ENOTFOUND redis.railway.internal

What This Error Means

The error code ENOTFOUND means that your application could not resolve the redis.railway.internal hostname to an IP address when trying to connect to the Redis database.

Why This Error Can Occur

This error can occur for a few different reasons, but the main reason is because your application uses the ioredis package to connect to the Redis database, or uses a package that uses ioredis as a dependency such as bullmq.

By default, ioredis will only do an IPv4 (A record) lookup for the redis.railway.internal hostname.

That presents a problem given that Railway's private network uses only IPv6 (AAAA records).

The lookup will fail because the A records for redis.railway.internal do not exist.

Some other reasons that this error can occur would be -

• Your application and Redis database are in different projects.

• You are trying to connect to a Redis database locally with the private hostname and port.

For either of these reasons, the issue arises because the private network is scoped to a single environment within a project, and would not be accessible from your local machine or other projects.

If the Redis database is in the same project as your application, and you are not trying to connect to a Redis database locally, ioredis is the likely cause of the error.

Solutions

The solution depends on the package you are using to connect to the Redis database, though the solution is the same for both.

ioredis

Using ioredis directly in your application

ioredis has an option to do a dual stack lookup, which will try to resolve the redis.railway.internal hostname using both IPv4 and IPv6 addresses (A and AAAA records).

To enable this, in your REDIS_URL environment variable, you can set the family to 0 to enable dual stack lookup.

import Redis from 'ioredis';

const redis = new Redis(process.env.REDIS_URL + '?family=0');

const ping = await redis.ping();

Using bullmq

Similarly, for bullmq since it uses ioredis as a dependency, you can set the family option to 0 in your connection object.

import { Queue } from "bullmq";

const redisURL = new URL(process.env.REDIS_URL);

const queue = new Queue("Queue", {
    connection: {
        family: 0,
        host: redisURL.hostname,
        port: redisURL.port,
        username: redisURL.username,
        password: redisURL.password
    }
});

const jobs = await queue.getJobs();

console.log(jobs);

Other packages

Above we covered the two most common packages that can cause this error, but there are other packages that use ioredis as a dependency that may also cause this error.

If you are using a package that uses ioredis as a dependency, you can try to find a way to set the family option to 0 either in your connection object or in your REDIS_URL environment variable. Similar to the examples above.

Redis database in a different project

Create a new Redis database in the same project as your application, and connect it to the Redis database using the private network as shown in the examples above.

Read about best pracices to get the most out of the platform here.

Connecting to a Redis database locally

The easiest way to connect to a Redis database locally is to use the public network.

You can do this is by using the REDIS_PUBLIC_URL environment variable to connect to the Redis database.

import Redis from 'ioredis';

const redis = new Redis(process.env.REDIS_PUBLIC_URL);

const ping = await redis.ping();