This project is created to simulate MySQL locks using a Docker environment to help understand the behavior of online DDL operations and their impact on database locks, as discussed in this article.

• Docker
• Docker Compose

Clone the repository:

git clone <repository-url>
cd dummy-mlocks

Copy the example environment file:

cp .env.example .env

Update the .env file with your configurations if needed.

• DB_CONTAINER : The name of the Docker container running the MySQL database. Possible values are mlocks-v8 for MySQL 8.3 or mlocks-v5 for MySQL 5.7.
• EXEC_DELAY : The delay in seconds used for simulating long-running operations.
• ALGORITHM_LOCK : The algorithm used for online DDL operations. Possible values are INSTANT, INPLACE, or COPY.

Build and start the Docker containers:

make start

The Makefile includes several convenient functions for managing the Docker environment:

• make migrate : Re-runs database migrations using the migrations.sql file.
• make show : Displays the tables in the database.
• make dql : Runs a long-running SELECT query on the bar table.
• make dml : Runs a long-running UPDATE query.
• make ddl-index : Adds an index to the foo table.
• make ddl-fk : Adds a foreign key to the bar table.
• make ddl-column : Adds a new column to the foo table.
• make select [table] : Runs a simple SELECT query against the specified table (limits to 10 rows).
• make update [table] [column] [value] : Updates the first record in the specified table.
• make locks : Displays the current MySQL locks.
• make wlocks : Watches the current MySQL locks in real-time.
• make connect : Connects to the MySQL CLI.
• make bash : Connects to the Docker container's bash shell.
• make logs : Displays Docker logs.

Clean Up To stop and remove all running containers and networks created by Docker Compose, run:

make stop