Connecting to RabbitMQ container with docker-compose - docker

Question

I want to run RabbitMQ in one container, and a worker process in another. The worker process needs to access RabbitMQ.
I'd like these to be managed through docker-compose.
This is my docker-compose.yml file so far:
version: "3"
services:
rabbitmq:
image: rabbitmq
command: rabbitmq-server
expose:
- "5672"
- "15672"
worker:
build: ./worker
depends_on:
- rabbitmq
# Allow access to docker daemon
volumes:
- /var/run/docker.sock:/var/run/docker.sock
So I've exposed the RabbitMQ ports. The worker process accesses RabbitMQ using the following URL:
amqp://guest:guest#rabbitmq:5672/
Which is what they use in the official tutorial, but localhost has been swapped for rabbitmq, since the the containers should be discoverable with a hostname identical to the container name:
By default Compose sets up a single network for your app. Each container for a service joins the default network and is both reachable by other containers on that network, and discoverable by them at a hostname identical to the container name.
Whenever I run this, I get an connection refused error:
Recreating ci_rabbitmq_1 ... done
Recreating ci_worker_1 ... done
Attaching to ci_rabbitmq_1, ci_worker_1
worker_1 | dial tcp 127.0.0.1:5672: connect: connection refused
ci_worker_1 exited with code 1
I find this interesting because it's using the IP 127.0.0.1 which (I think) is localhost, even though I specified rabbitmq as the hostname. I'm not an expert on docker networking, so maybe this is desired.
I'm happy to supply more information if needed!
Edit
There is an almost identical question here. I think I need to wait until rabbitmq is up and running before starting worker. I tried doing this with a healthcheck:
version: "2.1"
services:
rabbitmq:
image: rabbitmq
command: rabbitmq-server
expose:
- "5672"
- "15672"
healthcheck:
test: [ "CMD", "nc", "-z", "localhost", "5672" ]
interval: 10s
timeout: 10s
retries: 5
worker:
build: .
depends_on:
rabbitmq:
condition: service_healthy
(Note the different version). This doesn't work, however - it will always fail as not-healthy.

Answer 1

Aha! I fixed it. #Ijaz was totally correct - the RabbitMQ service takes a while to start, and my worker tries to connect before it's running.
I tried using a delay, but this failed when the RabbitMQ took longer than usual.
This is also indicative of a larger architectural problem - what happens if the queuing service (RabbitMQ in my case) goes offline during production? Right now, my entire site fails. There needs to be some built-in redundancy and polling.
As described this this related answer, we can use healthchecks in docker-compose 3+:
version: "3"
services:
rabbitmq:
image: rabbitmq
command: rabbitmq-server
expose:
- 5672
- 15672
healthcheck:
test: [ "CMD", "nc", "-z", "localhost", "5672" ]
interval: 5s
timeout: 15s
retries: 1
worker:
image: worker
restart: on-failure
depends_on:
- rabbitmq
Now, the worker container will restart a few times while the rabbitmq container stays unhealthy. rabbitmq immediately becomes healthy when nc -z localhost 5672 succeeds - i.e. when the queuing is live!

Answer 2

Here is the correct working example :
version: "3.8"
services:
rabbitmq:
image: rabbitmq:3.7.28-management
#container_name: rabbitmq
volumes:
- ./etc/rabbitmq/conf:/etc/rabbitmq/
- ./etc/rabbitmq/data/:/var/lib/rabbitmq/
- ./etc/rabbitmq/logs/:/var/log/rabbitmq/
environment:
RABBITMQ_ERLANG_COOKIE: ${RABBITMQ_ERLANG_COOKIE:-secret_cookie}
RABBITMQ_DEFAULT_USER: ${RABBITMQ_DEFAULT_USER:-admin}
RABBITMQ_DEFAULT_PASS: ${RABBITMQ_DEFAULT_PASS:-admin}
ports:
- 5672:5672 #amqp
- 15672:15672 #http
- 15692:15692 #prometheus
healthcheck:
test: [ "CMD", "rabbitmqctl", "status"]
interval: 5s
timeout: 20s
retries: 5
mysql:
image: mysql
restart: always
volumes:
- ./etc/mysql/data:/var/lib/mysql
- ./etc/mysql/scripts:/docker-entrypoint-initdb.d
environment:
MYSQL_ROOT_PASSWORD: root
MYSQL_DATABASE: mysqldb
MYSQL_USER: ${MYSQL_DEFAULT_USER:-testuser}
MYSQL_PASSWORD: ${MYSQL_DEFAULT_PASSWORD:-testuser}
ports:
- "3306:3306"
healthcheck:
test: ["CMD", "mysqladmin" ,"ping", "-h", "localhost"]
timeout: 20s
retries: 10
trigger-batch-process-job:
build: .
environment:
- RMQ_USER=${RABBITMQ_DEFAULT_USER:-admin}
- RMQ_PASS=${RABBITMQ_DEFAULT_PASS:-admin}
- RMQ_HOST=${RABBITMQ_DEFAULT_HOST:-rabbitmq}
- RMQ_PORT=${RABBITMQ_DEFAULT_PORT:-5672}
- DB_USER=${MYSQL_DEFAULT_USER:-testuser}
- DB_PASS=${MYSQL_DEFAULT_PASSWORD:-testuser}
- DB_SERVER=mysql
- DB_NAME=mysqldb
- DB_PORT=3306
depends_on:
mysql:
condition: service_healthy
rabbitmq:
condition: service_healthy

Answer 3

Maybe you dont need to expose/map the ports on the host if you are just accessing the service from another container.
From the documentation:
Expose Expose ports without publishing them to the host machine - they’ll only be accessible to linked services. Only the internal port
can be specified.
expose:
- "3000"
- "8000"
So it should be like this:
version: "3"
services:
rabbitmq:
image: rabbitmq
command: rabbitmq-server
expose:
- "5672"
- "15672"
worker:
build: ./worker
depends_on:
- rabbitmq
# Allow access to docker daemon
volumes:
- /var/run/docker.sock:/var/run/docker.sock
also make sure to connect to rabitmq only when its ready to server on port.

Answer 4

Most clean way for docker compose v3.8
version: "3.8"
services:
worker:
build: ./worker
rabbitmq:
condition: service_healthy
rabbitmq:
image: library/rabbitmq
ports:
- 5671:5671
- 5672:5672
healthcheck:
test: [ "CMD", "nc", "-z", "localhost", "5672" ]
interval: 5s
timeout: 10s
retries: 3