X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?p=controller.git;a=blobdiff_plain;f=opendaylight%2Fmd-sal%2Fsal-akka-raft%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fcontroller%2Fcluster%2Fraft%2Fbehaviors%2FAbstractRaftActorBehavior.java;h=fd2fbd332c7a58bab6f60b01e37b2193ad98c3e7;hp=ef5f11e37aef4fe7490887a27d91caedb0e50c51;hb=HEAD;hpb=7f946f22fa31489740b730f3a9a7f7772ef38f6b

diff --git a/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractRaftActorBehavior.java b/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractRaftActorBehavior.java
index ef5f11e37a..055a053500 100644
--- a/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractRaftActorBehavior.java
+++ b/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractRaftActorBehavior.java
@@ -5,85 +5,97 @@
  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
  * and is available at http://www.eclipse.org/legal/epl-v10.html
  */
-
 package org.opendaylight.controller.cluster.raft.behaviors;
 
+import static java.util.Objects.requireNonNull;
+
 import akka.actor.ActorRef;
 import akka.actor.Cancellable;
-import java.util.Random;
+import akka.cluster.Cluster;
+import akka.cluster.Member;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
-import org.opendaylight.controller.cluster.raft.ClientRequestTracker;
 import org.opendaylight.controller.cluster.raft.RaftActorContext;
 import org.opendaylight.controller.cluster.raft.RaftState;
 import org.opendaylight.controller.cluster.raft.ReplicatedLogEntry;
-import org.opendaylight.controller.cluster.raft.SerializationUtils;
-import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
 import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
 import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
+import org.opendaylight.controller.cluster.raft.messages.RaftRPC;
 import org.opendaylight.controller.cluster.raft.messages.RequestVote;
 import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
+import org.opendaylight.controller.cluster.raft.persisted.ApplyJournalEntries;
 import org.slf4j.Logger;
 import scala.concurrent.duration.FiniteDuration;
 
 /**
- * Abstract class that represents the behavior of a RaftActor
- * <p/>
- * All Servers:
- * <ul>
- * <li> If commitIndex > lastApplied: increment lastApplied, apply
- * log[lastApplied] to state machine (§5.3)
- * <li> If RPC request or response contains term T > currentTerm:
- * set currentTerm = T, convert to follower (§5.1)
+ * Abstract class that provides common code for a RaftActor behavior.
  */
 public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
-
     /**
-     * Information about the RaftActor whose behavior this class represents
+     * Information about the RaftActor whose behavior this class represents.
      */
     protected final RaftActorContext context;
 
     /**
-     *
+     * Used for message logging.
      */
-    protected final Logger LOG;
+    @SuppressFBWarnings("SLF4J_LOGGER_SHOULD_BE_PRIVATE")
+    protected final Logger log;
 
     /**
-     *
+     * Prepended to log messages to provide appropriate context.
      */
-    private Cancellable electionCancel = null;
+    private final String logName;
 
     /**
-     *
+     * The RaftState corresponding to his behavior.
      */
-    protected String leaderId = null;
-
-    private long replicatedToAllIndex = -1;
+    private final RaftState state;
 
-    private final String logName;
+    /**
+     * Used to cancel a scheduled election.
+     */
+    private Cancellable electionCancel = null;
 
-    private final RaftState state;
+    /**
+     * The index of the last log entry that has been replicated to all raft peers.
+     */
+    private long replicatedToAllIndex = -1;
 
-    protected AbstractRaftActorBehavior(RaftActorContext context, RaftState state) {
-        this.context = context;
-        this.state = state;
-        this.LOG = context.getLogger();
+    AbstractRaftActorBehavior(final RaftActorContext context, final RaftState state) {
+        this.context = requireNonNull(context);
+        this.state = requireNonNull(state);
+        log = context.getLogger();
 
         logName = String.format("%s (%s)", context.getId(), state);
     }
 
+    public static RaftActorBehavior createBehavior(final RaftActorContext context, final RaftState state) {
+        return switch (state) {
+            case Candidate -> new Candidate(context);
+            case Follower -> new Follower(context);
+            case IsolatedLeader -> new IsolatedLeader(context);
+            case Leader -> new Leader(context);
+            case PreLeader -> new PreLeader(context);
+        };
+    }
+
     @Override
-    public RaftState state() {
+    public final RaftState state() {
         return state;
     }
 
