From 5f0c449dd50fa84ff741e09f34cad5330c6e4745 Mon Sep 17 00:00:00 2001 From: Andrew Morgan Date: Mon, 4 Mar 2019 13:56:49 +0000 Subject: [PATCH] Prevent replication wedging --- synapse/replication/tcp/protocol.py | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/synapse/replication/tcp/protocol.py b/synapse/replication/tcp/protocol.py index 49ae5b3355..a6df04d851 100644 --- a/synapse/replication/tcp/protocol.py +++ b/synapse/replication/tcp/protocol.py @@ -451,7 +451,7 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol): @defer.inlineCallbacks def subscribe_to_stream(self, stream_name, token): - """Subscribe the remote to a streams. + """Subscribe the remote to a stream. This invloves checking if they've missed anything and sending those updates down if they have. During that time new updates for the stream @@ -478,10 +478,30 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol): # Now we can send any updates that came in while we were subscribing pending_rdata = self.pending_rdata.pop(stream_name, []) + batch_updates = [] 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)) + # If the token is null, it is part of a batch update. Batches + # are multiple updates that share a single token. To denote + # this, the token is set to None for all tokens in the batch + # except for the last. If we find a None token, we keep looking + # through tokens until we find one that is not None and then + # process all previous updates in the batch as if they had the + # final token. + if not token or len(batch_updates) > 0: + batch_updates.append(update) + if token and not token > current_token: + # This batch is older than current_token, dismiss + batch_updates = [] + continue + if token: + # Send all updates that are part of this batch with the + # found token + for update in batch_updates: + self.send_command(RdataCommand(stream_name, token, update)) + else: + # 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)