seba-631-632: exporter enhancements for logger and topics

Change-Id: If10e56a7ccfce758712ea02df9656d4f413dbf84
diff --git a/topic-listener.go b/topic-listener.go
new file mode 100644
index 0000000..9b0f2dc
--- /dev/null
+++ b/topic-listener.go
@@ -0,0 +1,52 @@
+// Copyright 2018 Open Networking Foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"os"
+	"os/signal"
+	"sync"
+
+	"github.com/Shopify/sarama"
+	"gerrit.opencord.org/kafka-topic-exporter/common/logger"
+)
+
+func topicListener(topic *string, master sarama.Consumer, wg sync.WaitGroup) {
+	logger.Info("Starting topicListener for [%s]", *topic)
+	defer wg.Done()
+	consumer, err := master.ConsumePartition(*topic, 0, sarama.OffsetOldest)
+	if err != nil {
+		logger.Error("topicListener panic")
+		panic(err)
+	}
+	signals := make(chan os.Signal, 1)
+	signal.Notify(signals, os.Interrupt)
+	doneCh := make(chan struct{})
+	go func() {
+		for {
+			select {
+			case err := <-consumer.Errors():
+				logger.Error("%s", err)
+			case msg := <-consumer.Messages():
+				logger.Debug("Message on %s: %s", *topic, string(msg.Value))
+				export(topic, msg.Value)
+			case <-signals:
+				logger.Warn("Interrupt is detected")
+				doneCh <- struct{}{}
+			}
+		}
+	}()
+	<-doneCh
+}