You will need to create a custom type and unmarshal method. Plenty of
example if you search for "golang custom json unmarshal".
As I've only had to implement it for a couple of simple types I can't offer
my own valid example.
On Thursday, 14 September 2023 at 14:36:12 UTC+1 Tobias Klausmann wrote:
> Hi!
>
> I am trying to write Prometheus exporter for stats queried fro the Kea
> DHCP server. Unfortunatly, the JSON is structured very badly if I want
> to use the base library JSON Unmarshal functionality:
>
> {
> "arguments": {
> "cumulative-assigned-addresses": [ [ 1, "2023-09-13 12:08:09.597483" ],
> ... ],
> "pkt4-decline-received": [ [ 0, "2023-09-13 08:01:35.964113" ], ... ],
> "subnet[1].assigned-addresses": [ [ 1, "2023-09-13 08:01:36.014127" ], ...
> ],
> "subnet[1].cumulative-assigned-addresses": [ [ 0, "2023-09-13
> 08:01:36.014006" ], ... ],
> "subnet[1].declined-addresses": [ [ 0, "2023-09-13 08:01:36.014069" ], ...
> ],
> "subnet[1].reclaimed-declined-addresses": [ [ 0, "2023-09-13
> 08:01:36.014074" ], ... ],
> "subnet[1].reclaimed-leases": [ [ 0, "2023-09-13 08:01:36.014080" ], ... ],
> "subnet[1].total-addresses": [ [ 15, "2023-09-13 08:01:36.013997" ], ... ],
> "subnet[1].v4-reservation-conflicts": [ [ 0, "2023-09-13 08:01:36.014010"
> ], ... ],
> "subnet[2].assigned-addresses": [ [ 4, "2023-09-14 13:32:20.906085" ], ...
> ],
> "subnet[2].cumulative-assigned-addresses": [ [ 4, "2023-09-14
> 13:32:20.906090" ], ... ],
> "subnet[2].declined-addresses": [ [ 0, "2023-09-13 08:01:36.014088" ], ...
> ],
> "subnet[2].reclaimed-declined-addresses": [ [ 0, "2023-09-13
> 08:01:36.014096" ], ... ],
> "subnet[2].reclaimed-leases": [ [ 3, "2023-09-14 00:08:10.270122" ], ... ],
> "subnet[2].total-addresses": [ [ 223, "2023-09-13 08:01:36.014015" ], ...
> ],
> "subnet[2].v4-reservation-conflicts": [ [ 0, "2023-09-13 08:01:36.014025"
> ], ... ],
> "subnet[3].assigned-addresses": [ [ 1, "2023-09-13 08:01:36.014135" ], ...
> ]
> ... rest of subnet[3] and more subnets
> },
> "result": 0
> }
>
>
> The int, timestamp lists are already Not Great, but I can deal with
> those.
>
> The problem is the series of subnet[x] fields. They vary depending on
> how many subnets the server serves, and nothing in the JSON indicates
> how many there are. And even if it did: getting the stdlib JSON
> Unmarshaler to actually pick them up (without hardcoded struct tags)
> seems impossible, short of essentially writing my own JSON Unmarshaler
> from scratch.
>
> So I have three questions:
>
> 1. Am I missing some wildcard-ish functionality where I can tell the
> stdlib JSON Unmarshaler just make a slice out of all the JSON
> elements that fit a pattern?
> 2. Is there a Golang JSON library that is better suited to dealing with
> this?
> 3. What other options do I have (besides "use another
> language/exporter", "make upstream produce better JSON" and "write
> your own parser")?
>
> Best & TIA,
> Tobias
>
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