Simple Apache Pulsar Producer & Consumer Example

Prereq's

You'll need docker installed. You can stand up Apache Pulsar on your local by executing the following docker command. Note this command will mount a volume call data in the directory where you run the command. I have set up the .gitignore to ignore this folder for you.

$ docker run -it \
  -p 6650:6650 \
  -p 8080:8080 \
  -v $PWD/data:/pulsar/data \
  apachepulsar/pulsar:1.22.0-incubating \
  bin/pulsar standalone --advertised-address 127.0.0.1

8080 is mapped to the admin interface. You can see metrics by hitting http://localhost:8080/admin/persistent/sample/standalone/ns1/my-topic/stats in your browser.

6650 is the port you connect to with a Pulsar client.

To build the project execute the following command from the root folder of the project

$ mvn package

To execute the application run, also in the root folder.

$ java -Dexec.mainClass="org.apache.pulsar.example.PulsarExample"

You should see output similar to the below

######## Producing Messages Below ########


Not lucky message: 2:90:-1
Not lucky message: 2:91:-1
Not lucky message: 2:92:-1
Not lucky message: 2:93:-1
Not lucky message: 2:94:-1
Lucky number 5 Message Id is: 2:95:-1
Not lucky message: 2:96:-1
Not lucky message: 2:97:-1
Not lucky message: 2:98:-1
Not lucky message: 2:99:-1


######## Consuming Messages Below ########


Not lucky response: 2:90:-1
Not lucky response: 2:91:-1
Not lucky response: 2:92:-1
Not lucky response: 2:93:-1
Not lucky response: 2:94:-1
lucky number 5 id 2:95:-1, message lucky-five: 
Not lucky response: 2:96:-1
Not lucky response: 2:97:-1
Not lucky response: 2:98:-1
Not lucky response: 2:99:-1

You can see in the main class that I am grabbing the luckyNumberMessageId
after pushing it to the Pulsar topic.

if (i == luckyNumber) {
    bytes = "lucky-five".getBytes();
    luckyNumberMessageId = producer.send(bytes);
    System.out.println("Lucky number 5 Message Id is: " + luckyNumberMessageId);

}

I am then printing a special message once I pull the correct message off of the pulsar topic.

if (luckyNumberMessageId !=  null && msg.getMessageId().equals(luckyNumberMessageId)) {
    System.out.printf("Lucky number 5 id %s, message %s: \n", msg.getMessageId(), response);
    consumer.acknowledge(msg);
}

I borrowed most of this from http://pulsar.incubator.apache.org/docs/latest/clients/Java/. Hope this helps anyone looking for a short "how-to".