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[AIT-96] feat: add msgpack suppport for websocket transport #648

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[AIT-96] feat: add msgpack suppport for websocket transport #648

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53504cd
feat: add msgpack support for WebSocket communication
ttypic Dec 9, 2025
4d57f96
feat: run both msgpack and json encoded messages on websocket
ttypic Dec 9, 2025
7a2e014
chore: improve exception handling for WebSocket message processing
ttypic Dec 12, 2025
78d8233
chore: implicit `raw` and `use_bin_type` flags for consistency
ttypic Dec 12, 2025
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3 changes: 3 additions & 0 deletions ably/realtime/connectionmanager.py
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Original file line number Diff line number Diff line change
Expand Up @@ -154,6 +154,9 @@ async def __get_transport_params(self) -> dict:
params["v"] = protocol_version
if self.connection_details:
params["resume"] = self.connection_details.connection_key
# RTN2a: Set format to msgpack if use_binary_protocol is enabled
if self.options.use_binary_protocol:
params["format"] = "msgpack"
return params

async def close_impl(self) -> None:
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3 changes: 2 additions & 1 deletion ably/realtime/realtime_channel.py
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Original file line number Diff line number Diff line change
Expand Up @@ -558,7 +558,8 @@ def _on_message(self, proto_msg: dict) -> None:
elif action == ProtocolMessageAction.MESSAGE:
messages = []
try:
messages = Message.from_encoded_array(proto_msg.get('messages'), context=self.__decoding_context)
messages = Message.from_encoded_array(proto_msg.get('messages'),
cipher=self.cipher, context=self.__decoding_context)
self.__decoding_context.last_message_id = messages[-1].id
self.__channel_serial = channel_serial
Comment on lines +561 to 564
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⚠️ Potential issue | 🟡 Minor

🧩 Analysis chain

🏁 Script executed:

cat -n ably/realtime/realtime_channel.py | sed -n '555,575p'

Repository: ably/ably-python

Length of output: 1352

🏁 Script executed:

rg -n --type=py '\.from_encoded_array\s*\(' --max-count=20

Repository: ably/ably-python

Length of output: 487

🏁 Script executed:

# Find the Message.from_encoded_array definition to understand its signature
ast-grep --pattern 'def from_encoded_array($$$)'

Repository: ably/ably-python

Length of output: 262

🏁 Script executed:

# Search for tests or comments about MESSAGE action with empty/missing messages
rg -n --type=py 'ProtocolMessageAction\.MESSAGE|proto_msg.*messages' -A 3 -B 3 | head -50

Repository: ably/ably-python

Length of output: 3967

🏁 Script executed:

# Check if there are any proto message construction examples in tests
rg -n --type=py 'messages.*\[\]|messages.*None' -B 2 -A 2 | head -40

Repository: ably/ably-python

Length of output: 2758

🏁 Script executed:

# Look at exception handling patterns in similar code sections
cat -n ably/realtime/realtime_channel.py | sed -n '540,580p'

Repository: ably/ably-python

Length of output: 2486

🏁 Script executed:

# Check if there's any validation or protocol specification for MESSAGE action messages field
rg -n --type=py 'MESSAGE|messages' ably/realtime/realtime_channel.py | grep -i 'protocol\|spec\|doc' | head -20

Repository: ably/ably-python

Length of output: 283

🏁 Script executed:

# Look at how proto_msg is constructed/parsed to understand if messages key is always present
rg -n --type=py 'def _on_message|proto_msg.*=' ably/realtime/realtime_channel.py | head -10

Repository: ably/ably-python

Length of output: 115

🏁 Script executed:

# Check if there are any edge cases in tests that exercise empty message scenarios
rg -n --type=py 'messages.*=.*\[\]' test/ -B 2 -A 2 | head -30

Repository: ably/ably-python

Length of output: 2124

Guard against missing/empty messages when updating last_message_id.
Line 561–563 can crash with TypeError (if proto_msg.get('messages') is None) or IndexError (if the list is empty). The exception handler at line 565 only catches AblyException, so these errors will propagate uncaught.

-            messages = Message.from_encoded_array(proto_msg.get('messages'),
-                                                  cipher=self.cipher, context=self.__decoding_context)
-            self.__decoding_context.last_message_id = messages[-1].id
+            raw_messages = proto_msg.get('messages') or []
+            messages = Message.from_encoded_array(
+                raw_messages,
+                cipher=self.cipher,
+                context=self.__decoding_context,
+            )
+            if messages:
+                self.__decoding_context.last_message_id = messages[-1].id
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
messages = Message.from_encoded_array(proto_msg.get('messages'),
cipher=self.cipher, context=self.__decoding_context)
self.__decoding_context.last_message_id = messages[-1].id
self.__channel_serial = channel_serial
raw_messages = proto_msg.get('messages') or []
messages = Message.from_encoded_array(
raw_messages,
cipher=self.cipher,
context=self.__decoding_context,
)
if messages:
self.__decoding_context.last_message_id = messages[-1].id
self.__channel_serial = channel_serial

except AblyException as e:
Expand Down
29 changes: 24 additions & 5 deletions ably/transport/websockettransport.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,8 @@
from enum import IntEnum
from typing import TYPE_CHECKING

import msgpack

from ably.http.httputils import HttpUtils
from ably.types.connectiondetails import ConnectionDetails
from ably.util.eventemitter import EventEmitter
Expand Down Expand Up @@ -71,6 +73,7 @@ def __init__(self, connection_manager: ConnectionManager, host: str, params: dic
self.is_disposed = False
self.host = host
self.params = params
self.format = params.get('format', 'json')
super().__init__()

def connect(self):
Expand Down Expand Up @@ -189,12 +192,23 @@ async def ws_read_loop(self):
raise AblyException('ws_read_loop started with no websocket', 500, 50000)
try:
async for raw in self.websocket:
msg = json.loads(raw)
task = asyncio.create_task(self.on_protocol_message(msg))
task.add_done_callback(self.on_protcol_message_handled)
# Decode based on format
try:
msg = self.decode_raw_websocket_frame(raw)
task = asyncio.create_task(self.on_protocol_message(msg))
task.add_done_callback(self.on_protcol_message_handled)
except Exception as e:
log.exception(
f"WebSocketTransport.decode(): Unexpected exception handling channel message: {e}"
)
except ConnectionClosedOK:
return

def decode_raw_websocket_frame(self, raw: str | bytes) -> dict:
if self.format == 'msgpack':
return msgpack.unpackb(raw, raw=False)
return json.loads(raw)

def on_protcol_message_handled(self, task):
try:
exception = task.exception()
Expand Down Expand Up @@ -231,8 +245,13 @@ async def close(self):
async def send(self, message: dict):
if self.websocket is None:
raise Exception()
raw_msg = json.dumps(message)
log.info(f'WebSocketTransport.send(): sending {raw_msg}')
# Encode based on format
if self.format == 'msgpack':
raw_msg = msgpack.packb(message, use_bin_type=True)
log.info(f'WebSocketTransport.send(): sending msgpack message (length: {len(raw_msg)} bytes)')
else:
raw_msg = json.dumps(message)
log.info(f'WebSocketTransport.send(): sending {raw_msg}')
await self.websocket.send(raw_msg)

def set_idle_timer(self, timeout: float):
Expand Down
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