grpclog: refactor to move implementation to grpclog/internal

[easwars]

Idea behind the refactor:

• Public API for logging should be provided by the grpclog package
• Implementation should mostly reside in grpclog/internal package
• Any functionality that is not exposed externally, but is available to grpc packages should be in internal/grpclog
• Package grpclog will take a dependency on grpclog/internal
• Package internal/grpclog will take a dependency on grpclog

Also introduces a few methods for depth logging to the external grpclog package.

RELEASE NOTES: none

[easwars]

Things that I'm not thrilled about with this PR:

• Because grpclog.Logger, grpclog.LoggerV2 and grpclog.DepthLoggerV2 are now type aliases pointing to interfaces defined in the grpclog/internal package, there is one more level of clicking required to look at these interfaces from the godoc.
  • But I feel this is still OK since it improves the overall code organization and eliminates duplicated interfaces (which was also previously missing a method)
• The implementation of the component logger is still in the grpclog package.
  • This can be moved over to grpclog/internal if we really want to, but will require exporting the componentData type because there is a type assertion for this in grpclog.SetLoggerV2

[codecov]

Codecov Report

Attention: Patch coverage is 53.17460% with 59 lines in your changes missing coverage. Please review.

Project coverage is 81.97%. Comparing base (6d7f07c) to head (f0ab028).
Report is 2 commits behind head on master.

Files	Patch %	Lines
grpclog/internal/loggerv2.go	52.00%	23 Missing and 1 partial ⚠️
grpclog/internal/logger.go	0.00%	20 Missing ⚠️
grpclog/grpclog.go	70.27%	9 Missing and 2 partials ⚠️
grpclog/loggerv2.go	71.42%	2 Missing ⚠️
grpclog/logger.go	0.00%	1 Missing ⚠️
internal/grpclog/prefix_logger.go	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7465      +/-   ##
==========================================
+ Coverage   81.61%   81.97%   +0.35%     
==========================================
  Files         359      360       +1     
  Lines       27532    27533       +1     
==========================================
+ Hits        22470    22569      +99     
+ Misses       3835     3778      -57     
+ Partials     1227     1186      -41     

Files	Coverage Δ
grpclog/component.go	77.27% <100.00%> (ø)
grpclog/logger.go	0.00% <0.00%> (ø)
internal/grpclog/prefix_logger.go	95.83% <85.71%> (ø)
grpclog/loggerv2.go	60.00% <71.42%> (+2.50%)	⬆️
grpclog/grpclog.go	65.51% <70.27%> (+6.05%)	⬆️
grpclog/internal/logger.go	0.00% <0.00%> (ø)
grpclog/internal/loggerv2.go	52.00% <52.00%> (ø)

... and 26 files with indirect coverage changes

[arvindbr8]

LGTM, only nits

[arvindbr8]

nit:

Suggested change

	import (
	"google.golang.org/grpc/grpclog/internal"
	)
	import "google.golang.org/grpc/grpclog/internal"

[easwars]

Done.

[arvindbr8]

Can we do something that is specific to that one usage? example: https://github.com/grpc/grpc-go/blob/master/scripts/vet.sh#L125

[easwars]

Done. But I also had to leave the current line in there.

• New check with fail if there are any usages of the deprecated Logger interface from anywhere other than prefix_logger.go.
• Once that check passes, this will ensure that the usage in prefix_logger.go does not cause vet to fail.

[arvindbr8]

nit: to stick to the other patterns how about?

Suggested change

	if pl == nil {
	return true
	}
	return pl.logger.V(l)
	if pl != nil {
	return pl.logger.V(l)
	}
	return true

[easwars]

Done.