-    public String logName() {
+    protected final String logName() {
         return logName;
     }
 
     @Override
-    public void setReplicatedToAllIndex(long replicatedToAllIndex) {
+    public void setReplicatedToAllIndex(final long replicatedToAllIndex) {
         this.replicatedToAllIndex = replicatedToAllIndex;
     }
 
@@ -102,34 +114,27 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
      *
      * @param sender         The actor that sent this message
      * @param appendEntries  The AppendEntries message
-     * @return
+     * @return a new behavior if it was changed or the current behavior
      */
     protected abstract RaftActorBehavior handleAppendEntries(ActorRef sender,
         AppendEntries appendEntries);
 
-
     /**
-     * appendEntries first processes the AppendEntries message and then
-     * delegates handling to a specific behavior
+     * Handles the common logic for the AppendEntries message and delegates handling to the derived class.
      *
-     * @param sender
-     * @param appendEntries
-     * @return
+     * @param sender the ActorRef that sent the message
+     * @param appendEntries the message
+     * @return a new behavior if it was changed or the current behavior
      */
-    protected RaftActorBehavior appendEntries(ActorRef sender,
-        AppendEntries appendEntries) {
+    protected RaftActorBehavior appendEntries(final ActorRef sender, final AppendEntries appendEntries) {
 
         // 1. Reply false if term < currentTerm (§5.1)
         if (appendEntries.getTerm() < currentTerm()) {
-            if(LOG.isDebugEnabled()) {
-                LOG.debug("{}: Cannot append entries because sender term {} is less than {}",
-                        logName(), appendEntries.getTerm(), currentTerm());
-            }
+            log.info("{}: Cannot append entries because sender's term {} is less than {}", logName(),
+                    appendEntries.getTerm(), currentTerm());
 
-            sender.tell(
-                new AppendEntriesReply(context.getId(), currentTerm(), false,
-                    lastIndex(), lastTerm()), actor()
-            );
+            sender.tell(new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex(), lastTerm(),
+                    context.getPayloadVersion(), false, false, appendEntries.getLeaderRaftVersion()), actor());
             return this;
         }
 
@@ -147,23 +152,39 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
      *
      * @param sender             The actor that sent this message
      * @param appendEntriesReply The AppendEntriesReply message
-     * @return
+     * @return a new behavior if it was changed or the current behavior
      */
     protected abstract RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
         AppendEntriesReply appendEntriesReply);
 
     /**
-     * requestVote handles the RequestVote message. This logic is common
-     * for all behaviors
+     * Handles the logic for the RequestVote message that is common for all behaviors.
      *
-     * @param sender
-     * @param requestVote
-     * @return
+     * @param sender the ActorRef that sent the message
+     * @param requestVote the message
+     * @return a new behavior if it was changed or the current behavior
      */
-    protected RaftActorBehavior requestVote(ActorRef sender, RequestVote requestVote) {
+    protected RaftActorBehavior requestVote(final ActorRef sender, final RequestVote requestVote) {
+
+        log.debug("{}: In requestVote:  {} - currentTerm: {}, votedFor: {}, lastIndex: {}, lastTerm: {}", logName(),
+                requestVote, currentTerm(), votedFor(), lastIndex(), lastTerm());
 
-        LOG.debug("{}: In requestVote:  {}", logName(), requestVote);
+        boolean grantVote = canGrantVote(requestVote);
 
+        if (grantVote) {
+            context.getTermInformation().updateAndPersist(requestVote.getTerm(), requestVote.getCandidateId());
+        }
+
+        RequestVoteReply reply = new RequestVoteReply(currentTerm(), grantVote);
+
+        log.debug("{}: requestVote returning: {}", logName(), reply);
+
+        sender.tell(reply, actor());
+
+        return this;
+    }
+
+    protected boolean canGrantVote(final RequestVote requestVote) {
         boolean grantVote = false;
 
