yyds-fswatch 0.1.8

A high-performance, asyncio-native, and developer-friendly file watching library.

🚀 yyds-fswatch

中文文档 (Chinese Version)

yyds-fswatch is a high-performance, asyncio-native, and developer-friendly file system watching library for Python. It is designed to fully replace and outperform the traditional watchdog library.

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🌟 Core Advantages (vs Watchdog)

Feature	yyds-fswatch (This Library)	watchdog
API Usability	4-level progressive API (Decorators / Callbacks / Sync Iter / Async Iter)	Verbose Observer + Handler class inheritance system
Async Integration	Native coroutine support (async with and async for)	Requires manual threadpools or loop.call_soon_threadsafe bridging
Linux Performance	Zero additional threads (ctypes non-blocking inotify + loop.add_reader)	Starts an independent Python blocking thread for each Emitter
Atomic Save Support	$100%$ compatible. File watches automatically fall back to parent directory + top-level filter	Direct file watching fails and loses watch handle upon Vim/VSCode atomic saves
Debounce & Coalesce	Built-in 50ms sliding window state machine	No debouncing; saving one file triggers dozens of redundant modified events
GitIgnore Pruning	Parses root and nested .gitignore dynamically, pruning directories at registration	No nested parsing/pruning; large repos easily exhaust descriptors
Rename Sync	Robust transaction-packet & cookie pairing. Automatically updates subdirectory path mappings	Subdirectory path mappings get out of sync, reporting stale paths for events
Overflow Resilience	Supported. Emits an overflow event when system buffers are saturated, continuing normally	Unsupported. Misses events silently or crashes the watch thread
Root Self-Healing	Supported. Pauses and polls when root directories are deleted/unmounted, auto-recovering	Unsupported. Crashes with FileNotFoundError or terminates silently

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📦 Installation

To install yyds-fswatch via pip:

pip install -U yyds-fswatch

Or install from source inside the project directory:

pip install .

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🛠️ Progressive API Usage Examples

yyds-fswatch provides four API levels to suit different integration needs.

1. Level 1: Decorator Mode

The most intuitive mode, supporting both synchronous and asynchronous callback functions.

from yyds_fswatch import FSWatcher

w = FSWatcher("./watch_dir", recursive=True, debounce=0.05)

@w.on("created")
def on_created(event):
    print(f"🔥 [CREATED] {'Directory' if event.is_directory else 'File'}: {event.src_path}")

@w.on("modified")
def on_modified(event):
    print(f"⚡ [MODIFIED]: {event.src_path}")

@w.on("deleted")
def on_deleted(event):
    print(f"🗑️ [DELETED]: {event.src_path}")

@w.on("moved")
def on_moved(event):
    print(f"📦 [MOVED]: {event.src_path} -> {event.dest_path}")

# Start watching (blocks current thread; run in a separate thread if non-blocking is needed)
try:
    w.start()
except KeyboardInterrupt:
    w.stop()

2. Level 2: One-Liner Callback

Ideal for quick scripts and debugging.

from yyds_fswatch import watch

# Blocks and runs callback on any file changes
watch("./watch_dir", on_change=lambda event: print(f"⚡ Event: {event.event_type} on {event.src_path}"))

3. Level 3: Sync Standard Iterator

Uses the with context manager to process file events sequentially like a generator.

from yyds_fswatch import FSWatcher

# Starts a background thread within the context and auto-cleans resources upon exit
with FSWatcher("./watch_dir", debounce=0.05) as w:
    for event in w:
        print(f"🔄 [Sync Iter] {event.event_type.upper()}: {event.src_path}")
        if event.event_type == "deleted" and "stop_trigger" in event.src_path:
            break  # Exiting the loop will cleanly terminate the watcher

4. Level 4: Async Native Iterator - ✨ Recommended

Integrates seamlessly with modern async frameworks (FastAPI, Sanic, Tornado). Pure asyncio, zero extra threads.

import asyncio
from yyds_fswatch import FSWatcher

async def main():
    # Pure async context manager and iterator
    async with FSWatcher("./watch_dir", debounce=0.05) as w:
        async for event in w:
            print(f"👀 [Async Iter] {event.event_type.upper()}: {event.src_path}")

asyncio.run(main())

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🛡️ Deep Technical Optimization Details

1. Atomic Save Filtering: For file watches (e.g. data.json), the system automatically monitors its parent directory and intercepts MOVED_TO and CREATE events. It filters out intermediate temporary files, guaranteeing that updates are $100%$ captured regardless of the editor's write mechanism.
2. High-Performance Prefix Matching: Bypasses the expensive try-except ValueError and Path.resolve() system calls during event filtering. Uses in-memory absolute path checks and precomputed string prefix matching to achieve a throughput of over 100,000 checks per second.
3. Robust Lifecycle & Memory Safety: When exiting standard/async loops or catching KeyboardInterrupt, the library cleanly shuts down async event queue hooks. Additionally, a close() mechanism is provided to purge the ignore filter's LRU cache and break cyclic references, allowing Python's GC to immediately collect resources.
4. System Buffer Overflow Prevention (Overflow Event): Under extreme file system activity, OS event queues can saturate (Linux IN_Q_OVERFLOW / Windows ERROR_MORE_DATA). The watcher handles these gracefully by emitting an "overflow" event and continuing monitoring, preventing locks or crash loops.
5. Hierarchical Nested .gitignore Support: Automatically traverses and dynamically parses .gitignore files nested at any subdirectory depth, creating parent-child regex associations for precise, Git-compliant tree pruning.
6. Self-Healing Root Recovery: If a watched root directory is deleted or unmounted, the watcher pauses native OS watches and falls back to a low-overhead retry loop. Monitoring is automatically re-established the moment the path reappears.

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📈 Long-Term Resource Stability (Production Ready)

yyds-fswatch is designed for mission-critical, long-running daemon processes (e.g., chat bots, automated deployment monitors, web servers). It enforces strict resource bounds to run indefinitely (months/years) without memory drift or handle leaks:

• Bounded LRU Cache: The .gitignore filter is backed by a cached lookup capped at a maximum of 4,096 entries (lru_cache(maxsize=4096)). Memory consumption remains constant ($O(1)$) and never leaks even when scanning millions of unique files.
• Idle CPU Overhead is $0.00%$: All native platform drivers (Linux inotify, macOS FSEvents, Windows ReadDirectoryChangesW) are event-driven and wait in the OS kernel until events occur. No polling threads or busy-waiting loops are active when idle.
• Auto-Expiring State Machine: Temporary states (such as rename cookie matching and debouncing queues) auto-expire and purge themselves within 50ms, maintaining a baseline size of zero when idle.
• Watches Pruning & Handle Safety: Subdirectory watches are pruned dynamically at startup based on .gitignore rules (avoiding ENOSPC descriptor limits). System handles/file descriptors are synchronized dynamically when folders are deleted, and are safely closed upon stop.