[asterisk-dev] [Code Review] Threadpool Support

Mark Michelson reviewboard at asterisk.org
Tue Jan 15 15:28:58 CST 2013

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(Updated Jan. 15, 2013, 3:28 p.m.)

Review request for Asterisk Developers.


This addresses David's findings

* Fixed up some doxygen and updated copyright
* Listener objects are now opaque
* alloc and destroy callbacks no longer exist
* taskprocessors created with listeners now check that the named taskprocessor does not already exist
* The initial size of a threadpool is now communicated in the options struct

I think this covers everything :)


This review adds a generic threadpool for Asterisk.

The threadpool implementation here is very similar to the one implemented in Asterisk SCF. Since this is implemented in C, the "is a" semantics offered by C++ are not available, so that had to be worked around.

The threadpool, when created, creates a taskprocessor. The threadpool itself exists as the private data on a taskprocessor listener. In this way, the threadpool can react to changes on the taskprocessor by informing its threadpool listener.

The threadpool informs its listeners of various changes:
- When a task gets pushed into the threadpool
- When the threadpool's task list has become empty
- When the state of the threadpool's threads has changed, such as when an active thread goes idle or an idle thread is destroyed.

The threadpool listener can react to these changes as it sees fit. This allows for different policies to be adopted by different modules.

The offers some options for automatic behavior for common forms of operation. At allocation, an idle timeout can be specified in order to allow for idle threads to automatically get removed from the threadpool once they have been idle for a certain amount of time. Also, an automatic increment can be specified if the threadpool has tasks added to it and no idle threads are available to handle the task. With these, it may be possible for listeners only to intervene in certain situations. More options can possibly be added if they are not too policy-specific.

This set of changes is dependent on the set of taskprocessor changes introduced in https://reviewboard.asterisk.org/r/2200 . Since these changes were developed in the same branch as the taskprocessor changes, it means that all the taskprocessor changes are also included in this review. While there are minor changes in the taskprocessor code here as compared to the code in review 2200, they are very minor changes, and so close scrutiny of the taskprocessor changes is not as important as the threadpool code itself.

This addresses bug ASTERISK-20691.

Diffs (updated)

  /trunk/main/taskprocessor.c 379127 
  /trunk/include/asterisk/threadpool.h PRE-CREATION 
  /trunk/include/asterisk/taskprocessor.h 379127 
  /trunk/main/threadpool.c PRE-CREATION 
  /trunk/tests/test_taskprocessor.c PRE-CREATION 
  /trunk/tests/test_threadpool.c PRE-CREATION 

Diff: https://reviewboard.asterisk.org/r/2242/diff


A suite of unit tests have been added to ensure that the threadpool works as expected. They all pass.



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