Signal-Controlled Logger Library Documentation

Key Features

Signal Control

Three real-time signals for dynamic control:

State dump trigger
Logging enable/disable toggle
Log level adjustment

Logging Levels

Three configurable detail levels:

MIN: Critical messages only
STANDARD: Regular operational logs
MAX: Detailed debugging information

Thread Safety

Features ensuring thread-safe operation:

Atomic operations for state management
Mutex protection for file operations
Signal-safe handler implementation

Architecture Overview

graph TD A[Application] --> B[Logger Library] B --> C[Signal Handlers] B --> D[Log File Management] B --> E[State Management] C --> F[Dump Signal] C --> G[Toggle Signal] C --> H[Level Signal] D --> I[Thread-Safe Logging] E --> J[Atomic State] E --> K[Configuration]

Function Call Flow

sequenceDiagram participant App as Application participant Log as Logger participant Sig as Signal Handlers participant File as File System App->>Log: logger_init() Log->>File: Open log file App->>Log: logger_setup_signals() Log->>Sig: Register handlers App->>Log: logger_log() Log->>Log: Check level & enabled Log->>File: Write message Note over App,File: Asynchronous Signals Sig->>Log: handle_dump_signal() Sig->>Log: handle_toggle_signal() Sig->>Log: handle_level_signal()

Memory & Performance Optimizations

Atomic Operations
Use of atomic types for thread-safe state management without heavy locks
Buffer Management
Fixed-size buffers with MAX_LOG_MESSAGE_SIZE to prevent memory allocation during logging
Line Buffering
Implementation of line buffering (setvbuf) for optimal I/O performance
Minimal Critical Sections
File mutex locked only during actual write operations
Signal Handler Safety
Async-signal-safe operations in signal handlers to prevent deadlocks

Code Structure

classDiagram class LoggerState { +atomic_bool is_logging_enabled +atomic_uint log_level +FILE* log_file +const char* dump_file_prefix +pthread_mutex_t file_mutex +atomic_uint_least64_t dump_counter } class LoggerConfig { +const char* log_file_path +const char* dump_file_prefix +void (*dump_state_callback)() } class SignalHandlers { +handle_dump_signal() +handle_toggle_signal() +handle_level_signal() } LoggerState --> LoggerConfig LoggerState --> SignalHandlers