Without this change, logging (even if unused) may account for a
substantial portion of bitcoin-node's and/or client's runtime cpu usage, due
to libmultiprocess's expensive message serialization.
This (along with some recent upstream changes) avoids the overhead by opting
out of log handling for messages that we're not interested in.
Info, Warning, and Error are logged unconditionally to match our behavior
elsewhere. See BCLog::Logger::GetCategoryLogLevel .
Use EventLoopRef to avoid reference counting bugs and be more exception safe
and deal with removal of addClient/removeClient methods in
https://github.com/bitcoin-core/libmultiprocess/pull/160
A test update is also required due to
https://github.com/bitcoin-core/libmultiprocess/pull/160 to deal with changed
reference count semantics. In IpcPipeTest(), it is now necessary to destroy
the client Proxy object instead of just the client Connection object to
decrease the event loop reference count and allow the loop to exit so the test
does not hang on shutdown.
These are currently empty structs but they will be used to pass some
function and object pointers from bitcoin application code to IPC hooks
that run, for example, when a remote object is created or destroyed, or
a new process is created.
