[Code Examples] Redis XRANGE in Node.js

Use Case(s)

Redis XRANGE command is typically used when you want to fetch a range of messages from a stream, based on their IDs. It's useful when analyzing patterns over time in data or retrieving specific portions of the stream.

Code Examples

Basic usage of XRANGE:

First, install the 'redis' package using npm:

npm install redis

Then use XRANGE command:

const redis = require('redis');
const client = redis.createClient();

client.xrange('mystream', '-', '+', (err, messages) => {
  if (err) console.error(err);
  else console.log(messages);
});

client.quit();

In this example, "-" and "+" are special symbols denoting the minimum and maximum ID possible, so it fetches all messages from the stream. 'mystream' is the name of the stream.

Limiting the number of messages with COUNT:

const redis = require('redis');
const client = redis.createClient();

client.xrange('mystream', '-', '+', 'COUNT', 5, (err, messages) => {
  if (err) console.error(err);
  else console.log(messages);
});

client.quit();

Here, we've added the 'COUNT' option followed by the number 5, which limits the number of returned messages to 5.

Best Practices

Be sure you understand the order of IDs in Redis streams. It is lexicographical, but not numerical. So an ID of "130" is considered less than "15" because "130" lexicographically comes before "15".
When handling large streams, remember to use the 'COUNT' option to limit the number of returned entries and avoid overloading your application.

Common Mistakes

Not handling errors in the callback function. Always include error handling in your Node callbacks.
Not closing the client connection after you're done. This can lead to resource leaks.