fix: checkpoint token for paginated execution state

Author: maschnetwork

examples/src/main/java/com/amazonaws/lambda/durable/examples/ManyAsyncStepsExample.java

@@ -0,0 +1,60 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+package com.amazonaws.lambda.durable.examples;
+
+import com.amazonaws.lambda.durable.DurableContext;
+import com.amazonaws.lambda.durable.DurableFuture;
+import com.amazonaws.lambda.durable.DurableHandler;
+import java.time.Duration;
+import java.util.ArrayList;
+
+/**
+ * Performance test example demonstrating concurrent async steps.
+ *
+ * <p>This example tests the SDK's ability to handle many concurrent operations:
+ *
+ * <ul>
+ *   <li>Creates async steps in a loop
+ *   <li>Each step performs a simple computation
+ *   <li>All results are collected and summed
+ * </ul>
+ */
+public class ManyAsyncStepsExample extends DurableHandler<ManyAsyncStepsExample.Input, String> {
+
+    private static final int STEP_COUNT = 500;
+
+    public record Input(int multiplier) {}
+
+    @Override
+    public String handleRequest(Input input, DurableContext context) {
+        var startTime = System.currentTimeMillis();
+        var multiplier = input.multiplier() > 0 ? input.multiplier() : 1;
+
+        context.getLogger().info("Starting {} async steps with multiplier {}", STEP_COUNT, multiplier);
+
+        // Create 100 async steps
+        var futures = new ArrayList<DurableFuture<Integer>>(STEP_COUNT);
+        for (var i = 0; i < STEP_COUNT; i++) {
+            var index = i;
+            var future = context.stepAsync("compute-" + i, Integer.class, () -> index * multiplier);
+            futures.add(future);
+        }
+
+        context.getLogger().info("All {} async steps created, collecting results", STEP_COUNT);
+
+        // Collect all results
+        var totalSum = 0L;
+        for (var future : futures) {
+            totalSum += future.get();
+        }
+
+        var executionTimeMs = System.currentTimeMillis() - startTime;
+        context.getLogger()
+                .info("Completed {} steps, total sum: {}, execution time: {}ms", STEP_COUNT, totalSum, executionTimeMs);
+
+        // Wait 10 seconds to test replay
+        context.wait("post-compute-wait", Duration.ofSeconds(10));
+
+        return String.format("Completed %d async steps. Sum: %d, Time: %dms", STEP_COUNT, totalSum, executionTimeMs);
+    }
+}

examples/src/test/java/com/amazonaws/lambda/durable/examples/ManyAsyncStepsExampleTest.java

@@ -0,0 +1,59 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+package com.amazonaws.lambda.durable.examples;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.amazonaws.lambda.durable.model.ExecutionStatus;
+import com.amazonaws.lambda.durable.testing.LocalDurableTestRunner;
+import org.junit.jupiter.api.Test;
+
+class ManyAsyncStepsExampleTest {
+
+    @Test
+    void testManyAsyncSteps() {
+        var handler = new ManyAsyncStepsExample();
+        var runner = LocalDurableTestRunner.create(ManyAsyncStepsExample.Input.class, handler);
+
+        var input = new ManyAsyncStepsExample.Input(2);
+        var result = runner.runUntilComplete(input);
+
+        assertEquals(ExecutionStatus.SUCCEEDED, result.getStatus());
+
+        var output = result.getResult(String.class);
+        assertNotNull(output);
+        assertTrue(output.contains("500 async steps"));
+
+        // Sum of 0..499 * 2 = 499 * 500 / 2 * 2 = 249500
+        assertTrue(output.contains("249500"));
+    }
+
+    @Test
+    void testManyAsyncStepsWithDefaultMultiplier() {
+        var handler = new ManyAsyncStepsExample();
+        var runner = LocalDurableTestRunner.create(ManyAsyncStepsExample.Input.class, handler);
+
+        var input = new ManyAsyncStepsExample.Input(1);
+        var result = runner.runUntilComplete(input);
+
+        assertEquals(ExecutionStatus.SUCCEEDED, result.getStatus());
+
+        // Sum of 0..499 = 499 * 500 / 2 = 124750
+        assertTrue(result.getResult(String.class).contains("124750"));
+    }
+
+    @Test
+    void testOperationsAreTracked() {
+        var handler = new ManyAsyncStepsExample();
+        var runner = LocalDurableTestRunner.create(ManyAsyncStepsExample.Input.class, handler);
+
+        var result = runner.runUntilComplete(new ManyAsyncStepsExample.Input(1));
+
+        assertEquals(ExecutionStatus.SUCCEEDED, result.getStatus());
+
+        // Verify some operations are tracked
+        assertNotNull(result.getOperation("compute-0"));
+        assertNotNull(result.getOperation("compute-499"));
+        assertNotNull(result.getOperation("compute-250"));
+    }
+}