Docker Compose wait for container X before starting Y

I am using rabbitmq and a simple python sample from here together with docker-compose. My problem is that I need to wait for rabbitmq to be fully started. From what I searched so far, I don't know how to wait with container x (in my case worker) until y (rabbitmq) is started.

I found this blog post where he checks if the other host is online. I also found this docker command:

> wait > > Usage: docker wait CONTAINER [CONTAINER...] > > Block until a container stops, then print its exit code.

Waiting for a container to stop is maybe not what I am looking for but if it is, is it possible to use that command inside the docker-compose.yml? My solution so far is to wait some seconds and check the port, but is this the way to achieve this? If I don't wait, I get an error.

docker-compose.yml

worker:
    build: myapp/.
    volumes:
    - myapp/.:/usr/src/app:ro

    links:
    - rabbitmq
rabbitmq:
    image: rabbitmq:3-management

python hello sample (rabbit.py):

import pika
import time

import socket

pingcounter = 0
isreachable = False
while isreachable is False and pingcounter < 5:
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    try:
        s.connect(('rabbitmq', 5672))
        isreachable = True
    except socket.error as e:
        time.sleep(2)
        pingcounter += 1
    s.close()

if isreachable:
    connection = pika.BlockingConnection(pika.ConnectionParameters(
            host="rabbitmq"))
    channel = connection.channel()

    channel.queue_declare(queue='hello')

    channel.basic_publish(exchange='',
                          routing_key='hello',
                          body='Hello World!')
    print (" [x] Sent 'Hello World!'")
    connection.close()

Dockerfile for worker:

FROM python:2-onbuild
RUN ["pip", "install", "pika"]

CMD ["python","rabbit.py"]

Update Nov 2015:

A shell script or waiting inside your program is maybe a possible solution. But after seeing this Issue I am looking for a command or feature of docker/docker-compose itself.

They mention a solution for implementing a health check, which may be the best option. A open tcp connection does not mean your service is ready or may remain ready. In addition to that I need to change my entrypoint in my dockerfile.

So I am hoping for an answer with docker-compose on board commands, which will hopefully the case if they finish this issue.

Update March 2016

There is a proposal for providing a built-in way to determine if a container is "alive". So docker-compose can maybe make use of it in near future.

Update June 2016

It seems that the healthcheck will be integrated into docker in Version 1.12.0

Update January 2017

I found a docker-compose solution see: https://stackoverflow.com/questions/31746182/docker-compose-wait-for-container-x-before-starting-y/41854997#41854997

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

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 Dockerfiles 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.

you can also just add it to the command option eg.

command: bash -c "sleep 5; start.sh"

https://github.com/docker/compose/issues/374#issuecomment-156546513

to wait on a port you can also use something like this

command: bash -c "while ! curl -s rabbitmq:5672 > /dev/null; do echo waiting for xxx; sleep 3; done; start.sh"

to increment the waiting time you can hack a bit more:

command: bash -c "for i in {1..100} ; do if ! curl -s rabbitmq:5672 > /dev/null ; then echo waiting on rabbitmq for $i seconds; sleep $i; fi; done; start.sh"

restart: on-failure did the trick for me..see below

---
version: '2.1'
services:
  consumer:
    image: golang:alpine
    volumes:
      - ./:/go/src/srv-consumer
    working_dir: /go/src/srv-consumer
    environment:
      AMQP_DSN: "amqp://guest:guest@rabbitmq:5672"
    command: go run cmd/main.go
    links:
          - rabbitmq
    restart: on-failure

  rabbitmq:
    image: rabbitmq:3.7-management-alpine
    ports:
      - "15672:15672"
      - "5672:5672"
   

For container start ordering use

depends_on:

For waiting previous container start use script

entrypoint: ./wait-for-it.sh db:5432

This article will help you https://docs.docker.com/compose/startup-order/

Tried many different ways, but liked the simplicity of this: https://github.com/ufoscout/docker-compose-wait

The idea that you can use ENV vars in the docker compose file to submit a list of services hosts (with ports) which should be "awaited" like this: WAIT_HOSTS: postgres:5432, mysql:3306, mongo:27017.

