kasthack.AsyncSynchronized

What

kasthack.AsyncSynchronized is a library for making types with asynchronous methods thread safe without falling back to synchronous IO or manually writing proxies.

Why does this exist?

Originally, I needed thread-safe versions of Stream, TextReader, and 'TextWriter' that support async IO. It turns out that TextReader.Synchronized and TextWriter.Synchronized create wrappers which internally fall back to synchronous operations, and Stream.Synchronized doesn't modify async behavior at all. So, I wrote this library that wraps objects into dynamic proxies that enter a SemaphoreSlim on every call.

Implementation

Current version is a PoC whiich relies on Castle.DynamicProxies, so

• It's not exactly fact as there's a ton of reflection under the hood on every call.
• Only virtual members or interface methods get synchronized.
• Non-virtual properties seem to be broken in the proxy library.
• Proxied types must have parameterless constructors(maybe, I've just missed a configuration option somewhere is Castle)
  • You can bypass this by passing an interface as a type parameter.

This library can be rewritten with compile-time code generators or at least with Reflection.Emit.

Usage

1. Take an instance of a type with virtual/abstract members1
2. Call .Synchronized() extension method.
3. Enjoy thread safety.

Properties

.Synchronized(...) doesn't create read locks on property getters by default. You can change this behavior by passing false in allowGetters parameter.

Examples

Check out kasthack.AsyncSynchronized.Tests project.

Performance

Here's a comparison between empty method calls and synchronized wrappers on my laptop:

Empty method:

Method	Mean	Error	StdDev
AsyncTask	18.191 ns	0.1127 ns	0.1054 ns
AsyncTaskWithResult	17.065 ns	0.3587 ns	0.2995 ns
Int	1.988 ns	0.0400 ns	0.0334 ns
Property	2.117 ns	0.0796 ns	0.0917 ns
TaskWithResult	3.330 ns	0.1103 ns	0.1227 ns
Void	2.250 ns	0.0281 ns	0.0250 ns

Synchronized:

Method	Mean	Error	StdDev
AsyncTask	234.2 ns	2.49 ns	2.33 ns
AsyncTaskWithResult	400.9 ns	6.84 ns	5.71 ns
Int	336.0 ns	4.11 ns	3.64 ns
Property	347.2 ns	3.31 ns	2.77 ns
TaskWithResult	368.8 ns	3.52 ns	3.12 ns
Void	215.8 ns	4.28 ns	8.03 ns