How to connect to Redis from inside Docker container using redis-rs?

Question

Code

https://github.com/thiskevinwang/rust-redis-docker/tree/for-stackoverflow

Context:

Written in Rust

Cargo.toml:

[dependencies]
redis = "0.16.0"
hyper = "0.13"

Local development ✅

Things that work:

running a redis docker container bitnami/redis, published with -p 6379:6379
redis-cli can connect to this docker container successfully
browser can hit the rust code at localhost:3000
- GET / displays some text ✅
- GET /redis increments a counter in redis, and displays it ✅

Running rust-code in docker ❌

The rust docker container fails to connect to the redis docker container

running the same redis docker container bitnami/redis,
browser can hit the rust-container at localhost:3000
- GET / displays some text, as before ✅
- GET /redis causes rust code to panic ❌
  
  Connection refused (os error 111)

I'm not sure if this is a problem with me incorrectly handling "docker networking" or if I'm using the redis crate incorrectly (although documentation is pretty sparse).

TIL [Armin Ronacher](https://stackoverflow.com/users/19990/armin-ronacher) is the author of `redis-rs` — Kevin Wang, Jun 28 '20 at 17:14

score 3 · Accepted Answer · answered Jun 28 '20 at 17:22

You have this in docker-compose.yaml:

services:
  hyper:
    build: .
    ports:
      - "3000:3000"
    expose:
      - "3000"
    links:
      - redis # links this container to "redis" container
  redis:
    image: "bitnami/redis:latest"
    ports:
      - "6379:6379"
    expose:
      - "6379"

From the Docker Compose docs on links:

Containers for the linked service are reachable at a hostname identical to the alias, or the service name if no alias was specified.

So therefore the error is on line 70 in main.rs:

let client = redis::Client::open("redis://127.0.0.1:6379")?;

That doesn't work since the redis instance is not running in the same container as your Rust code. You have to connect to it through the link established in your docker compose file, which in this case would be:

let client = redis::Client::open("redis://redis:6379")?;

Once you make this fix fetching GET localhost:3000/redis returns successfully.

Magic! Thanks for such a fast answer/solution @pretzelhammer! — Kevin Wang, Jun 28 '20 at 17:39
You don't need `links:` or `expose:` for this to work; you can connect to the port a container process is listening on via its Compose service name without special setup. [Networking in Compose](https://docs.docker.com/compose/networking/) describes this further. (You do still need to change the host name in the connection string, since `localhost` is generally "this container".) — David Maze, Jun 29 '20 at 00:49

How to connect to Redis from inside Docker container using redis-rs?

Code

Local development ✅

Running rust-code in docker ❌

1 Answers1