Worker.tidentifies a worker rpc serverspawn(serve) starts a worker Rpc server in another process (the same process)clientconnects to a worker Rpc serverrundispatches on a connection to a worker Rpc server
It is highly recommended for Rpc\_parallel.start\_app and Rpc\_parallel.Make
calls to be top-level. But the real requirements are:
- The master’s state is initialized before any calls to
spawn. This will be achieved either byRpc\_parallel.start\_apporRpc\_parallel.Expert.start\_master\_server\_exn. - Spawned workers (runs of your executable with a certain environment variable
set) must start running as a worker. This will be achieved either by
Rpc\_parallel.start\_apporRpc\_parallel.Expert.worker\_command. - Spawned workers must be able to find their function implementations when they
start running as a worker. These implementations are gathered on the
application of the
Rpc\_parallel.Makefunctor. - The worker implementations must be defined completely and in the same order, regardless of master and worker code paths. This is necessary for the masters and workers to agree on certain generated ids.
Uncaught exceptions in workers will always result in the worker shutting down. The master can be notified of these exceptions in multiple ways:
- If the exception occured in a function implementation
fbeforefis determined, the exception will be returned back to the caller. E.g. the caller ofspawnorrunwill get anError.tdescribing the exception. - If the exception occured after
fis determined,on\_failure exnwill be called (inMonitor.current ()at the time ofspawn) in the spawning process. - If
redirect\_stderrspecifies a file, the worker will also write its exception to that file before shutting down.
The master’s Rpc server will be started with the max\_message\_size,
heartbeat\_config, and handshake\_timeout settings passed in to
start\_app=/=init\_master\_exn.
Each worker’s Rpc server will be started with the settings passed in upon
spawn or serve of that worker.
All client calls will use the corresponding Rpc settings for the given
worker/master that it is connecting to.