A new JobCounter class is introduced. The JobCounter keeps
a reference count of Jobs in flight to the JobQueue. When
NetworkOPs needs to stop, in addition to other work, it calls
JobCounter::join(), which waits until all Jobs in flight
have been destroyed before returning. This ensures that all
NetworkOPs Jobs are completed before NetworkOPs declares
itself stopped().
Also, once a JobCounter is join()ed, it refuses to produce
more counted Jobs for the JobQueue. So, once all old Jobs
in flight are done, then NetworkOPs will add no additional
Jobs to the JobQueue.
Other classes besides NetworkOPs should also be able to use
JobCounter. NetworkOPs is a first test case.
Also unneeded #includes were removed from files touched for
other reasons.
The DatabaseImp has threads that asynchronously call JobQueue to
perform database reads. Formerly these threads had the same
lifespan as Database, which was until the end-of-life of
ApplicationImp. During shutdown these threads could call JobQueue
after JobQueue had already stopped. Or, even worse, occasionally
call JobQueue after JobQueue's destructor had run.
To avoid these shutdown conditions, Database is made a Stoppable,
with JobQueue as its parent. When Database stops, it shuts down
its asynchronous read threads. This prevents Database from
accessing JobQueue after JobQueue has stopped, but allows
Database to perform stores for the remainder of shutdown.
During development it was noted that the Database::close()
method was never called. So that method is removed from Database
and all derived classes.
Stoppable is also adjusted so it can be constructed using either
a char const* or a std::string.
For those files touched for other reasons, unneeded #includes
are removed.
An alternative to the unity build, the classic build compiles each
translation unit individually. This adds more modules to the classic build:
* Remove unity header app.h
* Add missing includes as needed
* Remove obsolete NodeStore backend code
* Add app/, core/, crypto/, json/, net/, overlay/, peerfinder/ to classic build
