From 44124646579f5d7f0579bc70395723d4c0bdbcb5 Mon Sep 17 00:00:00 2001
From: Lauren Perry <lauren.perry@codethink.co.uk>
Date: Fri, 13 Feb 2015 13:23:16 +0000
Subject: Add protocol versioning for distbuild systems

---
 distbuild/initiator.py            |  5 +++--
 distbuild/initiator_connection.py | 12 ++++++++++++
 distbuild/protocol.py             | 10 +++++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/distbuild/initiator.py b/distbuild/initiator.py
index ddea8cb3..7f82827c 100644
--- a/distbuild/initiator.py
+++ b/distbuild/initiator.py
@@ -83,11 +83,12 @@ class Initiator(distbuild.StateMachine):
             repo=self._repo_name,
             ref=self._ref,
             morphology=self._morphology,
-            original_ref=self._original_ref
+            original_ref=self._original_ref,
+            protocol_version=distbuild.protocol.VERSION
         )
         self._jm.send(msg)
         logging.debug('Initiator: sent to controller: %s', repr(msg))
-        
+
     def _handle_json_message(self, event_source, event):
         distbuild.crash_point()
 
diff --git a/distbuild/initiator_connection.py b/distbuild/initiator_connection.py
index c7f9dec7..86df28f1 100644
--- a/distbuild/initiator_connection.py
+++ b/distbuild/initiator_connection.py
@@ -102,6 +102,18 @@ class InitiatorConnection(distbuild.StateMachine):
 
         try:
             if event.msg['type'] == 'build-request':
+                if (event.msg.get('protocol_version') !=
+                   distbuild.protocol.VERSION):
+                    msg = distbuild.message('build-failed',
+                        id=event.msg['id'],
+                        reason=('Protocol version mismatch between server & '
+                                'initiator: distbuild network uses distbuild '
+                                'protocol version %i, but client uses version'
+                                ' %i.', distbuild.protocol.VERSION,
+                                event.msg.get('protocol_version')))
+                    self.jm.send(msg)
+                    self._log_send(msg)
+                    return
                 new_id = self._idgen.next()
                 self.our_ids.add(new_id)
                 self._route_map.add(event.msg['id'], new_id)
diff --git a/distbuild/protocol.py b/distbuild/protocol.py
index ffce1fe7..f2c74819 100644
--- a/distbuild/protocol.py
+++ b/distbuild/protocol.py
@@ -1,6 +1,6 @@
 # distbuild/protocol.py -- abstractions for the JSON messages
 #
-# Copyright (C) 2012, 2014  Codethink Limited
+# Copyright (C) 2012, 2014 - 2015  Codethink Limited
 # 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -19,12 +19,20 @@
 '''Construct protocol message objects (dicts).'''
 
 
+# Version refers to an integer that should be incremented by one each time a
+# time a change is introduced that would break server/initiator compatibility
+
+
+VERSION = 1
+
+
 _required_fields = {
     'build-request': [
         'id',
         'repo',
         'ref',
         'morphology',
+        'protocol_version',
     ],
     'build-progress': [
         'id',
-- 
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