Add timing stats to verbose download output.

When using the swift command-line tool to evaluate a Swift cluster, it
can be very handy to get some insight into the download timing.  This
patch adds timing data to verbose output for the download command.  For
each downloaded file, the printed line will also contain:
 - The time it took to send the request and receive the header
 - The total time the request took (including writing the file out
   locally)
 - The average throughput of the download

Change-Id: Ib4a995623af973bb1eed4fb52c8c0e5da935964d

bin/swift

@@ -24,7 +24,7 @@ from os.path import basename, dirname, getmtime, getsize, isdir, join
 from Queue import Empty, Queue
 from sys import argv, exc_info, exit, stderr, stdout
 from threading import current_thread, enumerate as threading_enumerate, Thread
-from time import sleep
+from time import sleep, time
 from traceback import format_exception
 from urllib import quote, unquote
 
@@ -350,8 +350,10 @@ def st_download(parser, args, print_queue, error_queue):
         else:
             raise Exception("Invalid queue_arg length of %s" % len(queue_arg))
         try:
+            start_time = time()
             headers, body = \
                 conn.get_object(container, obj, resp_chunk_size=65536)
+            header_receipt = time()
             content_type = headers.get('content-type')
             if 'content-length' in headers:
                 content_length = int(headers.get('content-length'))
@@ -402,11 +404,15 @@ def st_download(parser, args, print_queue, error_queue):
                 mtime = float(headers['x-object-meta-mtime'])
                 utime(path, (mtime, mtime))
             if options.verbose:
+                finish_time = time()
+                time_str = 'headers %.3fs, total %.3fs, %.3fs MB/s' % (
+                    header_receipt - start_time, finish_time - start_time,
+                    float(read_length) / (finish_time - start_time) / 1000000)
                 if conn.attempts > 1:
-                    print_queue.put('%s [after %d attempts' %
-                                    (path, conn.attempts))
+                    print_queue.put('%s [%s after %d attempts]' %
+                                    (path, time_str, conn.attempts))
                 else:
-                    print_queue.put(path)
+                    print_queue.put('%s [%s]' % (path, time_str))
         except ClientException, err:
             if err.http_status != 404:
                 raise