Microservices Communication with Redis Streams

//Below is some code for how you would use Redis to listen for the stream events:

async function listenToStream(
  onMessage: (message: any, messageId: string) => Promise<void>,
) {
  // using node-redis
  const redis = getNodeRedisClient();
  const streamKeyName = 'PAYMENTS_STREAM'; //stream name
  const groupName = 'PAYMENTS_CON_GROUP'; //listening consumer group name (custom)
  const consumerName = 'ORDERS_CON'; //listening consumer name (custom)
  const readMaxCount = 100;

  // Check if the stream group already exists
  if (!(await redis.exists(streamKeyName))) {
    const idPosition = '0'; //0 = start, $ = end or any specific id
    await nodeRedisClient.xGroupCreate(streamKeyName, groupName, idPosition, {
      MKSTREAM: true,
    });
  }

  // setup a loop to listen for stream events
  while (true) {
    // read set of messages from different streams
    const dataArr = await nodeRedisClient.xReadGroup(
      commandOptions({
        isolated: true,
      }),
      groupName,
      consumerName,
      [
        {
          // you can specify multiple streams in array
          key: streamKeyName,
          id: '>', // Next entry ID that no consumer in this group has read
        },
      ],
      {
        COUNT: readMaxCount, // Read n entries at a time
        BLOCK: 0, // block for 0 (infinite) seconds if there are none.
      },
    );

    for (let data of dataArr) {
      for (let messageItem of data.messages) {
        //process the message received (in our case, updateOrderStatus)
        await onMessage(messageItem.message, messageItem.id);

        // acknowledge individual messages after processing
        nodeRedisClient.xAck(streamKeyName, groupName, messageItem.id);
      }
    }
  }
}

// `listenToStream` listens for events and calls the `onMessage` callback to further handle the events.
listenToStream({
  onMessage: updateOrderStatus,
});

const updateOrderStatus: IMessageHandler = async (message, messageId) => {
  /*
   message = {
      orderId: "",
      paymentId: "",
      orderStatusCode:"",
      userId: "",
    }
    */
  // updates orderStatus and paymentId in database accordingly for the order which has fulfilled payment
  // updateOrderStatusInRedis(orderId,paymentId,orderStatusCode,userId)
  // updateOrderStatusInMongoDB(orderId,paymentId,orderStatusCode,userId)
};