+
+ protected int getMajorityVoteCount(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
+ // election based on it's known peers.
+ // If a peer was added during normal operation and raft replicas
+ // came to know about them then the new peer would also need to be
+ // taken into consideration when calculating this value.
+ // Here are some examples for what the numMajority would be for n
+ // peers
+ // 0 peers = 1 numMajority -: (0 + 1) / 2 + 1 = 1
+ // 2 peers = 2 numMajority -: (2 + 1) / 2 + 1 = 2
+ // 4 peers = 3 numMajority -: (4 + 1) / 2 + 1 = 3
+
+ int numMajority = 0;
+ if (numPeers > 0) {
+ int self = 1;
+ numMajority = (numPeers + self) / 2 + 1;
+ }
+ return numMajority;
+
+ }
+
+
+ /**
+ * 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.
+ *
+ * @param snapshotCapturedIndex
+ */
+ 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(LOG.isTraceEnabled()) {
+ LOG.trace("{}: performSnapshotWithoutCapture: snapshotCapturedIndex: {}, lastApplied: {}, tempMin: {}",
+ logName, snapshotCapturedIndex, lastApplied, tempMin);
+ }
+
+ 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);
+ } else if(tempMin > getReplicatedToAllIndex()) {
+ // It's possible a follower was lagging and an install snapshot advanced its match index past
+ // the current replicatedToAllIndex. Since the follower is now caught up we should advance the
+ // replicatedToAllIndex (to tempMin). The fact that tempMin wasn't found in the log is likely
+ // due to a previous snapshot triggered by the memory threshold exceeded, in that case we
+ // trim the log to the last applied index even if previous entries weren't replicated to all followers.
+ setReplicatedToAllIndex(tempMin);
+ }
+ }
+
+ protected String getId(){
+ return context.getId();
+ }
+