* The previous one-way hearbeat was elegant, but comlicated to
understand and without giving much extra value compared to this approach.
* The previous one-way heartbeat have some kind of bug when joining
several (10-20) nodes at approximately the same time (but not exactly
the same time) with a false failure detection triggered by the extra heartbeat,
which would not heal.
* This ping-pong approach will increase network traffic slightly, but heartbeat
messages are small and each node is limited to monitor (default) 5 peers.
* No reason to use the System.currentTimeMillis base
* Remove the global VectorClock counter completely,
current count for a node is in the VectorClock itself
* Replace unreachable Set with Reachability table
* Unreachable members stay in member Set
* Downing a live member was moved it to the unreachable Set,
and then removed from there by the leader. That will not
work when flipping back to reachable, so a Down member must
be detected as unreachable before beeing removed. Similar
to Exiting. Member shuts down itself if it sees itself as
Down.
* Flip back to reachable when failure detector monitors it as
available again
* ReachableMember event
* Can't ignore gossip from aggregated unreachable (see SurviveNetworkInstabilitySpec)
* Make use of ReachableMember event in cluster router
* End heartbeat when acknowledged, EndHeartbeatAck
* Remove nr-of-end-heartbeats from conf
* Full reachability info in JMX cluster status
* Don't use interval after unreachable for AccrualFailureDetector history
* Add QuarantinedEvent to remoting, used for Reachability.Terminated
* Prune reachability table when all reachable
* Update documentation
* Performance testing and optimizations
Check VectorClock for common case first and cache hashCodes. See #3441
Make ClusterDaemon a bit more testable. See #3441
Changing VectorClock and GossipOverview to TreeMaps. See #3441
Make VectorClock private[cluster] and remove unused code. See #3441
* Removed leader commands for Shutdown and Exit
* Member shutdown itself when it sees itself as Exiting
* Singleton cluster with status Exiting will shutdown itself,
in case the Exiting gossip never arrives
* Exiting member not part convergence check
* Exiting member is removed by leader (on convergence) when the
exiting member is in the unreachable set, i.e. sucessfully shutdown
* Reverted the change made for #3266, i.e. Exiting is
detected as unreachable again.
* Adjust ClusterSingletonManager to new Exiting behaviour
* Fix bug in HeartbeatSender, which caused it to continue to
send heartbeats to removed nodes, instead of rebalancing
* Refactoring of leaderActions method
* Leaving section in docs
* Assign internal upNumber when member is moved to Up
* Public API Member.isOlder
* Change cluster singleton to use oldest member instead of leader
* Update samples and docs
* When seen same the gossip chat is initated with GossipStatus
message containing the vclock only
* Remove conversation flag in GossipEnvelope
* Ordinary tell instead of actorSelection when replying
* Disallow join requests when already part of a cluster
* Remove wipe state when joining, since join can only be
performed from empty state
* When trying to join, only accept gossip from that member
* Ignore gossips from unknown (and unreachable) members
* Make sure received gossip contains selfAddress
* Test join of fresh node with same host:port
* Remove JoinTwoClustersSpec
* Welcome message as reply to Join
* Retry unsucessful join request
* AddressUidExtension
* Uid in cluster Member identifier
To be able to distinguish nodes with same host:port
after restart.
* Ignore gossip with wrong uid
* Renamed Remove command to Shutdown
* Use uid in vclock identifier
* Update sample, Member apply is private
* Disabled config duration syntax and cleanup of io settings
* Update documentation
