mirror of
https://gitlab.com/libvirt/libvirt.git
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6df7d55d39
The generator was disabled for the new event callbacks, since they need to be hand written. This patch adds the C and python glue to expose the new APIs in the python binding. The python example program is extended to demonstrate of the code * python/libvirt-override.c: Registration and dispatch of events at the C layer * python/libvirt-override-virConnect.py: Python glue for events * examples/domain-events/events-python/event-test.py: Demo use of new event callbacks
486 lines
17 KiB
Python
486 lines
17 KiB
Python
#!/usr/bin/python -u
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#
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#
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#
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#################################################################################
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# Start off by implementing a general purpose event loop for anyones use
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#################################################################################
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import sys
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import getopt
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import os
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import libvirt
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import select
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import errno
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import time
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import threading
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#
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# This general purpose event loop will support waiting for file handle
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# I/O and errors events, as well as scheduling repeatable timers with
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# a fixed interval.
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#
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# It is a pure python implementation based around the poll() API
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#
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class virEventLoopPure:
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# This class contains the data we need to track for a
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# single file handle
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class virEventLoopPureHandle:
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def __init__(self, handle, fd, events, cb, opaque):
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self.handle = handle
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self.fd = fd
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self.events = events
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self.cb = cb
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self.opaque = opaque
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def get_id(self):
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return self.handle
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def get_fd(self):
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return self.fd
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def get_events(self):
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return self.events
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def set_events(self, events):
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self.events = events
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def dispatch(self, events):
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self.cb(self.handle,
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self.fd,
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events,
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self.opaque[0],
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self.opaque[1])
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# This class contains the data we need to track for a
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# single periodic timer
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class virEventLoopPureTimer:
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def __init__(self, timer, interval, cb, opaque):
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self.timer = timer
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self.interval = interval
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self.cb = cb
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self.opaque = opaque
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self.lastfired = 0
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def get_id(self):
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return self.timer
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def get_interval(self):
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return self.interval
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def set_interval(self, interval):
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self.interval = interval
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def get_last_fired(self):
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return self.lastfired
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def set_last_fired(self, now):
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self.lastfired = now
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def dispatch(self):
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self.cb(self.timer,
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self.opaque[0],
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self.opaque[1])
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def __init__(self, debug=False):
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self.debugOn = debug
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self.poll = select.poll()
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self.pipetrick = os.pipe()
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self.nextHandleID = 1
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self.nextTimerID = 1
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self.handles = []
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self.timers = []
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self.quit = False
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# The event loop can be used from multiple threads at once.
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# Specifically while the main thread is sleeping in poll()
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# waiting for events to occur, another thread may come along
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# and add/update/remove a file handle, or timer. When this
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# happens we need to interrupt the poll() sleep in the other
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# thread, so that it'll see the file handle / timer changes.
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#
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# Using OS level signals for this is very unreliable and
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# hard to implement correctly. Thus we use the real classic
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# "self pipe" trick. A anonymous pipe, with one end registered
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# with the event loop for input events. When we need to force
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# the main thread out of a poll() sleep, we simple write a
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# single byte of data to the other end of the pipe.
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self.debug("Self pipe watch %d write %d" %(self.pipetrick[0], self.pipetrick[1]))
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self.poll.register(self.pipetrick[0], select.POLLIN)
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def debug(self, msg):
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if self.debugOn:
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print msg
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# Calculate when the next timeout is due to occurr, returning
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# the absolute timestamp for the next timeout, or 0 if there is
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# no timeout due
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def next_timeout(self):
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next = 0
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for t in self.timers:
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last = t.get_last_fired()
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interval = t.get_interval()
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if interval < 0:
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continue
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if next == 0 or (last + interval) < next:
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next = last + interval
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return next
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# Lookup a virEventLoopPureHandle object based on file descriptor
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def get_handle_by_fd(self, fd):
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for h in self.handles:
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if h.get_fd() == fd:
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return h
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return None
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# Lookup a virEventLoopPureHandle object based on its event loop ID
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def get_handle_by_id(self, handleID):
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for h in self.handles:
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if h.get_id() == handleID:
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return h
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return None
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# This is the heart of the event loop, performing one single
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# iteration. It asks when the next timeout is due, and then
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# calcuates the maximum amount of time it is able to sleep
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# for in poll() pending file handle events.
