🚀 Getting started with Strapi

Wrapper for tulios' KafkaJS library to be used with Strapi apps. You are going to need a live Kafka instance/cluster to be running. The Strapi app will be able to act as publisher and/or subscriber. As added bonus, you can setup multiple publishers as well as subscribers within the same Strapi app; e.g., one for logging, one for notifications, one for... You name it.

Installation

Add the library to your Strapi project. Learn more

yarn add @indoomni/strapi-plugin-kafkajs
yarn install
yarn build

Configuration

Add the following configuration attributes to your server.js.

# config/server.js or config/env/**/server.js
# -------------------------------------------

module.exports = ({ env }) => ({
  host: env('HOST'),
  port: env.int('PORT'),
  app: {
    env: env('ENV'),
    name: env('APP_NAME'),
    keys: env.array('APP_KEYS'),
  },
  // ...
  kafkajs: {
    enabled: true,
    config: {
      publishers: [
        {
          enabled: true,
          clientId: `${env('APP_NAME')}_${env('ENV')}_log_pub`,
          topic: `Ngapi_${env('ENV')}_logs`,
          brokers: ['kafka:9092'],
        },
      ],
      subscribers: [
        {
          enabled: true,
          clientId: `${env('APP_NAME')}_${env('ENV')}_log_sub`,
          topic: `Ngapi_${env('ENV')}_logs`,
          brokers: ['kafka:9092'],
          handler: 'kafka-logger.js',
        },
      ],
    },
  },
  // ...
});

Notice the publishers attribute. Here, you can add multiple producers where each one will be identified by its clientId. When connection to each broker(s) is established, you will be able to publish messages/jobs into the said topic.

Now, notice the subscribers attribute. Here, you can add multiple consumers where each one will be identified also by its clientId. When connection to each broker(s) is established, the subscriber will merge into available consumer groups managed by the broker and its Zookeeper, and will subscribe (or "listen" if that's your thing) to the said topic. The library will automatically poll for new messages/jobs; any incoming message/job will be fed into an asynchronous "eachMessage" function in the Javascript file pointed by the handler attribute. We'll discuss this along.

How to publish messages or jobs?

Anywhere in your code (for example in a middleware to stream access logs to the some logger on the other side), write as in the following snippet. Refer to the publisher controller inside the library, and call publish function. Keep note of the set client ID and topic set up in the Configuration step.

# src/middlewares/kafkaLogger.js
# ------------------------------

// ...
setTimeout(async () => {
  const log = {
    uuid: ctx.uuid,
    timestamp: ctx.timestamp,
    timer: Math.ceil(Date.now() - start) + 'ms',
    request,
    response,
    stack: ctx.stack,
  };
  const clientId = `${strapi.appName}_${strapi.appEnv}_log_pub`;
  const topic = `Ngapi_${strapi.appEnv}_logs`;
  const message = JSON.stringify(log);
  await strapi
    .plugin('kafkajs')
    .controller('publisher')
    .publish(clientId, topic, message);
}, 0);
// ...

How to subscribe to messages or jobs?

Remember the handler attribute from the Configuration step? In the example configuration, it should point to your own implementation, named .../src/handler.js. If you put the JS file somewhere else, just modify the path. The path is relative to folder src in your code.

# src/handler.js
# --------------

'use strict';

module.exports = {
  eachMessage: async ({
    topic,
    partition,
    offset,
    message,
  }) => {
    const payload = message.value.toString();
    strapi.log.info(
      `I am sample handler file ${__filename}, edit me..`,
    );
    strapi.log.info(
      `Received message from topic: ${topic} partition: ${partition} offset: ${offset}`,
    );
    try {
      let object;
      if ((object = JSON.parse(payload))) {
        strapi.log.info('Do something...');
        // Do something..
        strapi.log.info('Done!');
      }
    } catch (err) {
      strapi.log.info('Pass!');
    }
  },
};

📚 Learn more

• KafkaJS - tulios' excellent KafkaJS library page on npmjs.com.
• Resource center - Strapi resource center.
• Strapi documentation - Official Strapi documentation.
• Strapi tutorials - List of tutorials made by the core team and the community.
• Kafka Docker Hub page
• Zookeeper Docker Hub page

Feel free to check out my GitHub repository. Your feedback and contributions are welcome!