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Redis: Streams

A Redis stream is a data structure that acts like an append-only log but also implements several operations to overcome some of the limits of a typical append-only log. We can use streams to record and simultaneously syndicate events in real time.

  • Redis generates a unique ID for each stream entry.
  • Streams keep messages in Redis for as long as you want (configurable).
  • Consumers can read at their own pace, even if they were offline.
  • We can acknowledge messages (XACK) and track delivery.

Similar like pub/sub we need A producer and consumers to implement redis streams in our system.

Basic Example​

Lets create a basic example of redis streams using XADD and XREAD command.

Setup​

To run redis server you can install it directly in your machine or using virtualization. For me I prefer to use docker and here is how to do it.

Run a detached container with name my-redis using latest redis image and expose the port 6379.

docker run -d -p 6379:6379 --name my-redis redis

Run redis-cli inside the newly created redis container.

➜ redis_streams docker exec -it my-redis redis-cli         
127.0.0.1:6379>

XADD​

This is the simplest form of adding a message to a Redis Stream. Each message will have a unique ID and some data fields.

127.0.0.1:6379> XADD mystream * message Hello
"1740039025432-0"
  • mystream: name of the stream, redis will create the stream if not exist.
  • *: Stream ID, will auto-generate a unique ID if the ID argument specified is the *.
  • message Hello: Key value pair data, message is the key and value is Hello.

XREAD​

Read data from one or multiple streams. This command has an option to block if items are not available.

127.0.0.1:6379> XREAD COUNT 1 STREAMS mystream 0
1) 1) "mystream"
   2) 1) 1) "1740039025432-0"
         2) 1) "message"
            2) "Hello"
  • COUNT 1: Return maximum 1 element for each stream.
  • STREAMS mystream 0:
    • mystream: Name of the stream.
    • 0: Read element from the start.

References​