ayafileio 1.4.5

Cross-platform async file API for Python. Blazing fast like Shameimaru Aya.

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ayafileio

当前是英文 | chinese version

"The fastest file I/O in Gensokyo, swift as the Wind God Maiden."
— Aya Shameimaru, always flying at full speed

Cross-platform asynchronous file I/O library using native async I/O where available.
Windows leverages IOCP (I/O Completion Ports), Linux uses io_uring (kernel 5.1+), and macOS uses Dispatch I/O (GCD) for truly non-blocking file operations.

changes

see -> CHANGES

🏆 The Only True Async on All Three Major Platforms

Platform	Backend	True Async	Description
Windows	IOCP	✅	NT kernel native I/O Completion Ports
Linux	io_uring	✅	Next-gen async I/O (kernel 5.1+)
macOS	Dispatch I/O	✅	GCD kernel-level async I/O

ayafileio is the only Python library providing true async file I/O on Windows, Linux, and macOS.

📸 Key Features

Feature	Description
🍃 Zero thread overhead	No background threads on true async platforms
📰 Kernel-level completion	IOCP / io_uring / Dispatch I/O direct to kernel
⚡ High concurrency	Handles thousands of concurrent file operations
🎴 Familiar API	aiofiles-compatible, supports async/await
📖 Text & binary support	Automatic encoding/decoding in text modes
🔧 Unified configuration	Runtime tunable parameters for all backends
🌍 Cross-platform	Windows, Linux, and macOS
🐍 Latest Python	Supports 3.10–3.14, including 3.14t free-threading

🛠️ Installation

pip install ayafileio

System requirements:

• Python 3.10+
• Windows 7+ / Linux (kernel 5.1+ for io_uring) / macOS 10.10+
• No external dependencies, precompiled wheels available

🚀 Quick Start

import asyncio
import ayafileio

async def main():
    # Write to a file — fast as the wind
    async with ayafileio.open("example.txt", "w") as f:
        await f.write("Hello, async world!\n")

    # Read with automatic decoding
    async with ayafileio.open("example.txt", "r", encoding="utf-8") as f:
        content = await f.read()
        print(content)

    # Binary operations
    async with ayafileio.open("data.bin", "rb") as f:
        data = await f.read(1024)
        await f.seek(0, 0)

asyncio.run(main())

⚡ Performance Best Practice

ayafileio's file open/close overhead is already in the microsecond range, but for maximum performance, avoid reopening the same file in a loop.

# ❌ DO NOT DO THIS: repeated open/close in a loop
for i in range(10000):
    async with ayafileio.open("data.bin", "rb") as f:
        data = await f.read()

# ✅ DO THIS: open once, operate many times
async with ayafileio.open("data.bin", "rb") as f:
    for i in range(10000):
        await f.seek(0)
        data = await f.read()

The latter is ~6x faster — it eliminates 9999 unnecessary coroutine scheduling round-trips.

🔍 Backend Information

Check which backend is currently in use:

import ayafileio

info = ayafileio.get_backend_info()
print(info)
# Windows: {'platform': 'windows', 'backend': 'iocp', 'is_truly_async': True}
# Linux:   {'platform': 'linux', 'backend': 'io_uring', 'is_truly_async': True}
# macOS:   {'platform': 'macos', 'backend': 'dispatch_io', 'is_truly_async': True}

⚙️ Unified Configuration

ayafileio provides a unified configuration system that allows runtime tuning:

import ayafileio

# View current configuration
config = ayafileio.get_config()
print(config)

# Update configuration
ayafileio.configure({
    "io_worker_count": 8,
    "buffer_size": 131072,      # 128KB buffer
    "close_timeout_ms": 2000,
})

# Reset to defaults
ayafileio.reset_config()

Configuration Options

Option	Default	Description
handle_pool_max_per_key	64	Max cached handles per file (Windows)
handle_pool_max_total	2048	Max total cached handles (Windows)
io_worker_count	0	IO worker threads, 0=auto
buffer_pool_max	512	Max cached buffers
buffer_size	65536	Buffer size in bytes
close_timeout_ms	4000	Close timeout for pending I/O (ms)
iocp_batch_size	64	IOCP batch completion harvest size (Windows, 1–256)
io_uring_queue_depth	256	io_uring queue depth (Linux)
io_uring_sqpoll	False	Enable SQPOLL mode (Linux)

📚 API Reference

AsyncFile class

class AsyncFile(Generic[T]):
    def __init__(
        self, path: str | Path, mode: str = "rb",
        encoding: str | None = None,
        newline: str | None = None,
        errors: str | None = None,
        auto_flush: bool = False
    ): ...

    # 读取
    async def read(self, size: int = -1) -> T: ...
    async def readline() -> T: ...
    async def readlines(hint: int = -1) -> list[T]: ...
    async def readall() -> T: ...                        # read(-1) 别名
    async def readinto(buf: bytearray | memoryview) -> int: ...  # 零拷贝 [仅二进制]
    async def chunk(chunk_size: int, *, buf: bytearray | memoryview | None = None) -> AsyncGenerator[memoryview, None]: ...  # 流式分块 [仅二进制]

    # 写入
    async def write(self, data: str | bytes) -> int: ...
    async def writelines(lines) -> None: ...              # 批量写入

    # 位置
    async def seek(self, offset: int, whence: int = 0) -> int: ...
    async def tell() -> int: ...
    async def truncate(size: int) -> None: ...