         //  Reply false if term < currentTerm (§5.1)
@@ -173,7 +194,7 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
             // If votedFor is null or candidateId, and candidate’s log is at
             // least as up-to-date as receiver’s log, grant vote (§5.2, §5.4)
         } else if (votedFor() == null || votedFor()
-            .equals(requestVote.getCandidateId())) {
+                .equals(requestVote.getCandidateId())) {
 
             boolean candidateLatest = false;
 
@@ -184,27 +205,16 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
             // the log with the later term is more up-to-date. If the logs
             // end with the same term, then whichever log is longer is
             // more up-to-date.
-            if (requestVote.getLastLogTerm() > lastTerm()) {
-                candidateLatest = true;
-            } else if ((requestVote.getLastLogTerm() == lastTerm())
-                && requestVote.getLastLogIndex() >= lastIndex()) {
+            if (requestVote.getLastLogTerm() > lastTerm()
+                || requestVote.getLastLogTerm() == lastTerm() && requestVote.getLastLogIndex() >= lastIndex()) {
                 candidateLatest = true;
             }
 
             if (candidateLatest) {
                 grantVote = true;
-                context.getTermInformation().updateAndPersist(requestVote.getTerm(),
-                    requestVote.getCandidateId());
             }
         }
-
-        RequestVoteReply reply = new RequestVoteReply(currentTerm(), grantVote);
-
-        LOG.debug("{}: requestVote returning: {}", logName(), reply);
-
-        sender.tell(reply, actor());
-
-        return this;
+        return grantVote;
     }
 
     /**
@@ -217,24 +227,24 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
      *
      * @param sender           The actor that sent this message
      * @param requestVoteReply The RequestVoteReply message
-     * @return
+     * @return a new behavior if it was changed or the current behavior
      */
     protected abstract RaftActorBehavior handleRequestVoteReply(ActorRef sender,
         RequestVoteReply requestVoteReply);
 
     /**
-     * Creates a random election duration
+     * Returns a duration for election with an additional variance for randomness.
      *
-     * @return
+     * @return a random election duration
      */
     protected FiniteDuration electionDuration() {
-        long variance = new Random().nextInt(context.getConfigParams().getElectionTimeVariance());
+        long variance = ThreadLocalRandom.current().nextInt(context.getConfigParams().getElectionTimeVariance());
         return context.getConfigParams().getElectionTimeOutInterval().$plus(
                 new FiniteDuration(variance, TimeUnit.MILLISECONDS));
     }
 
     /**
-     * stop the scheduled election
+     * Stops the currently scheduled election.
      */
     protected void stopElection() {
         if (electionCancel != null && !electionCancel.isCancelled()) {
@@ -242,152 +252,147 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
         }
     }
 
+    protected boolean canStartElection() {
+        return context.getRaftPolicy().automaticElectionsEnabled() && context.isVotingMember();
+    }
+
     /**
-     * schedule a new election
+     * Schedule a new election.
      *
-     * @param interval
+     * @param interval the duration after which we should trigger a new election
      */
-    protected void scheduleElection(FiniteDuration interval) {
+    // Non-final for testing
+    protected void scheduleElection(final FiniteDuration interval) {
         stopElection();
 
-        // Schedule an election. When the scheduler triggers an ElectionTimeout
-        // message is sent to itself
-        electionCancel =
-            context.getActorSystem().scheduler().scheduleOnce(interval,
-                context.getActor(), new ElectionTimeout(),
-                context.getActorSystem().dispatcher(), context.getActor());
+        // Schedule an election. When the scheduler triggers an ElectionTimeout message is sent to itself
+        electionCancel = context.getActorSystem().scheduler().scheduleOnce(interval, context.getActor(),
+                ElectionTimeout.INSTANCE, context.getActorSystem().dispatcher(), context.getActor());
     }
 
     /**
-     * Get the current term
-     * @return
+     * Returns the current election term.
+     *
+     * @return the current term
      */
     protected long currentTerm() {
         return context.getTermInformation().getCurrentTerm();
     }
 
