How to connect to a Redis container using Docker Compose?

Question

This docker-compose.yml seems to work OK:

version: '3'
services:
  web:
    image: web-app
    command: bundle exec rackup
    ports:
     - "9292:9292"
    links:
      - redis
  redis:
    image: redis

Command:

docker build -t web-app .; docker-compose up

The Web App is expecting a REDIS_URL config. Web App Dockerfile:

ENV REDIS_URL redis:6379

It seems that the Web App cannot connect to the Redis:

Redis::CannotConnectError - Error connecting to Redis on 127.0.0.1:6379 (Errno::ECONNREFUSED):

So, what is the Redis URL for the Web App?

Do I need to expose the Redis port (6379)?

EDIT:

Thanks to @Andy Shinn, I see the redis url should be redis://6379.
Now I get Errno::EINVAL - Invalid argument - connect(2) for 0.0.24.235:6379. This may have to do with Redis v 3.2.8. I'll try another version and see if it works.

EDIT #2:

3.2.8 works fine with the app on my local machine, so that is not the issue.

Is redis running at that point? What happens if you start them all, and then restart the web after a bit -> that way you know that redis has been started. — Nanne
– Nanne, Commented Feb 21, 2017 at 20:04
That error says the web service is trying to connect to redis at the local IP (127.0.0.1) and not the REDIS_URL which should be the redis DNS name from the link. What kind of application is this? Is it designed to use the REDIS_URL? It would be helpful to post a bit more about the application (Dockerfile, how it uses the REDIS_URL, etc). — Andy Shinn
– Andy Shinn, Commented Feb 21, 2017 at 20:41
Yes, it is configured to use the REDIS_URL. It's a Sinatra app. Other configs work, and production has a REDIS_URL. — B Seven
– B Seven, Commented Feb 21, 2017 at 22:14
@Nanne - Does not seem to be a timing issue. Redis starts before the web app. — B Seven
– B Seven, Commented Feb 21, 2017 at 22:17
Is 0.0.24.235 the IP it's attempting to reach now, or a copy/paste error? — BMitch
– BMitch, Commented Feb 21, 2017 at 22:48

B Seven · Accepted Answer · 2017-02-22 17:40:28Z

57

The issue is that redis is "variable" that will be interpolated in the Dockerfile.

ENV REDIS_URL redis:6379

But the Redis URL should start with the literal redis.

So, the fix is updating the docker compose:

redis_db:
  image: redis:3.2.8

The desired config is:

REDIS_URL=redis://redis_db:6379

Thanks to BMitch and Andy Shinn for helping me figure this out.

edited Feb 22, 2017 at 17:40

answered Feb 22, 2017 at 0:37

B Seven

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4 Comments

B Seven Over a year ago

FWIW, Mongo URL's can have the same issue because they start with mongodb://.

calvin sugianto Over a year ago

do you have any idea how REDIS_URL looks like if i set a password?

Luke Vincent Over a year ago

@calvin redis://user:secret@localhost:6379/0?foo=bar&qux=baz

abhijithvijayan Over a year ago

this saved a lot of time. thank you

Pavlo Sukhorukov · Accepted Answer · 2024-06-03 10:31:44Z

2

I had the same issue. Resolved it by just specifying the network. So in your case it'll be

version: '3'
services:
  web:
    image: web-app
    command: bundle exec rackup
    ports:
     - "9292:9292"
    links:
      - redis
    networks:
      - mynetwork
  redis:
    image: redis
    networks:
      - mynetwork
networks:
  mynetwork:

And in this case redis host is redis

answered Jun 3, 2024 at 10:31

Pavlo Sukhorukov

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Comments

Nishan B · Accepted Answer · 2022-05-21 08:20:45Z

0

The create client config is updated in the new version

doc for the same https://github.com/redis/node-redis/blob/master/docs/client-configuration.md

answered May 21, 2022 at 8:20

Nishan B

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