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package com.teambytes.inflatable.raft.protocol
import akka.actor.ActorRef
import com.teambytes.inflatable.raft.model.Term
import com.teambytes.inflatable.raft.ClusterConfiguration
// todo simplify maybe, 1 metadata class would be enough I guess
@SerialVersionUID(1L)
private[protocol] trait StateMetadata extends Serializable {
type Candidate = ActorRef
sealed trait Metadata {
/**
* A raft cluster proxy aware version of `self` - should always be used it `self` is about to be exposed to external actors.
*
* In practice, this will be `self` if __not__ running in clustered mode, and the [[com.teambytes.inflatable.raft.cluster.ClusterRaftActor]]
* `ActorRef` that proxies this actor when in a clustered enviroment.
*/
implicit def clusterSelf: ActorRef // todo rethink if needed, better yet rewrite ClusterRaftActor to be properly transparent for RaftActor if possible.
def votes: Map[Term, Candidate]
def currentTerm: Term
def config: ClusterConfiguration
def isConfigTransitionInProgress = config.isTransitioning
/** Since I'm the Leader "everyone but myself" */
def membersExceptSelf = config.members filterNot { _ == clusterSelf }
def members = config.members
/** A member can only vote once during one Term */
def canVoteIn(term: Term) = term >= currentTerm && votes.get(term).isEmpty
/** A member can only vote once during one Term */
def cannotVoteIn(term: Term) = term < currentTerm || votes.get(term).isDefined
}
case class Meta(
clusterSelf: ActorRef,
currentTerm: Term,
config: ClusterConfiguration,
votes: Map[Term, Candidate]
) extends Metadata {
// transition helpers
def forNewElection: ElectionMeta = ElectionMeta(clusterSelf, currentTerm.next, 0, config, votes)
def withVote(term: Term, candidate: ActorRef) = {
copy(votes = votes updated (term, candidate))
}
def withConfig(conf: ClusterConfiguration): Meta = copy(config = conf)
}
object Meta {
def initial(implicit self: ActorRef) = new Meta(self, Term(0), ClusterConfiguration(isLocal = false), Map.empty)
}
case class ElectionMeta(
clusterSelf: ActorRef,
currentTerm: Term,
votesReceived: Int,
config: ClusterConfiguration,
votes: Map[Term, Candidate]
) extends Metadata {
def hasMajority = votesReceived > config.members.size / 2
// transistion helpers
def incVote = copy(votesReceived = votesReceived + 1)
def incTerm = copy(currentTerm = currentTerm.next)
def withVoteFor(term: Term, candidate: ActorRef) = copy(votes = votes + (term -> candidate))
def forLeader: LeaderMeta = LeaderMeta(clusterSelf, currentTerm, config)
def forFollower: Meta = Meta(clusterSelf, currentTerm, config, Map.empty)
def forNewElection: ElectionMeta = this.forFollower.forNewElection
}
case class LeaderMeta(
clusterSelf: ActorRef,
currentTerm: Term,
config: ClusterConfiguration
) extends Metadata {
val votes = Map.empty[Term, Candidate]
// todo duplication; yeah, having 3 meta classes was a bad idea. todo make one Meta class
def withConfig(conf: ClusterConfiguration): LeaderMeta = copy(config = conf)
def forFollower: Meta = Meta(clusterSelf, currentTerm, config, Map.empty)
}
}
