[SPARK-5402] log executor ID at executor-construction time

also rename "slaveHostname" to "executorHostname"

Author: Ryan Williams <ryan.blake.williams@gmail.com>

Closes #4195 from ryan-williams/exec and squashes the following commits:

e60a7bb [Ryan Williams] log executor ID at executor-construction time

core/src/main/scala/org/apache/spark/executor/Executor.scala

@@ -41,11 +41,14 @@ import org.apache.spark.util.{SparkUncaughtExceptionHandler, AkkaUtils, Utils}
  */
 private[spark] class Executor(
     executorId: String,
-    slaveHostname: String,
+    executorHostname: String,
     env: SparkEnv,
     isLocal: Boolean = false)
   extends Logging
 {
+
+  logInfo(s"Starting executor ID $executorId on host $executorHostname")
+
   // Application dependencies (added through SparkContext) that we've fetched so far on this node.
   // Each map holds the master's timestamp for the version of that file or JAR we got.
   private val currentFiles: HashMap[String, Long] = new HashMap[String, Long]()
@@ -58,12 +61,12 @@ private[spark] class Executor(
   @volatile private var isStopped = false
 
   // No ip or host:port - just hostname
-  Utils.checkHost(slaveHostname, "Expected executed slave to be a hostname")
+  Utils.checkHost(executorHostname, "Expected executed slave to be a hostname")
   // must not have port specified.
-  assert (0 == Utils.parseHostPort(slaveHostname)._2)
+  assert (0 == Utils.parseHostPort(executorHostname)._2)
 
   // Make sure the local hostname we report matches the cluster scheduler's name for this host
-  Utils.setCustomHostname(slaveHostname)
+  Utils.setCustomHostname(executorHostname)
 
   if (!isLocal) {
     // Setup an uncaught exception handler for non-local mode.