fix: don't block heartbeat response when fsm is busy

jraft-core/src/main/java/com/alipay/sofa/jraft/FSMCaller.java

@@ -65,6 +65,14 @@ interface LastAppliedLogIndexListener {
      */
     boolean onCommitted(final long committedIndex);
 
+    /**
+     * Given specified <tt>requiredCapacity</tt> determines if that amount of space
+     * is available to submit new tasks to fsm. Returns true when available.
+     * @param requiredCapacity
+     * @return Returns true when available.
+     */
+    public boolean hasAvailableCapacity(final int requiredCapacity);
+
     /**
      * Called when loading snapshot.
      *

jraft-core/src/main/java/com/alipay/sofa/jraft/core/BallotBox.java

@@ -53,6 +53,7 @@ public class BallotBox implements Lifecycle<BallotBoxOptions>, Describer {
     private long                      lastCommittedIndex = 0;
     private long                      pendingIndex;
     private final SegmentList<Ballot> pendingMetaQueue   = new SegmentList<>(false);
+    private BallotBoxOptions          opts;
 
     @OnlyForTest
     long getPendingIndex() {
@@ -84,6 +85,7 @@ public boolean init(final BallotBoxOptions opts) {
             LOG.error("waiter or closure queue is null.");
             return false;
         }
+        this.opts = opts;
         this.waiter = opts.getWaiter();
         this.closureQueue = opts.getClosureQueue();
         return true;
@@ -128,7 +130,8 @@ public boolean commitAt(final long firstLogIndex, final long lastLogIndex, final
             // removal request, we think it's safe to commit all the uncommitted
             // previous logs, which is not well proved right now
             this.pendingMetaQueue.removeFromFirst((int) (lastCommittedIndex - this.pendingIndex) + 1);
-            LOG.debug("Committed log fromIndex={}, toIndex={}.", this.pendingIndex, lastCommittedIndex);
+            LOG.debug("Node {} committed log fromIndex={}, toIndex={}.", this.opts.getNodeId(), this.pendingIndex,
+                lastCommittedIndex);
             this.pendingIndex = lastCommittedIndex + 1;
             this.lastCommittedIndex = lastCommittedIndex;
         } finally {
@@ -168,13 +171,13 @@ public boolean resetPendingIndex(final long newPendingIndex) {
         final long stamp = this.stampedLock.writeLock();
         try {
             if (!(this.pendingIndex == 0 && this.pendingMetaQueue.isEmpty())) {
-                LOG.error("resetPendingIndex fail, pendingIndex={}, pendingMetaQueueSize={}.", this.pendingIndex,
-                    this.pendingMetaQueue.size());
+                LOG.error("Node {} resetPendingIndex fail, pendingIndex={}, pendingMetaQueueSize={}.",
+                    this.opts.getNodeId(), this.pendingIndex, this.pendingMetaQueue.size());
                 return false;
             }
             if (newPendingIndex <= this.lastCommittedIndex) {
-                LOG.error("resetPendingIndex fail, newPendingIndex={}, lastCommittedIndex={}.", newPendingIndex,
-                    this.lastCommittedIndex);
+                LOG.error("Node {} resetPendingIndex fail, newPendingIndex={}, lastCommittedIndex={}.",
+                    this.opts.getNodeId(), newPendingIndex, this.lastCommittedIndex);
                 return false;
             }
             this.pendingIndex = newPendingIndex;
@@ -203,7 +206,7 @@ public boolean appendPendingTask(final Configuration conf, final Configuration o
         final long stamp = this.stampedLock.writeLock();
         try {
             if (this.pendingIndex <= 0) {
-                LOG.error("Fail to appendingTask, pendingIndex={}.", this.pendingIndex);
+                LOG.error("Node {} fail to appendingTask, pendingIndex={}.", this.opts.getNodeId(), this.pendingIndex);
                 return false;
             }
             this.pendingMetaQueue.add(bl);
@@ -231,6 +234,11 @@ public boolean setLastCommittedIndex(final long lastCommittedIndex) {
                     lastCommittedIndex);
                 return false;
             }
+            if (!this.waiter.hasAvailableCapacity(1)) {
+                LOG.warn("Node {} fsm is busy, can't set lastCommittedIndex to be {}, lastCommittedIndex={}.",
+                    this.opts.getNodeId(), lastCommittedIndex, this.lastCommittedIndex);
+                return false;
+            }
             if (lastCommittedIndex < this.lastCommittedIndex) {
                 return false;
             }

jraft-core/src/main/java/com/alipay/sofa/jraft/core/FSMCallerImpl.java

@@ -251,6 +251,14 @@ private boolean enqueueTask(final EventTranslator<ApplyTask> tpl) {
         return true;
     }
 
