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changelog

This changelog follows the patterns described here: https://keepachangelog.com/en/1.0.0/.

[unreleased]

async-raft 0.6.1

fixed

  • Fixed #105 where function set_target_state missing else condition.
  • Fixed #106 which ensures that counting of replicas to determine a new commit value only considers entries replicated as part of the current term.
  • Fixed a bug where NonVoter nodes could be restarted and come back as voting members.

async-raft 0.6.0

The big news for this release is that we are now based on Tokio 1.0! Big shoutout to @xu-cheng for doing all of the heavy lifting for the Tokio 1.0 update, along with many other changes which are part of this release.

It is important to note that 0.6.0 does include two breaking changes from 0.5: the new RaftStorage::ShutdownError associated type, and Tokio 1.0. Both of these changes are purely code related, and it is not expected that they will negatively impact running systems.

changed

  • Updated to Tokio 1.0!
  • BREAKING: this introduces a RaftStorage::ShutdownError associated type. This allows for the Raft system to differentiate between fatal storage errors which should cause the system to shutdown vs errors which should be propagated back to the client for application specific error handling. These changes only apply to the RaftStorage::apply_entry_to_state_machine method.
  • A small change to Raft startup semantics. When a node comes online and successfully recovers state (the node was already part of a cluster), the node will start with a 30 second election timeout, ensuring that it does not disrupt a running cluster.
  • #89 removes the Debug bounds requirement on the AppData & AppDataResponse types.
  • The Raft type can now be cloned. The clone is very cheap and helps to facilitate async workflows while feeding client requests and Raft RPCs into the Raft instance.
  • The Raft.shutdown interface has been changed slightly. Instead of returning a JoinHandle, the method is now async and simply returns a result.
  • The ClientWriteError::ForwardToLeader error variant has been modified slightly. It now exposes the data (generic type D of the type) of the original client request directly. This ensures that the data can actually be used for forwarding, if that is what the parent app wants to do.
  • Implemented #12. This is a pretty old issue and a pretty solid optimization. The previous implementation of this algorithm would go to storage (typically disk) for every process of replicating entries to the state machine. Now, we are caching entries as they come in from the leader, and using only the cache as the source of data. There are a few simple measures needed to ensure this is correct, as the leader entry replication protocol takes care of most of the work for us in this case.
  • Updated / clarified the interface for log compaction. See the guide or the updated do_log_compaction method docs for more details.

added

  • #97 adds the new Raft.current_leader method. This is a convenience method which builds upon the Raft metrics system to quickly and easily identify the current cluster leader.

fixed

  • Fixed #98 where heartbeats were being passed along into the log consistency check algorithm. This had the potential to cause a Raft node to go into shutdown under some circumstances.
  • Fixed a bug where the timestamp of the last received heartbeat from a leader was not being stored, resulting in degraded cluster stability under some circumstances.

memstore 0.2.0

changed

  • Updated async-raft dependency to 0.6.0 & updated storage interface as needed.

fixed

  • Fixed #76 by moving the process of replicating log entries to the state machine off of the main task. This ensures that the process never blocks the main task. This also includes a few nice optimizations mentioned below.

0.5.5

changed

  • Added #[derive(Serialize, Deserialize)] to RaftMetrics, State.

0.5.4

fixed

  • Fixed #82 where client reads were not behaving correctly for single node clusters. Single node integration tests have been updated to ensure this functionality is working as needed.

0.5.3

fixed

  • Fixed #79 ... for real this time! Add an integration test to prove it.

0.5.2

fixed

  • Fixed #79. The Raft core state machine was not being properly updated in response to shutdown requests. That has been addressed and shutdowns are now behaving as expected.

0.5.1

changed

  • ChangeConfigError::NodeNotLeader now returns the ID of the current cluster leader if known.
  • Fix off-by-one error in get_log_entries during the replication process.
  • Added #[derive(Serialize, Deserialize)] to Config, ConfigBuilder & SnapshotPolicy.

