FilePath.installIfNecessaryFrom is used by the DownloadFromUrlInstaller when installing things like the JDK. The current implementation issues a regular GET request just to access the 'last modified' header. This also seems to be triggered per executor resulting in lots of stress on the server hosting the JDK zip/tar.gz.

installIfNecessaryFrom could be changed to read the cached timestamp first, and issue that in the 'If-Modified-Since' header. http://docs.oracle.com/javase/6/docs/api/java/net/URLConnection.html#setIfModifiedSince%28long%29