I definitely have a deadlock problem with Shepherd and I do believe I've found
it.
shepherd 1.0.3
This is in service-controller when the service has been stopped:
(when logger
(put-message logger 'terminate))
But in service-builtin-logger, this is called every time a line is read:
(or pid
(and service
(eq? 'running (service-status service))
(match (service-running-value service)
((? process? process)
(process-id process))
(value
value))))
service-status -> service-control-message -> put-message to the service
The fibers documentation says put-message is blocking. Surely this is a
deadlock.
The value of `pid' can be cached and we might avoid the deadlock.
But this happens ONLY if a line of output is read while the service is 'running.
If output only comes while the service is 'starting/'stopping, we will keep
calling service-status.
Potential fix:
At the time spawn-service-builtin-logger is called in fork+exec-command, we
already know the pid.
Maybe just prepend the pid to the `command' argument if you want it to appear
in the log output.
