netdev - Re: [PATCH iproute2 net-next 3/5] bridge: add json support for bridge fdb show

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Date:	Fri, 17 Jun 2016 12:04:27 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Anuradha Karuppiah <anuradhak@...ulusnetworks.com>
Cc:	Roopa Prabhu <roopa@...ulusnetworks.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
	Julien Fortin <julien@...ulusnetworks.com>
Subject: Re: [PATCH iproute2 net-next 3/5] bridge: add json support for
 bridge fdb show

On Fri, 17 Jun 2016 11:04:54 -0700
Anuradha Karuppiah <anuradhak@...ulusnetworks.com> wrote:

> On Tue, May 31, 2016 at 12:22 PM, Anuradha Karuppiah
> <anuradhak@...ulusnetworks.com> wrote:
> > On Tue, May 31, 2016 at 11:59 AM, Stephen Hemminger
> > <stephen@...workplumber.org> wrote:
> >> On Fri, 27 May 2016 21:37:14 -0700
> >> Roopa Prabhu <roopa@...ulusnetworks.com> wrote:
> >>
> >>> Sample output:
> >>> $bridge -j fdb show
> >>> [{
> >>>         "mac": "44:38:39:00:69:88",
> >>>         "dev": "swp2s0",
> >>>         "vlan": 2,
> >>>         "master": "br0",
> >>>         "state": "permanent"
> >>>     },{
> >>>         "mac": "00:02:00:00:00:01",
> >>>         "dev": "swp2s0",
> >>>         "vlan": 2,
> >>>         "master": "br0"
> >>>     },{
> >>>         "mac": "00:02:00:00:00:02",
> >>>         "dev": "swp2s1",
> >>>         "vlan": 2,
> >>>         "master": "br0"
> >>>     },{
> >>>         "mac": "44:38:39:00:69:89",
> >>>         "dev": "swp2s1",
> >>>         "master": "br0",
> >>>         "state": "permanent"
> >>>     },{
> >>>         "mac": "44:38:39:00:69:89",
> >>>         "dev": "swp2s1",
> >>>         "vlan": 2,
> >>>         "master": "br0",
> >>>         "state": "permanent"
> >>>     },{
> >>>         "mac": "44:38:39:00:69:88",
> >>>         "dev": "br0",
> >>>         "master": "br0",
> >>>         "state": "permanent"
> >>>     }
> >>>     ]
> >>
> >> In most JSON I have seen, the output would be:
> >>
> >> {
> >>   "fdb" : [
> >>      {
> >>          "mac": "44:38:39:00:69:88",
> >>          "dev": "swp2s0",
> >>          "vlan": 2,
> >>          "master": "br0",
> >>          "state": "permanent"
> >>      },
> >> ...
> >>    ]
> >> }
> >>
> >> I.e never a bare array.
> >>
> > Yes Stephen, Adding an extra level would be one way to force the
> > format to json-object. And that would definitely be the way to do it
> > if we ever added a top level json dump - something like - "bridge -j
> > show".
> >
> > But in the case of "bridge -j fdb show" that level is redundant. To be
> > consistent we would have to add that extra level to all json dumps
> > (even if they were already objects; such as the "bridge -j vlan
> > show").The google json style guide recommends against adding hierarchy
> > unless needed. And it is not that uncommon in java to have a
> > json-array of objects for e.g. http://json-schema.org/example1.html
> > talks about a schema that is an "array of products".
> >
> > What do you recommend?
> 
> Hi Stephen,
> We did a bit more digging around and found that other folks use json
> output with top level array as well. Here’s a docker networks json
> output sample -
> 
> vagrant@...t-21 ~ $ docker network inspect red
> [
>     {
>         "Name": "red",
>         "Id": "d2fff9bafd7564c4012aa49f322fcd8f5743cc5ceb465dc218af5ba22c920981",
>         "Scope": "global",
>         "Driver": "overlay",
>         "EnableIPv6": false,
>         "IPAM": {
>             "Driver": "default",
>             "Options": {},
>             "Config": [
>                 {
>                     "Subnet": "10.252.20.0/24"
>                 }
>             ]
>         },
>         "Internal": false,
>         "Containers": {
>             "c92084c1ebfb4f0a601537298c273078862207e3b564787ddd6ef564efbaca47":
> {
>                 "Name": "ctr21",
>                 "EndpointID":
> "e7468a70f13f1ea7b15445ab555374892ac41f71ea9023af1d9ede668bfd8742",
>                 "MacAddress": "02:42:0a:fc:14:03",
>                 "IPv4Address": "10.252.20.3/24",
>                 "IPv6Address": ""
>             },
>             "ep-9bfc004b4046512f0f0104fe022d3686f5237ae08475741f8d520552cbb63d45":
> {
>                 "Name": "ctr22",
>                 "EndpointID":
> "9bfc004b4046512f0f0104fe022d3686f5237ae08475741f8d520552cbb63d45",
>                 "MacAddress": "02:42:0a:fc:14:02",
>                 "IPv4Address": "10.252.20.2/24",
>                 "IPv6Address": ""
>             }
>         },
>         "Options": {},
>         "Labels": {}
>     }
> ]
> 
> Adding an additional namespace to all the json outputs (just to avoid
> a top-level json-array for some) seems redundant. If a namespace is
> needed for other reasons we can definitely add it. So we think it
> would be better to just go with the top-level json-array for a
> list/set-of-objects outputs.

Ok, resubmit. I never claimed to be a JSON expert :=)