twistd sometimes errors with "reactor already installed"

	ivank reported
Trac ID	trac#3785
Type	defect
Created	2009-04-17 16:30:05Z

When using twistd -r , and dropin.cache is not generated yet, and imports the reactor (or imports anything that imports the reactor), twistd fails with:

"/usr/local/bin/twistd: The specified reactor cannot be used, failed with error: reactor already installed."

This only happens if the reactor is imported when the plugin file is loaded (imported?). It does not happen if the reactor is imported in makeService.

I don't believe this is documented anywhere, the error is uninformative, and the failure is hard to track down.

trac-id__3785 3785
type__defect defect
reporter__ivank ivank
priority__normal normal
milestone__ 
branch__ 
branch_author__ 
status__new new
resolution__None None
component__core core
keywords__documentation_twistd documentation twistd
time__1239985805000000 1239985805000000
changetime__1279126898000000 1279126898000000
version__None None
owner__ivank ivank

Start at the twistd entry point and trace reactor selection, plugin loading, and the makeService path. Reproduce the failure with a non-select reactor, an ungenerated dropin.cache, and a plugin that imports the reactor, then compare it with importing the reactor in makeService. Done means the reported startup failure is addressed or made informative, with the behavior documented.