use zap instead of logrus

[kazegusuri]

use github.com/uber-go/zap instead of github.com/Sirupsen/logrus for access/error logs. This breaks compatibility about log format and achieves fully json logging.

zap is very complex to use (ex: omitempty), but slightly faster than other loggers. This is a benchmark before/after this changes for gaurun.LogPush.

before

go test github.com/mercari/gaurun/gaurun -benchmem -benchtime 5s -bench .   
BenchmarkLogPushIOSOmitempty-4        500000         12257 ns/op        1816 B/op         18 allocs/op
BenchmarkLogPushIOSFull-4             500000         13893 ns/op        2008 B/op         18 allocs/op

after

go test github.com/mercari/gaurun/gaurun -benchmem -benchtime 5s -bench .     
BenchmarkLogPushIOSOmitempty-4       1000000          6060 ns/op         945 B/op          4 allocs/op
BenchmarkLogPushIOSFull-4            1000000          6303 ns/op         945 B/op          4 allocs/op

2 allocs for zap logging. 2 allocs for ptime's format conversion.

EDIT:

After removing format conversion and computing the value instead.

go test github.com/mercari/gaurun/gaurun -benchmem -benchtime 5s -bench . 
BenchmarkLogPushIOSOmitempty-4       2000000          4574 ns/op         929 B/op          2 allocs/op
BenchmarkLogPushIOSFull-4            1000000          5030 ns/op         929 B/op          2 allocs/op

change list

• log format change
  • [info] {"message": "...", ...} to {"level":"info","message":"..."...}
• time format
  • 2015/08/04 15:32:35 JST (local time) to 2016-08-30T01:18:04Z (UTC)

[kazegusuri]

current time format is t.Format("2006/01/02 15:04:05 MST") such as 2015/08/04 15:32:35 JST at local time. This PR changes the format to t.Format(time.RFC3339) such as 2016-08-30T01:18:04Z at UTC. If we need to keep time format, I will fix with zap.TimeFormatter.

[cubicdaiya]

LogSetupFatal() looks better to me than LogSetupError().

[cubicdaiya]

@kazegusuri How is the progress?

[kazegusuri]

Remove WIP from title, please take a look.

[cubicdaiya]

Unify time format, please.

[cubicdaiya]

Specify version of zap.