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#
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# It then goes into the poll() sleep.
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#
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# When poll() returns, there will zero or more file handle
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# events which need to be dispatched to registered callbacks
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# It may also be time to fire some periodic timers.
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#
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# Due to the coarse granularity of schedular timeslices, if
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# we ask for a sleep of 500ms in order to satisfy a timer, we
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# may return upto 1 schedular timeslice early. So even though
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# our sleep timeout was reached, the registered timer may not
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# technically be at its expiry point. This leads to us going
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# back around the loop with a crazy 5ms sleep. So when checking
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# if timeouts are due, we allow a margin of 20ms, to avoid
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# these pointless repeated tiny sleeps.
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def run_once(self):
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sleep = -1
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next = self.next_timeout()
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self.debug("Next timeout due at %d" % next)
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if next > 0:
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now = int(time.time() * 1000)
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if now >= next:
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sleep = 0
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else:
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sleep = (next - now) / 1000.0
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self.debug("Poll with a sleep of %d" % sleep)
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events = self.poll.poll(sleep)
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# Dispatch any file handle events that occurred
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for (fd, revents) in events:
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# See if the events was from the self-pipe
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# telling us to wakup. if so, then discard
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# the data just continue
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if fd == self.pipetrick[0]:
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data = os.read(fd, 1)
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continue
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h = self.get_handle_by_fd(fd)
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if h:
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self.debug("Dispatch fd %d handle %d events %d" % (fd, h.get_id(), revents))
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h.dispatch(self.events_from_poll(revents))
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now = int(time.time() * 1000)
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for t in self.timers:
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interval = t.get_interval()
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if interval < 0:
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continue
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want = t.get_last_fired() + interval
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# Deduct 20ms, since schedular timeslice
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# means we could be ever so slightly early
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if now >= (want-20):
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self.debug("Dispatch timer %d now %s want %s" % (t.get_id(), str(now), str(want)))
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t.set_last_fired(now)
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t.dispatch()
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# Actually the event loop forever
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def run_loop(self):
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self.quit = False
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while not self.quit:
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self.run_once()
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def interrupt(self):
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os.write(self.pipetrick[1], 'c')
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# Registers a new file handle 'fd', monitoring for 'events' (libvirt
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# event constants), firing the callback cb() when an event occurs.
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# Returns a unique integer identier for this handle, that should be
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# used to later update/remove it
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def add_handle(self, fd, events, cb, opaque):
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handleID = self.nextHandleID + 1
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self.nextHandleID = self.nextHandleID + 1
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h = self.virEventLoopPureHandle(handleID, fd, events, cb, opaque)
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self.handles.append(h)
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self.poll.register(fd, self.events_to_poll(events))
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self.interrupt()
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self.debug("Add handle %d fd %d events %d" % (handleID, fd, events))
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return handleID
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# Registers a new timer with periodic expiry at 'interval' ms,
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# firing cb() each time the timer expires. If 'interval' is -1,
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# then the timer is registered, but not enabled
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# Returns a unique integer identier for this handle, that should be
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# used to later update/remove it
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def add_timer(self, interval, cb, opaque):
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timerID = self.nextTimerID + 1
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self.nextTimerID = self.nextTimerID + 1
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h = self.virEventLoopPureTimer(timerID, interval, cb, opaque)
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self.timers.append(h)
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self.interrupt()
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self.debug("Add timer %d interval %d" % (timerID, interval))
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return timerID
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# Change the set of events to be monitored on the file handle
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def update_handle(self, handleID, events):
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h = self.get_handle_by_id(handleID)
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if h:
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h.set_events(events)
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self.poll.unregister(h.get_fd())
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self.poll.register(h.get_fd(), self.events_to_poll(events))
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self.interrupt()
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self.debug("Update handle %d fd %d events %d" % (handleID, h.get_fd(), events))
