[asio-users] Waiting on pending work

[Rory J. <rs...@gm...>]

I found this old thread that asked a similar question, but wanted to bring
it up again: https://sourceforge.net/p/asio/mailman/message/24964454/

In my application, there is a single io_context set up that has two
threads, and is held open by adding another executor by:
  asio::any_io_executor work_ {asio::require(io_context_.get_executor(),
asio::execution::outstanding_work.tracked)};

Then, in individual classes, I use asio::make_strand to derive individual
strands from the single io_context, and work gets assigned through the
strands.

At each class's shutdown, I want to make sure the work is completed before
destroying the class. Currently, I use a std::binary_semaphore, acquire the
semaphore when work first starts, then release the semaphore when the work
cycle exits, whether it exits by a socket error, finish signal, or
exception. Then I acquire the semaphore in the destructor, which forces the
destructor to wait for the semaphore to be released.

The main application is responsible for terminating work_ and the
io_context, which occurs after the individual classes destroy themselves.

This works fine, but is messy and requires careful analysis of the code to
make sure I acquire and release the semaphore correctly in all possible
sequences of events.

It would be much easier to set up a wait on all work done by the thread,
but I do not see a way to do so. Is there some method of setting up a wait
that I'm not aware of?