Nova uses nova.utils.spawn* to create new threads. This so far relied on
a GreenPool to provide GreenThreads. We changes this pool to a
futurist.GreenThreadPoolExecutor to have an interface where the
implementation can be swapped out to futurist.ThreadPoolExecutor to get
native threads instead.
This is an interface change on utils.spawn as it will return
futurist.Future instead of GreenThread. So couple of fixes needed across
nova to use:
* .result() instead of .wait()
* .add_done_callback() instead of .link(). Here we needed to change the
usage as the new callback does not forward args, so we rely on
closures instead.
This is also an interface and a behavior change for utils.spawn_n as it
now calls utils.spawn internally. This means that top of the above
detailed interface change there is behavior change for spawn_n.
The spawn creates GreenThread a wrapper around greenlet while spawn_n
created only the underlying greenlet. The greenlet cannot be managed
the same way as a more intelligent GreenThread, including the return
value but not limited to it, e.g. the whole cancellation mechanism
is missing from greenlet too. After this patch spawn_n will also use
GreenThread instead of naked greenlet. We consider the resulting small
performance change negligible.
Also the way we implement SpawnIsSynchronousFixture in our test is
adapted along with other test fixture adaptation to call / mock the
right functions.
Change-Id: I3494660e1aaa1db46f9f08494cb5817ec7020cc5
Signed-off-by: Balazs Gibizer <gibi@redhat.com>
d90e7726c0