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# Change the periodic frequency of the timer
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def update_timer(self, timerID, interval):
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for h in self.timers:
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if h.get_id() == timerID:
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h.set_interval(interval);
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self.interrupt()
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self.debug("Update timer %d interval %d" % (timerID, interval))
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break
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# Stop monitoring for events on the file handle
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def remove_handle(self, handleID):
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handles = []
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for h in self.handles:
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if h.get_id() == handleID:
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self.poll.unregister(h.get_fd())
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self.debug("Remove handle %d fd %d" % (handleID, h.get_fd()))
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else:
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handles.append(h)
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self.handles = handles
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self.interrupt()
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# Stop firing the periodic timer
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def remove_timer(self, timerID):
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timers = []
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for h in self.timers:
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if h.get_id() != timerID:
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timers.append(h)
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self.debug("Remove timer %d" % timerID)
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self.timers = timers
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self.interrupt()
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# Convert from libvirt event constants, to poll() events constants
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def events_to_poll(self, events):
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ret = 0
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if events & libvirt.VIR_EVENT_HANDLE_READABLE:
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ret |= select.POLLIN
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if events & libvirt.VIR_EVENT_HANDLE_WRITABLE:
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ret |= select.POLLOUT
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if events & libvirt.VIR_EVENT_HANDLE_ERROR:
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ret |= select.POLLERR;
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if events & libvirt.VIR_EVENT_HANDLE_HANGUP:
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ret |= select.POLLHUP;
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return ret
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# Convert from poll() event constants, to libvirt events constants
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def events_from_poll(self, events):
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ret = 0;
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if events & select.POLLIN:
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ret |= libvirt.VIR_EVENT_HANDLE_READABLE;
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if events & select.POLLOUT:
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ret |= libvirt.VIR_EVENT_HANDLE_WRITABLE;
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if events & select.POLLNVAL:
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ret |= libvirt.VIR_EVENT_HANDLE_ERROR;
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if events & select.POLLERR:
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ret |= libvirt.VIR_EVENT_HANDLE_ERROR;
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if events & select.POLLHUP:
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ret |= libvirt.VIR_EVENT_HANDLE_HANGUP;
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return ret;
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###########################################################################
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# Now glue an instance of the general event loop into libvirt's event loop
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###########################################################################
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# This single global instance of the event loop wil be used for
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# monitoring libvirt events
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eventLoop = virEventLoopPure(debug=False)
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# This keeps track of what thread is running the event loop,
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# (if it is run in a background thread)
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eventLoopThread = None
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# These next set of 6 methods are the glue between the official
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# libvirt events API, and our particular impl of the event loop
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#
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# There is no reason why the 'virEventLoopPure' has to be used.
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# An application could easily may these 6 glue methods hook into
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# another event loop such as GLib's, or something like the python
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# Twisted event framework.
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def virEventAddHandleImpl(fd, events, cb, opaque):
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global eventLoop
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return eventLoop.add_handle(fd, events, cb, opaque)
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def virEventUpdateHandleImpl(handleID, events):
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global eventLoop
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return eventLoop.update_handle(handleID, events)
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def virEventRemoveHandleImpl(handleID):
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global eventLoop
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return eventLoop.remove_handle(handleID)
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def virEventAddTimerImpl(interval, cb, opaque):
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global eventLoop
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return eventLoop.add_timer(interval, cb, opaque)
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def virEventUpdateTimerImpl(timerID, interval):
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global eventLoop
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return eventLoop.update_timer(timerID, interval)
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def virEventRemoveTimerImpl(timerID):
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global eventLoop
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return eventLoop.remove_timer(timerID)
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# This tells libvirt what event loop implementation it
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# should use
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def virEventLoopPureRegister():
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libvirt.virEventRegisterImpl(virEventAddHandleImpl,
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virEventUpdateHandleImpl,
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virEventRemoveHandleImpl,
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virEventAddTimerImpl,
