[ISSUE #305] Support fast advance commit index by appending no-op entry

dledger/src/main/java/io/openmessaging/storage/dledger/DLedgerConfig.java

@@ -112,6 +112,13 @@ public class DLedgerConfig {
  // max interval in ms for each append request
  private int maxBatchAppendIntervalMs = 1000;
 
+ /**
+ * When node change from candidate to leader, it maybe always keep the old commit index although this index's entry has been
+ * replicated to more than half of the nodes (it will keep until a new entry is appended in current term).
+ * The reason why this scenario happens is that leader can't commit the entries which are belong to the previous term.
+ */
+ private boolean enableFastAdvanceCommitIndex = false;
+
  public String getDefaultPath() {
  return storeBaseDir + File.separator + "dledger-" + selfId;
  }
@@ -544,4 +551,12 @@ public int getResetSnapshotEntriesButKeepLastEntriesNum() {
  public void setResetSnapshotEntriesButKeepLastEntriesNum(int resetSnapshotEntriesButKeepLastEntriesNum) {
  this.resetSnapshotEntriesButKeepLastEntriesNum = resetSnapshotEntriesButKeepLastEntriesNum;
  }
+
+ public boolean isEnableFastAdvanceCommitIndex() {
+ return enableFastAdvanceCommitIndex;
+ }
+
+ public void setEnableFastAdvanceCommitIndex(boolean enableFastAdvanceCommitIndex) {
+ this.enableFastAdvanceCommitIndex = enableFastAdvanceCommitIndex;
+ }
 }

dledger/src/main/java/io/openmessaging/storage/dledger/DLedgerEntryPusher.java

@@ -449,7 +449,7 @@ private void resetBatchAppendEntryRequest() {
  batchAppendEntryRequest.setGroup(memberState.getGroup());
  batchAppendEntryRequest.setRemoteId(peerId);
  batchAppendEntryRequest.setLeaderId(leaderId);
- batchAppendEntryRequest.setLocalId(memberState.getSelfId());
+ batchAppendEntryRequest.setLocalId(selfId);
  batchAppendEntryRequest.setTerm(term);
  batchAppendEntryRequest.setType(PushEntryRequest.Type.APPEND);
  batchAppendEntryRequest.clear();

dledger/src/main/java/io/openmessaging/storage/dledger/DLedgerServer.java

@@ -96,6 +96,8 @@ public class DLedgerServer extends AbstractDLedgerServer {
 
  private final ScheduledExecutorService executorService;
 
+ private FastAdvanceCommitIndexService fastAdvanceCommitIndexService;
+
  private StateMachineCaller fsmCaller;
 
  private volatile boolean isStarted = false;
@@ -133,6 +135,10 @@ public DLedgerServer(DLedgerConfig dLedgerConfig, NettyServerConfig nettyServerC
  stateMachine = new NoOpStatemachine();
  }
  this.fsmCaller = new StateMachineCaller(this.dLedgerStore, stateMachine, this.dLedgerEntryPusher);
+ if (this.dLedgerConfig.isEnableFastAdvanceCommitIndex()) {
+ this.fastAdvanceCommitIndexService = new FastAdvanceCommitIndexService();
+ this.dLedgerLeaderElector.addRoleChangeHandler(this.fastAdvanceCommitIndexService);
+ }
  }
 
  /**
@@ -156,6 +162,10 @@ public DLedgerServer(DLedgerConfig dLedgerConfig, DLedgerRpcService dLedgerRpcSe
  return t;
  });
  this.fsmCaller = new StateMachineCaller(this.dLedgerStore, new NoOpStatemachine(), this.dLedgerEntryPusher);
+ if (this.dLedgerConfig.isEnableFastAdvanceCommitIndex()) {
+ this.fastAdvanceCommitIndexService = new FastAdvanceCommitIndexService();
+ this.dLedgerLeaderElector.addRoleChangeHandler(this.fastAdvanceCommitIndexService);
+ }
  }
 
  /**
@@ -491,7 +501,8 @@ public CompletableFuture<PushEntryResponse> handlePush(PushEntryRequest request)
  }
 
  @Override
- public CompletableFuture<InstallSnapshotResponse> handleInstallSnapshot(InstallSnapshotRequest request) throws Exception {
+ public CompletableFuture<InstallSnapshotResponse> handleInstallSnapshot(
+ InstallSnapshotRequest request) throws Exception {
  try {
  PreConditions.check(memberState.getSelfId().equals(request.getRemoteId()), DLedgerResponseCode.UNKNOWN_MEMBER, "%s != %s", request.getRemoteId(), memberState.getSelfId());
  PreConditions.check(memberState.getGroup().equals(request.getGroup()), DLedgerResponseCode.UNKNOWN_GROUP, "%s != %s", request.getGroup(), memberState.getGroup());
@@ -709,4 +720,33 @@ enum RpcServiceMode {
  SHARED
  }
 
