Allow users to customize max header size

Also increases the default value from 8192 to 16384

The former max header (8192) is exceeded in the following scenario
- Auth tokens built with a keystone v3 API catalog
- A catalog with approximately 8 or more endpoints defined

Equivalent fixes have been proposed in other projects

Change-Id: Ic714166440e2aa08b619ab1e5e5e0cf3cea3e309
Closes-Bug: 1190149

etc/glance-api.conf

@@ -73,6 +73,12 @@ sql_idle_timeout = 3600
 # this value to the number of CPUs present on your machine.
 workers = 1
 
+# Maximum line size of message headers to be accepted.
+# max_header_line may need to be increased when using large tokens
+# (typically those generated by the Keystone v3 API with big service
+# catalogs)
+# max_header_line = 16384
+
 # Role used to identify an authenticated user as administrator
 #admin_role = admin
 

glance/common/wsgi.py

@@ -79,6 +79,11 @@ eventlet_opts = [
                       'only supported \'poll\', however \'selects\' may be '
                       'appropriate for some platforms. See '
                       'http://eventlet.net/doc/hubs.html for more details.')),
+    cfg.IntOpt('max_header_line', default=16384,
+               help=_('Maximum line size of message headers to be accepted. '
+                      'max_header_line may need to be increased when using '
+                      'large tokens (typically those generated by the '
+                      'Keystone v3 API with big service catalogs')),
 ]
 
 
@@ -177,6 +182,7 @@ class Server(object):
     """Server class to manage multiple WSGI sockets and applications."""
 
     def __init__(self, threads=1000):
+        eventlet.wsgi.MAX_HEADER_LINE = CONF.max_header_line
         self.threads = threads
         self.children = []
         self.running = True