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virEventUpdateTimerImpl,
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virEventRemoveTimerImpl)
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# Directly run the event loop in the current thread
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def virEventLoopPureRun():
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global eventLoop
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eventLoop.run_loop()
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# Spawn a background thread to run the event loop
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def virEventLoopPureStart():
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global eventLoopThread
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virEventLoopPureRegister()
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eventLoopThread = threading.Thread(target=virEventLoopPureRun, name="libvirtEventLoop")
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eventLoopThread.setDaemon(True)
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eventLoopThread.start()
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##########################################################################
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# Everything that now follows is a simple demo of domain lifecycle events
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##########################################################################
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def eventToString(event):
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eventStrings = ( "Added",
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"Removed",
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"Started",
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"Suspended",
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"Resumed",
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"Stopped",
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"Saved",
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"Restored" );
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return eventStrings[event];
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def myDomainEventCallback1 (conn, dom, event, detail, opaque):
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print "myDomainEventCallback1 EVENT: Domain %s(%s) %s %d" % (dom.name(), dom.ID(), eventToString(event), detail)
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def myDomainEventCallback2 (conn, dom, event, detail, opaque):
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print "myDomainEventCallback2 EVENT: Domain %s(%s) %s %d" % (dom.name(), dom.ID(), eventToString(event), detail)
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def myDomainEventRebootCallback(conn, dom, opaque):
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print "myDomainEventRebootCallback: Domain %s(%s)" % (dom.name(), dom.ID())
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def myDomainEventRTCChangeCallback(conn, dom, utcoffset, opaque):
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print "myDomainEventRTCChangeCallback: Domain %s(%s) %d" % (dom.name(), dom.ID(), utcoffset)
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def myDomainEventWatchdogCallback(conn, dom, action, opaque):
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print "myDomainEventWatchdogCallback: Domain %s(%s) %d" % (dom.name(), dom.ID(), action)
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def myDomainEventIOErrorCallback(conn, dom, srcpath, devalias, action, opaque):
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print "myDomainEventIOErrorCallback: Domain %s(%s) %s %s %d" % (dom.name(), dom.ID(), srcpath, devalias, action)
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def myDomainEventGraphicsCallback(conn, dom, phase, localAddr, remoteAddr, authScheme, subject, opaque):
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print "myDomainEventGraphicsCallback: Domain %s(%s) %d %s" % (dom.name(), dom.ID(), phase, authScheme)
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def usage():
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print "usage: "+os.path.basename(sys.argv[0])+" [uri]"
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print " uri will default to qemu:///system"
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def main():
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try:
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opts, args = getopt.getopt(sys.argv[1:], "h", ["help"] )
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except getopt.GetoptError, err:
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# print help information and exit:
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print str(err) # will print something like "option -a not recognized"
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usage()
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sys.exit(2)
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for o, a in opts:
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if o in ("-h", "--help"):
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usage()
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sys.exit()
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if len(sys.argv) > 1:
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uri = sys.argv[1]
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else:
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uri = "qemu:///system"
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print "Using uri:" + uri
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# Run a background thread with the event loop
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virEventLoopPureStart()
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vc = libvirt.open(uri)
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# Close connection on exit (to test cleanup paths)
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old_exitfunc = getattr(sys, 'exitfunc', None)
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def exit():
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print "Closing " + str(vc)
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vc.close()
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if (old_exitfunc): old_exitfunc()
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sys.exitfunc = exit
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#Add 2 callbacks to prove this works with more than just one
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vc.domainEventRegister(myDomainEventCallback1,None)
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vc.domainEventRegisterAny(None, libvirt.VIR_DOMAIN_EVENT_ID_LIFECYCLE, myDomainEventCallback2, None)
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vc.domainEventRegisterAny(None, libvirt.VIR_DOMAIN_EVENT_ID_REBOOT, myDomainEventRebootCallback, None)
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vc.domainEventRegisterAny(None, libvirt.VIR_DOMAIN_EVENT_ID_RTC_CHANGE, myDomainEventRTCChangeCallback, None)
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vc.domainEventRegisterAny(None, libvirt.VIR_DOMAIN_EVENT_ID_IO_ERROR, myDomainEventIOErrorCallback, None)
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vc.domainEventRegisterAny(None, libvirt.VIR_DOMAIN_EVENT_ID_WATCHDOG, myDomainEventWatchdogCallback, None)
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vc.domainEventRegisterAny(None, libvirt.VIR_DOMAIN_EVENT_ID_GRAPHICS, myDomainEventGraphicsCallback, None)
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# The rest of your app would go here normally, but for sake
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# of demo we'll just go to sleep. The other option is to
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# run the event loop in your main thread if your app is
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# totally event based.
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while 1:
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time.sleep(1)
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if __name__ == "__main__":
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main()
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