autotoc_md1612

doc_id: "LOG-ARCH-003" doc_title: "Dependency Architecture" doc_version: "1.0.0" doc_date: "2026-04-04" doc_status: "Released" project: "logger_system"

category: "ARCH"

Dependency Architecture

‍SSOT: This document is the single source of truth for Dependency Architecture.

Overview

logger_system follows a strict unidirectional dependency model using a tiered architecture. The bidirectional dependency risk identified in Issue #252 has been resolved.

Dependency Tiers

Tier 0: common_system (ILogger, IExecutor, Result<T>)
           ^            ^
           |            |
Tier 1: thread_system   |
           ^            |
           |            |
Tier 2: logger_system --+
           (optional: LOGGER_USE_THREAD_SYSTEM)

Tier 0 (common_system): Provides shared interfaces (ILogger, IExecutor) and types (Result<T>). No dependencies on higher tiers.
Tier 1 (thread_system): Depends only on common_system. Uses ILogger for logging via dependency injection.
Tier 2 (logger_system): Depends on common_system (required) and thread_system (optional, LOGGER_USE_THREAD_SYSTEM=OFF by default).

Abstraction Interfaces

Interface	Defined In	Purpose
`ILogger`	common_system	Allows thread_system to log without depending on logger_system
`IExecutor`	common_system	Allows logger_system to use thread pools without tight coupling
`Result<T>`	common_system	Shared error handling type across all tiers

Resolved: Bidirectional Dependency (Issue #252)

Previous State

Both systems could optionally depend on each other:

logger_system -> thread_system via LOGGER_USE_THREAD_SYSTEM=ON
thread_system -> logger_system via BUILD_WITH_LOGGER_SYSTEM=ON

Current State (Resolved)

logger_system -> thread_system: Optional, off by default. Clean unidirectional dependency.
thread_system -> logger_system: Deprecated via thread_system#336. BUILD_WITH_LOGGER_SYSTEM is off by default and scheduled for removal in v0.5.0.0. thread_system now uses ILogger dependency injection from common_system instead.

CMake Guard

A transitional guard in CMakeLists.txt warns if both flags are enabled simultaneously. This guard will be removed once thread_system#336 is complete and BUILD_WITH_LOGGER_SYSTEM is removed.

Configuration

Recommended (Default)

cmake -B build # Both integrations OFF, standalone mode

With thread_pool Backend

cmake -B build -DLOGGER_USE_THREAD_SYSTEM=ON

Deprecated (Avoid)

# BUILD_WITH_LOGGER_SYSTEM is deprecated in thread_system

cmake -B build -DLOGGER_USE_THREAD_SYSTEM=ON -DBUILD_WITH_LOGGER_SYSTEM=ON

Migration Guide

If you are using BUILD_WITH_LOGGER_SYSTEM=ON in thread_system:

Set BUILD_WITH_LOGGER_SYSTEM=OFF
Inject an ILogger implementation at runtime instead:
#include <kcenon/logger/adapters/common_logger_adapter.h>

auto logger = std::make_shared<kcenon::logger::adapters::common_logger_adapter>();

thread_pool.set_logger(logger); // ILogger dependency injection

common_logger_adapter.h
Log level conversion between logger_system and common_system.

logger_system
Definition compatibility.h:17
This approach has no compile-time dependency on logger_system

Timeline

Milestone	Status	Description
Issue #252	Resolved	Bidirectional risk identified and analyzed
Issue #336	In Progress	thread_system deprecates BUILD_WITH_LOGGER_SYSTEM
v0.5.0.0	Planned	BUILD_WITH_LOGGER_SYSTEM removed from thread_system
Post-v0.5.0.0	Planned	CMake bidirectional guard can be removed from logger_system