So let's say you have the following docker-compose.yml file (copy/past from repo README):

version: "3"

services:

  mongo:
    image: mongo:3.4
    hostname: mongo
    ports:
      - "27017:27017"

  postgres:
    image: "postgres:9.4"
    hostname: postgres
    ports:
      - "5432:5432"

  mysql:
    image: "mysql:5.7"
    hostname: mysql
    ports:
      - "3306:3306"

  mySuperApp:
    image: "mySuperApp:latest"
    hostname: mySuperApp
    environment:
      WAIT_HOSTS: postgres:5432, mysql:3306, mongo:27017

Next, in order for services to wait, you need to add the following two lines to your Dockerfiles (into Dockerfile of the services which should await other services to start):

ADD https://github.com/ufoscout/docker-compose-wait/releases/download/2.5.0/wait /wait
RUN chmod +x /wait

The complete example of such sample Dockerfile (again from the project repo README):

FROM alpine

## Add your application to the docker image
ADD MySuperApp.sh /MySuperApp.sh

## Add the wait script to the image
ADD https://github.com/ufoscout/docker-compose-wait/releases/download/2.5.0/wait /wait
RUN chmod +x /wait

## Launch the wait tool and then your application
CMD /wait && /MySuperApp.sh

For other details about possible usage see README

If you want to start service only then another service successfully completed (for example migration, data population, etc), docker-compose version 1.29, comes with build in functionality for this - service_completed_successfully.

depends_on:
  <service-name>:
    condition: service_completed_successfully

According to specification:

> service_completed_successfully - specifies that a dependency is expected to run to successful completion before starting a dependent service

You can also solve this by setting an endpoint which waits for the service to be up by using netcat (using the docker-wait script). I like this approach as you still have a clean command section in your docker-compose.yml and you don't need to add docker specific code to your application:

version: '2'
services:
  db:
    image: postgres
  django:
    build: .
    command: python manage.py runserver 0.0.0.0:8000
    entrypoint: ./docker-entrypoint.sh db 5432
    volumes:
      - .:/code
    ports:
      - "8000:8000"
    depends_on:
      - db

Then your docker-entrypoint.sh:

#!/bin/sh

postgres_host=$1
postgres_port=$2
shift 2
cmd="$@"

# wait for the postgres docker to be running
while ! nc $postgres_host $postgres_port; do
  >&2 echo "Postgres is unavailable - sleeping"
  sleep 1
done

>&2 echo "Postgres is up - executing command"

# run the command
exec $cmd

This is nowadays documented in the official docker documentation.

PS: You should install netcat in your docker instance if this is not available. To do so add this to your Docker file :

RUN apt-get update && apt-get install netcat-openbsd -y 

There is a ready to use utility called "docker-wait" that can be used for waiting.

basing on this blog post https://8thlight.com/blog/dariusz-pasciak/2016/10/17/docker-compose-wait-for-dependencies.html

I configured my docker-compose.yml as shown below:

version: "3.1"

services:
  rabbitmq:
    image: rabbitmq:3.7.2-management-alpine
    restart: always
    environment:
      RABBITMQ_HIPE_COMPILE: 1
      RABBITMQ_MANAGEMENT: 1
      RABBITMQ_VM_MEMORY_HIGH_WATERMARK: 0.2
      RABBITMQ_DEFAULT_USER: "rabbitmq"
      RABBITMQ_DEFAULT_PASS: "rabbitmq"
    ports:
      - "15672:15672"
      - "5672:5672"
    volumes:
      - data:/var/lib/rabbitmq:rw

  start_dependencies:
    image: alpine:latest
    links:
      - rabbitmq
    command: >
      /bin/sh -c "
        echo Waiting for rabbitmq service start...;
        while ! nc -z rabbitmq 5672;
        do
          sleep 1;
        done;
        echo Connected!;
      "

volumes:
  data: {}

Then I do for run =>:

docker-compose up start_dependencies

rabbitmq service will start in daemon mode, start_dependencies will finish the work.

In version 3 of a Docker Compose file, you can use RESTART.

For example:

docker-compose.yml

worker:
    build: myapp/.
    volumes:
    - myapp/.:/usr/src/app:ro
    restart: on-failure
    depends_on:
    - rabbitmq
rabbitmq:
    image: rabbitmq:3-management

Note that I used depends_on instead of links since the latter is deprecated in version 3.

Even though it works, it might not be the ideal solution since you restart the docker container at every failure.

