Docker - Redis connect ECONNREFUSED 127.0.0.1:6379 - node.js

Question

I know this is a common error, but I literally spent the entire day trying to get past this error, trying everything I could find online. But I cant find anything that works for me.
I am very new to Docker and using it for my NodeJS + Express + Postgresql + Redis application.
Here is what I have for my docker-compose file:
version: "3.8"
services:
db:
image: postgres:14.1-alpine
restart: always
environment:
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=admin
ports:
- "5432:5432"
volumes:
- db:/var/lib/postgresql/data
- ./db/init.sql:/docker-entrypoint-initdb.d/create_tables.sql
cache:
image: redis:6.2-alpine
restart: always
ports:
- "6379:6379"
command: redis-server --save 20 1 --loglevel warning
volumes:
- cache:/data
api:
container_name: api
build:
context: .
# target: production
# image: api
depends_on:
- db
- cache
ports:
- 3000:3000
environment:
NODE_ENV: production
DB_HOST: db
DB_PORT: 5432
DB_USER: postgres
DB_PASSWORD: admin
DB_NAME: postgres
REDIS_HOST: cache
REDIS_PORT: 6379
links:
- db
- cache
volumes:
- ./:/src
volumes:
db:
driver: local
cache:
driver: local
Here is my app.js upper part:
const express = require('express')
const app = express()
const cors = require('cors')
const redis = require('redis')
const client = redis.createClient({
host: 'cache',
port: 6379,
legacyMode: true // Also tried without this line, same behavior
})
client.connect()
client.on('connect', () => {
log('Redis connected')
})
app.use(cors())
app.use(express.json())
And my Dockerfile:
FROM node:16.15-alpine3.14
WORKDIR ./
COPY package.json ./
RUN npm install
COPY ./ ./
EXPOSE 3000 6379
CMD [ "npm", "run", "serve" ]
npm run serve is nodemon ./app.js.
I also already tried to prune the system and network.
What am I missing? Help!

Answer 1

There are two things to put in mind here,
First of All Docker Network:
Containers are exposed to your localhost system, so as a "Server" you can access each of them directly through the browser or the command-line, But
Taken for granted that you only can access the containers because they are exposed to a default network that is accessible by the root of the system - the docker user which you can inspect by the way.
The deployed containers are not exposed to each other by default, so you need to define a virtual network and expose them to it so they can talk to each other through the ports or the host name -- which will be the container_name
So you need to do two things:
Add a container name to the redis, in the compose file just like you did on the API
Create a network and bind all the services to it, one way of doing that will be:
version: "3.8"
Network:
my-network:
name: my-network
services:
....
cache:
container_name: cache
image: redis:6.2-alpine
restart: always
ports:
- "6379:6379"
command: redis-server --save 20 1 --loglevel warning
volumes:
- cache:/data
networks: # add it in all containers that communicate together
- my-network
Then and only then you can call redis container name as the host, since docker network will create a host name for the service by the container name,
When deploying the whole compose file later, the containers will be created and all will be joined to the network by default on startup and that will allow you API app to communicate with Redis container via the docker container name as the host name
Refer to these resources for more details:
Networking on Docker Compose
Docker Network Overview
A side Unrelated note:
I personally used redis from npm for some testing projects, but I found that ioredis was much better with TypeScript projects and more expected in its behavior
To Avoid any problems with Redis, make sure to create a password and use it to connect, sometimes redis randomly considers the client as a ReadOnly client and fails to find a read replica, adding the password solved it for me