Conduct a behavioral study of the application

[aasheptunov]

Conduct a behavioral study of the application.

User story:
As a developer, I want to investigate the application's behavior by issues in order, so that to bring the application closer to prod-state.

DoD:

• Investigate the execution order of controllers when ODB accesses the database (will it block?).
• Investigate whether a transaction commit is required in case of a read-only database transaction.
• Investigate time mappers from the database.
• Investigate whether the transaction will be rolled back if an error occurs.

[aasheptunov]

• Investigate whether a transaction commit is required in case of a read-only database transaction. Using a transaction in our case might seem pointless, since we're reading a single field. However, as the number of actions increases, a transaction will be preferable, as it allows us to define the isolation level for a specific transaction.

  It's worth noting that the global transaction isolation level is currently set to READ COMMITTED (the default in PostgreSQL), which ensures that only committed values ​​are read from the database.

  Additionally, using transactions is considered good practice.

  However, I currently don't know how to determine the isolation level for a specific transaction via ODB. It seems I need to use db->execute() for this.

[aasheptunov]

Note: It seems like declaring the 'access' friend class is redundant in our implementation, but we need to check.

Documentation (point 4)
Code

[aasheptunov]

• Investigate whether the transaction will be rolled back if an error occurs.
  The test was performed by adding throw std::runtime_error("Simulated failure"); inside the transaction in the ToDoCommands::create_todo method.

  The result was as follows:

  • The error was caught by the try-catch handler (app-controller.cpp:68) and passed to the (app-controller.cpp:5) AppController::createInternalServerErrorResponse method.

    Server response:

    // Code 500
    {
      "error": "Simulated failure",
      "message": "Internal server error",
      "status": "Error"
    }
    

  • The new "toDo" was not created, indicating that the transaction was rolled back.