Support BFT mining coordinator being temporarily stopped while syncing

besu/src/main/java/org/hyperledger/besu/controller/IbftBesuControllerBuilder.java

@@ -253,9 +253,18 @@ protected MiningCoordinator createMiningCoordinator(
                         .getValue()
                         .getBlockPeriodSeconds()));
 
-    if (syncState.isInitialSyncPhaseDone()) {
-      ibftMiningCoordinator.enable();
-    }
+    syncState.subscribeSyncStatus(
+        syncStatus -> {
+          if (syncState.syncTarget().isPresent()) {
+            // We're syncing so stop doing other stuff
+            LOG.info("Stopping IBFT mining coordinator while we are syncing");
+            ibftMiningCoordinator.stop();
+          } else {
+            LOG.info("Starting IBFT mining coordinator following sync");
+            ibftMiningCoordinator.enable();
+            ibftMiningCoordinator.start();
+          }
+        });
 
     syncState.subscribeCompletionReached(
         new BesuEvents.InitialSyncCompletionListener() {

besu/src/main/java/org/hyperledger/besu/controller/QbftBesuControllerBuilder.java

@@ -295,9 +295,18 @@ protected MiningCoordinator createMiningCoordinator(
                         .getValue()
                         .getBlockPeriodSeconds()));
 
-    if (syncState.isInitialSyncPhaseDone()) {
-      miningCoordinator.enable();
-    }
+    syncState.subscribeSyncStatus(
+        syncStatus -> {
+          if (syncState.syncTarget().isPresent()) {
+            // We're syncing so stop doing other stuff
+            LOG.info("Stopping QBFT mining coordinator while we are syncing");
+            miningCoordinator.stop();
+          } else {
+            LOG.info("Starting QBFT mining coordinator following sync");
+            miningCoordinator.enable();
+            miningCoordinator.start();
+          }
+        });
 
     syncState.subscribeCompletionReached(
         new BesuEvents.InitialSyncCompletionListener() {

consensus/common/src/main/java/org/hyperledger/besu/consensus/common/bft/BftEventQueue.java

@@ -48,6 +48,11 @@ public void start() {
     started.set(true);
   }
 
+  /** Stop the event queue. Until it has been started no events will be queued for processing. */
+  public void stop() {
+    started.set(false);
+  }
+
   private boolean isStarted() {
     return started.get();
   }

consensus/common/src/main/java/org/hyperledger/besu/consensus/common/bft/BftExecutors.java

@@ -78,7 +78,7 @@ public static BftExecutors create(
 
   /** Start. */
   public synchronized void start() {
-    if (state != State.IDLE) {
+    if (state != State.IDLE && state != State.STOPPED) {
       // Nothing to do
       return;
     }

consensus/common/src/main/java/org/hyperledger/besu/consensus/common/bft/BftProcessor.java

@@ -44,8 +44,13 @@ public BftProcessor(final BftEventQueue incomingQueue, final EventMultiplexer ev
     this.eventMultiplexer = eventMultiplexer;
   }
 
+  /** Indicate to the processor that it should can be started */
+  public synchronized void start() {
+    shutdown = false;
+  }
+
   /** Indicate to the processor that it should gracefully stop at its next opportunity */
-  public void stop() {
+  public synchronized void stop() {
     shutdown = true;
   }
 
@@ -67,6 +72,8 @@ public void run() {
       while (!shutdown) {
         nextEvent().ifPresent(eventMultiplexer::handleBftEvent);
       }
+
+      incomingQueue.stop();
     } catch (final Throwable t) {
       LOG.error("BFT Mining thread has suffered a fatal error, mining has been halted", t);
     }

consensus/common/src/main/java/org/hyperledger/besu/consensus/common/bft/blockcreation/BftMiningCoordinator.java

@@ -93,7 +93,9 @@ public BftMiningCoordinator(
 
   @Override
   public void start() {
-    if (state.compareAndSet(State.IDLE, State.RUNNING)) {
+    if (state.compareAndSet(State.IDLE, State.RUNNING)
+        || state.compareAndSet(State.STOPPED, State.RUNNING)) {
+      bftProcessor.start();
       bftExecutors.start();
       blockAddedObserverId = blockchain.observeBlockAdded(this);
       eventHandler.start();
@@ -110,7 +112,7 @@ public void stop() {
       try {
         bftProcessor.awaitStop();
       } catch (final InterruptedException e) {
-        LOG.debug("Interrupted while waiting for IbftProcessor to stop.", e);
+        LOG.debug("Interrupted while waiting for BftProcessor to stop.", e);
         Thread.currentThread().interrupt();
       }
       bftExecutors.stop();
@@ -135,6 +137,11 @@ public boolean enable() {
 
   @Override
   public boolean disable() {
+    if (state.get() == State.PAUSED
+        || state.compareAndSet(State.IDLE, State.PAUSED)
+        || state.compareAndSet(State.RUNNING, State.PAUSED)) {
+      return true;
+    }
     return false;
   }