0.5.0

changed

The only thing which hasn't changed is that this crate is still an implementation of the Raft protocol. Pretty much everything else has changed.

  • Everything is built directly on Tokio now.
  • The guide has been updated.
  • Docs have been updated.
  • The Raft type is now the primary API of this crate, and is a simple struct with a few public methods.
  • Lots of fixes to the implementation of the protocol, ranging from subtle issues in joint consensus to non-voter syncing.

0.4.4

  • Implemented Error for config::ConfigError

0.4.3

Added a few convenience derivations.

  • Derive Eq on messages::MembershipConfig.
  • Derive Eq on metrics::State.
  • Derive PartialEq & Eq on metrics::RaftMetrics.
  • Update development dependencies.
  • Fixed bug #41 where nodes were not starting a new election timeout task after comign down from leader state. Thanks @lionesswardrobe for the report!

0.4.2

A few QOL improvements.

  • Fixed an issue where the value for current_leader was not being set to None when becoming a candidate. This isn't really a bug per se, as no functionality depended on this value as far as Raft is concerned, but it is an issue that impacts the metrics system. This value is now being updated properly.
  • Made the messages::ClientPayload::new_base constructor pub(crate) instead of pub, which is what the intention was originally, but I was apparently tired :).
  • Implemented #25. Implementing Display+Error for the admin error types.

0.4.1

A few bug fixes.

  • Fixed an issue where a node in a single-node Raft was not resuming as leader after a crash.
  • Fixed an issue where hard state was not being saved after a node becomes leader in a single-node Raft.
  • Fixed an issue where the client request pipeline (a Stream with the actix::StreamFinish) was being closed after an error was returned during processing of client requests (which should not cause the stream to close). This was unexpected and undocumented behavior, very simple fix though.

0.4.0

This changeset introduces a new AppDataResponse type which represents a concrete data type which must be sent back from the RaftStorage impl from the ApplyEntryToStateMachine handler. This provides a more direct path for returning application level data from the storage impl. Often times this is needed for responding to client requests in a timely / efficient manner.

  • AppDataResponse type has been added (see above).
  • A few handlers have been updated in the RaftStorage type. The handlers are now separated based on where they are invoked from the Raft node. The three changed handlers are:
    • AppendEntryToLog: this is the same. It is the initial step of handling client requests to apply an entry to the log. This is still where application level errors may be safely returned to the client.
    • ReplicateToLog: this is for replicating entries to the log. This is part of the replication process.
    • ApplyEntryToStateMachine: this is for applying an entry to the state machine as the final part of a client request. This is where the new AddDataResponse type must be returned.
    • ReplicateToStateMachine: this is for replicating entries to the state machine. This is part of the replication process.

0.3.1

Overhauled the election timeout mechanism. This uses an interval job instead of juggling a rescheduling processes. Seems to offer quite a lot more stability. Along with the interval job, we are using std::time::Instants for performing the comparisons against the last received heartbeat.

0.3.0

Another backwards incompatible change to the RaftStorage trait. It is now using associated types to better express the needed trait constraints. These changes were the final bit of work needed to get the entire actix-raft system to work with a Synchronous RaftStorage impl. Async impls continue to work as they have, the RaftStorage impl block will need to be updated to use the associated types though. The recommend pattern is as follows:

impl RaftStorage<..., ...> for MyStorage {
    type Actor = Self;
    type Context = Context<Self>; // Or SyncContext<Self>;
}

My hope is that this will be the last backwards incompatible change needed before a 1.0 release. This crate is still young though, so we will see.

0.2.0

  • Made a few backwards incompatible changes to the RaftStorage trait. Overwrite its third type parameter with actix::SyncContext<Self> to enable sync storage.
  • Also removed the RaftStorage::new constructor, as it is a bit restrictive. Just added some docs instead describing what is needed.

0.1.3

  • Added a few addition top-level exports for convenience.

0.1.2

  • Changes to the README for docs.rs.

0.1.1

  • Changes to the README for docs.rs.

0.1.0

  • Initial release!