Goodbye nvr.rsplit('-', 2), hello modularity
Hi all,
If you maintain any application in Fedora Infra (or outside) that
tries to parse things out of RPM names, you might be interested in
this.
For those wondering where I've been spending most of my time the last
few weeks: I've been deep in the internals of Bodhi fixing all kinds
of issues I've found between it and Modularity (turns out enabling
composing was just the beginning).
At some point, I was informed that for modules, they are throwing all
kinds of old assumptions out of the door.
One of those is the good old Name-Version-Release in RPM land.
Modules do not have an NVR, they have an NSVC: Name, Stream, Version, Context.
Name is the name of the module ("nodejs").
Stream is a stream, like "6", "7" or "8", these are crucial
for the
parallel availability that modules are trying to accomplish.
Version is a date/time stamp, used to indicate new versions in the
same name-stream.
Context is a hash of some information in the built module that makes
it so that the nodejs-6-20170314 built for Fedora 28 has a different
identifier than the one built for Fedora 29.
There are some additional fields for installed things (arch and
profile), but those aren't really important for things trying to
parse/show module names I think.
One of the interesting things they wanted to also allow: dashes in streams.
As a consequence, when you get an N-S-V.C as modules are represented
in Koji builds, doing a .rsplit('-', 2) will not give you Name,
Stream, Version.Context per se.
You could totally have a module called
nodejs-my-stream-5-20170314.abcd, with name=nodejs,
stream=my-stream-5, version=20170314, context=abcd.
There is no way for you to independently figure out what the NSVC
components are, you will need to ask Koji, and use its name, version
and release fields (with name=name, version=stream,
release=version(.context)).
Also as a consequence, modules should not be dash-separated in
anything the users see.
For user consumption, they are Name:Stream:Version:Context, so you may
need to manually convert between one representation and the other if
you need to look up in koji or other systems versus display to users.
Also, note that if you are touching older modules in Koji (e.g.
because you go through all koji builds), modules before February 19th
will be lacking the Context field.
However, I've been told that those modules will not be used, so unless
you or your app goes spelunking in koji (for fun and profit), you
should never see those.
I hope that this is useful information for anyone else finding
themselves having to parse NVRs/NSVs.
Regards,
Patrick