Include hostname in log (#10)

Output host hostname in log

Author: MickayG

README.md

@@ -113,6 +113,7 @@ Each log message will be written to a single Kafka message. The message within K
 	"ContainerId": "be2af19df661fb08561a8a99c734f637f9dc1397c43d88379479fceb5fc0666d",
 	"ContainerImageName": "hello-world",
 	"ContainerImageId": "sha256:48b5124b2768d2b917edcb640435044a97967015485e812545546cbed5cf0233",
+	"Hostname": "docker-master",
 	"Tag": "common",
 	"Err": null
 }
@@ -130,6 +131,7 @@ Each log message will be written to a single Kafka message. The message within K
  | ContainerId | Id of the container that generated the log message |
  | ContainerImageName | Name of the container's image |
  | ContainerImageId | ID of the container's image |
+ | Hostname | Hostname of the server running the container |
  | Tag | The log tag |
  | Err | Usually null, otherwise will be a string containing and error from the logdriver |
 

driver.go

@@ -32,6 +32,7 @@ type LogMessage struct {
 	ContainerId        string
 	ContainerImageName string
 	ContainerImageId   string
+	Hostname           string
 	Tag                string
 
 	// Err is an error associated with a message. Completeness of a message
@@ -188,6 +189,7 @@ func writeLogsToKafka(lf *logPair, topic string, keyStrategy KeyStrategy, tag st
 		msg.ContainerName = lf.info.ContainerName
 		msg.ContainerImageName = lf.info.ContainerImageName
 		msg.ContainerImageId = lf.info.ContainerImageID
+		msg.Hostname = getHostname()
 		msg.Tag = tag
 
 		err := WriteMessage(topic, msg, lf.info.ContainerID, keyStrategy, lf.producer)

driver_test.go

@@ -16,7 +16,7 @@ import (
 	"io/ioutil"
 	"encoding/json"
 	"strconv"
-
+	"os"
 )
 
 
@@ -95,6 +95,26 @@ func TestJsonIncludesContainerInformation(t *testing.T) {
 	assert.Equal(t, expectedContainerImageName, outMsg.ContainerImageName)
 }
 
+func TestJsonIncludesHostname(t *testing.T) {
+	expectedHostname,_ := os.Hostname()
+
+	producer := NewProducer(t)
+	defer producer.Close()
+
+	logMsg := newLogEntry("alpha")
+
+	stream := createBufferForLogMessages([]logdriver.LogEntry{logMsg})
+
+	lf := createLogPair(producer, stream)
+
+	producer.ExpectInputAndSucceed()
+	writeLogsToKafka(&lf, "topic", KEY_BY_TIMESTAMP, TAG)
+
+	recvMsg := <-producer.Successes()
+	outMsg := unmarshallMessage(recvMsg, t)
+	assert.Equal(t, expectedHostname, outMsg.Hostname)
+}
+
 func TestTagCanBeOverridenWithEnvironmentVariable(t *testing.T) {
 	overrideTag := "overide"
 	defaultTag := "default"
@@ -169,7 +189,6 @@ func TestReadingSingleLineFromOnePartition(t *testing.T) {
 	config := sarama.NewConfig()
 	consumer := mocks.NewConsumer(t, config)
 
-
 	expectedLine := "alpha"
 	expectedSource := "stdout"
 	expectedPartial := false

environment.go

@@ -182,3 +182,16 @@ func getEnvVarOrDefault(logCtx logger.Info, envVarName string, defaultValue stri
 	}
 	return value
 }
+
+func getHostname() string {
+	hostname, err := os.Hostname()
+	if err != nil {
+		//In the event that an error occured, set the hostname to an empty string as we're unable to retrieve it
+		hostname = ""
+
+		//Only log at debug level, we don't want to flood the system if this should happen for a particular reason (permissions perhaps?)
+		logrus.WithField("err", err).Debug("Unable to retrieve hostname")
+	}
+
+	return hostname
+}