Re: [Libvir] Re: Asynchronous notifications of domain start/stop

Daniel P. Berrange wrote: Understood ... If I understand what you're saying here, you are proposing that libvirt provides a call like this following (don't worry about specifics): virEventDomainNotify (virConnectPtr, int state, void (*f)(...)); The implementation of this call is that it sets up a xenstore watch, and registers the xenstore fd with the previously defined virEventAddHandleFunc (implemented by the main app / app's event loop code). When the event happens, xenstore fd gets some data available, app's event loop triggers this, and calls into libvirt, which then calls the app's callback function ("f"). Is that right? In the remote case it's more tricky. What does the remote's callback function do when it gets an event? (This could happen pretty asynchronously relative to other communications going on -- eg. in the middle of a round of TLS chatter). Choices seem to be: (1) Send the data OOB, unencrypted[1]. (2) Piggy-back the notification on to the reply to the next call [not asynchronous]. (3) Try to work out where we are in the TLS message and if necessary queue the event up and wait for a "safe" place to insert the message in the protocol. (3) seems fairly do-able. Rich. [1] TLS 1.1 includes support for OOB data, but it's not really clear if GnuTLS supports that. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903