Re: [ndctl PATCH] ndctl/list: Drop named list objects from verbose listing

[Dan Williams <dan.j.williams@intel.com>]

On Wed, Feb 19, 2020 at 10:12 AM Jeff Moyer <jmoyer@redhat.com> wrote:
>
> Dan Williams <dan.j.williams@intel.com> writes:
>
> > On Wed, Feb 19, 2020 at 9:56 AM Jeff Moyer <jmoyer@redhat.com> wrote:
> >>
> >> Dan Williams <dan.j.williams@intel.com> writes:
> >>
> >> > The only expected difference between "ndctl list -R" and "ndctl list
> >> > -Rv" is some additional output fields. Instead it currently results in
> >> > the region array being contained in a named "regions" list object.
> >> >
> >> > # ndctl list -R -r 0
> >> > [
> >> >   {
> >> >     "dev":"region0",
> >> >     "size":4294967296,
> >> >     "available_size":0,
> >> >     "max_available_extent":0,
> >> >     "type":"pmem",
> >> >     "persistence_domain":"unknown"
> >> >   }
> >> > ]
> >> >
> >> > # ndctl list -Rv -r 0
> >> > {
> >> >   "regions":[
> >> >     {
> >> >       "dev":"region0",
> >> >       "size":4294967296,
> >> >       "available_size":0,
> >> >       "max_available_extent":0,
> >> >       "type":"pmem",
> >> >       "numa_node":0,
> >> >       "target_node":2,
> >> >       "persistence_domain":"unknown",
> >> >       "namespaces":[
> >> >         {
> >> >           "dev":"namespace0.0",
> >> >           "mode":"fsdax",
> >> >           "map":"mem",
> >> >           "size":4294967296,
> >> >           "sector_size":512,
> >> >           "blockdev":"pmem0",
> >> >           "numa_node":0,
> >> >           "target_node":2
> >> >         }
> >> >       ]
> >> >     }
> >> >   ]
> >> > }
> >> >
> >> > Drop the named list, by not including namespaces in the listing. Extra
> >> > objects only appear at the -vv level. "ndctl list -v" and "ndctl list
> >> > -Nv" are synonyms and behave as expected.
> >> >
> >> > # ndctl list -Rv -r 0
> >> > [
> >> >   {
> >> >     "dev":"region0",
> >> >     "size":4294967296,
> >> >     "available_size":0,
> >> >     "max_available_extent":0,
> >> >     "type":"pmem",
> >> >     "numa_node":0,
> >> >     "target_node":2,
> >> >     "persistence_domain":"unknown"
> >> >   }
> >> > ]
> >> >
> >>
> >> Will this break existing code that parses the javascript output?
> >
> > Always a potential for that. That said, I'd rather attempt to make it
> > symmetric and replace it if someone screams, rather than let this
> > quirk persist because it makes it impossible to ingest region data
> > with the same script across -R and -Rv.
>
> Yeah, I see where you're coming from.  However, script authors will
> still have to deal with older versions of ndctl in the wild (for many
> years).  If the decision was up to me, I'd live with the wart in favor
> of not breaking scripts when ndctl gets updated.  Users hate that.

Let's do a compromise, because users also hate nonsensical legacy that
they can't avoid. How about an environment variable,
"NDCTL_LIST_LINT", that users can set to opt into the latest /
cleanest output format with the understanding that the clean up may
regress scripts that were dependent on the old bugs.
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