test(s3stream/util): test FutureTicker (#859)

Signed-off-by: Ning Yu <[email protected]>

s3stream/src/main/java/com/automq/stream/utils/FutureTicker.java

@@ -22,23 +22,48 @@
 import java.util.concurrent.TimeUnit;
 
 /**
- * A ticker base on {@link CompletableFuture}
- * TODO more docs and tests
+ * A ticker base on {@link CompletableFuture}. It is used to batch operations.
+ * <p>
+ * For example, if we want to batch operations every 100ms, we can use the following code:
+ * <pre>
+ * {@code
+ * FutureTicker ticker = new FutureTicker(100, TimeUnit.MILLISECONDS, executor);
+ * while (true) {
+ *     ticker.tick().thenAccept(v -> operation());
+ *     Thread.sleep(1);
+ * }
+ * }
+ * </pre>
+ * Operations will be batched every 100ms.
  */
 public class FutureTicker {
 
     private final Executor delayedExecutor;
 
     private CompletableFuture<Void> currentTick = CompletableFuture.completedFuture(null);
 
+    /**
+     * Create a ticker with a delay and a executor
+     * @param delay the delay
+     * @param unit the time unit of the delay
+     * @param executor the executor, the {@link CompletableFuture} returned by {@link #tick()} will be completed by this executor
+     */
     public FutureTicker(long delay, TimeUnit unit, Executor executor) {
         this.delayedExecutor = CompletableFuture.delayedExecutor(delay, unit, executor);
     }
 
+    /**
+     * Tick the ticker. It returns a future which will complete after the delay.
+     * If the ticker is already ticking, the same future will be returned.
+     * It is thread safe to call this method.
+     */
     public CompletableFuture<Void> tick() {
         return maybeNextTick();
     }
 
+    /**
+     * Generate a new tick if the current tick is done
+     */
     private synchronized CompletableFuture<Void> maybeNextTick() {
         if (currentTick.isDone()) {
             // a future which will complete after delay

s3stream/src/test/java/com/automq/stream/utils/FutureTickerTest.java

@@ -0,0 +1,63 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 com.automq.stream.utils;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+class FutureTickerTest {
+
+    private FutureTicker ticker = new FutureTicker(10, TimeUnit.MILLISECONDS, Executors.newSingleThreadExecutor());
+
+    @BeforeEach
+    void setUp() {
+        ticker = new FutureTicker(10, TimeUnit.MILLISECONDS, Executors.newSingleThreadExecutor());
+    }
+
+    @Test
+    void testFirstTick() {
+        CompletableFuture<Void> tick = ticker.tick();
+        assertNotNull(tick);
+        assertFalse(tick.isDone());
+    }
+
+    @Test
+    void testTwoTicks() {
+        CompletableFuture<Void> tick1 = ticker.tick();
+        CompletableFuture<Void> tick2 = ticker.tick();
+        assertSame(tick1, tick2);
+    }
+
+    @Test
+    void testDelay() throws InterruptedException {
+        CompletableFuture<Void> tick1 = ticker.tick();
+        Thread.sleep(20);
+        CompletableFuture<Void> tick2 = ticker.tick();
+        assertFalse(tick2.isDone());
+        assertNotSame(tick1, tick2);
+    }
+}