[GitHub] [iotdb] fanhualta commented on a change in pull request #3191: New features of cluster scalability and multi-raft

[GitBox <gi...@apache.org>]

fanhualta commented on a change in pull request #3191:
URL: https://github.com/apache/iotdb/pull/3191#discussion_r644121915



##########
File path: cluster/src/main/java/org/apache/iotdb/cluster/server/member/DataGroupMember.java
##########
@@ -314,97 +321,61 @@ public synchronized boolean addNode(Node node, NodeAdditionResult result) {
       if (insertIndex > 0) {
         allNodes.add(insertIndex, node);
         peerMap.putIfAbsent(node, new Peer(logManager.getLastLogIndex()));
-        // remove the last node because the group size is fixed to replication number
-        Node removedNode = allNodes.remove(allNodes.size() - 1);
-        peerMap.remove(removedNode);
         // if the local node is the last node and the insertion succeeds, this node should leave
         // the group
         logger.debug("{}: Node {} is inserted into the data group {}", name, node, allNodes);
-        return removedNode.equals(thisNode);
       }
-      return false;
+      return insertIndex > 0;
     }
   }
 
   /**
-   * Process the election request from another node in the group. To win the vote from the local
-   * member, a node must have both meta and data logs no older than then local member, or it will be
-   * turned down.
+   * Try to add a Node into the group to which the member belongs.
    *
-   * @param electionRequest
-   * @return Response.RESPONSE_META_LOG_STALE if the meta logs of the elector fall behind
-   *     Response.RESPONSE_LOG_MISMATCH if the data logs of the elector fall behind Response.SUCCESS
-   *     if the vote is given to the elector the term of local member if the elector's term is no
-   *     bigger than the local member
+   * @return true if this node should leave the group because of the addition of the node, false
+   *     otherwise
    */
-  @Override
-  long checkElectorLogProgress(ElectionRequest electionRequest) {
-    // to be a data group leader, a node should also be qualified to be the meta group leader
-    // which guarantees the data group leader has the newest partition table.
-    long thatTerm = electionRequest.getTerm();
-    long thatMetaLastLogIndex = electionRequest.getLastLogIndex();
-    long thatMetaLastLogTerm = electionRequest.getLastLogTerm();
-    long thatDataLastLogIndex = electionRequest.getDataLogLastIndex();
-    long thatDataLastLogTerm = electionRequest.getDataLogLastTerm();
-    logger.info(
-        "{} received an dataGroup election request, term:{}, metaLastLogIndex:{}, metaLastLogTerm:{}, dataLastLogIndex:{}, dataLastLogTerm:{}",
-        name,
-        thatTerm,
-        thatMetaLastLogIndex,
-        thatMetaLastLogTerm,
-        thatDataLastLogIndex,
-        thatDataLastLogTerm);
-
-    // check meta logs
-    // term of the electors' MetaGroupMember is not verified, so 0 and 1 are used to make sure
-    // the verification does not fail
-    long metaResponse = metaGroupMember.checkLogProgress(thatMetaLastLogIndex, thatMetaLastLogTerm);
-    if (metaResponse == Response.RESPONSE_LOG_MISMATCH) {
-      return Response.RESPONSE_META_LOG_STALE;
-    }
-
-    long resp = checkLogProgress(thatDataLastLogIndex, thatDataLastLogTerm);
-    if (resp == Response.RESPONSE_AGREE) {
-      logger.info(
-          "{} accepted an dataGroup election request, term:{}/{}, dataLogIndex:{}/{}, dataLogTerm:{}/{}, metaLogIndex:{}/{},metaLogTerm:{}/{}",
-          name,
-          thatTerm,
-          term.get(),
-          thatDataLastLogIndex,
-          logManager.getLastLogIndex(),
-          thatDataLastLogTerm,
-          logManager.getLastLogTerm(),
-          thatMetaLastLogIndex,
-          metaGroupMember.getLogManager().getLastLogIndex(),
-          thatMetaLastLogTerm,
-          metaGroupMember.getLogManager().getLastLogTerm());
-      setCharacter(NodeCharacter.FOLLOWER);
-      lastHeartbeatReceivedTime = System.currentTimeMillis();
-      setVoteFor(electionRequest.getElector());
-      updateHardState(thatTerm, getVoteFor());
-    } else {
-      logger.info(
-          "{} rejected an dataGroup election request, term:{}/{}, dataLogIndex:{}/{}, dataLogTerm:{}/{}, metaLogIndex:{}/{},metaLogTerm:{}/{}",
-          name,
-          thatTerm,
-          term.get(),
-          thatDataLastLogIndex,
-          logManager.getLastLogIndex(),
-          thatDataLastLogTerm,
-          logManager.getLastLogTerm(),
-          thatMetaLastLogIndex,
-          metaGroupMember.getLogManager().getLastLogIndex(),
-          thatMetaLastLogTerm,
-          metaGroupMember.getLogManager().getLastLogTerm());
+  public boolean addNode(Node node, NodeAdditionResult result) {
+    if (logger.isDebugEnabled()) {
+      logger.debug("{}: start to add node {}", name, node);
+    }
+
+    // mark slots that do not belong to this group any more
+    Set<Integer> lostSlots =
+        ((SlotNodeAdditionResult) result)
+            .getLostSlots()
+            .getOrDefault(new RaftNode(getHeader(), getRaftGroupId()), Collections.emptySet());
+    for (Integer lostSlot : lostSlots) {
+      slotManager.setToSending(lostSlot, false);
+    }
+    slotManager.save();
+
+    synchronized (allNodes) {
+      preAddNode(node);
+      if (allNodes.contains(node) && allNodes.size() > config.getReplicationNum()) {
+        // remove the last node because the group size is fixed to replication number
+        Node removedNode = allNodes.remove(allNodes.size() - 1);
+        peerMap.remove(removedNode);
+
+        if (removedNode.equals(leader.get()) && !removedNode.equals(thisNode)) {
+          // if the leader is removed, also start an election immediately
+          synchronized (term) {
+            setCharacter(NodeCharacter.ELECTOR);

Review comment:
       Why?




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