Summary

Create a comprehensive guide for developing custom collectors, covering the CRTP base class pattern, platform-specific implementations, thread safety, and testing strategies.

Parent Issue

Part of: [EPIC] docs: Address documentation gaps across all ecosystem systems (kcenon/common_system#325)

Background (Why)

monitoring_system has 18 built-in collectors across 4 categories (core, utility, hardware, container). The system is designed for extensibility via collector_base.h (CRTP pattern) and the plugin system. However, there is no dedicated guide for creating custom collectors. The plugin_development_guide.md covers plugin-level integration but not the collector implementation details.

Source files:

• include/kcenon/monitoring/collectors/collector_base.h — CRTP base class
• include/kcenon/monitoring/interfaces/metric_collector_interface.h — Collector interface
• include/kcenon/monitoring/factory/collector_adapters.h — Factory registration
• include/kcenon/monitoring/factory/metric_factory.h — Collector creation

Scope (What)

Create docs/guides/COLLECTOR_DEVELOPMENT.md covering:

1. Collector Architecture

• collector_base<Derived> CRTP pattern explanation
• metric_collector_interface contract
• Collection lifecycle: initialize → collect → report → cleanup
• Registration via metric_factory

2. Implementing a Custom Collector

class my_collector : public collector_base<my_collector> {
    // Step-by-step implementation guide
};

3. Platform-Specific Collectors

• How existing collectors handle Linux/macOS/Windows
• platform/metrics_provider.h platform abstraction
• Conditional compilation patterns
• Stub behavior on unsupported platforms

4. Thread Safety Requirements

• What thread safety guarantees collectors must provide
• Thread-local buffer integration
• Atomic operations for metric updates
• Safe shutdown procedures

5. Factory Registration

• How to register via metric_factory
• Dynamic loading via plugin system
• Configuration-driven collector selection

6. Testing Custom Collectors

• Unit testing patterns
• Mock metric reporting
• Performance benchmarking
• Platform-specific testing strategies

7. Reference: Built-in Collector Catalog

Acceptance Criteria

• CRTP pattern fully explained with diagrams
• Complete custom collector implementation walkthrough
• Platform-specific implementation patterns documented
• Thread safety requirements clearly stated
• Factory registration process documented
• Testing guide with examples
• Built-in collector reference table