[extension/jaegerremotesampling] remove jaeger sampling dependency

[ary82]

Description

Copy the required code from jaeger to extension/jaegerremotesampling:

• Modify files to remove dependencies
• Add required code from plugin/sampling/strategyprovider/static
• Add required code from cmd/collector/app/sampling to internal

Link to tracking issue

Fixes #36976

Testing

• Add grpc_handler_test.go from cmd/collector/app/sampling/grpc_handler_test.go
• Add provider_test.go from plugin/sampling/strategyprovider/static/provider_test.go with plugin/sampling/strategyprovider/static/fixtures

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ary82 / name: Aryan Goyal (b07a06d, 57479e2, 94c5d1f, 518347e, 7ba9b6c, cb8d0ff, fe2045a, cd9aac8, 8a33757, 7818970, 877511a, e9749c9)

[yurishkuro]

The organization of the components needs to be improved, it's all over the place. I would recommend

internal/
  source/
    source.go - define interface
    filesource/ - define reading from file
    remotesource/ - a proxy that reads from a remote service
  server/
    grpc/ - grpc server that uses Source
    http/ - http server that uses Source and defines its own JSON model

[yurishkuro]

this does not seem to be populated or used

[ary82]

It is used by the filesource(currently in newProvider in provider.go, will update the PR soon):

	if !h.options.IncludeDefaultOpStrategies {
		h.logger.Warn("Default operations level strategies will not be included for Ratelimiting service strategies." +
			"This behavior will be changed in future releases. " +
			"Cf. https://github.com/jaegertracing/jaeger/issues/5270")
		h.parseStrategies_deprecated(strategies)
	} else {
		h.parseStrategies(strategies)
	}

[yurishkuro]

if provider only takes two arguments I would just pass them directly without this extra struct

[yurishkuro]

internal.Provider is an interface. You have two possible implementations, File and Remote. Calling this function newProvider when it's actually creating FileProvider is misleading

[yurishkuro]

also, the main Config calls this Source, so I would get rid of "provider" nomenclature altogether and have FileSource & RemoteSource (both should be in internal package)

[ary82]

That makes sense, I'll try and improve it

[ary82]

Still need to clean up a bit before updating the PR, but here's the new internal package structure:

└── internal
    ├── mocks
    │   └── mock_source.go (Needed for grpc_test and http_test. Should I just include these in both the test files and skip making this package?)
    ├── server
    │   ├── grpc
    │   │   ├── grpc.go
    │   │   ├── grpc_handler.go
    │   │   ├── grpc_handler_test.go
    │   │   └── grpc_test.go
    │   └── http
    │       ├── http.go
    │       └── http_test.go
    └── source
        ├── interface.go
        ├── filesource
        │   ├── constants.go
        │   ├── fixtures/ (used for testing)
        │   ├── model.go
        │   ├── options.go
        │   ├── filesource.go (previously provider.go; newProvider will be renamed NewFileSource function that returns a source.Source)
        │   └── filesource_test.go
        └── remotesource
            ├── manager.go
            ├── manager_test.go
            ├── remote_strategy_cache.go
            ├── remote_strategy_cache_test.go
            └── remote_strategy_store.go (rename NewRemoteStrategyStore to NewRemoteSource, returns a source.Source)

[yurishkuro]

where are these used? Do they need to be in the root package? It seems these define the data types for JSON output, so should be next to http server code.

[ary82]

I think http uses the response from the Source interface's GetSamplingStrategy for the JSON output, which is github.com/jaegertracing/jaeger/proto-gen/api_v2.SamplingStrategyResponse.

This is used by the filesource to load the strategies

[yurishkuro]

lgtm! Let's makes sure all CI checks are green.

[ary82]

Sorry, closing was a misclick on Close with comment
The CI showed errors on the linter. Here's what the linter says:

jaegerremotesampling/internal/source/filesource/filesource.go:378:12: Error return value of `enc.Encode` is not checked (errcheck)
	enc.Encode(*s)
	         ^
jaegerremotesampling/internal/source/filesource/filesource.go:380:12: Error return value of `dec.Decode` is not checked (errcheck)
	dec.Decode(&copyValue)
	         ^
jaegerremotesampling/internal/source/filesource/filesource_test.go:71:11: Error return value of `w.Write` is not checked (errcheck)
			w.Write([]byte("bad-content"))
			      ^
jaegerremotesampling/internal/source/filesource/filesource_test.go:85:11: Error return value of `w.Write` is not checked (errcheck)
			w.Write([]byte(*strategy.Load()))
			      ^
jaegerremotesampling/internal/source/filesource/filesource_test.go:512:17: Error return value of `os.WriteFile` is not checked (errcheck)
				os.WriteFile(snapshotFile, strategyJson, 0o644)
				           ^
jaegerremotesampling/internal/source/filesource/filesource_test.go:544:17: Error return value of `os.WriteFile` is not checked (errcheck)
				os.WriteFile(snapshotFile, strategyJson, 0o644)
				           ^
jaegerremotesampling/internal/source/filesource/filesource_test.go:371:21: G306: Expect WriteFile permissions to be 0600 or less (gosec)
	require.NoError(t, os.WriteFile(dstFile, srcBytes, 0o644))
	                  ^
jaegerremotesampling/internal/source/filesource/filesource_test.go:392:21: G306: Expect WriteFile permissions to be 0600 or less (gosec)
	require.NoError(t, os.WriteFile(dstFile, []byte(newStr), 0o644))
	                  ^
jaegerremotesampling/internal/source/filesource/filesource_test.go:469:21: G306: Expect WriteFile permissions to be 0600 or less (gosec)
	require.NoError(t, os.WriteFile(tempFile.Name(), []byte("bad value"), 0o644))

• For the file permissions in filesource_test.go, should the permissions really be 600?
• As for the errchecks in filesource in Encode and Decode, these are only used in the test and are safe to be ignored. Also should be moved to the test file(edit: fixed)