This allows avoid race condition between registering event handlers and
performing some action. The important thing is the event sent after
registering event handlers in qubesd. This means state changes (like
VM start/stop) after 'connection-established' event will be included in
event stream.
QubesOS/qubes-issues#2622
Standard methods return only one value, after operation is completed,
but events-related methods may return multiple values during the method
execution time. Provide a callback for such cases.
Also, according to specification, avoid sending both event and non-event
values.
QubesOS/qubes-issues#2622
Allow method handler to decide if operation could be cancelled. If yes,
when connection to the qubesd is terminated (and
protocol.connection_lost get called) the operation is cancelled using
standard asyncio method - in which case asyncio.CancelledError is thrown
inside method handler. This needs to be explicitly enabled, because
cancellable methods are much harder to write, to maintain consistent
system state.
Caveat: protocol.connection_lost is called only when trying to send some
data to it (and it's already terminated). Which makes this whole
mechanism useful only for events. Otherwise, when sending some data (and
possibly detecting that connection is broken), the operation is already
completed.
QubesOS/qubes-issues#2622
- Get rid of @not_in_api, exchange for explicit @api() decorator.
- Old @no_payload decorator becomes an argument (keyword-only).
- Factor out AbstractQubesMgmt class to be a base class for other mgmt
backends.
- Use async def instead of @asyncio.coroutine.
QubesOS/qubes-issues#2622
This also means we don't check if a VM with given name (in case of
VMProperty) exists in the system, at this stage. But this is ok, lets
not duplicate work of property setter.
QubesOS/qubes-issues#2622
In theory any call could modify config (through events), but lets keep
writes to qubes.xml low. In any case, qubes.xml will be eventually
written (either at next config-modifying call, or daemon exit).
Sanitization of input value is tricky here, and also very important at
the same time. If property define value type (and it's something more
specific than 'str'), use that. Otherwise allow only printable ASCII
characters, and let appropriate event and setter handle value.
At this point I've reviewed all QubesVM properties in this category and
added appropriate setters where needed.
QubesOS/qubes-issues#2622
