Fixed: #1645 Impossible to shut down server before it has started #1646
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Fixes yhirose#1645. `Server::stop` does nothing if the server is not running. This can cause a program to hang it it calls stop before the server processing thread has had time to initialize. It would make sense for a server that has been stopped to refuse to start, but that would be backwards incompatible. Instead, we introduce a new method: `decommission`. It sets the server object to stop and refuse to start. This means it does not matter in which order concurrent threads end up calling `listen` and `decommission`, the result is always that the listening thread will exit.
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Added a new method
decommissiontoServer. This method allows you to shut down the server without caring about if it has already started or not. This avoids the need to wait in a loop for the server thread to be finished starting up before you can safely do operations that could decide to stop it.Waiting for the server thread to finish starting is convenient with
Server::wait_until_ready, but if the server thread performs initializations that could throw exceptions, causing the server to never start up, callingwait_until_readywill hang the program. The only way to guarantee this won't happen in any possible ordering of events is to have an operation that will causelisten_*to exit immediately, whether or not it is called before or after. That is whatdecommissionprovides.Fixes: #1645