Ideally it would only be called once, and in future maybe it can, but
right now we need to cope with these cases:
* Downstream parent notifies us of disconnection (DEL_ROUTE)
* We notify ourself of disconnection
* We notify ourself and so does downstream parent
It's case 3 that causes the error.
When Stream.connect() fails, have it just use on_disconnect(). Now there
is a single disconnect cleanup path.
Remove cutpasted DiagLogStream setup/destruction, and move it into the
base class (temporarily), and only manage the lifetime of its underlying
FD via Side.close(). This cures another EBADF failure.
The previous approach was crap since it left e.g. socketpair instances
lying around for GC with their underlying FD already closed, coupled
with FD number reuse, led to random madness when GC finally runs.
Now poller is start enough to know a start_receive() during an iteration
does not cause events yielded by that iteration to associate with the
wrong descriptor.
These changes are tangentially related to the associated ticket, but
event versioning is still the underlying issue.
Receiving DEL_ROUTE without a corresponding ADD_ROUTE is now legit
behaviour, so don't print an error in this case.
Don't print an error for dropped messages if the reply_to indicates the
sender doesn't care about a response (dead and no_reply)
Earlier commit moved Stream.routes attribute into a private map
belonging to RouteMonitor, to make upgrades smoother. This adds a new
accessor method to RouteMonitor.
Now rather than simply propagate DEL_ROUTE upwards towards the parent,
we broadcast it downward to any stream that ever sent a message toward
any of the routes that have just become disconnected.
When unpickling a context, arrange for there to be a single instance
representing that context, managed by the corresponding router. This
context_by_id() was already in use by parent.py, it just needs to move
down.
This to eventually reach the point where a single Context exists that
needs 'disconnect' fired on it, so all sleeping receivers are definitely
woken.