On Wed, Oct 07, 2015 at 02:12:44PM +0200, Ancor Gonzalez Sosa wrote:
As part of the PBI titles "Evaluate design of future-proof storage subsystem", I took a look to the content of https://github.com/aschnell/libstorage-bgl-eval/
This mail can be considered to some extend a follow up of previous evaluations and discussions in this mailing list. Most feedback received from those threads has been already taken into account into the current prototype. Thus, some topics discussed there are outdated but some information is still useful. http://lists.opensuse.org/yast-devel/2014-10/msg00045.html http://lists.opensuse.org/yast-devel/2014-12/msg00016.html
First impression ================
First thing I noticed in that repository is the lack of information about building and installing. In every github's README I expect to find: (1) how to build the thing, (2) how to compile the inline docs or a link to an up-to-date compiled version, (3) in (open)SUSE related stuff I also expect instructions to download or build a rpm.
It's a prototype and development was halted abrupt eight months ago.
Only some (maybe too Ruby-centric) comments follow.
Casting and Storage.some_method ===============================
Things like this look quite un-ruby:
tmp1 = devicegraph.find_device(42) assert(Storage.disk?(tmp1)) assert(Storage.to_disk(tmp1)) assert(!Storage.partition_table?(tmp1)) assert_raises(Storage.DeviceHasWrongType { Storage.to_partition_table(tmp1) }
I would have expected things like
tmp1.disk? tmp1.to_partition_table
At least in C++ such a interface looks like a very bad idea since for *every* new class you have to modify the base class. With such a design ABI stability is not possible.
In fact, I wouldn't expect to have to perform this kind of casts,
These cast should not be needed often as I already wrote in http://lists.opensuse.org/yast-devel/2014-12/msg00025.html.
at most I would expect to do more rubist things like
tmp1.is_a?(Storage::Disk) tmp1.respond_to?(:whatever_method)
Query interface ===============
The API contains methods like these:
device_graph.find_device(numeric_id) Storage::BlkDevice.find(device_graph, "/dev/sda") Storage::Filesystem.find_by_mountpoint(device_graph, "/") Storage::Filesystem.find_by_label(device_graph, "someLabel")
Questions that come to my mind.
a) Is device_graph always an object representing the whole graph?
The devicegraph always represents the whole graph.
Can I do things like this to restrict the search to a subtree?
disk1 = Storage::Disk.find(device_graph, "/dev/sda") sub_graph = disk1.to_device_graph # or maybe sub_graph = device_graph.sub_graph(disk1.sid) # or any other thing that makes sense
In theory there are many ways to get a subgraph, look at the functions in Device.h.
Storage::Filesystem.find_by_mountpoint(sub_graph, "/")
Do you have a real use-case for that? Adding subgraphs looks like a lot of work so might not be worthwhile.
b) Adding find_by_xx at demand over time doesn't look very future-proof. I would prefer to see something like Rails's #find_by, i.e.
Storage::Filesystem.find(device_graph, mountpoint: "/") Storage::Filesystem.find(device_graph, mountpoint: "/", label: "blah")
Too ruby-centric and not easy to implement in a cross-language way, I guess. But asking does not hurt. :-)
As I already wrote in http://lists.opensuse.org/yast-devel/2014-12/msg00028.html if someone takes care of bindings for a target language more things are possible.
c) Just brainstorming. The approach in (b) could be pushed to the limit to have things like this. But actually I'm not sure if it's a good idea, just braindump.
device_graph.find(sid: numeric_id) device_graph.find(type: :filesystem, mountpoint: "/")
Lack of inline documentation ============================
Right now, the code is the documentation. I have to say that the code is very nicely structured, so it was really easy to me to browse for the methods I wanted to check (and they were all fairly small and understandable as well). But it's time to start adding documentation to the whole thing.
It's a prototype and development was halted abrupt eight months ago.
Nitpicking: boolean as parameters =================================
This is something that was already mentioned by Martin in one of the mails referred at the top. Calls like this are not 100% obvious
sda.descendants(false)
It would be nicer to have something like sda.descendants(:direct) or sda.descendants(direct: true)
Looks difficult as already mentioned in http://lists.opensuse.org/yast-devel/2014-12/msg00025.html
Nickpicking: 42 ===============
I found the usage of 42 and 43 for the sids in examples and tests a little bit confusing. I grepped the source code and found that we simply use autoincremental integer to assign the sids starting with 42.
Nothing against it, but please make it more obvious (and robust, in case we decide 42 is not cool anymore) in the testsuites. :-)
There is no technical reason to change the initial value for the
storage id so FMPOV spending time on changing the testsuites is
not justified.
Regards,
Arvin
--
Arvin Schnell,