On Monday, 10 June 2019 17:35:52 CEST Richard W.M. Jones wrote:
Sorry for the late reply to this ...
On Tue, Apr 30, 2019 at 06:28:01PM +0200, Pino Toscano wrote:
> On Friday, 9 February 2018 19:01:53 CEST Richard W.M. Jones wrote:
> > My contention is that the libguestfs git repository is too large and
> > unwieldy. There are too many separate, unrelated projects and as a
> > result of that the source has too many dependencies and takes too long
> > to build and test.
> >
> > The project divides (sort of) naturally into layers -- the library,
> > the bindings, the various virt tools -- and could be split along those
> > lines into separate projects which can then be released and evolve at
> > their own pace.
>
> As also other answers to this email say, splitting tools, and bindings
> may be very complex, and thus for now it is still a too far goal.
>
> However...
>
> > My suggested split would be something like this:
> >
> > [...]
> > virt-v2v and virt-p2v
>
> I'd rather split virt-p2v in its own repository. There are various
> reasons for this:
> - it does not use libguestfs (the library), just the tools for testing
> stuff
> - the communication with virt-v2v is done via network, and its
> capabilities are dynamically probed (so theoretically virt-p2v, and
> virt-v2v can be used even when their versions are odd)
> - it is written only in C
>
> However, even if it looks simple, in reality there are number of common
> things used from the rest of the libguestfs tree:
> 1) gnulib
We hardly use gnulib in virt-p2v. I think it's only used for
ignore-value.h, getprogname.h, and c-ctype.h, all of which are likely
to be easily worked around.
True, however for now it can stay, as it is one obstacle less for the split.
> 3) auto-cleanup bits (e.g. CLEANUP_FREE), although only few are
used
> (CLEANUP_FREE, CLEANUP_FREE_STRING_LIST, CLEANUP_PCLOSE,
> CLEANUP_FCLOSE, and CLEANUP_XMLFREETEXTWRITER)
> 4) other internal macros, i.e. guestfs-utils.h
Common code is a bit tricker, as is ...
So far it is ~4K of bits of code copied, with ~9K more of straight
copies of libxml2-cleanups.c + libxml2-writer-macros.h from
common/utils.
> 5) the list of credits generated by the generator
> (i.e. generator/authors.ml)
> 6) the p2v configuration generated by the generator
> (i.e. generator/p2v_config.ml)
... the generator and ...
(5) is more shared with the rest, while (6) is basically p2v-only
material.
> 7) test images/data (phony images, and virt-tools)
test data.
Luckly this is easy to recreate locally.
> 8) the miniexpect module, right now out of the p2v subdirectory
This is only used by virt-p2v I think, so it could go with virt-p2v or
be made into a separate project.
Right, the upstream is somewhere else, so another "import from $URL"
commit will not be any worse than what we have now.
> Possible solutions may/might be:
> 1) add own submodule (use its own set of modules)
I think we should ditch gnulib as much as possible, so see above.\
Surely we can work on removing it after the split, step by step, if
needed/wanted.
So while I'm not a massive fan of git submodules, now that I have
used
them a few times with riscv stuff, they do solve a certain problem as
long as they are managed carefully. I think the common code and the
generator are cases where a submodule or two would work.
TBH I've always found submodules tricky and problematic to use:
- they are fixed to a certain revision (so no way to dynamically follow
the branch of another repo)
- the URL is the same for all the users, meaning you cannot reuse the
same authenticated/secure protocols that your repo has
- they create a certain burden when switching to a tag/branch/commit
whose revision of a submodule is different than what is at the current
branch
- even more problematic when switching commit, and in the old commit
a subdirectory is a real directory while in the latest HEAD is a
submodule (or viceversa)
Does this mean we need to move immediately to a submodule if just
splitting virt-p2v, or copy code as you suggest? Maybe not, because
you can imagine for just this project copying the code needed from the
common/ directory, and creating a new "mini-generator" for the project
which handles the little bits that need to be generated in virt-p2v.
I'm actually solving in a different way, i.e. avoiding altogether the
generator for p2v stuff.
However in the long term if we split up everything a submodule or
two
does seem to make sense, so maybe we should start there?
ATM I have enough work needed just to split p2v, so I'd prefer to delay
this conversation to a later time...
> The other problem is how to split the repository, as the various
bits
> are in different places:
> a) git filter-branch --subdirectory-filter p2v
> + very small repo with the current p2v subdirectory
> + preserves the history of the p2v subdirectory, with branches and tags
> - missing all the other bits, which will have no history
> - not usable to build older releases (e.g. for bisecting)
I'm not exactly sure what this does. Is this something to do with
preserving the history? TBH I don't think we need to bother with the
history -- it exists still in libguestfs.git.
Yes, this is for preserving history, at least for the most important
parts (the sources of p2v).
--
Pino Toscano