Docker compose wait for database service initialisation - mysql

Question

I have a spring boot project which I'd like to containerize using docker.
I have a couple of spring boot applications which connect to same MySql server.
My spring applications requires the database to be completely setup (i.e. all the tables to be created and some data to be inserted in some of the tables) in order to start.
I am using Docker version 18.09.0 and docker-compose version 1.23.1 and ubuntu 16.04 LTS
I have two files create.sql and insert.sql, which I use to initialise the database to be used by the application.
I create the images using the command docker-compose.yml and it runs successfully and creates the images.
I have the following questions.
I assume when using docker-compose, a container starts as soon as all its dependent containers have started. Is there a way to wait for the mysql server to be up and ready to accept connections, before my API container gets started?
If I chose to create containers separately for the applications and mysql, and not use docker-compose, how do I make sure that my applications connect to the mysql container?
Is there any other tool which might help me achieve this?
Note:
I have tried to use docker inspect <container_id> to find the the IpAddress for the mysql container and use it to connect, but it doesn't work as well.
The following are the files I am using to create images.
docker-compose.yml file.
version: '3'
services:
demo-mysql:
image: demo-mysql
build: ./demo-mysql
volumes:
- /mnt/data/mysql-data:/var/lib/mysql
ports:
- 3306:3306
environment:
- MYSQL_ROOT_PASSWORD=root
- MYSQL_DATABASE=demo
- MYSQL_PASSWORD=root
demo-api:
image: demo-api-1.0
build: ./api
depends_on:
- demo-mysql
ports:
- 8080:8080
environment:
- DATABASE_HOST=demo-mysql
- DATABASE_USER=root
- DATABASE_PASSWORD=root
- DATABASE_NAME=demo
- DATABASE_PORT=3306
demo1-app:
image: demo1-app-1.0
build: ./demo1
depends_on:
- demo-mysql
ports:
- 8090:8090
environment:
- DATABASE_HOST=demo-mysql
- DATABASE_USER=root
- DATABASE_PASSWORD=root
- DATABASE_NAME=demo
- DATABASE_PORT=3306
The following is the Dockerfile for the spring boot project
FROM java:8
VOLUME /tmp
ARG DATA_PATH=/src/main/resources
ARG APP_PORT=8080
EXPOSE ${APP_PORT}
ADD /build/libs/demo-api.jar demo-api.jar
ENTRYPOINT ["java","-jar","demo-api.jar"]
The following is the Dockerfile I used to create my mysql image
FROM mysql:5.7
ENV MYSQL_DATABASE=demo \
MYSQL_USER=root \
MYSQL_ROOT_PASSWORD=root
ADD ./1.0/create.sql /docker-entrypoint-initdb.d
ADD ./1.0/insert.sql /docker-entrypoint-initdb.d
EXPOSE 3306

Answer 1

Use the healthcheck feature of docker-compose (https://docs.docker.com/compose/compose-file/#healthcheck).
Something like this:
services:
demo-mysql:
image: demo-mysql
build: ./demo-mysql
volumes:
- /mnt/data/mysql-data:/var/lib/mysql
ports:
- 3306:3306
environment:
- MYSQL_ROOT_PASSWORD=root
- MYSQL_DATABASE=demo
- MYSQL_PASSWORD=root
healthcheck:
test: ["CMD-SHELL", 'mysqladmin ping']
interval: 10s
timeout: 2s
retries: 10
The depending containers will not start until the demo-mysql container is healthy

Answer 2

After trying several approaches, IMO the simplest and most elegant option is using the jwilder/dockerize utility image with its -wait flag. Here is a simple example where I need a MySQL database to be ready before starting my app:
version: "3.8"
services:
# Start MySQL.
db:
image: mysql
# Wait for MySQL to be joinable.
check-db-started:
image: jwilder/dockerize:0.6.1
depends_on:
- db
command: 'dockerize -wait=tcp://db:3306'
# Only start myapp once MySQL is joinable.
myapp:
image: myapp:latest
depends_on:
- check-db-started