Module startup_error

Defines a unified error type for failures that can occur during application initialization. Defines the single, top-level error type for all application startup failures.

This module contains the StartupError enum, which aggregates every possible error that can occur during the application’s initialization phase. By consolidating all potential failures into a single type, it provides a unified and robust error handling mechanism for the main function.

Design and Purpose

The StartupError enum is the root of the error handling tree for the entire application launch sequence. It is designed using the thiserror crate to provide several key benefits:

• Unified Error Type: Functions involved in the startup process can return a Result<_, StartupError>, simplifying the function signatures and error propagation logic.

• Automatic Conversion: Through #[from] and #[error(transparent)], many lower-level errors (like ConfigError) are automatically converted into a StartupError variant, reducing boilerplate code.

• Rich Context and Source Chaining: Most variants use #[source] to wrap the original error. This preserves the full error chain, allowing logs to display not just that a subsystem failed to initialize, but exactly why it failed, including the original error from the underlying library.

Error Categories

The startup errors can be grouped into several logical categories:

1. Configuration and Environment Errors: Failures related to loading or parsing the configuration file, invalid command-line arguments, or environment checks (e.g., NotRoot, PidCheckError).

2. Subsystem Initialization Failures: The largest category, covering failures when setting up core components like the logger, database connection, or IPC messaging (LoggingSetupFailure, Database, Messaging).

3. Hardware Interface Failures: Errors that occur when initializing communication with physical hardware, such as Controllino, GPIO pins, I2C devices, or specific sensors (ControllinoSetupFailure, I2cSetupFailure, Ds18b20SetupFailure). These are often conditionally compiled based on the target hardware.

Enums

StartupError

Contains top-level error definitions for errors which may happen at startup. No additional parameter to identify the module is required here.