plzcall911 / utility-threadpool-ios

The thread pool and URL dispatch library used by Lightstreamer's iOS client library since v. 1.2

Thread Pool library for iOS

The thread pool and URL dispatch library used by Lightstreamer's iOS client library since v. 1.2

What this library does

This code was written to solve two specific problems of iOS' SDK and runtime:

1. NSOperationQueues are unbound with non-concurrent operations, and even with concurrent operations their maxConcurrentOperationCount is not strictly enforced;

2. iOS runtime has a limit of 5 concurrent NSURLConnections to the same end-point; above this limit connections are going to time-out.

For more informations on this topic, please read the article on Lightstreamer's blog on this specific topic:

• http://blog.lightstreamer.com/2013/01/on-ios-url-connection-parallelism-and.html

What is included:

• an LSThreadPool class that lets you execute invocations on a fixed thread pool, and

• an LSURLDispatcherPool class that uses a thread pool to keep the number of concurrent connections by end-point under control.

• a bonus LSTimerThread class that lets you run timed invocation without using the main thread.

LSThreadPool

Use of LSThreadPool is really simple. Create it with a defined size and name (name will be used for logging):

// Create thread pool
LSThreadPool *threadPool= [[LSThreadPool alloc] initWithName:@"Test" size:4];

Then schedule invocations with its scheduleInvocationForTarget:selector: or scheduleInvocationForTarget:selector:withObject: methods. E.g.:

[threadPool scheduleInvocationForTarget:self selector:@selector(addOne)];

Finally, dispose of the thread pool before releasing it when done:

[threadPool dispose];
[threadPool release];

LSURLDispatcher

The LSURLDispatcher is a singleton and is able to automatically initialize itself. Use it to start a connection request toward a NSURLRequest in one of three possible ways:

• as a synschronous request: in this case the dispatcher will download the request URL and deliver it as a NSData; if the end-point is already at its connection limit, the dispatcher will wait until it can connect;

• as a short request: the dispatcher will connect and send events to your delegate as the connection proceeds; if the end-point is already at its connection limit, the dispatcher will wait until it can connect;

• as a long request: the dispatcher will connect only if the end-point is below its connection limit, otherwise it will raise an exception.

E.g.:

NSURL *url= [NSURL URLWithString:@"http://some/url"];
NSURLRequest *req= [NSURLRequest requestWithURL:url];

LSURLDispatchOperation *op= [[LSURLDispatcher sharedDispatcher] dispatchShortRequest:req delegate:self];

You can also query the dispatcher to know if the a long operation is going to succeed or not (that it: to know if the connection has been reached or not). E.g.:

if (![[LSURLDispatcher sharedDispatcher] isLongRequestAllowed:req])
	NSLog(@"Connection limit reached");

All request will be operated on a separate thread. Each end-point has its own thread pool.

Test cases

A couple of simple test cases are included, which will show the strict enforcement on thread pool size and the strict enforcement of the connection limit per end-point.

License

This software is part of Lightstreamer's iOS client library since version 1.2. It is released as open source under the Apache License 2.0. See LICENSE for more informations.