     /**
-     * Get the candidate for whom we voted in the current term
-     * @return
+     * Returns the id of the candidate that this server voted for in current term.
+     *
+     * @return the candidate for whom we voted in the current term
      */
     protected String votedFor() {
         return context.getTermInformation().getVotedFor();
     }
 
     /**
-     * Get the actor associated with this behavior
-     * @return
+     * Returns the actor associated with this behavior.
+     *
+     * @return the actor
      */
-    protected ActorRef actor() {
+    protected final ActorRef actor() {
         return context.getActor();
     }
 
     /**
-     * Get the term from the last entry in the log
+     * Returns the term of the last entry in the log.
      *
-     * @return
+     * @return the term
      */
     protected long lastTerm() {
         return context.getReplicatedLog().lastTerm();
     }
 
     /**
-     * Get the index from the last entry in the log
+     * Returns the index of the last entry in the log.
      *
-     * @return
+     * @return the index
      */
     protected long lastIndex() {
         return context.getReplicatedLog().lastIndex();
     }
 
     /**
-     * Find the client request tracker for a specific logIndex
+     * Returns the actual index of the entry in replicated log for the given index or -1 if not found.
      *
-     * @param logIndex
-     * @return
+     * @return the log entry index or -1 if not found
      */
-    protected ClientRequestTracker findClientRequestTracker(long logIndex) {
-        return null;
-    }
+    protected long getLogEntryIndex(final long index) {
+        if (index == context.getReplicatedLog().getSnapshotIndex()) {
+            return context.getReplicatedLog().getSnapshotIndex();
+        }
 
-    /**
-     * Find the client request tracker for a specific logIndex
-     *
-     * @param logIndex
-     * @return
-     */
-    protected ClientRequestTracker removeClientRequestTracker(long logIndex) {
-        return null;
-    }
+        ReplicatedLogEntry entry = context.getReplicatedLog().get(index);
+        if (entry != null) {
+            return entry.getIndex();
+        }
 
+        return -1;
+    }
 
     /**
-     * Find the log index from the previous to last entry in the log
+     * Returns the actual term of the entry in the replicated log for the given index or -1 if not found.
      *
-     * @return
+     * @return the log entry term or -1 if not found
      */
-    protected long prevLogIndex(long index){
-        ReplicatedLogEntry prevEntry =
-            context.getReplicatedLog().get(index - 1);
-        if (prevEntry != null) {
-            return prevEntry.getIndex();
+    protected long getLogEntryTerm(final long index) {
+        if (index == context.getReplicatedLog().getSnapshotIndex()) {
+            return context.getReplicatedLog().getSnapshotTerm();
         }
+
+        ReplicatedLogEntry entry = context.getReplicatedLog().get(index);
+        if (entry != null) {
+            return entry.getTerm();
+        }
+
         return -1;
     }
 
     /**
-     * Find the log term from the previous to last entry in the log
-     * @return
+     * Returns the actual term of the entry in the replicated log for the given index or, if not present, returns the
+     * snapshot term if the given index is in the snapshot or -1 otherwise.
+     *
+     * @return the term or -1 otherwise
      */
-    protected long prevLogTerm(long index){
-        ReplicatedLogEntry prevEntry =
-            context.getReplicatedLog().get(index - 1);
-        if (prevEntry != null) {
-            return prevEntry.getTerm();
+    protected long getLogEntryOrSnapshotTerm(final long index) {
+        if (context.getReplicatedLog().isInSnapshot(index)) {
+            return context.getReplicatedLog().getSnapshotTerm();
         }
-        return -1;
+
+        return getLogEntryTerm(index);
     }
 
