38 lines
1.7 KiB
Markdown
38 lines
1.7 KiB
Markdown
---
|
|
layout: pattern
|
|
title: Half-Sync/Half-Async
|
|
folder: half-sync-half-async
|
|
permalink: /patterns/half-sync-half-async/
|
|
categories: Concurrency
|
|
tags:
|
|
- Performance
|
|
---
|
|
|
|
## Intent
|
|
The Half-Sync/Half-Async pattern decouples synchronous I/O from
|
|
asynchronous I/O in a system to simplify concurrent programming effort without
|
|
degrading execution efficiency.
|
|
|
|
## Class diagram
|
|
|
|
|
|
## Applicability
|
|
Use Half-Sync/Half-Async pattern when
|
|
|
|
* a system possesses following characteristics:
|
|
* the system must perform tasks in response to external events that occur asynchronously, like hardware interrupts in OS
|
|
* it is inefficient to dedicate separate thread of control to perform synchronous I/O for each external source of event
|
|
* the higher level tasks in the system can be simplified significantly if I/O is performed synchronously.
|
|
* one or more tasks in a system must run in a single thread of control, while other tasks may benefit from multi-threading.
|
|
|
|
## Real world examples
|
|
|
|
* [BSD Unix networking subsystem](https://www.dre.vanderbilt.edu/~schmidt/PDF/PLoP-95.pdf)
|
|
* [Real Time CORBA](http://www.omg.org/news/meetings/workshops/presentations/realtime2001/4-3_Pyarali_thread-pool.pdf)
|
|
* [Android AsyncTask framework](http://developer.android.com/reference/android/os/AsyncTask.html)
|
|
|
|
## Credits
|
|
|
|
* [Douglas C. Schmidt and Charles D. Cranor - Half Sync/Half Async](https://www.dre.vanderbilt.edu/~schmidt/PDF/PLoP-95.pdf)
|
|
* [Pattern Oriented Software Architecture Volume 2: Patterns for Concurrent and Networked Objects](https://www.amazon.com/gp/product/0471606952/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0471606952&linkCode=as2&tag=javadesignpat-20&linkId=889e4af72dca8261129bf14935e0f8dc)
|