Allow a VM to specify its migration type as a default choice. The valid
options are "default" (i.e. behave as now), "live" which forces a live
migration only, and "shutdown" which forces a shutdown migration only.
The new option is treated as a VM meta option and is set to default if
not found.
Gevent was completely failure. The API would block during large file
uploads with no obvious solutions beyond "use gunicorn", which is not
suited to this. I originally had this working with the Flask "debug"
server, so just move to using that all the time. SSL is added using a
custom context with the OpenSSL library, so include that as a
dependency.
Use exclusive locks during API events which change VM state. This is
fairly critical to avoid potential duplicate updates. Only implemented
for these specifically required functions to avoid major performance
hits elsewhere.
Avoids situations where two migrates, to different nodes, happen in
rapid succession. Aborts the migration if the current target node no
longer matches what was set at the start of the execution.
The VM migration code was very old, very spaghettified, and prone to
strange failures.
Improve this by taking cues from the node primary migration. Use
synchronization between the nodes to ensure lockstep completion of the
migration in discrete steps.
A proper queue can be built later to integrate with this code more
cleanly.
References #108
By default, Werkzeug would require the entire file (be it an OVA or
image file) to be uploaded and saved to a temporary, fake file under
`/tmp`, before any further processing could occur. This blocked most of
the execution of these functions until the upload was completed.
This entirely defeated the purpose of what I was trying to do, which was
to save the uploads directly to the temporary blockdev in each case,
thus avoiding any sort of memory or (host) disk usage.
The solution is two-fold:
1. First, ensure that the `location='args'` value is set in
RequestParser; without this, the `files` portion would be parsed
during the argument parsing, which was the original source of this
blocking behaviour.
2. Instead of the convoluted request handling that was being done
originally here, instead entirely defer the parsing of the `files`
arguments until the point in the code where they are ready to be
saved. Then, using an override stream_factory that simply opens the
temporary blockdev, the upload can commence while being written
directly out to it, rather than using `/tmp` space.
This does alter the error handling slightly; it is impossible to check
if the argument was passed until this point in the code, so it may take
longer to fail if the API consumer does not specify a file as they
should. This is a minor trade-off and I would expect my API consumers to
be sane here.
Joshua Boniface