('kafka-node'),
    HighLevelProducer = kafka.HighLevelProducer,
    client = new kafka.Client(),
    producer = new HighLevelProducer(client);
// Create topics sync 
producer.createTopics(['t','t1'], false, function (err, data) {
    console.log(data);
});
// Create topics async 
producer.createTopics(['t'], true, function (err, data) {});
producer.createTopics(['t'], function (err, data) {});// Simply omit 2nd arg 
  • client: client which keeps a connection with the Kafka server. Note: it's recommend that create new client for different consumers.
  • payloads: Array,array of FetchRequest, FetchRequest is a JSON object like:
{
   topic: 'topicName',
   offset: 0, //default 0 
}
  • options: options for consumer,
{
    groupId: 'kafka-node-group',//consumer group id, default `kafka-node-group` 
    // Auto commit config 
    autoCommit: true,
    autoCommitIntervalMs: 5000,
    // The max wait time is the maximum amount of time in milliseconds to block waiting if insufficient data is available at the time the request is issued, default 100ms 
    fetchMaxWaitMs: 100,
    // This is the minimum number of bytes of messages that must be available to give a response, default 1 byte 
    fetchMinBytes: 1,
    // The maximum bytes to include in the message set for this partition. This helps bound the size of the response. 
    fetchMaxBytes: 1024 * 1024,
    // If set true, consumer will fetch message from the given offset in the payloads 
    fromOffset: false,
    // If set to 'buffer', values will be returned as raw buffer objects. 
    encoding: 'utf8'
}

Example:

var kafka = require('kafka-node'),
    Consumer = kafka.Consumer,
    client = new kafka.Client(),
    consumer = new Consumer(
        client,
        [
            { topic: 't', partition: 0 }, { topic: 't1', partition: 1 }
        ],
        {
            autoCommit: false
        }
    );

By default, we will consume messages from the last committed offset of the current group

  • onMessage: Function, callback when new message comes

Example:

consumer.on('message', function (message) {
    console.log(message);
});

Add topics to current consumer, if any topic to be added not exists, return error

  • topics: Array, array of topics to add
  • cb: Function,the callback
  • fromOffset: Boolean, if true, the consumer will fetch message from the specified offset, otherwise it will fetch message from the last commited offset of the topic.

Example:

consumer.addTopics(['t1', 't2'], function (err, added) {
});
 
or
 
consumer.addTopics([{ topic: 't1', offset: 10 }], function (err, added) {
}, true);
  • topics: Array, array of topics to remove
  • cb: Function, the callback

Example:

consumer.removeTopics(['t1', 't2'], function (err, removed) {
});

Commit offset of the current topics manually, this method should be called when a consumer leaves

  • cb: Function, the callback

Example:

consumer.commit(function(err, data) {
});

Set offset of the given topic

  • topic: String

  • partition: Number

  • offset: Number

Example:

consumer.setOffset('topic', 0, 0);

Pause the consumer. Calling pause does not automatically stop messages from being emitted. This is because pause just stops the kafka consumer fetch loop. Each iteration of the fetch loop can obtain a batch of messages (limited by fetchMaxBytes).

Resume the consumer. Resumes the fetch loop.

Pause specify topics

consumer.pauseTopics([
    'topic1',
    { topic: 'topic2', partition: 0 }
]);

Resume specify topics

consumer.resumeTopics([
    'topic1',
    { topic: 'topic2', partition: 0 }
]);
  • force: Boolean, if set to true, it forces the consumer to commit the current offset before closing, default false

Example

consumer.close(true, cb);
consumer.close(cb); //force is disabled 
  • client: client which keeps a connection with the Kafka server.
  • payloads: Array,array of FetchRequest, FetchRequest is a JSON object like:
{
   topic: 'topicName'
}
  • options: options for consumer,
{
    // Consumer group id, deafult `kafka-node-group` 
    groupId: 'kafka-node-group',
    // Optional consumer id, defaults to groupId + uuid 
    id: 'my-consumer-id',
    // Auto commit config 
    autoCommit: true,
    autoCommitIntervalMs: 5000,
    // The max wait time is the maximum amount of time in milliseconds to block waiting if insufficient data is available at the time the request is issued, default 100ms 
    fetchMaxWaitMs: 100,
    // This is the minimum number of bytes of messages that must be available to give a response, default 1 byte 
    fetchMinBytes: 1,
    // The maximum bytes to include in the message set for this partition. This helps bound the size of the response. 
    fetchMaxBytes: 1024 * 1024,
    // If set true, consumer will fetch message from the given offset in the payloads 
    fromOffset: false,
    // If set to 'buffer', values will be returned as raw buffer objects. 
    encoding: 'utf8'
}

Example:

var kafka = require('kafka-node'),
    HighLevelConsumer = kafka.HighLevelConsumer,
    client = new kafka.Client(),
    consumer = new HighLevelConsumer(
        client,
        [
            { topic: 't' }, { topic: 't1' }
        ],
        {
            groupId: 'my-group'
        }
    );

By default, we will consume messages from the last committed offset of the current group

  • onMessage: Function, callback when new message comes

Example:

consumer.on('message', function (message) {
    console.log(message);
});

Add topics to current consumer, if any topic to be added not exists, return error

  • topics: Array, array of topics to add
  • cb: Function,the callback
  • fromOffset: Boolean, if true, the consumer will fetch message from the specified offset, otherwise it will fetch message from the last commited offset of the topic.

