Kafka-node

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

The Zookeeper integration does the following jobs:

• Loads broker metadata from Zookeeper before we can communicate with the Kafka server
• Watches broker state, if broker changes, the client will refresh broker and topic metadata stored in the client

Install Kafka

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

API

Client

Client(connectionString, clientId, [zkOptions])

• 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

close(cb)

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

• cb: Function, the callback

Producer

Producer(client, [options])

• client: client which keeps a connection with the Kafka server.
• options: set requireAcks and ackTimeoutMs for producer, the default value is {requireAcks: 1, ackTimeoutMs: 100}

var kafka = require('kafka-node'),
    Producer = kafka.Producer,
    client = new kafka.Client(),
    producer = new Producer(client);

Events

• 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.

send(payloads, cb)

• 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
   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) {})

createTopics(topics, async, cb)

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

HighLevelProducer

HighLevelProducer(client, [options])

• client: client which keeps a connection with the Kafka server. Round-robins produce requests to the available topic partitions
• options: set requireAcks and ackTimeoutMs for producer, the default value is {requireAcks: 1, ackTimeoutMs: 100}

var kafka = require('kafka-node'),
    HighLevelProducer = kafka.HighLevelProducer,
    client = new kafka.Client(),
    producer = new HighLevelProducer(client);

Events

• 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.

send(payloads, cb)

• 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
   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);
    });
});

createTopics(topics, async, cb)

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

Consumer

Consumer(client, payloads, options)

• 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, deafult `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 * 10,
    // 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
        }
    );

on('message', onMessage);

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);
});

on('error', function (err) {})

on('offsetOutOfRange', function (err) {})

addTopics(topics, cb, fromOffset)

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);

removeTopics(topics, cb)

• topics: Array, array of topics to remove
• cb: Function, the callback

Example:

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

commit(cb)

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) {
});

setOffset(topic, partition, offset)

Set offset of the given topic

• topic: String

• partition: Number

• offset: Number

Example:

consumer.setOffset('topic', 0, 0);

pause()

Pause the consumer

resume()

Resume the consumer

pauseTopics(topics)

Pause specify topics

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

resumeTopics(topics)

Resume specify topics

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

close(force, cb)

• 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

HighLevelConsumer

HighLevelConsumer(client, payloads, options)

• 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,

{
    groupId: 'kafka-node-group',//consumer group id, deafult `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 * 10,
    // 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'
        }
    );

on('message', onMessage);

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);
});

on('error', function (err) {})

on('offsetOutOfRange', function (err) {})

addTopics(topics, cb, fromOffset)

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);

removeTopics(topics, cb)

• topics: Array, array of topics to remove
• cb: Function, the callback

Example:

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

commit(cb)

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) {
});

setOffset(topic, partition, offset)

Set offset of the given topic

• topic: String

• partition: Number

• offset: Number

Example:

consumer.setOffset('topic', 0, 0);

pause()

Pause the consumer

resume()

Resume the consumer

close(force, cb)

• 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

Offset

Offset(client)

• client: client which keeps a connection with the Kafka server.

events

• ready: when zookeeper is ready
• connect when broker is ready

fetch(payloads, cb)

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] } }
    });

commit(groupId, payloads, cb)

• 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) {
    });

fetchCommits(groupid, payloads, cb)

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) {
    });

Todo

• Compression: gzip & snappy (√)

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.