     /**
-     * Apply the provided index to the state machine
+     * Applies the log entries up to the specified index that is known to be committed to the state machine.
      *
-     * @param index a log index that is known to be committed
+     * @param index the log index
      */
     protected void applyLogToStateMachine(final long index) {
-        long newLastApplied = context.getLastApplied();
         // Now maybe we apply to the state machine
-        for (long i = context.getLastApplied() + 1;
-             i < index + 1; i++) {
-            ActorRef clientActor = null;
-            String identifier = null;
-            ClientRequestTracker tracker = removeClientRequestTracker(i);
-
-            if (tracker != null) {
-                clientActor = tracker.getClientActor();
-                identifier = tracker.getIdentifier();
-            }
-            ReplicatedLogEntry replicatedLogEntry =
-                context.getReplicatedLog().get(i);
+        for (long i = context.getLastApplied() + 1; i < index + 1; i++) {
 
+            ReplicatedLogEntry replicatedLogEntry = context.getReplicatedLog().get(i);
             if (replicatedLogEntry != null) {
                 // Send a local message to the local RaftActor (it's derived class to be
                 // specific to apply the log to it's index)
-                actor().tell(new ApplyState(clientActor, identifier,
-                    replicatedLogEntry), actor());
-                newLastApplied = i;
+
+                final ApplyState applyState = getApplyStateFor(replicatedLogEntry);
+
+                log.debug("{}: Setting last applied to {}", logName(), i);
+
+                context.setLastApplied(i);
+                context.getApplyStateConsumer().accept(applyState);
             } else {
                 //if one index is not present in the log, no point in looping
                 // around as the rest wont be present either
-                LOG.warn(
-                        "{}: Missing index {} from log. Cannot apply state. Ignoring {} to {}",
+                log.warn("{}: Missing index {} from log. Cannot apply state. Ignoring {} to {}",
                         logName(), i, i, index);
                 break;
             }
         }
-        if(LOG.isDebugEnabled()) {
-            LOG.debug("{}: Setting last applied to {}", logName(), newLastApplied);
-        }
-        context.setLastApplied(newLastApplied);
 
         // send a message to persist a ApplyLogEntries marker message into akka's persistent journal
         // will be used during recovery
@@ -396,40 +401,56 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
         actor().tell(new ApplyJournalEntries(context.getLastApplied()), actor());
     }
 
-    protected Object fromSerializableMessage(Object serializable){
-        return SerializationUtils.fromSerializable(serializable);
-    }
+    /**
+     * Create an ApplyState message for a particular log entry so we can determine how to apply this entry.
+     *
+     * @param entry the log entry
+     * @return ApplyState for this entry
+     */
+    abstract ApplyState getApplyStateFor(ReplicatedLogEntry entry);
 
     @Override
-    public RaftActorBehavior handleMessage(ActorRef sender, Object message) {
-        if (message instanceof AppendEntries) {
-            return appendEntries(sender, (AppendEntries) message);
-        } else if (message instanceof AppendEntriesReply) {
-            return handleAppendEntriesReply(sender, (AppendEntriesReply) message);
-        } else if (message instanceof RequestVote) {
-            return requestVote(sender, (RequestVote) message);
-        } else if (message instanceof RequestVoteReply) {
-            return handleRequestVoteReply(sender, (RequestVoteReply) message);
+    public RaftActorBehavior handleMessage(final ActorRef sender, final Object message) {
+        if (message instanceof AppendEntries appendEntries) {
+            return appendEntries(sender, appendEntries);
+        } else if (message instanceof AppendEntriesReply appendEntriesReply) {
+            return handleAppendEntriesReply(sender, appendEntriesReply);
+        } else if (message instanceof RequestVote requestVote) {
+            return requestVote(sender, requestVote);
+        } else if (message instanceof RequestVoteReply requestVoteReply) {
+            return handleRequestVoteReply(sender, requestVoteReply);
+        } else {
+            return null;
         }
-        return this;
     }
 
-    @Override public String getLeaderId() {
-        return leaderId;
+    @Override
+    public RaftActorBehavior switchBehavior(final RaftActorBehavior behavior) {
+        return internalSwitchBehavior(behavior);
+    }
+
+    protected RaftActorBehavior internalSwitchBehavior(final RaftState newState) {
+        return internalSwitchBehavior(createBehavior(context, newState));
     }
 