Example:

consumer.addTopics(['t1', 't2'], function (err, added) {
});
 
or
 
consumer.addTopics([{ topic: 't1', offset: 10 }], function (err, added) {
}, true);
  • topics: Array, array of topics to remove
  • cb: Function, the callback

Example:

consumer.removeTopics(['t1', 't2'], function (err, removed) {
});

Commit offset of the current topics manually, this method should be called when a consumer leaves

  • cb: Function, the callback

Example:

consumer.commit(function(err, data) {
});

Set offset of the given topic

  • topic: String

  • partition: Number

  • offset: Number

Example:

consumer.setOffset('topic', 0, 0);

Pause the consumer. Calling pause does not automatically stop messages from being emitted. This is because pause just stops the kafka consumer fetch loop. Each iteration of the fetch loop can obtain a batch of messages (limited by fetchMaxBytes).

Resume the consumer. Resumes the fetch loop.

  • force: Boolean, if set to true, it forces the consumer to commit the current offset before closing, default false

Example:

consumer.close(true, cb);
consumer.close(cb); //force is disabled 
  • client: client which keeps a connection with the Kafka server.
  • ready: when zookeeper is ready
  • connect when broker is ready

Fetch the available offset of a specific topic-partition

  • payloads: Array,array of OffsetRequest, OffsetRequest is a JSON object like:
{
   topic: 'topicName',
   partition: 0, //default 0 
   // time: 
   // Used to ask for all messages before a certain time (ms), default Date.now(), 
   // Specify -1 to receive the latest offsets and -2 to receive the earliest available offset. 
   time: Date.now(),
   maxNum: 1 //default 1 
}
  • cb: Function, the callback

Example

var kafka = require('kafka-node'),
    client = new kafka.Client(),
    offset = new kafka.Offset(client);
    offset.fetch([
        { topic: 't', partition: 0, time: Date.now(), maxNum: 1 }
    ], function (err, data) {
        // data 
        // { 't': { '0': [999] } } 
    });
  • groupId: consumer group
  • payloads: Array,array of OffsetCommitRequest, OffsetCommitRequest is a JSON object like:
{
   topic: 'topicName',
   partition: 0, //default 0 
   offset: 1,
   metadata: 'm', //default 'm' 
}

Example

var kafka = require('kafka-node'),
    client = new kafka.Client(),
    offset = new kafka.Offset(client);
    offset.commit('groupId', [
        { topic: 't', partition: 0, offset: 10 }
    ], function (err, data) {
    });

Fetch the last committed offset in a topic of a specific consumer group

  • groupId: consumer group
  • payloads: Array,array of OffsetFetchRequest, OffsetFetchRequest is a JSON object like:
{
   topic: 'topicName',
   partition: 0 //default 0 
}

Example

var kafka = require('kafka-node'),
    client = new kafka.Client(),
    offset = new kafka.Offset(client);
    offset.fetchCommits('groupId', [
        { topic: 't', partition: 0 }
    ], function (err, data) {
    });

Example

    var partition = 0;
    var topic = 't';
    offset.fetchLatestOffsets([topic], function (error, offsets) {
        if (error)
            return handleError(error);
        console.log(offsets[topic][partition]);
    });

Troubleshooting / FAQ

Error:

BrokerNotAvailableError: Could not find the leader

Call client.refreshMetadata() before sending the first message. Reference issue #354

This module uses the debug module so you can just run below before starting your app.

export DEBUG=kafka-node:*
  1. Call offset.fetchLatestOffsets to get fetch the latest offset
  2. Consume from returned offset

Reference issue #342

This error can occur when a HLC is killed and restarted quickly. The ephemeral nodes linked to the previous session are not relinquished in zookeeper when SIGINT is sent and instead relinquished when zookeeper session timeout is reached. The timeout can be adjusted using the sessionTimeout zookeeper option when the Client is created (the default is 30000ms).

Example handler:

process.on('SIGINT', function () {
    highLevelConsumer.close(true, function () {
        process.exit();
    });
});

Alternatively, you to avoid this issue entirely by omitting the HLC's id and a unique one will be generated for you.

Reference issue #90

Your partition will be stuck if the fetchMaxBytes is smaller than the message produced. Increase fetchMaxBytes value should resolve this issue.

Reference to issue #339

  1. Create a async.queue with message processor and concurrency of one (the message processor itself is wrapped with setImmediate so it will not freeze up the event loop)
  2. Set the queue.drain to resume the consumer
  3. The handler for consumer's message event pauses the consumer and pushes the message to the queue.

Running Tests

On the Mac you can either install docker-machine or Docker for Mac.

Docker machine:

brew install docker docker-machine docker-compose
docker-machine create --driver virtualbox dev
npm test
npm run stopDocker

LICENSE - "MIT"

Copyright (c) 2015 Sohu.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.