Programming: Concurrency Patterns

Resources

Wikipedia: Concurrency Patterns

https://en.wikipedia.org/wiki/Concurrency_pattern

Monitor Object

Manages task execution within a single thread.

Active Object

Decouple thread an object is created in from the thread the object's code will be executed in.
without exposing lock/queue/etc details to the caller.

Thread/Subprocess objects are frequently exposed this way (ex: QtCore.QThread)

• Caller instantiates a proxy object
• On a method call, the proxy returns a Future/Promise object is created (in background, a request is enqueued)
• In background, a worker performs item from queue
• You may wait/join on the Future/Promise to wait for it to return it's results

Producer/Consumer

Safely parallelized task enqueueing/execution.

• A producer adds data to a synchronized queue
• A variable number of consumers process data from a synchronized queue in a loop
• When producer is finished, send a poison pill for each worker, informing it to break/exit the loop gracefully
• Join on worker threads (wait to close)

Blocking Queue

Generic FIFO in shared memory, with put/take methods protected by a lock.
Empowers the Producer/Consumer pattern.

• If the queue has a fixed-size, put blocks until the queue has room for another item.
• Setting max queue size may keep you from running out of memory in high volume producers