On Thu, Jan 07, 2016 at 03:32:39PM -0500, Jay Pipes wrote: > On 01/07/2016 03:01 PM, Jim Rollenhagen wrote: > >On Thu, Jan 07, 2016 at 02:41:12PM -0500, Sean Dague wrote: > >>On 01/07/2016 02:09 PM, Jim Rollenhagen wrote: > >>>Hi all, > >>> > >>>A change to global-requirements[1] introduces mimic, which is an http > >>>server that can mock various APIs, including nova and ironic, including > >>>control of error codes and timeouts. The ironic team plans to use this > >>>for testing python-ironicclient without standing up a full ironic > >>>environment. > >>> > >>>Here's the catch - mimic is built on twisted. I know twisted was > >>>previously removed from OpenStack (or at least people said "pls no", I > >>>don't know the full history). We didn't intend to stealth-introduce > >>>twisted back into g-r, but it was pointed out to me that it may appear > >>>this way, so here I am letting everyone know. lifeless pointed out that > >>>when tests are failing, people may end up digging into mimic or twisted > >>>code, which most people in this community aren't familiar with AFAIK, > >>>which is a valid point though I hope it isn't required often. > >>> > >>>So, the primary question here is: do folks have a problem with adding > >>>twisted here? We're holding off on Ironic changes that depend on this > >>>until this discussion has happened, but aren't reverting the g-r change > >>>until we decide one way or another. > >>> > >>>// jim > >>> > >>>[1] https://review.openstack.org/#/c/220268/ > >> > >>What is the advantage of running another server like this over using > >>requests-mock (which is used by other OpenStack projects for testing > >>today)? The only difference here seems to be that you actually execute > >>requests code in one case and not in the other. > >> > >>Requests-mock debugging when things go wrong seems a bit simpler. > >> > >>This is less about twisted and more about trying to not introduce yet > >>another way to mock code in the tree that people need to understand. > >> > >> -Sean > > > >We'd be using this for functional tests, not unit, where we can't really > >inject mocks. The idea is that we could run a full functional suite > >against either mimic or a full ironic environment, just by changing a > >test setting. > > I don't really see the point of a separate project like Mimic that has a > whole bunch of reimplementations (mocked out) of all sorts of OpenStack (and > RAX-specific) API services. It's just a great way to introduce a larger > surface area for bugs to creep in -- since you have to keep the Mimic > interfaces up to date with the real interfaces. Better to keep something > like this -- if it is TRULY needed -- in-tree with the API service itself, > so that the chances of divergence are reduced. This is similar to the > fakevirt driver in Nova. It's in tree for good reason: when someone changes > the virt driver interface, the fakevirt driver goes boom and needs to be > changed in a corresponding fashion in the same patch.
I tend to think our REST APIs are much more stable than internal python APIs, and so we can manage the divergence much easier. Also, mimic can simulate: * old versions (less needed with all the microversion stuff) * old bugs that were shipped * misconfigurations * networking errors * the passage of time (including timeouts) We probably don't want to keep a catalog of old bugs and misconfigurations in tree forever. > What value does a functional test against an HTTP API service that does > nothing (other than introduce greater surface area for bugs) actually offer > over unit tests anyway? Testing the full stack of the client instead of mocking the bottom half of requests is a big one. Lekha and Glyph gave a talk on Mimic in Paris; it may be enlightening. https://www.youtube.com/watch?v=HKUUQme3dwA // jim __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
