[Fix #204] Eliminate delay between binding and log checking

**Bug**: In the existing history server, there is a `spark.history.updateInterval` seconds delay before application logs show up on the UI.

**Cause**: This is because the following events happen in this order: (1) The background thread that checks for logs starts, but realizes the server has not yet bound and so waits for N seconds, (2) server binds, (3) N seconds later the background thread finds that the server has finally bound to a port, and so finally checks for application logs.

**Fix**: This PR forces the log checking thread to start immediately after binding. It also documents two relevant environment variables that are currently missing.

Author: Andrew Or <andrewor14@gmail.com>

Closes #441 from andrewor14/history-server-fix and squashes the following commits:

b2eb46e [Andrew Or] Document SPARK_PUBLIC_DNS and SPARK_HISTORY_OPTS for the history server
e8d1fbc [Andrew Or] Eliminate delay between binding and checking for logs

1 files changed, 5 insertions, 0 deletions

diff --git a/core/src/main/scala/org/apache/spark/deploy/history/HistoryServer.scala b/core/src/main/scala/org/apache/spark/deploy/history/HistoryServer.scala
index cf64700f90..b8f56234d3 100644
--- a/core/src/main/scala/org/apache/spark/deploy/history/HistoryServer.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/history/HistoryServer.scala
@@ -98,6 +98,11 @@ class HistoryServer(
   def initialize() {
     attachPage(new HistoryPage(this))
     attachHandler(createStaticHandler(STATIC_RESOURCE_DIR, "/static"))
+  }
+
+  /** Bind to the HTTP server behind this web interface. */
+  override def bind() {
+    super.bind()
     logCheckingThread.start()
   }