RwLock: Reader-Writer lock

Introduction

We can simply protect a shared resource by a lock. But the performance is not good because each reader should run one-by-one.

A Reader-Writer lock can improve the performance by let readers running simultaneously.

By the way, a writer should wait until all readers done. In a frequently read situation, a new reader after the writer can also increase the read count, let read count never decrease to 0. This will starve writer.

RwLock:

1. Let readers running simultaneously.
2. Exclude "multiple readers" and each writer.
3. provide a flag "write_first" to prevent starve writer.

After 1.6.0, RwLock can support multi-thread(default) and multi-process. For multi-process scenario, use rwlock = RwLock(cross_process=True)

Version control

• cy-rwlock XX.YY.ZZ
  1. XX.YY match the latest git tag.
  2. ZZ will increase automatically when new commit appear in master branch.
  3. XX: Update when change architecture
  4. YY: Update when add or modify some features
  5. ZZ: Update when bugfix or minor changes.

Usage

Install

1. pip install cy_rwlock
2. download latest version from https://pypi.org/project/cy_rwlock/#files

Example

from rwlock import RwLock

rwlock = RwLock()

### READER
rwlock.acquire_r()
# read...
rwlock.release_r()

# OR
with rwlock.lock_r():
    # read...

### WRITER
rwlock.acquire_w()
# write...
rwlock.release_w()

# OR
with rwlock.lock_w():
    # write...

Unittest

• local(windows)
  • run scripts\run.bat
• github
  • auto run when push

Deploy

• PyPI version
  • convertd from git tag
    • see setup.py: convert_version()
• local(windows)
  • run scripts\deploy.bat
• github -> PyPI
  • When release in github