Port Kafka timer classes (#21)

*Motivation*

Need to port Kafka's coordinator algorithm. It requires using Kafka's timer and deplayed operations.

src/main/java/io/streamnative/kop/utils/timer/SystemTimer.java

@@ -0,0 +1,181 @@
+/**
+ * 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 io.streamnative.kop.utils.timer;
+
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import io.streamnative.kop.utils.timer.TimerTaskList.TimerTaskEntry;
+import java.util.Objects;
+import java.util.concurrent.DelayQueue;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Consumer;
+import javax.annotation.concurrent.ThreadSafe;
+import lombok.SneakyThrows;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.kafka.common.utils.Time;
+
+/**
+ * A system timer implementation.
+ */
+@Slf4j
+@ThreadSafe
+public class SystemTimer implements Timer {
+
+    /**
+     * Create a system timer builder.
+     *
+     * @return a system timer builder.
+     */
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    /**
+     * Builder to build a system timer.
+     */
+    public static class Builder {
+
+        private String executorName;
+        private long tickMs = 1;
+        private int wheelSize = 20;
+        private long startMs = Time.SYSTEM.hiResClockMs();
+
+        private Builder() {}
+
+        public Builder executorName(String executorName) {
+            this.executorName = executorName;
+            return this;
+        }
+
+        public Builder tickMs(long tickMs) {
+            this.tickMs = tickMs;
+            return this;
+        }
+
+        public Builder wheelSize(int wheelSize) {
+            this.wheelSize = wheelSize;
+            return this;
+        }
+
+        public Builder startMs(long startMs) {
+            this.startMs = startMs;
+            return this;
+        }
+
+        public SystemTimer build() {
+            Objects.requireNonNull(executorName, "No executor name is provided");
+
+            return new SystemTimer(
+                executorName,
+                tickMs,
+                wheelSize,
+                startMs
+            );
+        }
+
+    }
+
+    private final ExecutorService taskExecutor;
+    private final DelayQueue<TimerTaskList> delayQueue;
+    private final AtomicInteger taskCounter;
+    private final TimingWheel timingWheel;
+
+    // Locks used to protect data structures while ticking
+    private final ReentrantReadWriteLock readWriteLock;
+    private final Lock readLock;
+    private final Lock writeLock;
+    private final Consumer<TimerTaskEntry> reinsert;
+
+    private SystemTimer(String executorName,
+                        long tickMs,
+                        int wheelSize,
+                        long startMs) {
+        this.taskExecutor = Executors.newFixedThreadPool(
+            1, new ThreadFactoryBuilder()
+                .setDaemon(false)
+                .setNameFormat("system-timer-%d")
+                .build()
+        );
+        this.delayQueue = new DelayQueue();
+        this.taskCounter = new AtomicInteger(0);
+        this.timingWheel = new TimingWheel(
+            tickMs,
+            wheelSize,
+            startMs,
+            taskCounter,
+            delayQueue
+        );
+        this.readWriteLock = new ReentrantReadWriteLock();
+        this.readLock = readWriteLock.readLock();
+        this.writeLock = readWriteLock.writeLock();
+        this.reinsert = timerTaskEntry -> addTimerTaskEntry(timerTaskEntry);
+    }
+
+    @Override
+    public void add(TimerTask timerTask) {
+        readLock.lock();
+        try {
+            addTimerTaskEntry(new TimerTaskEntry(
+                timerTask, timerTask.delayMs + Time.SYSTEM.hiResClockMs()
+            ));
+        } finally {
+            readLock.unlock();
+        }
+    }
+
+    private void addTimerTaskEntry(TimerTaskEntry timerTaskEntry) {
+        if (!timingWheel.add(timerTaskEntry)) {
+            // Already expired or cancelled
+            if (!timerTaskEntry.cancelled()) {
+                taskExecutor.submit(timerTaskEntry.timerTask());
+            }
+        }
+    }
+
+    @SneakyThrows
+    @Override
+    public boolean advanceClock(long timeoutMs) {
+        TimerTaskList bucket = delayQueue.poll(timeoutMs, TimeUnit.MILLISECONDS);
+        if (null != bucket) {
+            writeLock.lock();
+            try {
+                while (null != bucket) {
+                    timingWheel.advanceClock(bucket.getExpiration());
+                    bucket.flush(reinsert);
+                    bucket = delayQueue.poll();
+                }
+            } finally {
+                writeLock.unlock();
+            }
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    @Override
+    public int size() {
+        return taskCounter.get();
+    }
+
+    @Override
+    public void shutdown() {
+        taskExecutor.shutdown();
+    }
+
+}

src/main/java/io/streamnative/kop/utils/timer/Timer.java

@@ -0,0 +1,51 @@
+/**
+ * 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 io.streamnative.kop.utils.timer;
+
+/**
+ * The timer interface to execute delayed operations.
+ */
+public interface Timer {
+
+    /**
+     * Add a new task to this executor. It will be executed after the task's delay
+     * (beginning from the time of submission)
+     *
+     * @param timerTask the task to add
+     */
+    void add(TimerTask timerTask);
+
+    /**
+     * Advance the internal clock, executing any tasks whose expiration has been
+     * reached within the duration of the passed timeout.
+     *
+     * @param timeoutMs
+     * @return whether or not any tasks were executed
+     */
+    boolean advanceClock(long timeoutMs);
+
+    /**
+     * Get the number of tasks pending execution.
+     *
+     * @return the number of tasks
+     */
+    int size();
+
+    /**
+     * Shutdown the timer service, leaving pending tasks unexecuted.
+     */
+    void shutdown();
+
+
+}

src/main/java/io/streamnative/kop/utils/timer/TimerTask.java

@@ -0,0 +1,50 @@
+/**
+ * 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 io.streamnative.kop.utils.timer;
+
+import io.streamnative.kop.utils.timer.TimerTaskList.TimerTaskEntry;
+
+/**
+ * Timer task.
+ */
+public abstract class TimerTask implements Runnable {
+
+    protected final long delayMs;
+    private TimerTaskEntry timerTaskEntry = null;
+
+    protected TimerTask(long delayMs) {
+        this.delayMs = delayMs;
+    }
+
+    public synchronized void cancel() {
+        if (null != timerTaskEntry) {
+            timerTaskEntry.remove();
+            timerTaskEntry = null;
+        }
+    }
+
+    synchronized void setTimerTaskEntry(TimerTaskEntry entry) {
+        // if this timerTask is already held by an existing timer task entry,
+        // we will remove such an entry first.
+        if (null != timerTaskEntry && timerTaskEntry != entry) {
+            timerTaskEntry.remove();
+        }
+        timerTaskEntry = entry;
+    }
+
+    synchronized TimerTaskEntry getTimerTaskEntry() {
+        return timerTaskEntry;
+    }
+
+}