Have a look to RESTART_POLICY as well. it let you fine tune the restart policy.

When you use Compose in production, it is actually best practice to use the restart policy :

> Specifying a restart policy like restart: always to avoid downtime

Not recommended for serious deployments, but here is essentially a "wait x seconds" command.

With docker-compose version 3.4 a start_period instruction has been added to healthcheck. This means we can do the following:

docker-compose.yml:

version: "3.4"
services:
  # your server docker container
  zmq_server:
    build:
      context: ./server_router_router
      dockerfile: Dockerfile

  # container that has to wait
  zmq_client:
    build:
      context: ./client_dealer/
      dockerfile: Dockerfile
    depends_on:
      - zmq_server
    healthcheck:
      test: "sh status.sh"
      start_period: 5s

status.sh:

#!/bin/sh

exit 0

What happens here is that the healthcheck is invoked after 5 seconds. This calls the status.sh script, which always returns "No problem". We just made zmq_client container wait 5 seconds before starting!

Note: It's important that you have version: "3.4". If the .4 is not there, docker-compose complains.

I currently also have that requirement of waiting for some services to be up and running before others start. Also read the suggestions here and on some other places. But most of them require that the docker-compose.yml some how has to be changed a bit. So I started working on a solution which I consider to be an orchestration layer around docker-compose itself and I finally came up with a shell script which I called docker-compose-profile. It can wait for tcp connection to a certain container even if the service does not expose any port to the host directy. The trick I am using is to start another docker container inside the stack and from there I can (usually) connect to every service (as long no other network configuration is applied). There is also waiting method to watch out for a certain log message. Services can be grouped together to be started in a single step before another step will be triggered to start. You can also exclude some services without listing all other services to start (like a collection of available services minus some excluded services). This kind of configuration can be bundled to a profile. There is a yaml configuration file called dcp.yml which (for now) has to be placed aside your docker-compose.yml file.

For your question this would look like:

command:
  aliases:
    upd:
      command: "up -d"
      description: |
        Create and start container. Detach afterword.

profiles:
  default:
    description: |
      Wait for rabbitmq before starting worker.
    command: upd
    steps:
      - label: only-rabbitmq
        only: [ rabbitmq ]
        wait:
          - 5@tcp://rabbitmq:5432
      - label: all-others

You could now start your stack by invoking

dcp -p default upd

or even simply by

dcp

as there is only a default profile to run up -d on.

There is a tiny problem. My current version does not (yet) support special waiting condition like the ony You actually need. So there is no test to send a message to rabbit.

I have been already thinking about a further waiting method to run a certain command on host or as a docker container. Than we could extend that tool by something like

...
        wait:
          - service: rabbitmq
            method: container
            timeout: 5
            image: python-test-rabbit
...

having a docker image called python-test-rabbit that does your check.

The benefit then would be that there is no need anymore to bring the waiting part to your worker. It would be isolated and stay inside the orchestration layer.

May be someone finds this helpful to use. Any suggestions are very welcome.

You can find this tool at https://gitlab.com/michapoe/docker-compose-profile

Here is the example where main container waits for worker when it start responding for pings:

version: '3'
services:
  main:
    image: bash
    depends_on:
     - worker
    command: bash -c "sleep 2 && until ping -qc1 worker; do sleep 1; done &>/dev/null"
    networks:
      intra:
        ipv4_address: 172.10.0.254
  worker:
    image: bash
    hostname: test01
    command: bash -c "ip route && sleep 10"
    networks:
      intra:
        ipv4_address: 172.10.0.11
networks:
  intra:
    driver: bridge
    ipam:
      config:
      - subnet: 172.10.0.0/24

However, the proper way is to use healthcheck (>=2.1).

One of the alternative solution is to use a container orchestration solution like Kubernetes. Kubernetes has support for init containers which run to completion before other containers can start. You can find an example here with SQL Server 2017 Linux container where API container uses init container to initialise a database

https://www.handsonarchitect.com/2018/08/understand-kubernetes-object-init.html

I just have 2 compose files and start one first and second one later. My script looks like that:

#!/bin/bash
#before i build my docker files
#when done i start my build docker-compose
docker-compose -f docker-compose.build.yaml up
#now i start other docker-compose which needs the image of the first
docker-compose -f docker-compose.prod.yml up