Plugin installation / Hudson upgrade are made more robust in the face of...

Plugin installation / Hudson upgrade are made more robust in the face of possible connection abortion.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@20749 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/UpdateCenter.java

@@ -583,6 +583,13 @@ public class UpdateCenter extends AbstractModelObject {
             in.close();
             out.close();
 
+            if (total!=-1 && total!=tmp.length()) {
+                // don't know exactly how this happens, but report like
+                // http://www.ashlux.com/wordpress/2009/08/14/hudson-and-the-sonar-plugin-fail-maveninstallation-nosuchmethoderror/
+                // indicates that this kind of inconsistency can happen. So let's be defensive
+                throw new IOException("Inconsistent file length: expected "+total+" but only got "+tmp.length());
+            }
+            
             return tmp;
         }