Cannot connect to multiple databases in the same Mysql container from JDBC (Tomcat)

General Discussions
1

I’m trying to connect to multiple databases in the same mysql container through Tomcat JDBC pooling. My composer config for the database part looks like this:

db:
  image: mysql:5.6
  container_name: mysql5-opencms
  restart: unless-stopped
  environment:
    MYSQL_ROOT_PASSWORD: ######
  volumes:
    - db-mysql5-opencms:/var/lib/mysql
  ports:
    - "3306:3306"
  command: ['mysqld', '--character-set-server=utf8mb4', '--collation-server=utf8mb4_unicode_ci', '--max_allowed_packet=67108864']

volumes:
  db-mysql5-opencms:

Tomcat is able to connect to the first two databases but get’s a timeout for any other database following these two. I tried several combinations and configurations, but it’s always the third pool that starts to fail. The very same Tomcat/JDBC configuration works fine with many databases on a non-docker server.

Resource pools : default idaba_om idaba_intern
Init. JDBC pool : opencms:default (jdbc:mysql://db:3306/opencms?characterEncoding=UTF-8)
Init. JDBC pool : opencms:idaba_om (jdbc:mysql://db:3306/idaba_om?characterEncoding=ISO8859_1)
Wait for DB : opencms:idaba_intern (jdbc:mysql://db:3306/idaba_intern), attempt 1, wait 5,000 ms.
Wait for DB : opencms:idaba_intern (jdbc:mysql://db:3306/idaba_intern), attempt 2, wait 5,000 ms.
Wait for DB : opencms:idaba_intern (jdbc:mysql://db:3306/idaba_intern), attempt 3, wait 5,000 ms.
Wait for DB : opencms:idaba_intern (jdbc:mysql://db:3306/idaba_intern), attempt 4, wait 5,000 ms.
Wait for DB : opencms:idaba_intern (jdbc:mysql://db:3306/idaba_intern), attempt 5, wait 5,000 ms.

Any idea what’s happening here?

2

I found the solution:

The official Tomcat docker container has no default character encoding set. Therefore every JDBC pooling connection needs the characterEncoding property set. e.g.:

jdbcUrl.params=?characterEncoding\=UTF-8

After changing that, everything works flawlessly.