Production usage

Get your Node.js app ready for production

The following sections explain how to handle situations that may occur in your production environment.

Handling errors

Node-Redis provides multiple events to handle various scenarios, among which the most critical is the error event.

This event is triggered whenever an error occurs within the client.

It is crucial to listen for error events.

If a client does not register at least one error listener and an error occurs, the system will throw that error, potentially causing the Node.js process to exit unexpectedly. See the EventEmitter docs for more details.

const client = createClient({
  // ... client options
});
// Always ensure there's a listener for errors in the client to prevent process crashes due to unhandled errors
client.on('error', error => {
    console.error(`Redis client error:`, error);
});

Handling reconnections

If network issues or other problems unexpectedly close the socket, the client will reject all commands already sent, since the server might have already executed them. The rest of the pending commands will remain queued in memory until a new socket is established. This behaviour is controlled by the enableOfflineQueue option, which is enabled by default.

The client uses reconnectStrategy to decide when to attempt to reconnect. The default strategy is to calculate the delay before each attempt based on the attempt number Math.min(retries * 50, 500). You can customize this strategy by passing a supported value to reconnectStrategy option:

1. Define a callback (retries: number, cause: Error) => false | number | Error (recommended)

const client = createClient({
  socket: {
    reconnectStrategy: function(retries) {
        if (retries > 20) {
            console.log("Too many attempts to reconnect. Redis connection was terminated");
            return new Error("Too many retries.");
        } else {
            return retries * 500;
        }
    }
  }
});
client.on('error', error => console.error('Redis client error:', error));

In the provided reconnection strategy callback, the client attempts to reconnect up to 20 times with a delay of retries * 500 milliseconds between attempts. After approximately two minutes, the client logs an error message and terminates the connection if the maximum retry limit is exceeded.

2. Use a numerical value to set a fixed delay in milliseconds.
3. Use false to disable reconnection attempts. This option should only be used for testing purposes.

Timeouts

To set a timeout for a connection, use the connectTimeout option:

const client = createClient({
  socket: {
    // setting a 10-second timeout  
    connectTimeout: 10000 // in milliseconds
  }
});
client.on('error', error => console.error('Redis client error:', error));