Implement retries on http

There is a bug either in buildservice or in iChain which sometimes
truncates data and sends empty Content-Length header (see bnc#656281).
This patch makes osc retry request to workaround this problem.

The number of retries are configurable in config file as http_retries.

osc/conf.py

@@ -85,6 +85,7 @@ DEFAULTS = { 'apiurl': 'https://api.opensuse.org',
              'debug': '0',
              'http_debug': '0',
              'http_full_debug': '0',
+             'http_retries': '3',
              'verbose': '1',
              'traceback': '0',
              'post_mortem': '0',
@@ -237,6 +238,9 @@ apiurl = %(apiurl)s
 # show HTTP traffic useful for debugging
 #http_debug = 1
 
+# number of retries on HTTP transfer
+#http_retries = 3
+
 # Skip signature verification of packages used for build.
 #no_verify = 1
 

osc/core.py

@@ -4494,8 +4494,19 @@ def streamfile(url, http_meth = http_GET, bufsize=8192, data=None, progress_obj=
     until EOF is reached. After each read bufsize bytes are yielded to the
     caller.
     """
-    f = http_meth.__call__(url, data = data)
-    cl = f.info().get('Content-Length')
+    cl = ''
+    retries = 0
+    # Repeat requests until we get reasonable Content-Length header
+    # Server (or iChain) is corrupting data at some point, see bnc#656281
+    while cl == '':
+        if retries >= int(conf.config['http_retries']):
+            raise oscerr.OscIOError(None, 'Content-Length is empty for %s, protocol violation' % url)
+        retries = retries + 1
+        if retries > 1 and conf.config['http_debug']:
+            print >>sys.stderr, '\n\nRetry %d --' % (retries - 1), url
+        f = http_meth.__call__(url, data = data)
+        cl = f.info().get('Content-Length')
+
     if cl is not None:
         cl = int(cl)