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Thread Pools
A thread pool (Wikipedia) accepts and executes lightweight work items called "tasks", using a carefully managed group of dedicated long-running worker threads. The worker threads perform the work items in parallel without forcing each work item to assume the burden of starting and destroying a dedicated thead.
Classes
ThreadPoolInterface
The ThreadPoolInterface abstract interface is
an extension of the OutOfLineExecutor (see the executors architecture
guide) abstract interface, adding startup, shutdown, and
join virtual member functions. It is the base class for our thread
pool classes.
ThreadPool
ThreadPool is the most basic concrete thread pool. The
number of worker threads is adaptive, but configurable with a min/max
range. Idle worker threads are reaped (down to the configured min), while
new worker threads can be created when needed (up to the configured max).
ThreadPoolTaskExecutor
ThreadPoolTaskExecutor is not a thread
pool, but rather a TaskExecutor that uses a ThreadPoolInterface and
a NetworkInterface to execute scheduled tasks. It's configured with a
ThreadPoolInterface over which it takes ownership, and a
NetworkInterface, of which it shares ownership. With these resources
it implements the elaborate TaskExecutor interface (see executors).
NetworkInterfaceThreadPool
NetworkInterfaceThreadPool is a
thread pool implementation that doesn't actually own any worker threads.
It runs its tasks on the background thread of a
NetworkInterface.
Incoming tasks that are scheduled from the NetworkInterface's thread
are run immediately. Otherwise they are queued to be run by the
NetworkInterface thread when it is available.
ThreadPoolMock
ThreadPoolMock is a ThreadPoolInterface. It is not
a mock of a ThreadPool. It has no configurable stored responses. It has
one worker thread and a pointer to a NetworkInterfaceMock, and with these
resources it simulates a thread pool well enough to be used by a
ThreadPoolTaskExecutor in unit tests.