Kafka-node

Kafka-node is a nodejs client with zookeeper integration for apache Kafka, only support the latest version of kafka 0.8 which is still under development, so this module is not production ready so far. Zookeeper does the following jobs:

• Load broker metadata from zookeeper before we can communicate with kafka server
• Watch broker state, if broker changed, client will refresh broker and topic metadata stored in 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)

• connectionString: zookeeper connection string, default localhost:2181/kafka0.8
• clientId: This is a user supplied identifier for the client application, default kafka-node-client

Producer

Producer(client)

• client: client which keep connect with kafka server.

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

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
   partition: '0', //default 0
}

• cb: Function, the callback

Example:

var kafka = require('kafka-node'),
    Producer = kafka.Producer,
    client = new kafka.Client(),
    producer = new Producer(client),
    payloads = [
        { topic: 'topic1', messages: 'hi', partition: 0 },
        { 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 in kafka server, only work when kafka server set auto.create.topics.enable true, our client simply send a metadata request to let server auto crate topics. when async set false, this method does not return util all topics are created, otherwise return 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

Consumer

Consumer(client, payloads, options)

• client: client which keep connect with kafka server.
• payloads: Array,array of FetchRequest, FetchRequest is a JSON object like:

{
   topic: 'topicName',
   partition: '0', //default 0 
   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
}

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 message 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)

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

Example:

consumer.addTopics(['t1', 't2'], function (err, added) {
});

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); 

close(force)

• force: Boolean, if set true, it force commit current offset before close, default false

Example

consumer.close(true);

Offset

Offset(client)

• client: client which keep connect with kafka server.

fetch(payloads, cb)

• payloads: Array,array of OffsetRequest, OffsetRequest is a JSON object like:

{
   topic: 'topicName',
   partition: '0', //default 0
   time: Date.now(), //used to ask for all messages before a certain time (ms), not support negative,default Date.now() 
   maxNum: 1 //default 1
}

• cb: Function, the callback

Example

var kafka = require('kafka'),
    client = new kafka.Client(),
    offset = new kafka.Offset(client);
    offset.fetch([
        { tiopic: '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', [
        { tiopic: 't', partition: 0, offset: 10 } 
    ], function (err, data) {
    });

Todo

• Compression: gzip & snappy

LICENSE - "MIT"

Copyright (c) 2013 Sohu.com

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