node-kfk

Node-Kfk

Why I need it

Kafka is not friendly enough for programmers who don’t have a clear knowledge on it.

Considering our usage are similar at most of the time, we want to provide a simple client for simple use case on kafka.

Usage

Install

npm i kfk -S

Kafka Producer

const conf = {
  'client.id': 'kafka',
  'metadata.broker.list': '127.0.0.1:9092',
}
const topicConf = {
}
const options = {
  debug: false,
}

const producer = new KafkaProducer(conf, topicConf, options)

await producer.connect()

console.log('connected')

while (true) {
  const msg = `${new Date().getTime()}-${crypto.randomBytes(20).toString('hex')}`

  await producer.produce(_.sample([
    'rdkafka-test0',
    'rdkafka-test1',
    'rdkafka-test2',
  ]), null, msg)
}

Kafka ALO(at least once) Consumer

const conf = {
  'group.id': 'alo-consumer-test-1',
  'metadata.broker.list': '127.0.0.1:9092',
}
const topicConf = {
  'auto.offset.reset': 'largest',
}
const options = {
  debug: false,
}

const consumer = new KafkaALOConsumer(conf, topicConf, options)
await consumer.connect()
await consumer.subscribe([
  'rdkafka-test0',
  'rdkafka-test1',
  'rdkafka-test2',
])

while (true) {
  await consumer.consume(message => {
    console.log(`topic: ${message.topic} offset : ${message.offset} val: ${message.value.toString('utf-8')}`)
  }, {
      size: 10,
      concurrency: 5,
    })
}

Kafka AMO(at most once) Consumer

const conf = {
  'group.id': 'amo-consumer-test-1',
  'metadata.broker.list': '127.0.0.1:9092',
}
const topicConf = {
  'auto.offset.reset': 'largest',
}
const options = {
  debug: false,
}

const consumer = new KafkaAMOConsumer(conf, topicConf, options)
await consumer.connect()
await consumer.subscribe([
  'rdkafka-test0',
  'rdkafka-test1',
  'rdkafka-test2',
])

while (true) {
  await consumer.consume(message => {
    console.log(`topic: ${message.topic} offset : ${message.offset} val: ${message.value.toString('utf-8')}`)
  }, {
      size: 10,
      concurrency: 5,
    })
}

Graceful Death

const gracefulDeath = async () => {
  await producer.die()
  await consumer.die()
  process.exit(0)
}
process.on('SIGINT', gracefulDeath)
process.on('SIGQUIT', gracefulDeath)
process.on('SIGTERM', gracefulDeath)

Deep Dive

Choose your right consumer

node-kfk provide two consumer choices for you: KafkaALOConsumer and KafkaAMOConsumer. ALO means At Least Once, and AMO means At Most Once.

At Least Once

If you cannot tolerate any message loss and you have handled the repetitive execution situation in your consumer function, you may want your consumer has at least once guarantee.

KafkaALOConsumer will monitor your consume callback function execute state and if there are any Error thrown in your consumer callback function (or process crashed), it will begin at the offsets you last consumed successfully.

At Most Once

If you do not very care about little messages loss when problem happens, but you want to make sure that every message only can be handled on time, you can just use the KafkaAMOConsumer.

KafkaAMOConsumer will auto commits the offsets when fetched the messages. It has better performance than KafkaALOConsumer, but not guarantee that all messages will be consumed.

Offset Management Detail

In KafkaAMOConsumer, node-kfk use the enable.auto.commit=true and enable.auto.offset.store=true options which completely depend on librdkafka to management the offsets and will auto commit the latest offsets periodically(the interval depends on auto.commit.interval.ms, default is 1000).

In KafkaALOConsumer, we still want librdkafka to commit automatically, but we need to control offsetStore manually(now we set enable.auto.commit=true and enable.auto.offset.store=false). When node-kfk ensure that all messages had been handled successfully, it will store the latest offsets in offsetStore, and wait for committed by librdkafka.

Others

The client has been tested on:

- os: linux
  env: KAFKA_VERSION=0.10.2.2
  node_js: 8
- os: linux
  env: KAFKA_VERSION=0.10.2.2
  node_js: 10
- os: linux
  env: KAFKA_VERSION=0.11.0.3
  node_js: 10
- os: linux
  env: KAFKA_VERSION=1.1.0
  node_js: 10
- os: linux
  env: KAFKA_VERSION=2.0.0
  node_js: 10

More detailed document for conf and topicConf params in librdkafka and node-rdkafka

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