def subscribe_to_stream(self, stream_name, token):
"""Subscribe the remote to a streams.
This invloves checking if they've missed anything and sending those
updates down if they have. During that time new updates for the stream
are queued and sent once we've sent down any missed updates.
"""
self.replication_streams.discard(stream_name)
self.connecting_streams.add(stream_name)
try:
# Get missing updates
updates, current_token = yield self.streamer.get_stream_updates(
stream_name,
token,
)
# Send all the missing updates
for update in updates:
token, row = update[0], update[1]
self.send_command(RdataCommand(stream_name, token, row))
# We send a POSITION command to ensure that they have an up to
# date token (especially useful if we didn't send any updates
# above)
self.send_command(PositionCommand(stream_name, current_token))
# Now we can send any updates that came in while we were subscribing
pending_rdata = self.pending_rdata.pop(stream_name, [])
for token, update in pending_rdata:
# Only send updates newer than the current token
if token > current_token:
self.send_command(RdataCommand(stream_name, token, update))
# They're now fully subscribed
self.replication_streams.add(stream_name)
except Exception as e:
logger.exception("[%s] Failed to handle REPLICATE command",
self.id())
self.send_error("failed to handle replicate: %r", e)
finally:
self.connecting_streams.discard(stream_name)
def stream_update(self, stream_name, token, data):
"""Called when a new update is available to stream to clients.
We need to check if the client is interested in the stream or not
"""
if stream_name in self.replication_streams:
# The client is subscribed to the stream
self.send_command(RdataCommand(stream_name, token, data))
elif stream_name in self.connecting_streams:
# The client is being subscribed to the stream
logger.debug("[%s] Queuing RDATA %r %r", self.id(), stream_name, token)
self.pending_rdata.setdefault(stream_name, []).append((token, data))
else:
# The client isn't subscribed
logger.debug("[%s] Dropping RDATA %r %r", self.id(), stream_name, token)