-    protected RaftActorBehavior switchBehavior(RaftActorBehavior behavior) {
-        LOG.info("{} :- Switching from behavior {} to {}", logName(), this.state(), behavior.state());
+    @SuppressWarnings("checkstyle:IllegalCatch")
+    protected RaftActorBehavior internalSwitchBehavior(final RaftActorBehavior newBehavior) {
+        if (!context.getRaftPolicy().automaticElectionsEnabled()) {
+            return this;
+        }
+
+        log.info("{} :- Switching from behavior {} to {}, election term: {}", logName(), state(),
+                newBehavior.state(), context.getTermInformation().getCurrentTerm());
         try {
             close();
-        } catch (Exception e) {
-            LOG.error("{}: Failed to close behavior : {}", logName(), this.state(), e);
+        } catch (RuntimeException e) {
+            log.error("{}: Failed to close behavior : {}", logName(), state(), e);
         }
-
-        return behavior;
+        return newBehavior;
     }
 
-    protected int getMajorityVoteCount(int numPeers) {
+
+    protected int getMajorityVoteCount(final int numPeers) {
         // Votes are required from a majority of the peers including self.
         // The numMajority field therefore stores a calculated value
         // of the number of votes required for this candidate to win an
@@ -454,26 +475,53 @@ public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
 
 
     /**
-     * Performs a snapshot with no capture on the replicated log.
-     * It clears the log from the supplied index or last-applied-1 which ever is minimum.
+     * Performs a snapshot with no capture on the replicated log. It clears the log from the supplied index or
+     * lastApplied-1 which ever is minimum.
      *
-     * @param snapshotCapturedIndex
+     * @param snapshotCapturedIndex the index from which to clear
      */
     protected void performSnapshotWithoutCapture(final long snapshotCapturedIndex) {
-        //  we would want to keep the lastApplied as its used while capturing snapshots
-        long lastApplied = context.getLastApplied();
-        long tempMin = Math.min(snapshotCapturedIndex, (lastApplied > -1 ? lastApplied - 1 : -1));
-
-        if (tempMin > -1 && context.getReplicatedLog().isPresent(tempMin))  {
-            LOG.debug("{}: fakeSnapshot purging log to {} for term {}", logName(), tempMin,
-                    context.getTermInformation().getCurrentTerm());
-
-            //use the term of the temp-min, since we check for isPresent, entry will not be null
-            ReplicatedLogEntry entry = context.getReplicatedLog().get(tempMin);
-            context.getReplicatedLog().snapshotPreCommit(tempMin, entry.getTerm());
-            context.getReplicatedLog().snapshotCommit();
-            setReplicatedToAllIndex(tempMin);
+        long actualIndex = context.getSnapshotManager().trimLog(snapshotCapturedIndex);
+
+        if (actualIndex != -1) {
+            setReplicatedToAllIndex(actualIndex);
         }
     }
 
+    protected final String getId() {
+        return context.getId();
+    }
+
+    // Check whether we should update the term. In case of half-connected nodes, we want to ignore RequestVote
+    // messages, as the candidate is not able to receive our response.
+    protected boolean shouldUpdateTerm(final RaftRPC rpc) {
+        if (!(rpc instanceof RequestVote requestVote)) {
+            return true;
+        }
+
+        log.debug("{}: Found higher term in RequestVote rpc, verifying whether it's safe to update term.", logName());
+        final Optional<Cluster> maybeCluster = context.getCluster();
+        if (!maybeCluster.isPresent()) {
+            return true;
+        }
+
+        final Cluster cluster = maybeCluster.orElseThrow();
+
+        final Set<Member> unreachable = cluster.state().getUnreachable();
+        log.debug("{}: Cluster state: {}", logName(), unreachable);
+
+        for (Member member : unreachable) {
+            for (String role : member.getRoles()) {
+                if (requestVote.getCandidateId().startsWith(role)) {
+                    log.debug("{}: Unreachable member: {}, matches candidateId in: {}, not updating term", logName(),
+                        member, requestVote);
+                    return false;
+                }
+            }
+        }
+
+        log.debug("{}: Candidate in requestVote:{} with higher term appears reachable, updating term.", logName(),
+            requestVote);
+        return true;
+    }
 }