kafka-avro
Advanced tools
Node.js bindings for librdkafka with Avro schema serialization.
The kafka-avro library is a wrapper that combines the node-rdkafka and avsc libraries to allow for Production and Consumption of messages on kafka validated and serialized by Avro.
Install the module using NPM:
npm install kafka-avro --save
The kafka-avro library operates in the following steps:
getConsumer() and getProducer() methods, which both return instances of the corresponding Constructors from the node-rdkafka library.The instances of "node-rdkafka" that are returned by kafka-avro are hacked so as to intercept produced and consumed messages and run them by the Avro de/serializer along with Confluent's Schema Registry Magic Byte and Schema Id.
You are highly encouraged to read the "node-rdkafka" documentation, as it explains how you can use the Producer and Consumer instances as well as check out the available configuration options of node-rdkafka.
The Kafka.CODES enumeration of constant values provided by the "node-rdkafka" library is also available as a static var at:
var KafkaAvro = require('kafka-avro');
console.log(KafkaAvro.CODES);
var KafkaAvro = require('kafka-avro');
var kafkaAvro = new KafkaAvro({
kafkaBroker: 'localhost:9092',
schemaRegistry: 'http://localhost:8081',
});
// Query the Schema Registry for all topic-schema's
// fetch them and evaluate them.
kafkaAvro.init()
.then(function() {
console.log('Ready to use');
});
When instantiating kafka-avro you may pass the following options:
kafkaBroker String REQUIRED The url or comma delimited strings pointing to your kafka brokers.schemaRegistry String REQUIRED The url to the Schema Registry.topics Array of Strings You may optionally define specific topics to be fetched by kafka-avro vs fetching schemas for all the topics which is the default behavior.fetchAllVersions Boolean Set to true to fetch all versions for each topic, use it when updating of schemas is often in your environment.parseOptions Object Schema parse options to pass to avro.parse(). parseOptions.wrapUnions is set to true by default.httpsAgent Object initialized https Agent classNOTICE: You need to initialize kafka-avro before you can produce or consume messages.
By invoking the kafkaAvro.getProducer() method, kafka-avro will instantiate a Producer, make it connect and wait for it to be ready before the promise is resolved.
kafkaAvro.getProducer({
// Options listed bellow
})
// "getProducer()" returns a Bluebird Promise.
.then(function(producer) {
var topicName = 'test';
producer.on('disconnected', function(arg) {
console.log('producer disconnected. ' + JSON.stringify(arg));
});
var value = new Buffer('value-' +i);
var key = 'key';
// if partition is set to -1, librdkafka will use the default partitioner
var partition = -1;
producer.produce(topicName, partition, value, key);
})
What kafka-avro basically does is wrap around node-rdkafka and intercept the produce method to validate and serialize the message.
NOTICE: You need to initialize kafka-avro before you can produce or consume messages.
By invoking the kafkaAvro.getConsumer() method, kafka-avro will instantiate a Consumer, listen on log, error and disconnect events and return it to you. Depending on the consuming pattern you follow you may or may not need to perform a connect().
When consuming topics using the data event you will need to perform a connect() as per node-rdkafka documentation:
kafkaAvro.getConsumer({
'group.id': 'librd-test',
'socket.keepalive.enable': true,
'enable.auto.commit': true,
})
// the "getConsumer()" method will return a bluebird promise.
.then(function(consumer) {
// Perform a consumer.connect()
return new Promise(function (resolve, reject) {
consumer.on('ready', function() {
resolve(consumer);
});
consumer.connect({}, function(err) {
if (err) {
reject(err);
return;
}
resolve(consumer); // depend on Promises' single resolve contract.
});
});
})
.then(function(consumer) {
// Subscribe and consume.
var topicName = 'test';
consumer.subscribe([topicName]);
consumer.consume();
consumer.on('data', function(rawData) {
console.log('data:', rawData);
});
});
kafkaAvro.getConsumerStream({
'group.id': 'librd-test',
'socket.keepalive.enable': true,
'enable.auto.commit': true,
},
{
'request.required.acks': 1
},
{
'topics': 'test'
})
.then(function(stream) {
stream.on('error', function(err) {
if (err) console.log(err);
process.exit(1);
});
stream.on('data', function (rawData) {
console.log('data:', rawData)
});
stream.on('error', function(err) {
console.log(err);
process.exit(1);
});
stream.consumer.on('event.error', function(err) {
console.log(err);
})
});
Same deal here, thin wrapper around node-rdkafka and deserialize incoming messages before they reach your consuming method.
kafka-avro intercepts all incoming messages and augments the object with one more property named parsed which contained the avro deserialized object. Here is a breakdown of the properties included in the message object you receive when consuming messages:
value Buffer The raw message buffer from Kafka.size Number The size of the message.key String|Number Partioning key used.topic String The topic this message comes from.offset Number The Kafka offset.partition Number The kafka partion used.parsed Object The avro deserialized message as a JS Object ltieral.schemaId Number The Registry Schema id of the consumed message.The KafkaAvro instance also provides the following methods:
The Kafka Avro library logs messages using the Bunyan logger. To enable logging you will have to define at least one of the needed ENV variables:
KAFKA_AVRO_LOG_LEVEL Set it a valid Bunyan log level value to activate console logging (Typically you'd need either info or debug as values.)KAFKA_AVRO_LOG_NO_COLORS Set this to any value to disable color when logging.WARNING The logger will not emit any messages as it was expected, there is an open issue on Bunyan's repository pending a solution on this. So no logging for now.
NOTICE This is a static method on the
KafkaAvroconstructor, not the instance. Therefore there is a single logger instance for the whole runtime.
Returns {Bunyan.Logger} Bunyan logger instance.
var KafkaAvro = require('kafka-avro');
var fmt = require('bunyan-format');
var kafkaLog = KafkaAvro.getLogger();
kafkaLog.addStream({
type: 'stream',
stream: fmt({
outputMode: 'short',
levelInString: true,
}),
level: 'info',
});
Read more about the bunyan-format package.
Serialize the provided value with Avro, including the magic Byte and schema id provided.
Returns {Buffer} Serialized buffer message.
type {avsc.Type} The avro type instance.schemaId {number} The Schema Id in the SR.value {*} Any value to serialize.Deserialize the provided message, expects a message that includes Magic Byte and schema id.
Returns {*} Deserialized message.
type {avsc.Type} The avro type instance.message {Buffer} Message in byte code.You can use docker-compose up to up all the stack before you call your integration tests with npm test. How the integration tests are outside the containers, you will need set you hosts file to :
127.0.0.1 kafka
grunt release
grunt release:minor for minor number jump.grunt release:major for major number jump.schemaId property on the consumed messages.connect() method manually, check the docs.connect() callbacks for both Consumer and Producer.0.7.0-ALPHA.3 which changes the consumer API by decoupling subscribing from consuming.0.7.0-ALPHA.2 of node-rdkafka which broke BC in 0.7.0-ALPHA.3.connect() invocation for consumers and producers.KafkaAvro.getLogger().getReadStream() method.serialize() and deserialize() methods.getConsumer() method.Copyright Waldo, Inc. Licensed under the MIT.
FAQs
Node.js bindings for librdkafka with Avro schema serialization.
We found that kafka-avro demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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