This article provides an example for making docker-compose wait for MySQL container to be ready before starting a dependent docker application container. We’ll use the docker-compose-wait tool tool, which is a small command line utility allowing to wait for a fixed amount of seconds and/or to wait until a TCP port is open on a target image.
You need to add the docker-compose-wait tool in your application Dockerfile.
# Download a template git clone https://github.com/kassambara/docker-compose-wait-for-container.git # Build the demo application cd docker-compose-wait-for-container/ex01-using-wait-tool docker-compose build # Running your app docker-compose run my_super_app # Stopping containers and cleaning docker-compose down rm -rf mysql
Step 0: Download a template
# Download a template git clone https://github.com/kassambara/docker-compose-wait-for-container.git cd docker-compose-wait-for-container/ex02-using-wait-tool
Project folder structure:
files/docker-compose-wait-for-container/ex01-using-wait-tool ├── docker-compose.yml └── my_super_app ├── Dockerfile └── sayhello
Essential project contents:
docker-compose.ymlto run all container services
my_super_appscripts: template Dockerfile to build your application. Here, this demo app will ask your name and then congratulate you!
Step 1: Add the docker-compose-wait tool to your application Dockerfile
Example of Dockerfile using the
FROM alpine:latest # Add hello scripts ADD sayhello /sayhello RUN chmod +x /sayhello # Add docker-compose-wait tool ------------------- ENV WAIT_VERSION 2.7.2 ADD https://github.com/ufoscout/docker-compose-wait/releases/download/$WAIT_VERSION/wait /wait RUN chmod +x /wait CMD ["/sayhello"]
Step 2: Modify your docker-compose.yml file
version: '3.6' services: mysql: image: "mysql:5.7" container_name: mysql restart: always volumes: - ./mysql:/var/lib/mysql environment: - MYSQL_ROOT_PASSWORD=your_password - MYSQL_USER=root - MYSQL_PASSWORD=your_password - MYSQL_DATABASE=wordpress ports: - "3306:3306" expose: - 3306 my_super_app: build: ./my_super_app image: "my_super_app:latest" container_name: my_supper_app depends_on: - mysql command: sh -c "/wait && /sayhello" environment: - WAIT_HOSTS=mysql:3306 - WAIT_HOSTS_TIMEOUT=300 - WAIT_SLEEP_INTERVAL=30 - WAIT_HOST_CONNECT_TIMEOUT=30
- The command
sh -c “/wait && /sayhello”will run the wait tool and then your application, here /sayhello.
- To make your docker application container wait for multiple hosts, the environment variable can be specified as for example
Additional configuration options. The behavior of the wait utility can be configured with the following environment variables:
- WAIT_HOSTS: comma separated list of pairs host:port for which you want to wait.
- WAIT_HOSTS_TIMEOUT: max number of seconds to wait for all the hosts to be available before failure. The default is 30 seconds.
- WAIT_HOST_CONNECT_TIMEOUT: The timeout of a single TCP connection to a remote host before attempting a new connection. The default is 5 seconds.
- WAIT_BEFORE_HOSTS: number of seconds to wait (sleep) before start checking for the hosts availability
- WAIT_AFTER_HOSTS: number of seconds to wait (sleep) once all the hosts are available
- WAIT_SLEEP_INTERVAL: number of seconds to sleep between retries. The default is 1 second.
Step 3: Building and running your app
# Building your app cd docker-compose-wait-for-container/ex01-using-wait-tool docker-compose build # Running your app docker-compose run my_super_app
Console log output looks like this (MySQL example):
After typing your name, you will see a congratulation message from my_super_app
Step 4: Stopping containers and cleaning
docker-compose down rm -rf mysql
This article describes how to make docker-compose wait for MySQL container using the docker-compose-wait tool.
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