+    @Override
+    public boolean hasAvailableCapacity(int requiredCapacity) {
+        if (this.shutdownLatch != null) {
+            return false;
+        }
+        return this.taskQueue.hasAvailableCapacity(requiredCapacity);
+    }
+
     @Override
     public boolean onCommitted(final long committedIndex) {
         return enqueueTask((task, sequence) -> {

jraft-core/src/main/java/com/alipay/sofa/jraft/core/NodeImpl.java

@@ -1017,6 +1017,7 @@ protected int adjustTimeout(final int timeoutMs) {
         final BallotBoxOptions ballotBoxOpts = new BallotBoxOptions();
         ballotBoxOpts.setWaiter(this.fsmCaller);
         ballotBoxOpts.setClosureQueue(this.closureQueue);
+        ballotBoxOpts.setNodeId(getNodeId());
         if (!this.ballotBox.init(ballotBoxOpts)) {
             LOG.error("Node {} init ballotBox failed.", getNodeId());
             return false;

jraft-core/src/main/java/com/alipay/sofa/jraft/core/ReadOnlyServiceImpl.java

@@ -234,7 +234,8 @@ private void handleReadIndex(final ReadOnlyOption option, final List<ReadIndexEv
         final List<ReadIndexState> states = events.stream()
                 .filter(it -> option.equals(it.readOnlyOptions))
                 .map(it -> {
-                    rb.addEntries(ZeroByteStringHelper.wrap(it.requestContext.get()));
+                	byte [] bytes = it.requestContext.get();
+                    rb.addEntries(ZeroByteStringHelper.wrap(bytes == null? new byte[0]: bytes));
                     return new ReadIndexState(it.requestContext, it.done, it.startTime);
                 })
                 .collect(Collectors.toList());

jraft-core/src/main/java/com/alipay/sofa/jraft/option/BallotBoxOptions.java

@@ -18,6 +18,7 @@
 
 import com.alipay.sofa.jraft.FSMCaller;
 import com.alipay.sofa.jraft.closure.ClosureQueue;
+import com.alipay.sofa.jraft.entity.NodeId;
 
 /**
  * Ballot box options.
@@ -30,6 +31,15 @@ public class BallotBoxOptions {
 
     private FSMCaller    waiter;
     private ClosureQueue closureQueue;
+    private NodeId       nodeId;
+
+    public NodeId getNodeId() {
+        return nodeId;
+    }
+
+    public void setNodeId(NodeId nodeId) {
+        this.nodeId = nodeId;
+    }
 
     public FSMCaller getWaiter() {
         return this.waiter;

jraft-core/src/main/java/com/alipay/sofa/jraft/option/NodeOptions.java

@@ -104,6 +104,7 @@ public class NodeOptions extends RpcOptions implements Copiable<NodeOptions> {
     // Describe a specific SnapshotStorage in format ${type}://${parameters}
     private String                          snapshotUri;
 
+    // Snapshot temp directory for writing. Default is null(not present), jraft will use a `temp` dir under #{snapshotUri}
     private String                          snapshotTempUri;
 
     // If enable, we will filter duplicate files before copy remote snapshot,

jraft-core/src/test/java/com/alipay/sofa/jraft/core/BallotBoxTest.java

@@ -148,9 +148,10 @@ public void testSetLastCommittedIndexLessThan() {
 
     @Test
     public void testSetLastCommittedIndex() {
+        Mockito.when(this.waiter.hasAvailableCapacity(1)).thenReturn(true);
         assertEquals(0, this.box.getLastCommittedIndex());
         assertTrue(this.box.setLastCommittedIndex(1));
         assertEquals(1, this.box.getLastCommittedIndex());
-        Mockito.verify(this.waiter, Mockito.only()).onCommitted(1);
+        Mockito.verify(this.waiter, Mockito.times(1)).onCommitted(1);
     }
 }