Created by Olga Pavlova
Olga.Pavlova@jetbrains.com

Task:
Debug the SpringBoot application by running it inside one container with the connection to the mysql database from another container.

It is a spring boot application for the local bus service.
The database image is already pre-populated and its name is: opavlova/db-mysql:5.7-test
    container mysql port: 3306
    db name: DOCKERDB
    password: root
    login: root

For it I have a docker-compose file with two services.
One contains only java for running the application. Another is the mysql database.


Steps:
1. Install Docker integration plugin if it is not installed
2. Create a SpringBoot run configuration with the docker-compose run target
-create a spring boot run configuration if not created (class  com.example.demo.DemoApplication)
-click on "Manage targets" in the "Run on" section
-click "Add new target..."->"Docker Compose..."
-the docker-compose file is auto-selected (or you can select any other file)
-select "java" service
-click "Next" and wait until the target image is built and java path is auto-detected
-click "Next" and see the detected JDK home and version
-click "Create" and see the created target in the Run Targets dialog
-click OK
-select in the "Run on" field the created target
Note: you can create a target using a Dockerfile, an image or a docker-compose file. But in this case we use a Compose target because we need to add the both services into one network, so the application from one container can have access to the database from another container.
5. Create a docker-compose run configuration with the database:
-go to Run configurations->Add->Docker->Docker Compose
-select docker-compose.yaml file
-select "db" Service in the "Service" field
-press "Apply"
6. DB should run before staring the application:
-open Spring Boot run configuration
-click "Modify options"
-select "Add before launch task" in the "Before Launch" section
-select "Run Another Configuration" task
-select the created docker-compose run configuration
-Apply
Spring Boot run configuration starts only if DB starts Ok, for it we have a healthcheck in the db compose service. If the database doesn't start(the service is unhealthy) then the Spring Boot run configuration will not be started.

Now you can run and debug the spring boot application.
The app is here: http://localhost:<local-port>/entitybus/post
Note: <local-port> is a random port provided by Docker, you can find it in the Run/Debug window, there will be something like "Application port 8080 is bound to local port 50855"
DB is available here: jdbc:mysql://0.0.0.0:13306/DOCKERDB


Problems, that can happen:
1. the target image build doesn't find java
 To fix:
 -maybe your image doesn't have java, take another image.
 -press "Previous" button and "Next" again, maybe for the first time something went wrong

2. the "connection link failure" in the application container
To fix:
-check the correctness of the database url from  src\main\resources\application.properties
It should be in our case jdbc:mysql://db:3306/DOCKERDB


3. The Spring Boot configuration doesn't start, Docker Compose with the database is started.
To fix:
-check the "Healthy" state of the service. Maybe it is unhealthy and the Spring Boot app cannot be run because of it.
You need to make it healthy(db should run ok).



Tips:
-run commands like "bash" etc inside the containers:
use DockerView->select a container->context menu-> "exec"

-select one of the services to run in the compose file:
go to the compose run configuration, select any service(s) in the "Services" field

-you can connect to the database via Database view:
go to the DataabseView->+->DataSource from Url
url: jdbc:mysql://0.0.0.0:13306/DOCKERDB

-you can check the working application:
upon executing GET request at http://127.0.0.1:<local port>/entitybus/post
Note: find the <local-port> in the Run/Debug window, there will be something like "Application port 8080 is bound to local port 50855"
So, then we have: http://127.0.0.1:50855/entitybus/post