Practical Microservices

Fetching and Processing Batches of Messages

You’ll write the function for reading messages from a streamhere. It’ll default to reading messages from position 0, but it will accept a fromPosition parameter to let you read from a different position in the stream. Right now is when we use that parameter:

video-tutorials/src/message-store/subscribe.js

function getNextBatchOfMessages () {
  return read(streamName, currentPosition + 1, messagesPerTick)
}

To get the next batch, you just delegate to read using the streamName, currentPosition + 1, and messagesPerTick values—currentPosition + 1 because the Eventide function that queries for the next batch of messages uses >= in the global_position conditional in its WHERE clause:

CREATE OR ...