These are chat archives for atomix/atomix
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LINEARIZABLErequires a heartbeat after applying the query to verify that the leader is still the leader.
LINEARIZABLE_LEASEskips the heartbeat and assumes if the leader hasn't transitioned to another state then it's still the leader. This risks a stale read in in rare cases (between the time a new leader is elected and the time the old leader steps down), but reduces latency by eliminating round trips for reads.
@aaudiber Copycat will no longer be officially maintained once we transition ONOS to the Atomix Raft implementation. I only get paid to maintain one Raft implementation 😜 Users will have to move to
atomix-raft which is just a way better version of Copycat anyways!
That said, the consolidation of Atomix's utilities, messaging, protocols, and algorithms in the Atomix proper repo doesn't change the dependency hierarchy.
atomix-raft is still a standalone Raft client/server. It just lives in the Atomix repo now. Moving it into the Atomix repo made sense since it will also house a variety of other distributed systems algorithms like gossip/anti-entropy, failure detection, etc. Below Atomix 2.0 is a library of distributed systems algorithms and utilities that can each be used by themselves. Atomix 2.0 just pieces them together to do all the things I mentioned: partitioning, failure detection, cluster management, messaging, primitives, etc. Those libraries like Raft/gossip/failure detection will be documented and will always be usable as standalone libraries because that's the way we intend to use them in ONOS. Maybe they'll be separated into their own repos again some time in the future, but for now having them all in the Atomix repo has eased the pain of refactoring.
atomix-raftas a standalone Raft client/server. Looking forward to using this new and improved version of Copycat :)
atomix-raftstandalone so I know it works :-)
Atomix 2.0 no longer has connections. We found the management of connections in Atomix to be a point of instability. Often clients switch servers too frequently during high throughout, and the overhead of setting up connections exacerbates the issue.
We also found connections between clients and followers to be unexpectedly expensive when events are frequently sent to clients. In ONOS, often every command will trigger an event. The problem is, if the client is connected to a follower, the command has to be replicated to that follower and committed to trigger the event to the client before the client can handle any later responses. So, of the client submits two commands to a follower and he first command triggers an event, often the client becomes blocked waiting for the event before it can complete the second command.
So, to mitigate these two problems, Atomix 2.0 uses peer-to-peer messaging (no connections), and events are always sent by the leader. That means connections are never created or closed - at least at the Raft level - and clients' responses are rarely blocked waiting for events. Perhaps this places a bit more load on the leader, but partitioning in Atomix 2.0 will scale leaders anyways.