[ASTS] feat(bucket-retrieval): Dynamic Task Scheduler for updating bu…

…cket list

atlasdb-impl-shared/src/main/java/com/palantir/atlasdb/sweep/asts/DynamicTaskScheduler.java

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+/*
+ * (c) Copyright 2024 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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 com.palantir.atlasdb.sweep.asts;
+
+import com.palantir.logsafe.SafeArg;
+import com.palantir.logsafe.logger.SafeLogger;
+import com.palantir.logsafe.logger.SafeLoggerFactory;
+import com.palantir.refreshable.Refreshable;
+import java.time.Duration;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+// This feels like it should already exist.
+public final class DynamicTaskScheduler {
+    private static final SafeLogger log = SafeLoggerFactory.get(DynamicTaskScheduler.class);
+    private final ScheduledExecutorService scheduledExecutorService;
+    private final Refreshable<Duration> automaticSweepRefreshDelay;
+    private final Runnable task;
+    private final AtomicBoolean isStarted = new AtomicBoolean(false);
+
+    private DynamicTaskScheduler(
+            ScheduledExecutorService scheduledExecutorService,
+            Refreshable<Duration> automaticSweepRefreshDelay,
+            Runnable task) {
+        this.scheduledExecutorService = scheduledExecutorService;
+        this.automaticSweepRefreshDelay = automaticSweepRefreshDelay;
+        this.task = task;
+    }
+
+    public static DynamicTaskScheduler create(
+            ScheduledExecutorService scheduledExecutorService,
+            Refreshable<Duration> automaticSweepRefreshDelay,
+            Runnable task) {
+        return new DynamicTaskScheduler(scheduledExecutorService, automaticSweepRefreshDelay, task);
+    }
+
+    public void start() {
+        if (isStarted.compareAndSet(false, true)) {
+            scheduleNextIteration(automaticSweepRefreshDelay.get());
+        } else {
+            log.warn("Attempted to start an already started task");
+        }
+    }
+
+    private void runOneIteration() {
+        Duration delay = automaticSweepRefreshDelay.get();
+        try {
+            log.info("Running task");
+            task.run();
+        } catch (Exception e) {
+            log.warn("Failed to run task. Will retry in the next interval", SafeArg.of("delay", delay), e);
+        }
+        scheduleNextIteration(delay);
+    }
+
+    private void scheduleNextIteration(Duration delay) {
+        log.info("Scheduling next iteration", SafeArg.of("delay", delay));
+        scheduledExecutorService.schedule(this::runOneIteration, delay.toMillis(), TimeUnit.MILLISECONDS);
+    }
+}

atlasdb-impl-shared/src/test/java/com/palantir/atlasdb/sweep/asts/DynamicTaskSchedulerTest.java

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+/*
+ * (c) Copyright 2024 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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 com.palantir.atlasdb.sweep.asts;
+
+import static com.palantir.logsafe.testing.Assertions.assertThat;
+
+import com.palantir.refreshable.Refreshable;
+import com.palantir.refreshable.SettableRefreshable;
+import java.time.Duration;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.jmock.lib.concurrent.DeterministicScheduler;
+import org.junit.jupiter.api.Test;
+
+public final class DynamicTaskSchedulerTest {
+    private final DeterministicScheduler scheduler = new DeterministicScheduler();
+    private final SettableRefreshable<Duration> taskDelay = Refreshable.create(Duration.ofSeconds(1));
+
+    private final AtomicInteger taskRunCount = new AtomicInteger(0);
+    private final Runnable task = taskRunCount::incrementAndGet;
+
+    private final DynamicTaskScheduler taskRunner = DynamicTaskScheduler.create(scheduler, taskDelay, task);
+
+    @Test
+    public void doesNotRunTaskBeforeStarted() {
+        tick(Duration.ofDays(1));
+        assertThat(taskRunCount.get()).isEqualTo(0);
+    }
+
+    @Test
+    public void runsFirstTaskAfterInitialDelayOnceStarted() {
+        taskRunner.start();
+        tick(Duration.ofMillis(999));
+        assertThat(taskRunCount.get()).isEqualTo(0);
+
+        tick(Duration.ofMillis(2));
+        assertThat(taskRunCount.get()).isEqualTo(1);
+    }
+
+    @Test
+    public void runsSubsequentTasksWithUpdatedDelaysOnNextSchedule() {
+        taskRunner.start();
+        taskDelay.update(Duration.ofSeconds(2));
+        tick(Duration.ofMillis(1001));
+        assertThat(taskRunCount.get()).isEqualTo(1);
+
+        tick(Duration.ofMillis(1001));
+        assertThat(taskRunCount.get()).isEqualTo(1);
+
+        taskDelay.update(Duration.ofMillis(100));
+        tick(Duration.ofSeconds(1));
+        assertThat(taskRunCount.get()).isEqualTo(2);
+
+        tick(Duration.ofMillis(100));
+        assertThat(taskRunCount.get()).isEqualTo(3);
+    }
+
+    private void tick(Duration duration) {
+        scheduler.tick(duration.toMillis(), TimeUnit.MILLISECONDS);
+    }
+}