Make mysql automatically log in via a my.cnf


If you ssh into your environment and try to connect to your database you will get an error

web@app.0:~$ mysql
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2 "No such file or directory")

That is why the documentation mentions connecting by supplying the parameters from PLATFORM_RELATIONSHIPS.

For example: mysql -h database.internal -P 3306 -u user main

However, I’d like to show a trick that allows you to simply type mysql and you will be logged in automatically.

web@app:~$ mysql
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 19


On your local development go to the source code of your project.

  • Create a folder configs with mkdir file_mounts
  • Create an empty file in that directory configs/.my.cnf
  • Make a link from your root directory to that file ln -s configs/.my.cnf .my.cnf
  • Add the mount folder to git: git add configs
  • Edit the file and add a mount point.
        source: local
        source_path: 'configs'
  • As a final step, add a script that automatically reads your PLATFORM_RELATIONSHIPS, and writes them to a .my.cnf:
    deploy: |
        set -e
        echo $PLATFORM_RELATIONSHIPS | base64 -d | jq -r 'to_entries[] | select(.value[].scheme=="mysql") | ["[client]|", "host=",.value[].host, "|user=", .value[].username, "|password=\"", .value[].password,"\""] | @tsv' | tr -d '\t'  | tr '|' '\n' > ~/.my.cnf
  • git commit the changes and push them to your environment


Now, when running the mysql you will automatically log you in to the database and no longer have to pass in the params.
If you are curious why that works, the .my.cnf gets written during the deploy hook, and gets read by the mysql client. You can show the contents of it by running cat .my.cnf