[openstack-dev] [Fuel] Pecan migration status

Przemyslaw Kaminski pkaminski at mirantis.com
Tue Mar 24 07:46:39 UTC 2015


I want to summarize work I've done in spare time on migrating our API to
Pecan [1]. This is partially based on previous Nicolay's work [2]. One
test is still failing there but it's some DB lock and I'm not 100% sure
that this is caused because something is yet not done on Pecan side or
just some bug popped out (I was getting a different DB lock before but
it disappeared after rebasing a fix for [5]).

My main commitment here is the 'reverse' method [3] which is not
provided by default in Pecan. I have kept compatibility with original
reverse method in our code. I have additionally added a 'qs' keyword
argument that is used for adding a query string to the URL (see

I decided to keep original Nicolay's idea of copying all handlers to v2
directory and not just modify original v1 handlers and concentrated
instead of removing hacks around Pecan as in [6] (with post_all,
post_one, put_all, put_one, etc). Merging current v2 into v1 should
drastically decrease the number of changed lines in this patchset.

I have so far found one fault in the URLs in our API that isn't easily
handled by Pecan (some custom _route function would help) and IMHO
should be fixed by rearranging URLs instead of adding _route hacks:
/nodes/interfaces and /nodes/1/interfaces require the same get_all
method in the interfaces controller. And /nodes/interfaces only usage is
for doing a batch node interface update via PUT. The current v2 can be
merged into v1 with some effort.

We sometimes use a PUT request without specifying an object's ID -- this
is unsupported in Pecan but can be easily hacked by giving a dummy
keyword argument to function's definition:

def put(self, dummy=None)

Some bugs in tests were found and fixed (for example, wrong content-type
in headers in [4]).

I haven't put enough thought into error handling there yet, some stuff
is implemented in hooks/error.py but I'm not fully satisfied with it.
Most unfinished stuff I was marking with a TODO(pkaminski).


[1] https://review.openstack.org/158661
[2] https://review.openstack.org/#/c/99069/6
[5] https://bugs.launchpad.net/fuel/+bug/1433528

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