Added support for automatic compression/decompression of messages.

This is done by adding the "compression" header to messages.
Currently supported compression formats are: zlib and bzip2.
Custom compression formats can be added using kombu.compression.register::

    >>> compression.register(encoder, decoder, content_type, aliases={})

e.g.::

    >>> compression.register(lambda x: x.encode("zlib"),
    ...                      lambda x: x.decode("zlib"),
    ...                      "application/x-zlib",
    ...                      aliases=["zlib", "gzip"])

To enable compression you use the ``compression`` argument to
:meth:`Producer.publish`. When these messages are then consumed by
kombu they will be automatically decompressed, other clients need to
decompress them manually by looking at the ``compression`` header.

Example using zlib compression:

    >>> producer.publish(message, serializer="json", compression="zlib")

Example using bzip2 compression:

    >>> producer.publish(message, serializer="json", compression="bz2")

kombu/backends/base.py

@@ -4,6 +4,7 @@ Backend base classes.
 
 """
 from kombu import serialization
+from kombu.compression import decompress
 from kombu.exceptions import MessageStateError
 
 ACKNOWLEDGED_STATES = frozenset(["ACK", "REJECTED", "REQUEUED"])
@@ -25,11 +26,15 @@ class BaseMessage(object):
         self.content_type = content_type
         self.content_encoding = content_encoding
         self.delivery_info = delivery_info
-        self.headers = headers
+        self.headers = headers or {}
-        self.properties = properties
+        self.properties = properties or {}
         self._decoded_cache = None
         self._state = "RECEIVED"
 
+        compression = self.headers.get("compression")
+        if compression:
+            self.body = decompress(self.body, compression)
+
     def decode(self):
         """Deserialize the message body, returning the original
         python structure sent by the publisher."""

kombu/compression.py

@@ -0,0 +1,35 @@
+_aliases = {}
+_encoders = {}
+_decoders = {}
+
+
+def register(encoder, decoder, content_type, aliases=[]):
+    _encoders[content_type] = encoder
+    _decoders[content_type] = decoder
+    _aliases.update((alias, content_type) for alias in aliases)
+
+
+def get_encoder(t):
+    t = _aliases.get(t, t)
+    return _encoders[t], t
+
+
+def get_decoder(t):
+    return _decoders[_aliases.get(t, t)]
+
+
+def compress(body, content_type):
+    encoder, content_type = get_encoder(content_type)
+    return encoder(body), content_type
+
+
+def decompress(body, content_type):
+    return get_decoder(content_type)(body)
+
+
+register(lambda x: x.encode("zlib"),
+         lambda x: x.decode("zlib"),
+         "application/x-gzip", aliases=["gzip", "zlib"])
+register(lambda x: x.encode("bz2"),
+         lambda x: x.decode("bz2"),
+         "application/x-bz2", aliases=["bzip2", "bzip"])

kombu/messaging.py

@@ -1,6 +1,7 @@
 from itertools import count
 
 from kombu import serialization
+from kombu.compression import compress
 from kombu.entity import Exchange, Binding
 from kombu.utils import maybe_list
 
@@ -66,7 +67,8 @@ class Producer(object):
             self.exchange.declare()
 
     def _prepare(self, body, serializer=None,
-            content_type=None, content_encoding=None):
+            content_type=None, content_encoding=None, compression=None,
+            headers=None):
         # No content_type? Then we're serializing the data internally.
         if not content_type:
             serializer = serializer or self.serializer
@@ -81,15 +83,19 @@ class Producer(object):
                 body = body.encode(content_encoding)
 
             # If they passed in a string, we can't know anything
-            # about it.  So assume it's binary data.
+            # about it. So assume it's binary data.
             elif not content_encoding:
                 content_encoding = 'binary'
 
+        if compression:
+            body, headers["compression"] = compress(body, compression)
+
         return body, content_type, content_encoding
 
     def publish(self, body, routing_key=None, delivery_mode=None,
             mandatory=False, immediate=False, priority=0, content_type=None,
-            content_encoding=None, serializer=None, headers=None):
+            content_encoding=None, serializer=None, headers=None,
+            compression=None):
         """Publish message to the specified exchange.
 
         :param body: Message body.
@@ -105,11 +111,13 @@ class Producer(object):
           with the message body.
 
         """
+        headers = headers or {}
         if routing_key is None:
             routing_key = self.routing_key
 
         body, content_type, content_encoding = self._prepare(
-                body, content_type, content_encoding)
+                body, serializer, content_type, content_encoding,
+                compression, headers)
         message = self.exchange.Message(body,
                                         delivery_mode,
                                         priority,