Programming: Concurrency Patterns
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Resources
Wikipedia: Concurrency Patterns https://en.wikipedia.org/wiki/Concurrency_pattern
Monitor Object
Safely share an object between multiple threads,
automatically wait in caller until a perform is done.
The caller does not need to know about the perform-lock, it will simply block until the monitor is able to process a new task.Say we only ever want to perform IO from one thread.
We create a WriterMonitor, which might have methods read/write
- in thread-1, we call read(), which blocks while in the background creates and performs a thread
- in thread-2, we call write(), it will automatically block until thread-1's read() call is finished, then it will take lock and write()
Active Object
Safely share an object between threads,
each method call on a proxy-object triggers an execution in a separate thread.
Hides the lock/queue logic from the caller.ex. update a progressbar in the UI thread from a background thread
- Background thread instantiates a proxy object
- On a method call, the proxy returns a Future/Promise (a request is enqueued to UI thread)
- The UI thread eventually performs the task
- 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)