add options to configure logger by interface

This commit provides users of this library with the ability to configure
any logger of their choosing to be passed into the various components of
this library. Doing so allows use cases such as using other open source
logging packages, e.g. logrus or zap, in conjunction with this library.

Closes #37

middleware/http/transport.go

@@ -56,7 +56,7 @@ type transport struct {
 	defaultTags       map[string]string
 	errHandler        ErrHandler
 	errResponseReader *ErrResponseReader
-	logger            *log.Logger
+	logger            zipkin.Logger
 	requestSampler    RequestSamplerFunc
 	remoteEndpoint    *model.Endpoint
 }
@@ -115,6 +115,13 @@ func TransportLogger(l *log.Logger) TransportOption {
 	}
 }
 
+// TransportZipkinLogger allows to plug a logger into the transport
+func TransportZipkinLogger(l zipkin.Logger) TransportOption {
+	return func(t *transport) {
+		t.logger = l
+	}
+}
+
 // TransportRequestSampler allows one to set the sampling decision based on
 // the details found in the http.Request. It has preference over the existing
 // sampling decision contained in the context. The function returns a *bool,

reporter/amqp/amqp.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/streadway/amqp"
 
+	"github.com/openzipkin/zipkin-go"
 	"github.com/openzipkin/zipkin-go/model"
 	"github.com/openzipkin/zipkin-go/reporter"
 )
@@ -29,7 +30,7 @@ type rmqReporter struct {
 	conn     *amqp.Connection
 	exchange string
 	queue    string
-	logger   *log.Logger
+	logger   zipkin.Logger
 }
 
 // ReporterOption sets a parameter for the rmqReporter
@@ -43,6 +44,14 @@ func Logger(logger *log.Logger) ReporterOption {
 	}
 }
 
+// GenericLogger sets the logger used to report errors in the collection
+// process.
+func GenericLogger(logger zipkin.Logger) ReporterOption {
+	return func(c *rmqReporter) {
+		c.logger = logger
+	}
+}
+
 // Exchange sets the Exchange used to send messages (
 // see https://github.com/openzipkin/zipkin/tree/master/zipkin-collector/rabbitmq
 // if want to change default routing key or exchange

reporter/http/http.go

@@ -26,6 +26,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/openzipkin/zipkin-go"
 	"github.com/openzipkin/zipkin-go/model"
 	"github.com/openzipkin/zipkin-go/reporter"
 )
@@ -47,7 +48,7 @@ type HTTPDoer interface {
 type httpReporter struct {
 	url           string
 	client        HTTPDoer
-	logger        *log.Logger
+	logger        zipkin.Logger
 	batchInterval time.Duration
 	batchSize     int
 	maxBacklog    int
@@ -233,6 +234,12 @@ func Logger(l *log.Logger) ReporterOption {
 	return func(r *httpReporter) { r.logger = l }
 }
 
+// GenericLogger sets the logger used to report errors in the collection
+// process.
+func GenericLogger(l zipkin.Logger) ReporterOption {
+	return func(r *httpReporter) { r.logger = l }
+}
+
 // Serializer sets the serialization function to use for sending span data to
 // Zipkin.
 func Serializer(serializer reporter.SpanSerializer) ReporterOption {

reporter/kafka/kafka.go

@@ -22,6 +22,7 @@ import (
 	"os"
 
 	"github.com/Shopify/sarama"
+	"github.com/openzipkin/zipkin-go"
 	"github.com/openzipkin/zipkin-go/model"
 	"github.com/openzipkin/zipkin-go/reporter"
 )
@@ -35,7 +36,7 @@ const defaultKafkaTopic = "zipkin"
 // broker.
 type kafkaReporter struct {
 	producer   sarama.AsyncProducer
-	logger     *log.Logger
+	logger     zipkin.Logger
 	topic      string
 	serializer reporter.SpanSerializer
 }
@@ -51,6 +52,14 @@ func Logger(logger *log.Logger) ReporterOption {
 	}
 }
 
+// GenericLogger sets the logger used to report errors in the collection
+// process.
+func GenericLogger(logger zipkin.Logger) ReporterOption {
+	return func(c *kafkaReporter) {
+		c.logger = logger
+	}
+}
+
 // Producer sets the producer used to produce to Kafka. For tweaking
 // the reporting settings (e.g. reporting timeout or authentication)
 // check the sarama.Config struct.