Node.js SDK

Overview
This document introduces the directions for using a Node.js client to connect to an elastic Topic of CKafka and send and receive messages.
Prerequisites
Install GCC
Install Node.js
Directions
Step 1: Preparing the Environment
Installing the C++ Dependency Database
1. Run the following command to switch to the Yum repository configuration directory /etc/yum.repos.d/.
 cd /etc/yum.repos.d/
2. Create the Yum repository configuration file confluent.repo.
   [Confluent.dist]
   name=Confluent repository (dist)
   baseurl=https://packages.confluent.io/rpm/5.1/7
   gpgcheck=1
   gpgkey=https://packages.confluent.io/rpm/5.1/archive.key
   enabled=1   
   [Confluent]
   name=Confluent repository
   baseurl=https://packages.confluent.io/rpm/5.1
   gpgcheck=1
   gpgkey=https://packages.confluent.io/rpm/5.1/archive.key
   enabled=1
3. Run the following command to install the C++ dependency database.
yum install librdkafka-devel
Installing the Node.js Dependency Database
1. Run the following command to specify the OpenSSL header file path for the preprocessor.
export CPPFLAGS=-I/usr/local/opt/openssl/include
2. Run the following command to specify the OpenSSL database path for the connector.
export LDFLAGS=-L/usr/local/opt/openssl/lib
3. Run the following command to install the Node.js dependency database.
npm install i --unsafe-perm node-rdkafka
Step 2: Creating a Topic and Subscription Relationship
1. On the Elastic Topic list page of the console, create a Topic.
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2. Click the ID of the Topic to enter the Basic Information page and obtain the username, password, and address information.
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3. In the Subscription Relationships tab, create a subscription relationship (consumption group).
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Step 2: Adding the Configuration File
module.exports = {
    'sasl_plain_username': 'your_user_name',
    'sasl_plain_password': 'your_user_password',
    'bootstrap_servers': ["xxx.xx.xx.xx:port"],
    'topic_name': 'xxx',
    'group_id': 'xxx'
}
Parameter
Description
bootstrapServers
The connection address. It can be obtained from the basic information page of an elastic Topic in the console.
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sasl_plain_username
The username. It can be obtained from the basic information page of an elastic Topic in the console.
sasl_plain_password
The user password. It can be obtained from the basic information page of an elastic Topic in the console.
topic_name
The topic name. It can be obtained from the basic information page of an elastic Topic in the console.
group.id
The consumption group name. It can be obtained from the subscription relationship list of an elastic Topic in the console.
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Step 3: Producing Messages
1. Write the message production program producer.js.
   const Kafka = require('node-rdkafka');
   const config = require('./setting');
   console.log("features:" + Kafka.features);
   console.log(Kafka.librdkafkaVersion);
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   var producer = new Kafka.Producer({
       'api.version.request': 'true',
       'bootstrap.servers': config['bootstrap_servers'],
       'dr_cb': true,
       'dr_msg_cb': true,
       'security.protocol' : 'SASL_PLAINTEXT',
       'sasl.mechanisms' : 'PLAIN',
       'sasl.username' : config['sasl_plain_username'],
       'sasl.password' : config['sasl_plain_password']
   });
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   var connected = false
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   producer.setPollInterval(100);
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   producer.connect();
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   producer.on('ready', function() {
   connected = true
   console.log("connect ok")
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   });
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   function produce() {
   try {
       producer.produce(
       config['topic_name'],
       new Buffer('Hello CKafka SASL'),
       null,
       Date.now()
       );
   } catch (err) {
       console.error('Error occurred when sending message(s)');
       console.error(err);
   }
   }
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   producer.on("disconnected", function() {
   connected = false;
   producer.connect();
   })
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   producer.on('event.log', function(event) {
       console.log("event.log", event);
   });
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   producer.on("error", function(error) {
       console.log("error:" + error);
   });
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   producer.on('delivery-report', function(err, report) {
       console.log("delivery-report: producer ok");
   });
   // Any errors we encounter, including connection errors
   producer.on('event.error', function(err) {
       console.error('event.error:' + err);
   })
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   setInterval(produce,1000,"Interval");
2. Run the following command to send the message.
node producer.js
3. View the execution result.
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Step 4: Consuming Messages
1. Create the message consumption program consumer.js.
    consumer.on('event.log', function(event) {
       console.log("event.log", event);
   });
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   consumer.on('error', function(error) {
       console.log("error:" + error);
   });
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   consumer.on('event', function(event) {
           console.log("event:" + event);
   });
   const Kafka = require('node-rdkafka');
   const config = require('./setting');
   console.log(Kafka.features);
   console.log(Kafka.librdkafkaVersion);
   console.log(config)
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   var consumer = new Kafka.KafkaConsumer({
       'api.version.request': 'true',
       'bootstrap.servers': config['bootstrap_servers'],
       'security.protocol' : 'SASL_PLAINTEXT',
       'sasl.mechanisms' : 'PLAIN',
       'message.max.bytes': 32000,
       'fetch.message.max.bytes': 32000,
       'max.partition.fetch.bytes': 32000,
       'sasl.username' : config['sasl_plain_username'],
       'sasl.password' : config['sasl_plain_password'],
       'group.id' : config['group_id']
   });
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   consumer.connect();
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   consumer.on('ready', function() {
   console.log("connect ok");
   consumer.subscribe([config['topic_name']]);
   consumer.consume();
   })
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   consumer.on('data', function(data) {
   console.log(data);
   });
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   consumer.on('event.log', function(event) {
       console.log("event.log", event);
   });
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   consumer.on('error', function(error) {
       console.log("error:" + error);
   });
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   consumer.on('event', function(event) {
           console.log("event:" + event);
   });
2. Run the following command to consume the message.
node consumer.js
3. View the execution result.
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Parameter	Description
bootstrapServers	The connection address. It can be obtained from the basic information page of an elastic Topic in the console.
sasl_plain_username	The username. It can be obtained from the basic information page of an elastic Topic in the console.
sasl_plain_password	The user password. It can be obtained from the basic information page of an elastic Topic in the console.
topic_name	The topic name. It can be obtained from the basic information page of an elastic Topic in the console.
group.id	The consumption group name. It can be obtained from the subscription relationship list of an elastic Topic in the console.

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Overview

Prerequisites

Directions

Step 1: Preparing the Environment

Installing the C++ Dependency Database

Installing the Node.js Dependency Database

Step 2: Creating a Topic and Subscription Relationship

Step 2: Adding the Configuration File

Step 3: Producing Messages

Step 4: Consuming Messages