Aggregate many Redis5 Streams to one Redis connection (XREAD collapsing)
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README.md


Redis Streams Aggregator

A connection collapser and toolkit built around Redis5's XADD and XREAD commands, powered by ioredis

   

What? Why?

Redis 5 adds Streams, a powerful new data structure which simplifies the construction of real-time applications. The new XREAD command blocks a redis connection while awaiting new data, allows reading from multiple streams, and can be canceled with the new CLIENT UNBLOCK command. This package wraps XREAD and XADD such that new subscriptions automatically UNBLOCK the existing stream, add their new subscription (and handle offset tracking), and restart the stream. The end effect is that you'll need only two Redis connections open - one for reading and one for writing (including the UNBLOCKing).

With redis-streams-aggregator, you can just call .subscribe() and .add() and leave the stream management to us!

Install

yarn add redis-streams-aggregator

Use

const RedisStreamsAgg = require("redis-streams-aggregator");
const streams = new RedisStreams(); // options like: { host: ..., port: ... } etc

// Sign up for XREAD, get all messages to 'testId' in real-time
streams.subscribe("testId", messages => {
  console.log("I got messages!", { messages });
});

// Write data to a stream (very thin wrapper around XADD)
streams.add("testId", { value: "foobar" });

API Documentation

Messages

Messages events provide arrays of "Message" objects, which have the following properties:

const Message = {
  offset: string,
  key: value,
  key2: value2...
}

For example, consider the following:

// Server
streams.add("testChannel", { foo: "bar" });

streams.subscribe("testChannel", "$", messages => {
  // messages === [
  //  [ "1518951480106-0", { foo: 'bar' } ]
  // ]
});

Server

RedisStreamsAggregator(options)

Where "options" is an object with the following properties:

Option Required Default Description
host no localhost Redis host uri
port no 6379 Redis port
serialize no JSON.stringify A function for encoding published objects
unserialize no JSON.parse A function for decoding published objects
const server = new RedisStreamsAggregator({
  host: "192.168.0.1",
  port: 6379
});

Server Events

  • ready - Connected to Redis
  • connect - A new socket has connected
  • error - An error has been encountered (connection to Redis failed, etc)