    # 控制
    async def flush(self) -> None: ...
    async def close(self) -> None: ...

    # 属性
    @property
    def closed(self) -> bool: ...
    @property
    def name(self) -> str: ...
    @property
    def mode(self) -> str: ...

    # 状态
    def readable() -> bool: ...
    def writable() -> bool: ...
    def seekable() -> bool: ...
    def fileno() -> int: ...
    def isatty() -> bool: ...

    # 迭代器
    def __aiter__(self) -> AsyncFile[T]: ...
    async def __anext__(self) -> T: ...

Supported Modes

Mode	Description
"r", "rb"	Read (text/binary)
"w", "wb"	Write (text/binary)
"a", "ab"	Append (text/binary)
"x", "xb"	Exclusive create (text/binary)
+ added	Read/write combinations

Configuration Functions

def configure(options: dict) -> None: ...      # Unified configuration
def get_config() -> dict: ...                   # Get current configuration
def reset_config() -> None: ...                 # Reset to defaults
def get_backend_info() -> dict: ...             # Get backend information

File Wrapping

def wrap_file(fd: int, mode: str = "rb", *, owns_fd: bool = False) -> AsyncFile[bytes]: ...

Wrap an existing file descriptor (int) or a file-like object with fileno() as an AsyncFile, backed by the optimal platform backend. Binary mode only.

Pool Management

def drain_handle_pool() -> None: ...            # Drain all cached file handles
def drain_buffer_pool() -> None: ...            # Drain all cached I/O buffers

Use drain_handle_pool() / drain_buffer_pool() to release pooled resources at runtime — useful after bulk tempfile operations or between benchmark rounds.

🧪 Performance Comparison

Scenario 1: Crawlee-style Dataset Append (open/write/close per record)

Simulating Crawlee's Dataset append pattern — 5,000 records, 50 concurrent writers, each writing a single line and closing the file:

Platform	ayafileio	aiofiles	Speedup
Windows (NVMe SSD)	41,336 items/s	9,658 items/s	4.28x
Linux (NVMe SSD)	17,688 items/s	11,455 items/s	1.54x
macOS (NVMe SSD)	29,837 items/s	25,522 items/s	1.17x
Windows (6yr old HDD)	20,251 items/s	13,011 items/s	1.56x

Key findings:

• On Windows enterprise SSD, ayafileio achieves 42x lower P99 latency (0.044ms vs 1.854ms)
• aiofiles shows 96.7% jitter under load; ayafileio only 16.2%
• Even on degraded hardware, ayafileio maintains predictable performance

Test environment: Windows 10/11, Ubuntu 22.04, macOS 14; GitHub Actions enterprise NVMe SSD

Scenario 2: Single-file High-concurrency Random Read

The true test of async I/O — 100,000 concurrent tasks performing random 256B reads on a single shared file handle. No open/close overhead, pure I/O path comparison:

Library	1K concur	10K concur	50K concur	100K concur
ayafileio (IOCP)	7,487 ops/s	46,616 ops/s	28,165 ops/s	19,290 ops/s
aiofiles (threadpool)	7,706 ops/s	7,320 ops/s	2,131 ops/s	2,130 ops/s
sync threadpool	9,492 ops/s	9,469 ops/s	8,840 ops/s	8,660 ops/s
ayafileio vs aiofiles	1.0x	6.4x	13.2x	9.1x

Key findings:

• At low concurrency (1K), all approaches are similar — IOCP setup overhead is amortized
• At 10K+ concurrency, aiofiles' thread pool saturates; throughput drops as concurrency increases — from 7,706 down to 2,130 ops/s (72% degradation)
• ayafileio with IOCP gains throughput at 10K (46,616 ops/s) due to batched completion harvesting via GetQueuedCompletionStatusEx
• At 100K concurrency, ayafileio is 9.1x faster than aiofiles on the same HDD
• The synchronous threadpool (mimicking aiofiles' approach) flatlines at ~8,800 ops/s regardless of concurrency — thread contention ceiling

Test environment: Windows 10, Python 3.14.5, WDC WD10EZEX 7200RPM HDD, 20MB file, 256B random reads

Scenario 3: Extreme Concurrency Stress — 500,000 Concurrent Reads

500,000 asyncio tasks all reading from a single file via IOCP — testing the library's absolute concurrency ceiling:

Metric	Value
Concurrent tasks	500,000
Completion time	21.6s
Throughput	23,116 ops/s
Peak memory (RSS)	~583 MB
Errors	0
Exceptions	0

ayafileio handles half a million concurrent IOCP reads on a single file handle with zero errors. The dual-IOCP worker architecture (2 threads total) processes all 500K completions while aiofiles would require thousands of threads for the same workload — and still be slower.

Tuning: Default Configuration is Optimal

We tested 14 different configuration combinations (iocp_batch_size, buffer_size, buffer_pool_max, io_worker_count) on the HDD at 100K concurrency. Result: every configuration scored within ±3% of the default. The library's auto-tuned defaults already saturate the disk's physical I/O limit — there is no software bottleneck left to tune.

For NVMe SSDs with >500K IOPS capability, increasing iocp_batch_size to 128–256 and buffer_size to 128KB may yield additional gains. Use ayafileio.configure() to experiment:

ayafileio.configure({
    "iocp_batch_size": 128,
    "buffer_size": 131072,
})

🤝 Contributing

Contributions are welcome! Please:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Add tests
4. Ensure benchmarks pass
5. Open a pull request

📄 License

MIT License — see LICENSE for details.

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"Slow is a crime, right?"
— Aya Shameimaru, editor-in-chief of Bunbunmaru News

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