MAPREDUCE-3999. Tracking link gives an error if the AppMaster hasn't started yet (Ravi Prakash via bobby)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1309108 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -234,6 +234,9 @@ Release 0.23.3 - UNRELEASED
     MAPREDUCE-3988. mapreduce.job.local.dir doesn't point to a single directory
     on a node. (Eric Payne via bobby)
 
+    MAPREDUCE-3999. Tracking link gives an error if the AppMaster hasn't
+    started yet (Ravi Prakash via bobby)
+
 Release 0.23.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/main/java/org/apache/hadoop/yarn/server/webproxy/WebAppProxyServlet.java

@@ -37,9 +37,9 @@ import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.apache.commons.httpclient.Header;
+import org.apache.commons.httpclient.HostConfiguration;
 import org.apache.commons.httpclient.HttpClient;
 import org.apache.commons.httpclient.HttpMethod;
-import org.apache.commons.httpclient.HostConfiguration;
 import org.apache.commons.httpclient.cookie.CookiePolicy;
 import org.apache.commons.httpclient.methods.GetMethod;
 import org.apache.commons.httpclient.params.HttpClientParams;
@@ -260,7 +260,24 @@ public class WebAppProxyServlet extends HttpServlet {
       URI trackingUri = ProxyUriUtils.getUriFromAMUrl(
           applicationReport.getOriginalTrackingUrl());
       if(applicationReport.getOriginalTrackingUrl().equals("N/A")) {
-        notFound(resp, "The MRAppMaster died before writing anything.");
+        String message;
+        switch(applicationReport.getFinalApplicationStatus()) {
+          case FAILED:
+          case KILLED:
+          case SUCCEEDED:
+            message =
+              "The requested application exited before setting a tracking URL.";
+            break;
+          case UNDEFINED:
+            message = "The requested application does not appear to be running "
+              +"yet, and has not set a tracking URL.";
+            break;
+          default:
+            //This should never happen, but just to be safe
+            message = "The requested application has not set a tracking URL.";
+            break;
+        }
+        notFound(resp, message);
         return;
       }