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Issue integrating mariaDB client with MySQL DB

I am running a java application with MySQL as the DB server. DB is a AWS RDS. The MySQL connector is published under GNU/GPL so it has to be substituted with something more lenient. Maria DB client claimed to be compatible. But ever since MariaDB client is being used we are seeing the below intermittent issue during DB intensive activities:
Excption:-
SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/Projectname] threw exception [Request processing failed; nested exception is org.springframework.transaction.CannotCreateTransactionException: Could not open Hibernate Session for transaction; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection] with root cause
java.sql.SQLNonTransientConnectionException: (conn=1530488) Connection is closed
at org.mariadb.jdbc.internal.util.exceptions.ExceptionFactory.createException(ExceptionFactory.java:73)
at org.mariadb.jdbc.internal.util.exceptions.ExceptionFactory.create(ExceptionFactory.java:187)
at org.mariadb.jdbc.internal.protocol.AbstractQueryProtocol.cmdPrologue(AbstractQueryProtocol.java:1940)
Caused by: org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:48)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)
Caused by: java.sql.SQLNonTransientConnectionException: Could not connect to address=(host=XXXXXXXXXX)(port=3306)(type=master) : (conn=1530487) could not load system variables
at org.mariadb.jdbc.internal.util.exceptions.ExceptionFactory.createException(ExceptionFactory.java:73)
at org.mariadb.jdbc.internal.util.exceptions.ExceptionFactory.create(ExceptionFactory.java:192)
at org.mariadb.jdbc.internal.protocol.AbstractConnectProtocol.connectWithoutProxy(AbstractConnectProtocol.java:1372)
I have tried increasing the time_wait and max_allowed_packet to the maximum allowed but the issue still exists.
Versions:-
MySQL - 5.7.26
MariaDB connector - 2.6.2

Just came across this, found an answer. On my side this was for an Aurora 1 MySQL DB (equiv to 5.6).
As per Diego Dupin in https://jira.mariadb.org/browse/CONJ-824:
only good solution is to use option `usePipelineAuth=false&useBatchMultiSend=false`
So your DB connection string might look like this:
jdbc:mysql://127.0.0.1:3307/mydbname?usePipelineAuth=false&useBatchMultiSend=false
More details:
Aurora proxy has a known race condition issue that results in skipping other
queries in proxy buffer. connection might be in hang waiting for query response.
During authentication, socket has a timeout, that will result throwing the error
you describe.
So if `usePipelineAuth` or `useBatchMultiSend` is enable, it might work ... or not.
All pipeline options (`usePipelineAuth` and `useBatchMultiSend`) must be disabled when using aurora.
Problem has been reported to aurora a few times without correction.

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

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.

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.

Some things you can check that might help you resolve this issue.
In application.properties try to use docker host IP address.
from
spring.datasource.url = jdbc:mysql://mysql:3306/DATABASE_URI_PATH
to
spring.datasource.url = jdbc:mysql://192.168.99.100:33060/DATABASE_URI_PATH
Note:
You will need to map your IP and port when you do docker run or ports in docker file.And use the same docker network among your containers.
Verify if you server app can reach your mysql or vice versa. Go inside the docker container and try to ping.

Do not close the application after an unsuccessful attempt to connect to the database java.net.ConnectException database: Connection refused

Spring Boot Data/Postgres.
Problem:
If the resource-database (postgres) is not available when the application starts, the application will fail with an error.
Caused by: org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
...
Caused by: java.net.ConnectException: Connection refused (Connection refused)
Question:
How can I get the application to automatically try to reconnect?
Assumptions:
Use Spring-Retry project to wrap #entityManagerFactory bean with retry attempts.

Have you tried handling the exception?
Try to handle this exception and upon the occurance, the appliaction can re-try connecting to the DB. Of course it would be beneficial to give the user the oportunity to decide if he wishes to re-try in order to avoid the infinite loop.
#KDecker, thank you for a valid point!

java.sql.SQLException: Invalid state, the Connection object is closed

I have a java web application that is running on jetty that connects to SQL server local database (I'm using hibernate). Both the application and the database are in the SAME PC. Everything runs smoothly until I disable the network adapter or unplug the Ethernet wire, at this moment I cannot access my web app and getting this (among other nested exceptions) exception:
Caused by: java.sql.SQLException: Invalid state, the Connection object is closed.
at net.sourceforge.jtds.jdbc.ConnectionJDBC2.checkOpen(ConnectionJDBC2.java:1713)
at net.sourceforge.jtds.jdbc.ConnectionJDBC2.setAutoCommit(ConnectionJDBC2.java:2223)
at org.jboss.resource.adapter.jdbc.BaseWrapperManagedConnection.checkTransaction (BaseWrapperManagedConnection.java:429)
at org.jboss.resource.adapter.jdbc.WrappedConnection.checkTransaction (WrappedConnection.java:525)
at org.jboss.resource.adapter.jdbc.WrappedConnection.commit(WrappedConnection.java:333)
at org.hibernate.transaction.JDBCTransaction.commitAndResetAutoCommit (JDBCTransaction.java:170)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:146)
... 51 more
Any thoughts?
P.S: If you need further info please tell me.

how to solve connection between DB and Application

Currently I am working on a project using spring, hibernate with Microsoft SQL, in this project there is a part to generate invoice. When I run this part to generate invoice it take around 5 to 15 min then I retrieve invoice List from Db and show it in UI. I got exception after it process for around 7 to 10 min.
Note: When I check in Db , invoice is already generated.
How can I solve this issue?
The exception as follows:
org.hibernate.exception.JDBCConnectionException: Cannot open connection
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:99)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449)
com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host 192.168.191.19, port 1433 has failed. Error: "Address already in use: connect. Verify the connection properties, check that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port, and that no firewall is blocking TCP connections to the port.".

I think the driver may be the problem.
Try using jtds driver instead of microsoft dirver.

Check your connection url pattern.Here is sample connection url pattern.
jdbc:sqlserver://localhost:1433;databaseName=AdventureWorks;integratedSecurity=true;