improve performance and correctness

* properly handle rebalances
* simplify code
* return on NewBroker instance and not interface

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

logger.go

@@ -0,0 +1,55 @@
+package kgo
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/twmb/franz-go/pkg/kgo"
+	"go.unistack.org/micro/v3/logger"
+)
+
+type mlogger struct {
+	l   logger.Logger
+	ctx context.Context
+}
+
+func (l *mlogger) Log(lvl kgo.LogLevel, msg string, args ...interface{}) {
+	var mlvl logger.Level
+	switch lvl {
+	case kgo.LogLevelNone:
+		return
+	case kgo.LogLevelError:
+		mlvl = logger.ErrorLevel
+	case kgo.LogLevelWarn:
+		mlvl = logger.WarnLevel
+	case kgo.LogLevelInfo:
+		mlvl = logger.InfoLevel
+	case kgo.LogLevelDebug:
+		mlvl = logger.DebugLevel
+	default:
+		return
+	}
+	if len(args) > 0 {
+		fields := make(map[string]interface{}, int(len(args)/2))
+		for i := 0; i <= len(args)/2; i += 2 {
+			fields[fmt.Sprintf("%v", args[i])] = args[i+1]
+		}
+		l.l.Fields(fields).Log(l.ctx, mlvl, msg)
+	} else {
+		l.l.Log(l.ctx, mlvl, msg)
+	}
+}
+
+func (l *mlogger) Level() kgo.LogLevel {
+	switch l.l.Options().Level {
+	case logger.ErrorLevel:
+		return kgo.LogLevelError
+	case logger.WarnLevel:
+		return kgo.LogLevelWarn
+	case logger.InfoLevel:
+		return kgo.LogLevelInfo
+	case logger.DebugLevel, logger.TraceLevel:
+		return kgo.LogLevelDebug
+	}
+	return kgo.LogLevelNone
+}