In a scenario where traffic is buffered and/or replayed this could
lead to noisy cluster behaviour

Changelog

UNRELEASED

• Bugfix: when restarting members, there was a chance foca would ask a member to ping its own previous identity. No harm done to the cluster state, but would lead to noise in the form of Error::DataFromOurselves in the member logs See: https://github.com/caio/foca/issues/34
• Bugfix: messages from known stale identities were being accepted instead being discarded. Unlikely to have impacted anyone that isn't replaying data

v0.17.0 - 2024-03-20

This release contains significant changes aimed at freeing users from having to manage their own version of a unique list of members.

Whilst upgrading won't be just trivially bumping the version, it's expected to be very easy and users will probably find themselves deleting more code than writing new one when doing it.

Memory and CPU usage should go down since members and cluster updates are now bound by the number of distinct addresses whereas previously it would grow with the number of distinct identities.

As this is a large change, users should be more cautious when upgrading and are welcome to open an issue in case of questions or problems.

• BREAKING: foca::Identity has been revamped and now requires a unique cluster-wide identifier (typically a socket address or a hostname). When multiple identities appear with the same Addr the conflict is handled by Identity::win_addr_conflict
• BREAKING: Custom broadcasts wire format has changed and handler implementations now only need to emit an identifier (Key) for each value being broadcast instead of managing the allocation See the BroadcastHandler documentation and examples for details
• Config::periodic_announce_to_down_members: Foca periodically tries to join with members it considers down, as an attempt to recover from a network partition. This setting is enabled by default for Config::new_wan and Config::new_lan
• There's now Notification::Rename that signals whenever an identity with a conflicting Addr in the cluster gets replaced by a newer one
• There's no need to manage the list of members externally anymore: Foca does it all for you and Foca::iter_members only lists the unique (by Identity::Addr), freshest identities
• examples/foca_insecure_udp_agent.rs now comes with a fully working custom broadcast example
• There's now a simple runtime::AccumulatingRuntime that's good enough for basic usage if you don't want to implement your own

v0.16.0 - 2023-10-01

• Introduce Foca::iter_membership_state that provides a view into the whole state facilitating state replication scenarios. Previously one would need to juggle Notification::MemberDown and Foca::iter_members to achieve the same

v0.15.0 - 2023-09-04

• Foca::leave_cluster doesn't consume self anymore, so users can keep using the instance; Even rejoin the cluster if they so wish. See: https://github.com/caio/foca/issues/30

v0.14.0 - 2023-09-03

• BREAKING Custom broadcast handlers now know which member sent the data they're handling to facilitate anti-entropy use-cases. See: https://github.com/caio/foca/issues/28
• Foca now only emits DEBUG and TRACE level traces when using the tracing feature See: https://github.com/caio/foca/issues/30
• The foca_insecure_udp_agent example now contains a more robust timer handler able to tolerate arbitrary runtime lags

v0.13.0 - 2023-07-09

• Foca will now gossip upon receiving messages that flag their identity as suspect
• Foca now resumes probing more quickly when recovering from an incorrect sequence of Timer events
• The Timer enum now has a very simple Ord implementation to facilitate dealing with out-of-order delivery. Sorting a slice of Timer events should leave them in the order they should be handled, starting from the first index. See: https://github.com/caio/foca/issues/26

v0.12.0 - 2023-06-18

• CRITICAL BUGFIX: uses of the functionality to notify down members introduced on v0.6.0 could end up in a situation with a seemingly endless flood of Message::TurnUndead payloads. Upgrade is highly recommended. See: https://github.com/caio/foca/issues/25

v0.11.0 - 2023-03-22

• config::PeriodicParams is now exposed correctly so users can setup periodic tasks without relying on and mutating the result from Config::new_{wan,lan} See: https://github.com/caio/foca/issues/24

v0.10.1 - 2023-02-26

• Foca now always randomizes the list of members it sends when replying to announce messages. Previously this shuffling would happen periodically, so a fast announce rate would end up seeing the same set of members for a while. See: https://github.com/caio/foca/issues/22

v0.10.0 - 2023-01-13

• Traces now include useful information even when running with less verbose level
• Bugfix: albeit rare, foca could end up choosing an identity with the same prefix for the indirect probe cycle, leading to a confusing error in the logs of the target about receiving a message from itself

v0.9.0 - 2023-01-07

• BREAKING: iter_members now yields an iterator of Member structs, previously if would yield Member::id. This allows users to bootstrap a foca instance with existing cluster state by feeding its output directly to Foca::apply_many
• BREAKING: Config::remove_down_after has been increased to 24h. The previous default value of 2 minutes was still too small and would lead to unreasonably large updates backlog on large clusters. See: https://github.com/caio/foca/issues/19
• Performance/Bugfix: now foca doesn't allocate when preparing a message to be sent

v0.8.0 - 2022-12-31

• Bugfix: foca would send garbage at the end of the payload when replying to Announce messages under certain scenarios. See: https://github.com/caio/foca/issues/18

v0.7.0 - 2022-11-27

• BREAKING: Config::remove_down_after now defaults to 2 minutes instead of 15 seconds: clients not using the auto-rejoin functionality will take longer to rejoin the cluster after being declared down. Clients whose identity implement Identity::renew have nothing to worry about.
• Bugfix: A foca instance could end up learning that its previous identity was as active member on the cluster, adding more false positives to the cluster chatter

v0.6.0 - 2022-11-13

• New features:
  • Config::notify_down_members: foca can now inform down members that keep talking to the cluster that their messages are being ignored
  • Config::periodic_announce: you can instruct foca to periodically ask its peers for more peers, so that it learns about every member in the cluster faster
  • Config::periodic_gossip: to help speed up the propagation of cluster updates
• BREAKING: Config::new_wan and Config::new_lan now enable every new feature in this release

v0.5.0 - 2022-10-24

• Foca now gracefully resumes probing when it detects an incorrect probe cycle. https://github.com/caio/foca/pull/13
• Fixed one more instance of missing cleanup when the cluster state changes mid probe cycle. https://github.com/caio/foca/issues/2
• Public entities now implement Eq along with PartialEq

v0.4.1 - 2022-07-23

• Bugfix: "Member not found" trace lowered from warn to debug, only affects users of the tracing feature

v0.4.0 - 2022-07-02

• Optional feature postcard-codec now requires postcard v1.0

v0.3.1 - 2022-05-29

• Configuration can now be changed at runtime via Foca::set_config
• Added Config::new_wan and Config::new_lan helpers to generate a good enough configuration based on a given cluster size (requires the std feature)
• Traces (from using the tracing feature) are a lot less noisy

v0.3.0 - 2022-05-29

• Yanked, released accidentally

v0.2.0 - 2022-04-18

• BREAKING BroadcastHandler now takes a generic parameter: the identity type used by Foca
• BroadcastHandler can now decide which members should receive custom broadcasts
• You can now ask Foca to disseminate broadcasts only, via Foca::broadcast
• Simple broadcasting example added at ./examples/broadcasting.rs
• Fixed a bug that could lead to incorrect behaviour when a Foca instance changed identities in the middle of a probe cycle https://github.com/caio/foca/issues/2

v0.1.0 - 2021-11-04

• First release