The error 'heroku error connecting to redis on localhost 6379' indicates that your application is trying to connect to a Redis server hosted on the same local machine (localhost) at port number 6379. However, this connection attempt is failing, which could be due to several reasons: 1) Redis server might not be running or properly configured on the specified port (6379) on your local machine; 2) Heroku does not support running Redis directly on the localhost; instead, it requires using a dedicated Redis add-on when deploying applications that require Redis; 3) The application's configuration settings might mistakenly point to the localhost when it should actually point to the correct Redis add-on URL on Heroku.
To resolve this issue, follow these steps:
Ensure that you have added a Redis add-on to your Heroku application. You can do this by running the following command in your terminal:
heroku addons:create heroku-redis.
Make sure that your application is using the proper environment variable for the Redis URL provided by Heroku. Check your application's configuration files and modify them if necessary to use the REDIS_URL environment variable in place of any hardcoded references to 'localhost' or '127.0.0.1'.
Update your application to read Redis connection details from the environment variable. For example, in a Node.js app with the 'redis' package installed, you might change your connection setup from
const client = redis.createClient(6379, 'localhost'); to
const client = redis.createClient(process.env.REDIS_URL);.
Finally, redeploy your application to Heroku after making the necessary changes. If the issue persists, double-check your application's logs for further information and ensure that the Redis add-on is correctly attached to your Heroku application.