Docker Compose wait for container X before starting Y
Quite recently they've added the depends_on
feature.
Edit:
As of compose version 2.1+ till version 3 you can use depends_on
in conjunction with healthcheck
to achieve this:
From the docs:
version: '2.1'
services:
web:
build: .
depends_on:
db:
condition: service_healthy
redis:
condition: service_started
redis:
image: redis
db:
image: redis
healthcheck:
test: "exit 0"
Before version 2.1
You can still use depends_on
, but it only effects the order in which services are started - not if they are ready before the dependant service is started.
It seems to require at least version 1.6.0.
Usage would look something like this:
version: '2'
services:
web:
build: .
depends_on:
- db
- redis
redis:
image: redis
db:
image: postgres
From the docs:
Express dependency between services, which has two effects:
- docker-compose up will start services in dependency order. In the following example, db and redis will be started before web.
- docker-compose up SERVICE will automatically include SERVICE’s dependencies. In the following example, docker-compose up web will also create and start db and redis.
Note: As I understand it, although this does set the order in which containers are loaded. It does not guarantee that the service inside the container has actually loaded.
For example, you postgres container might be up. But the postgres service itself might still be initializing within the container.
Natively that is not possible, yet. See also this feature request.
So far you need to do that in your containers CMD
to wait until all required services are there.
In the Dockerfile
s CMD
you could refer to your own start script that wraps starting up your container service. Before you start it, you wait for a depending one like:
Dockerfile
FROM python:2-onbuild
RUN ["pip", "install", "pika"]
ADD start.sh /start.sh
CMD ["/start.sh"]
start.sh
#!/bin/bash
while ! nc -z rabbitmq 5672; do sleep 3; done
python rabbit.py
Probably you need to install netcat in your Dockerfile
as well. I do not know what is pre-installed on the python image.
There are a few tools out there that provide easy to use waiting logic, for simple tcp port checks:
- wait-for-it
- dockerize
For more complex waits:
- goss - Explanation blog
Using restart: unless-stopped
or restart: always
may solve this problem.
If worker container
stops when rabbitMQ is not ready, it will be restarted until it is.
Finally found a solution with a docker-compose method. Since docker-compose file format 2.1 you can define healthchecks.
I did it in a example project you need to install at least docker 1.12.0+. I also needed to extend the rabbitmq-management Dockerfile, because curl isn't installed on the official image.
Now I test if the management page of the rabbitmq-container is available. If curl finishes with exitcode 0 the container app (python pika) will be started and publish a message to hello queue. Its now working (output).
docker-compose (version 2.1):
version: '2.1'
services:
app:
build: app/.
depends_on:
rabbit:
condition: service_healthy
links:
- rabbit
rabbit:
build: rabbitmq/.
ports:
- "15672:15672"
- "5672:5672"
healthcheck:
test: ["CMD", "curl", "-f", "http://localhost:15672"]
interval: 30s
timeout: 10s
retries: 5
output:
rabbit_1 | =INFO REPORT==== 25-Jan-2017::14:44:21 ===
rabbit_1 | closing AMQP connection <0.718.0> (172.18.0.3:36590 -> 172.18.0.2:5672)
app_1 | [x] Sent 'Hello World!'
healthcheckcompose_app_1 exited with code 0
Dockerfile (rabbitmq + curl):
FROM rabbitmq:3-management
RUN apt-get update
RUN apt-get install -y curl
EXPOSE 4369 5671 5672 25672 15671 15672
Version 3 no longer supports the condition form of depends_on. So i moved from depends_on to restart on-failure. Now my app container will restart 2-3 times until it is working, but it is still a docker-compose feature without overwriting the entrypoint.
docker-compose (version 3):
version: "3"
services:
rabbitmq: # login guest:guest
image: rabbitmq:management
ports:
- "4369:4369"
- "5671:5671"
- "5672:5672"
- "25672:25672"
- "15671:15671"
- "15672:15672"
healthcheck:
test: ["CMD", "curl", "-f", "http://localhost:15672"]
interval: 30s
timeout: 10s
retries: 5
app:
build: ./app/
environment:
- HOSTNAMERABBIT=rabbitmq
restart: on-failure
depends_on:
- rabbitmq
links:
- rabbitmq