Docs for the messaging protocol.

zipline/protocol.py

@@ -1,3 +1,46 @@
+"""
+The messaging protocol for Zipline.
+
+Asserts are in place because any protocol error corresponds to a
+programmer error so we want it to fail fast and in an obvious way
+so it doesn't happen again. ZeroMQ follows the same philosophy.
+
+Notes
+=====
+
+Msgpack
+-------
+Msgpack is the fastest seriaization protocol in Python at the
+moment. Its 100% C is typically orders of magnitude faster than
+json and pickle making it awesome for ZeroMQ.
+
+You can only serialize Python structural primitives: strings,
+numeric types, dicts, tuples and lists. Any any recursive
+combinations of these.
+
+Basically every basestring in Python corresponds to valid
+msgpack message since the protocol is highly error tolerant.
+Just keep in mind that if you ever unpack a raw msgpack string
+make sure it looks like what you intend and/or catch ValueError
+and TypeError exceptions.
+
+It also has the nice benefit of never invoking ``eval`` ( unlike
+json and pickle) which is a major security boon since it is
+impossible to arbitrary code for evaluation through messages.
+
+UltraJSON
+---------
+For anything going to the browser UltraJSON is the fastest
+serializer, its mostly C as well.
+
+The same domain of serialization as msgpack applies: Python
+structural primitives. It also has the additional constraint
+that anything outside of UTF8 can cause serious problems, so if
+you have a strong desire to JSON encode ancient Sanskrit
+( admit it, we all do ), just say no.
+
+"""
+
 import msgpack
 #import ujson
 #import ultrajson_numpy
@@ -14,6 +57,39 @@ def Enum(*options):
         _fields_ = [(o, c_ubyte) for o in options]
     return cstruct(*range(len(options)))
 
+def FrameExceptionFactory(name):
+    """
+    Exception factory with a closure around the frame class name.
+    """
+    class InvalidFrame(Exception):
+        def __init__(self, got):
+            self.got = got
+        def __str__(self):
+            return "Invalid {framcls} Frame: {got}".format(
+                framecls = name,
+                got = self.got,
+            )
+
+class namedict(object):
+    """
+    So that you can use:
+
+        foo.BAR
+        -- or --
+        foo['BAR']
+
+    For more complex strcuts use collections.namedtuple:
+    """
+
+    def __init__(self, dct):
+        self.__dict__.update(dct)
+
+# ================
+# Control Protocol
+# ================
+
+INVALID_CONTROL_FRAME = FrameExceptionFactory('CONTROL')
+
 CONTROL_PROTOCOL = Enum(
     'INIT'      , # 0 - req
     'INFO'      , # 1 - req
@@ -26,7 +102,36 @@ CONTROL_PROTOCOL = Enum(
     'EXCEPTION' , # 7 - rep
 )
 
-HEARTBEAT_PROTOCOL = {
-    'REQ' : '\x01',
-    'REP' : '\x02',
-}
+def CONTROL_FRAME(id, status):
+    assert isinstance(basestring, id)
+    assert isinstance(int, status)
+
+    return msgpack.dumps(tuple([id, status]))
+
+def CONTORL_UNFRAME(msg):
+    assert isinstance(basestring, msg)
+
+    try:
+        id, status = msgpack.loads(msg)
+        assert isinstance(basestring, id)
+        assert isinstance(int, status)
+
+        return id, status
+    except TypeError:
+        raise INVALID_CONTROL_FRAME(msg)
+    except ValueError:
+        raise INVALID_CONTROL_FRAME(msg)
+    #except AssertionError:
+        #raise INVALID_CONTROL_FRAME(msg)
+
+# ================
+# Heartbeat Protocol
+# ================
+
+# These encode the msgpack equivelant of 1 and 2. The heartbeat
+# frame should only be 1 byte on the wire.
+
+HEARTBEAT_PROTOCOL = namedict({
+    'REQ' : b'\x01',
+    'REP' : b'\x02',
+})