A node client for Kafka
var Kafka = require('franz-kafka')
var kafka = new Kafka({
zookeeper: ['localhost:2181'],
compression: 'gzip',
queueTime: 2000,
batchSize: 200,
logger: console
})
kafka.connect(function () {
// topics are Streams
var foo = kafka.topic('foo')
var bar = kafka.topic('bar')
// consume with a pipe
foo.pipe(process.stdout)
// or with the 'data' event
foo.on('data', function (data) { console.log(data) })
// produce with a pipe
process.stdin.pipe(bar)
// or just write to it
bar.write('this is a message')
// resume your consumer to get it started
foo.resume()
// don't forget to handle errors
foo.on('error', function (err) { console.error("STAY CALM") })
}
)To test the example first get kafka running. Follow steps 1 and 2 of the quick start guide
Then you can run node example.js to see messages getting produced and consumed.
var Kafka = require('franz-kafka')
var kafka = new Kafka({
brokers: [{ // an array of broker connection info
id: 0, // the server's broker id
host: 'localhost',
port: 9092
}],
// producer defaults
compression: 'none', // default compression for producing
maxMessageSize: 1000000, // limits the size of a produced message
queueTime: 5000, // milliseconds to buffer batches of messages before producing
batchSize: 200, // number of messages to bundle before producing
// consumer defaults
groupId: 'franz-kafka', // the consumer group name this instance is part of
minFetchDelay: 0, // minimum milliseconds to wait between fetches
maxFetchDelay: 10000, // maximum milliseconds to wait between fetches
maxFetchSize: 300*1024, // limits the size of a fetched message
logger: null // a logger that implements global.console (for debugging)
})An array of connection info of all the brokers this client can communicate with
The compression used when producing to kafka. May be, 'none', 'gzip', or 'snappy'
The largest size of a message produced to kafka. If a message exceeds this size,
the Topic will emit an 'error'. Note that batchSize affects the size of messages
because batches of messages are bundled as individual messages.
The time to buffer messages for bundling before producing to kafka. This option
is combined with batchSize. Whichever comes first will trigger a produce.
The number of messages to bundle before producing to kafka. This option
is combined with queueTime. Whichever comes first will trigger a produce.
The minimum time to wait between fetch requests to kafka. When a fetch returns
zero messages the client will begin exponential backoff between requests up to
maxFetchDelay until messages are available.
The maximum time to wait between fetch requests to kafka after exponential backoff has begun.
The maximum size of a fetched message. If a fetched message is larger than this size the Topic will emit an 'error' event.
Connects to the Kafka cluster and runs the callback once connected.
kafka.connect(function () {
console.log('connected')
//...
})Get a Topic for consuming or producing. The first argument is the topic name and the second are the topic options.
var foo = kafka.topic('foo', {
// default options
minFetchDelay: 0, // defaults to the kafka.minFetchDelay
maxFetchDelay: 10000, // defaults to the kafka.maxFetchDelay
maxFetchSize: 1000000, // defaults to the kafka.maxFetchSize
compression: 'none', // defaults to the kafka.compression
batchSize: 200, // defaults to the kafka.batchSize
queueTime: 5000, // defaults to the kafka.queueTime
partitions: {
consume: ['0-0:0'], // array of strings with the form 'brokerId-partitionId:startOffset'
produce: ['0:1'] // array of strings with the form 'brokerId:partitionCount'
}
})This structure describes which brokers and partitions the client will connect to for producing and consuming.
An array of partitions to consume and what offset to begin consuming from in the form of 'brokerId-partitionId:startOffset'. For example broker 2 partition 3 offset 5 is '2-3:5'
An array of brokers to produce to with the count of partitions in the form of 'brokerId:partitionCount'. For example broker 3 with 8 partitions is '3:8'
Fires when the client is connected to a broker.
A topic is a Stream that may be Readable for consuming and Writable for producing. Retrieve a topic from the kafka instance.
var topic = kafka.topic('a topic')Pause the consumer stream
Resume the consumer stream
Destroy the consumer stream
Sets the encoding of the data emitted by the data event.
encodingis one of: 'utf8', 'utf16le', 'ucs2', 'ascii', 'hex', or undefined for a raw Buffer
Write a message to the topic. Returns false if the message buffer is full.
datais a string or Bufferencodingis optional whendatais a string. Default is 'utf8'
Same as write
Pipe the stream of messages to the destination Writable Stream.
See Stream.pipe
Fires for each message. Data is a Buffer by default or a string if setEncoding
was called.
topic.on('data', function (data) { console.log('message data: %s', data) })Fires when the producer stream can handle more messages
topic.on('drain', function () { console.log('%s is ready to write', topic.name )})Fires when there is a produce or consume error. An Error object is emitted.
topic.on('error', function (error) { console.error(error.message)})Fires when a new offset is fetched. 'data' events emitted between 'offset' events all belong to the same offset in Kafka. The partition name and offset is emitted.
topic.on('offset', function(partition, offset) {
console.log("topic: %s partition: %s offset: %d", topic.name, partition, offset)
})ZooKeeper support is in development. Producer support is functional. Consumer support does not yet include partition balancing.
To produce using ZooKeeper use the zookeeper option in the Kafka constructor.
var kafka = new Kafka({
zookeeper: ['localhost:2181'] // array of 'host:port' zookeeper nodes
})
kafka.connect(function () {
console.log('connected via zookeeper')
})MIT