Re: [PATCH v2] btrfs-progs: device stats: add json output format

[Sidong Yang <realwakka@gmail.com>]

On Fri, Oct 30, 2020 at 06:55:25PM +0100, David Sterba wrote:
> On Sun, Oct 04, 2020 at 11:25:57AM +0000, Sidong Yang wrote:
> > Add supports for json formatting, this patch changes hard coded printing
> > code to formatted print with output formatter. Json output would be
> > useful for other programs that parse output of the command. but it
> > changes the text format.
> > 
> > Example text format:
> > 
> > device:                 /dev/vdb
> > write_io_errs:          0
> > read_io_errs:           0
> > flush_io_errs:          0
> > corruption_errs:        0
> > generation_errs:        0
> > 
> > Example json format:
> > 
> > {
> >   "__header": {
> >     "version": "1"
> >   },
> >   "device-stats": {
> >     "/dev/vdb": {
> >       "device": "/dev/vdb",
> >       "write_io_errs": "0",
> >       "read_io_errs": "0",
> >       "flush_io_errs": "0",
> >       "corruption_errs": "0",
> >       "generation_errs": "0"
> >     }
> >   },
> > }

Hi David!
Thanks for review.

> 
> The overall structure looks good, ie. the separate object 'device-stats'
> and then the contents. For that the device id should be either key to a
> map, or we can put it into an array (where device id must be present
> too).

Thanks, You mean that devid should be key to json map? And I think that 
using as key is better than using array. Example should be like this.

{
  "__header": {
    "version": "1"
  },
  "device-stats": {
    "1": {
      "devid": "1",
      "device": "/dev/vdb",
      "write_io_errs": "0",
      "read_io_errs": "0",
      "flush_io_errs": "0",
      "corruption_errs": "0",
      "generation_errs": "0"
    }
  },
}

If so, I'll write a new patch for this.

Thanks,
Sidong

> 
> A check if the format is usable you can try to write a sample tool that
> parses some of the data and prints them. So eg. using python or jq and
> print stats of device 1. Which points out that device id is missing for
> example.