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IBM Event Streams for IBM Cloud Kafka Java console sample application: Local Development guide

As pushing the application into IBM Cloud® does not require you to build the application locally, this guide is here to guide you through the process, should you wish to build the application locally.

We will not discuss establishing a connection from your laptop to Event Streams for IBM Cloud. This is described in the connection guide.

Prerequisites

  1. If you don't already have one, create an Event Streams service instance.

    1. Log in to the IBM Cloud console.

    2. Click Catalog.

    3. From the navigation pane, click Integration, click the Event Streams tile, and then select the Lite plan. The Event Streams service instance page opens.

    4. Enter a name for your service. You can use the default value.

    5. Click Create. The Event Streams Getting started page opens.

  2. If you don't already have them, install the following prerequisites:

Steps to Build the Sample

1. Create a topic

The topic is the core of Event Streams flows. Data passes through a topic from producing applications to consuming applications.

We'll be using the IBM Cloud console (UI) to create the topic, and will reference it when starting the application.

  1. Go to the Topics tab.

  2. Click New topic.

  3. Name your topic.

    The sample application is configured to connect to topic kafka-java-console-sample-topic. If the topic does not exist, it is created when the application is started.

  4. Keep the defaults set in the rest of the topic creation, click Next and then Create topic.

  5. The topic appears in the table. Congratulations, you have created a topic!

2. Create credentials

To allow the sample application to access your topic, we need to create some credentials for it.

  1. Go to Service credentials in the navigation pane.

  2. Click New credential.

  3. Give the credential a name so you can identify its purpose later. You can accept the default value.

  4. Give the credential the Manager role so that it can access the topics, and create them if necessary.

  5. Click Add. The new credential is listed in the table in Service credentials.

  6. Click View credentials to see the api_key and kafka_brokers_sasl values.

3. Clone the Github repository for the sample application

The sample application is stored here. Clone the event-streams-samples repository by running the clone command from the command line.

 git clone https://github.com/ibm-messaging/event-streams-samples.git

When the repository is cloned, from the command line change into the kafka-java-console-sample directory. 
cd event-streams-samples/kafka-java-console-sample

Build the contents of the kafka-java-console-sample directory. 
gradle clean && gradle build

4. Run the consuming application

Start the sample consuming application from the command line, replacing the kafka_brokers_sasl and api_key values.

The java -jar ./build/libs/kafka-java-console-sample-2.0.jar part of the command identifies the locations of the .JAR file to run within the cloned repository. You do not need to change this.

Use the kafka_brokers_sasl from the Service credentials created in Step 2. We recommend using all the kafka_brokers_sasl listed in the Service credentials that you created.

The kafka_brokers_sasl must be formatted as "host:port,host2:port2".
Format the contents of kafka_brokers_sasl in a text editor before entering it in the command line.

Then, use the api_key from the Service credentials created in Step 2. -consumer specifies that the consumer should start.

java -jar ./build/libs/kafka-java-console-sample-2.0.jar 
<kafka_brokers_sasl> <api_key> -consumer

An INFO No messages consumed is displayed when the consuming application is running, but there is no data being consumed.

5. Run the producing application

Open a new command line window and change into the kafka-java-console-sample directory.

cd event-streams-samples/kafka-java-console-sample

Then, start the sample producing application from the command line, replacing the kafka_brokers_sasl and api_key values with the same ones used to run the consumer.

Use the api_key from the Service credentials created in Step 2. -producer specifies that the producer should start.

java -jar ./build/libs/kafka-java-console-sample-2.0.jar
 <kafka_brokers_sasl> <api_key> -producer

6. Success!

When the producer starts, messages are produced to the topic. Messages are then consumed from the topic by the consuming application. You can verify the successful flow of messages when you see INFO Message consumed from the consumer.

The sample runs indefinitely until you stop it. To stop the process, run an exit command Ctrl+C.