Unable to acquire JDBC Connection on integration test when using Docker bridge network

Question

When I run maven test locally is passed. But got this error when I run it on CI server.

Error Message
Could not open JPA EntityManager for transaction; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
Stacktrace
org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
Caused by: org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: 
Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Caused by: java.net.UnknownHostException: mysql

When running local test, they all passed, maven test default setting provided by IntelliJ IDEA is used.
Since the error complains about database connection, so I checked by Jenkins Audit to Database Plugin. Connection Successful!

The connection parameter in my application.properties also corresponds to this

spring.datasource.url=jdbc:mysql://mysql:3306/database?useLegacyDatetimeCode=false&serverTimezone=Asia/Shanghai
spring.datasource.username=root
spring.datasource.password=password
spring.datasource.maxActive=5

The MySQL in the URL is the MySQL docker container name. If change it with localhost or private IP in docker container inspect mysql the error message is the same, while the Stacktrace is a little different on last two lines.

for localhost

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Caused by: java.net.ConnectException: Connection refused (Connection refused)

for private IP

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. 
Caused by: java.net.SocketTimeoutException: connect timed out

The different I think is the host in URL, localhost is used for the local test. While the Jenkins server used Docker bridge network.

The container status is:

docker container ls
CONTAINER ID        IMAGE                 COMMAND                  CREATED             STATUS              PORTS
                                          NAMES
51ea7c7864a4        mysql:5.7             "docker-entrypoint.s…"   19 hours ago        Up 19 hours         0.0.0.0:3306->3306/tcp                             mysql
de364f7b5eaf        maven:3-jdk-8         "/usr/local/bin/mvn-…"   21 hours ago        Up 21 hours
                                          optimistic_stallman
a6545591e358        jenkinsci/blueocean   "/sbin/tini -- /usr/…"   43 hours ago        Up 43 hours         0.0.0.0:50000->50000/tcp, 0.0.0.0:2048->8080/tcp   frosty_cray

When I run the JUnit test in IntelliJ, it fails sometimes on the local environment. The error log is like:

Caused by: org.h2.jdbc.JdbcSQLException: Schema "DATABASE" not found; SQL statement:
TRUNCATE TABLE database.data_log 

I have searched the issue, it's said h2 database use upper case by default. After run maven test, this issue will go if run JUnit test in IDE again. But this should be not related to the root cause.

Search on the error message, find some similar question but with different nested exception:

Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException

SpingREST: Could not open JPA EntityManager for transaction; nested exception is org.hiberna

Could not open JPA EntityManager for transaction; org.hibernate.exception.GenericJDBCException: Could not open connection

Could not open JPA EntityManager for transaction in spring

All of them is about nested exception is javax.persistence.PersistenceException
But nested exception is org.hibernate.exception.JDBCConnectionException: is my situation. Read Connect Java to a MySQL database
however since that plugin connects OK, means the connection from Jenkins container to MySQL container is fine.

Summarise:
1. local test with maven passed
2. Jenkins plugin connect to MySQL success
3. Integration test fails when run from Jenkins
4. local test environment is WIN10 64bit; Jenkins run in docker container on Ubuntu 16.04 64bit server, with MySQL 5.7 container connects to the same bridge network.

Answer 1

you should bind docker container mysql port to a port in VM.

This is well explained in the below thread.

Worth trying...
How to connect with MySQL DB running as container in docker?

Answer 2

Thanks to @rohit-thomas. We narrow down the question to something related to the host of the URL.
The simple answer is changing the host of the JDBC URL in the spring boot application.properties to the docker host IP address. From
spring.datasource.url=jdbc:mysql://mysql:3306/database?
to
spring.datasource.url=jdbc:mysql://172.17.0.1:3306/database?

From inside of a Docker container, how do I connect to the localhost of the machine?
This post also helps as the final solution.

ip addr show docker0
4: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default        
    ...   
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       ...

My conclusion is:
The Jenkins container builds from an image is able to communicate with the MySQL container with its container name or private address on docker bridge network. However, as the application built by the Jenkins is not able to do that. Since the MySQL container port has bound to the host machine, the application could communicate with MySQL container through the host port.

If the conclusion is wrong, comments are welcome.