[NC-1508] Added iBFT 2.0 BlockTimerExpiry Event and realated timer ma…

…nagement class (#58)



Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/BlockTimer.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import tech.pegasys.pantheon.consensus.ibft.ibftevent.BlockTimerExpiry;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.util.time.Clock;
+
+import java.util.Optional;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+
+/** Class for starting and keeping organised block timers */
+public class BlockTimer {
+  private final ScheduledExecutorService timerExecutor;
+  private Optional<ScheduledFuture<?>> currentTimerTask;
+  private final IbftEventQueue queue;
+  private final long minimumTimeBetweenBlocksMillis;
+  private final Clock clock;
+
+  /**
+   * Construct a BlockTimer with primed executor service ready to start timers
+   *
+   * @param queue The queue in which to put block expiry events
+   * @param minimumTimeBetweenBlocksMillis Minimum timestamp difference between blocks
+   * @param timerExecutor Executor service that timers can be scheduled with
+   * @param clock System clock
+   */
+  public BlockTimer(
+      final IbftEventQueue queue,
+      final long minimumTimeBetweenBlocksMillis,
+      final ScheduledExecutorService timerExecutor,
+      final Clock clock) {
+    this.queue = queue;
+    this.timerExecutor = timerExecutor;
+    this.currentTimerTask = Optional.empty();
+    this.minimumTimeBetweenBlocksMillis = minimumTimeBetweenBlocksMillis;
+    this.clock = clock;
+  }
+
+  /** Cancels the current running round timer if there is one */
+  public synchronized void cancelTimer() {
+    currentTimerTask.ifPresent(t -> t.cancel(false));
+    currentTimerTask = Optional.empty();
+  }
+
+  /**
+   * Whether there is a timer currently running or not
+   *
+   * @return boolean of whether a timer is ticking or not
+   */
+  public synchronized boolean isRunning() {
+    return currentTimerTask.map(t -> !t.isDone()).orElse(false);
+  }
+
+  /**
+   * Starts a timer for the supplied round cancelling any previously active block timer
+   *
+   * @param round The round identifier which this timer is tracking
+   * @param chainHeadHeader The header of the chain head
+   */
+  public synchronized void startTimer(
+      final ConsensusRoundIdentifier round, final BlockHeader chainHeadHeader) {
+    cancelTimer();
+
+    final long now = clock.millisecondsSinceEpoch();
+
+    // absolute time when the timer is supposed to expire
+    final long expiryTime = chainHeadHeader.getTimestamp() * 1_000 + minimumTimeBetweenBlocksMillis;
+
+    if (expiryTime > now) {
+      final long delay = expiryTime - now;
+
+      final Runnable newTimerRunnable = () -> queue.add(new BlockTimerExpiry(round));
+
+      final ScheduledFuture<?> newTimerTask =
+          timerExecutor.schedule(newTimerRunnable, delay, TimeUnit.MILLISECONDS);
+      currentTimerTask = Optional.of(newTimerTask);
+    } else {
+      queue.add(new BlockTimerExpiry(round));
+    }
+  }
+}

consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftEvents.java

@@ -22,6 +22,7 @@ public static IbftEvent fromMessage(final Message message) {
 
   public enum Type {
     ROUND_EXPIRY,
-    NEW_CHAIN_HEAD_HEADER
+    NEW_CHAIN_HEAD_HEADER,
+    BLOCK_TIMER_EXPIRY
   }
 }

consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/ibftevent/BlockTimerExpiry.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft.ibftevent;
+
+import tech.pegasys.pantheon.consensus.ibft.ConsensusRoundIdentifier;
+import tech.pegasys.pantheon.consensus.ibft.IbftEvent;
+import tech.pegasys.pantheon.consensus.ibft.IbftEvents.Type;
+
+import java.util.Objects;
+
+import com.google.common.base.MoreObjects;
+
+/** Event indicating a block timer has expired */
+public final class BlockTimerExpiry implements IbftEvent {
+  private final ConsensusRoundIdentifier roundIdentifier;
+
+  /**
+   * Constructor for a BlockTimerExpiry event
+   *
+   * @param roundIdentifier The roundIdentifier that the expired timer belonged to
+   */
+  public BlockTimerExpiry(final ConsensusRoundIdentifier roundIdentifier) {
+    this.roundIdentifier = roundIdentifier;
+  }
+
+  @Override
+  public Type getType() {
+    return Type.BLOCK_TIMER_EXPIRY;
+  }
+
+  public ConsensusRoundIdentifier getRoundIndentifier() {
+    return roundIdentifier;
+  }
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this).add("Round Identifier", roundIdentifier).toString();
+  }
+
+  @Override
+  public boolean equals(final Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    final BlockTimerExpiry that = (BlockTimerExpiry) o;
+    return Objects.equals(roundIdentifier, that.roundIdentifier);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(roundIdentifier);
+  }
+}