Re: [Openstack] Rationale behind using 'rpc:cast' instead of 'rpc:call' for the method "run_instance"

2012-03-05 Thread Chris Behrens
Right. We want the API to return as quickly as possible. It should not block. I'd argue that live migration should not block the API as well. Any errors should be reported via the instance faults table, but it's definitely less important than builds. Nicolae: Note that the scheduler also do

Re: [Openstack] Rationale behind using 'rpc:cast' instead of 'rpc:call' for the method "run_instance"

2012-03-05 Thread Vishvananda Ishaya
The use of cast is simply so we can return to the user more quickly instead of blocking waiting for a response. There are some cases where failure handling is a little more complicated and is simplified by using a call. The live migration is an example of this. It is much less frequently used

[Openstack] Rationale behind using 'rpc:cast' instead of 'rpc:call' for the method "run_instance"

2012-03-05 Thread Nicolae Paladi
Hi, this is my first posting in this mailing list, so if it's an RTFM question, please point me to the "FM" :-) I would like to know what is the rationale behind using an rpc:cast from scheduler/driver.py when e.g. launching an instance, while rpc.call in driver.py is used only for "trivial" meth