+ private class FastAdvanceCommitIndexService implements DLedgerLeaderElector.RoleChangeHandler {
+
+ @Override
+ public void handle(long term, MemberState.Role role) {
+ if (role == MemberState.Role.LEADER && term == memberState.currTerm() && memberState.getCommittedIndex() < memberState.getLedgerEndIndex()) {
+ DLedgerServer.this.handleRead(ReadMode.RAFT_LOG_READ, new ReadClosure() {
+ @Override
+ public void done(Status status) {
+ if (status != Status.ok()) {
+ LOGGER.error("[FastAdvanceCommitIndexService-{}] term: {} advance failed, status={}", term, memberState.getSelfId(), status);
+ } else {
+ LOGGER.info("[FastAdvanceCommitIndexService-{}] term: {} advance ok", term, memberState.getSelfId());
+ }
+ }
+ });
+ }
+ }
+
+ @Override
+ public void startup() {
+
+ }
+
+ @Override
+ public void shutdown() {
+
+ }
+ }
+
 }

dledger/src/main/java/io/openmessaging/storage/dledger/MemberState.java

@@ -282,7 +282,7 @@ public long getCommittedIndex() {
  public boolean leaderUpdateCommittedIndex(long term, long committedIndex) {
  if (!this.isLeader()) return false;
  // prevent back to an old state
- if (term != this.currTerm && committedIndex <= this.committedIndex) {
+ if (term < this.currTerm || committedIndex <= this.committedIndex) {
  return false;
  }
  logger.debug("[MemberState] leader update committed index from {} to {}", this.committedIndex, committedIndex);
@@ -291,7 +291,7 @@ public boolean leaderUpdateCommittedIndex(long term, long committedIndex) {
  }
 
  public boolean followerUpdateCommittedIndex(long committedIndex) {
- if (!this.isFollower()) return false;
+ if (this.isLeader()) return false;
  if (committedIndex <= this.committedIndex) {
  return false;
  }

dledger/src/main/java/io/openmessaging/storage/dledger/common/Status.java

@@ -41,4 +41,10 @@ public static Status error(DLedgerResponseCode code) {
  return new Status(code);
  }
 
+ @Override
+ public String toString() {
+ return "Status{" +
+ "code=" + code +
+ '}';
+ }
 }

dledger/src/main/java/io/openmessaging/storage/dledger/statemachine/ApplyEntryIterator.java

@@ -55,7 +55,7 @@ public int getCompleteAckNums() {
  public boolean hasNext() {
  while (inner.hasNext()) {
  ApplyEntry applyEntry = inner.next();
- if (filter.test(applyEntry.getEntry())) {
+ if (applyEntry != null && filter.test(applyEntry.getEntry())) {
  nextTask = applyEntry;
  return true;
  }

dledger/src/test/java/io/openmessaging/storage/dledger/AppendAndGetTest.java

@@ -39,7 +39,7 @@ public class AppendAndGetTest extends ServerTestHarness {
  public void testSingleServerInMemory() throws Exception {
  String group = UUID.randomUUID().toString();
  String selfId = "n0";
- String peers = "n0-localhost:10001";
+ String peers = String.format("n0-localhost:%d", nextPort());
  launchServer(group, peers, selfId, selfId, DLedgerConfig.MEMORY);
  DLedgerClient dLedgerClient = launchClient(group, peers);
  for (long i = 0; i < 10; i++) {
@@ -58,7 +58,7 @@ public void testSingleServerInMemory() throws Exception {
  public void testSingleServerInFile() throws Exception {
  String group = UUID.randomUUID().toString();
  String selfId = "n0";
- String peers = "n0-localhost:10002";
+ String peers = String.format("n0-localhost:%d", nextPort());
  launchServer(group, peers, selfId, selfId, DLedgerConfig.FILE);
  DLedgerClient dLedgerClient = launchClient(group, peers);
  long expectedPos = 0L;
@@ -106,7 +106,7 @@ public void testThreeServerInMemory() throws Exception {
  @Test
  public void testThreeServerInFile() throws Exception {
  String group = UUID.randomUUID().toString();
- String peers = "n0-localhost:10006;n1-localhost:10007;n2-localhost:10008";
+ String peers = String.format("n0-localhost:%d;n1-localhost:%d;n2-localhost:%d", nextPort(), nextPort(), nextPort());
  DLedgerServer dLedgerServer0 = launchServer(group, peers, "n0", "n1", DLedgerConfig.FILE);
  DLedgerServer dLedgerServer1 = launchServer(group, peers, "n1", "n1", DLedgerConfig.FILE);
  DLedgerServer dLedgerServer2 = launchServer(group, peers, "n2", "n1", DLedgerConfig.FILE);

dledger/src/test/java/io/openmessaging/storage/dledger/AppendAndReadTest.java

@@ -43,7 +43,7 @@ protected String getBaseDir() {
  public void testSingleServerInMemory() {
  String group = UUID.randomUUID().toString();
  String selfId = "n0";
- String peers = "n0-localhost:" + nextPort();
+ String peers = String.format("n0-localhost:%d", nextPort());
  DLedgerServer dLedgerServer = launchServerWithStateMachineDisableSnapshot(group, peers, selfId, selfId, DLedgerConfig.MEMORY,
  102400, new RegisterStateMachine());
  dLedgerServer.registerUserDefineProcessors(Collections.singletonList(new RegisterReadProcessor(dLedgerServer)));
@@ -55,7 +55,7 @@ public void testSingleServerInMemory() {
  public void testSingleServerInFile() {
  String group = UUID.randomUUID().toString();
  String selfId = "n0";
- String peers = "n0-localhost:" + nextPort();
+ String peers = String.format("n0-localhost:%d", nextPort());
  DLedgerServer dLedgerServer = launchServerWithStateMachineDisableSnapshot(group, peers, selfId, selfId, DLedgerConfig.FILE,
  102400, new RegisterStateMachine());
  dLedgerServer.registerUserDefineProcessors(Collections.singletonList(new RegisterReadProcessor(dLedgerServer)));