file-sync-system

Local directory synchronization daemon with event-driven architecture, worker processes, and inotify-based change detection.

Overview

file-sync-system is a modular, event-driven file synchronization service for Linux. It monitors multiple source directories and keeps corresponding target directories up to date, reacting to filesystem changes in real time.

The system consists of:

• fss_manager — a long-running daemon that:

  • Tracks monitored directory pairs

  • Watches for file changes using inotify

  • Spawns isolated worker processes for sync operations

  • Handles sync queueing, backpressure, and logging

  • Communicates with a console client over named pipes

• fss_console — an interactive CLI client that:

  • Sends commands to the manager (add, cancel, status, sync, shutdown)

  • Receives structured responses from the manager

  • Logs all user actions and manager replies

• worker — an exec’d subprocess performing:

  • FULL directory synchronization

  • File-level updates (ADDED / MODIFIED / DELETED)

  • Low-level I/O with detailed structured reporting back to the manager

All communication between components uses FIFO pipes (fss_in, fss_out). All file operations use low-level POSIX primitives (open, read, write, unlink, stat, etc.).

Features

Event-driven design

Single poll() loop in the manager handles:

• Console commands

• inotify filesystem events

• Worker reports through non-blocking pipes

Real-time filesystem monitoring

• Uses inotify_add_watch / inotify_rm_watch

• Detects file ADDED, MODIFIED, and DELETED events

Worker pool with queueing

• Configurable max concurrent workers

• New tasks queued when the pool is saturated

• Workers run via fork + exec, report results to manager

Efficient file synchronization

• Skips unnecessary copies (size + mtime check)

• Preserves timestamps (utime) to maintain correctness

• Supports:

  • FULL directory sync

  • Target updates triggered by file-level changes

Structured logging

• Manager log: timestamped entries for all worker actions, PIDs, results

• Console log: user commands + manager responses

Config and startup options

• Config file supports multiple directory pairs

• Manager accepts command-line flags for log paths and worker limit

Build

make        # build all components
make clean
make erase-logs
make prepare_dirs

Individual targets:

make bin/fss_manager
make bin/fss_console
make bin/worker

Usage

Start the manager

./bin/fss_manager -l <manager_log_file> -c <config_file> -n <worker_limit>

Typical:

./bin/fss_manager -l logs/manager.log -c config/dirs.conf -n 4

Start the console client

./bin/fss_console -l <console_log_file>

Example:

./bin/fss_console -l logs/console.log

Console commands

Command	Description
add <src> <trg>	Monitor a directory pair
cancel <src>	Stop monitoring a directory
status <src>	Show state of a monitored pair
sync <src>	Trigger a FULL sync
shutdown	Stop the manager daemon

The console sends requests through fss_in and prints structured responses from fss_out.