In the nova.virt.libvirt.driver.LibvirtDriver. _get_new_connection method two different libvirt event handlers are registered, one for lifecycle events (_event_lifecycle_callback) and one for connection events (_close_callback). These callbacks are called by a native thread that is continually calling libvirt.virEventRunDefaultImpl() in the _native_thread method; the latter method's Docstring contains the following note:
This is a native thread which runs the default
libvirt event loop implementation. This processes
any incoming async events from libvirtd and queues
them for later dispatch. This thread is only
permitted to use libvirt python APIs, and the
driver.queue_event method. In particular any use
of logging is forbidden, since it will confuse
eventlet's greenthread integration
while this rule is adhered to by the _event_lifecycle_callback method, it is violated by _close_callback (the other callback) because it calls the _set_host_enabled method which, among other things, writes to the log.
The _close_callback method needs to be altered so that it does not execute any logic that may interfere with eventlet's greenthread integration.
Correction: the _close_callback is not being called by the native thread that is running _native_thread. It is being called by the native thread that is spawned by tpool.proxy_call which is used to instantiate the connection.