jsonpath library unmaintained?

[rustycl0ck]

The jsonpath library in use (github.com/kawamuray/jsonpath) has not been updated in the past 5 years and thus, looks unmaintained. Maybe we should consider moving to k8s.io/client-go/util/jsonpath (or any other up to date library), which is expected to be well maintained and has nice documentation too - https://kubernetes.io/docs/reference/kubectl/jsonpath.

[mirceaulinic]

To add up to this, run into some bug when trying to use this exporter:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0xf8 pc=0x8cdf69]

goroutine 1 [running]:
github.com/kawamuray/jsonpath.take1ByteSlice(0xc0000e5240, 0xa, 0xc0001a8af0, 0x9, 0x9, 0x0, 0x0)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/expression.go:401 +0x99
github.com/kawamuray/jsonpath.take2ByteSlice(0xc0000e5240, 0xa, 0x9, 0xc0003ce600, 0xc0000e54d0, 0x1, 0x0, 0x0, 0x0, 0x0)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/expression.go:408 +0x9d
github.com/kawamuray/jsonpath.evaluatePostFix(0xc0001b4dc0, 0x7, 0x8, 0xc0000e5418, 0xc0000e54f8, 0x0, 0x0, 0x0)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/expression.go:198 +0x1956
github.com/kawamuray/jsonpath.(*exprBucket).evaluate(0xc0000e56c8, 0xc0001a6488, 0x10, 0x203000)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/eval.go:305 +0x43e
github.com/kawamuray/jsonpath.(*query).trySpillOver(0xc0000aa750)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/eval.go:162 +0x156
github.com/kawamuray/jsonpath.pathEndValue(0xc0000aa750, 0xc000120c60, 0xc00015c010, 0xa49700)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/eval.go:282 +0x24f
github.com/kawamuray/jsonpath.(*Eval).Iterate(0xc000120c60, 0xc000394150, 0xffffffffffffff01)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/eval.go:102 +0x35d
github.com/kawamuray/jsonpath.(*Eval).Next(0xc000120c60, 0xc00058a240, 0x3e01)
	/home/mircea/go/pkg/mod/github.com/kawamuray/[email protected]/eval.go:140 +0x3f
github.com/prometheus-community/json_exporter/jsonexporter.(*ValueScraper).forTargetValue(0xc000190f80, 0xc0003aa000, 0x1f4a, 0x3e00, 0xc0000e5a78, 0x0, 0x0)
	/home/mircea/git/public/json_exporter/jsonexporter/scraper.go:64 +0xc3
github.com/prometheus-community/json_exporter/jsonexporter.(*ObjectScraper).Scrape(0xc000180920, 0xc0003aa000, 0x1f4a, 0x3e00, 0xc000186060, 0x0, 0x0)
	/home/mircea/git/public/json_exporter/jsonexporter/scraper.go:169 +0x89
github.com/prometheus-community/json_exporter/jsonexporter.(*Collector).Collect(0xc00018cfc0, 0xc000186060)
	/home/mircea/git/public/json_exporter/jsonexporter/collector.go:91 +0xe5
github.com/prometheus-community/json_exporter/harness.(*exporter).main(0xc000186050, 0xc000196160)
	/home/mircea/git/public/json_exporter/harness/exporter.go:85 +0x3be
github.com/urfave/cli.HandleAction(0x956e20, 0xc000190b40, 0xc000196160, 0x0, 0x0)
	/home/mircea/go/pkg/mod/github.com/urfave/[email protected]/app.go:528 +0x127
github.com/urfave/cli.(*App).Run(0xc0001f21c0, 0xc0000c0000, 0x7, 0x7, 0x0, 0x0)
	/home/mircea/go/pkg/mod/github.com/urfave/[email protected]/app.go:288 +0x5fc
github.com/prometheus-community/json_exporter/harness.Main(0xc0001e1c00)
	/home/mircea/git/public/json_exporter/harness/main.go:79 +0x5d
main.main()
	/home/mircea/git/public/json_exporter/json_exporter.go:25 +0xdf

This is when trying to parse JSON documents that have (as valid as it can be) null fields (e.g., field: null). I'd have reported this to https://github.com/kawamuray/jsonpath but even the Issues sections is disabled.

[rustycl0ck]

I just hit another issue. eval.Iterate() does not work. It always returns empty *Results

[SuperQ]

Seems like a good idea to me. @rustycl0ck Are you interested in doing this work?

[rustycl0ck]

Yes, I can take this up. But I'm not sure which library to replace with, right now. Currently I have just been working on #14 with the current library. I'll send a PR for that and can work on replacing the library later.
I think the other issues (namely #33 #44 #45) are more important and urgent to make this exporter actually usable. So I think this library upgrade can be postponed since it is not making the current situation any worse right now.