Returning condition variable instead of callback.
Remove CRs.
Use Data::Monad::CondVar.
Avoid undefined warnings.
Add tests for IDCounter.
Fix redundant YAML read.
Make more robust lock.
Add warn for open error, anyway (ref gh-101).
Add gurads for invalid request, not yet test implemented (ref gh-94).
Add tests for invalid requests (close gh-94).
Add gurad for no command.
Return given id for invoke as actual implementation.
Enable to store id information to temporary directory.
Fix incorrect handling for tcp_server.
Update comment according to analysis.