feat(idempotency): add automatic priming for DynamoDB persistence store

Priming.md

@@ -56,4 +56,6 @@ In order to generate the `classloaded.txt` file for a Java module in this projec
 - `classesloaded.txt` file includes test classes as well because the file is generated while running tests. This is not a problem because all the classes that are not found are ignored by `ClassPreLoader.preloadClasses()`. Also `beforeCheckpoint()` hook is not time-sensitive, it only runs once when a new Lambda version gets published. 
 
 ## Reference Implementation
-Working example is available in the [powertools-metrics](powertools-metrics/src/main/java/software/amazon/lambda/powertools/metrics/MetricsFactory.java). 
+Working examples are available in:
+- [powertools-metrics](powertools-metrics/src/main/java/software/amazon/lambda/powertools/metrics/MetricsFactory.java) - Automatic priming with `ClassPreLoader`
+- [powertools-idempotency-dynamodb](powertools-idempotency/powertools-idempotency-dynamodb/src/main/java/software/amazon/lambda/powertools/idempotency/persistence/dynamodb/DynamoDBPersistenceStore.java) - Invoke priming + Automatic priming 

powertools-idempotency/powertools-idempotency-dynamodb/pom.xml

@@ -65,6 +65,10 @@
             <groupId>org.crac</groupId>
             <artifactId>crac</artifactId>
         </dependency>
+        <dependency>
+            <groupId>software.amazon.lambda</groupId>
+            <artifactId>powertools-common</artifactId>
+        </dependency>
 
         <!-- Test dependencies -->
         <dependency>
@@ -106,6 +110,24 @@
     </dependencies>
 
     <profiles>
+        <profile>
+            <id>generate-classesloaded-file</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <configuration>
+                            <argLine>
+                                -Xlog:class+load=info:classesloaded.txt
+                                --add-opens java.base/java.util=ALL-UNNAMED
+                                --add-opens java.base/java.lang=ALL-UNNAMED
+                            </argLine>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
         <profile>
             <id>generate-graalvm-files</id>
             <!-- The AWS DynamoDBClient uses com.amazonaws.xray.interceptors.TracingInterceptor if available on the

powertools-idempotency/powertools-idempotency-dynamodb/src/main/java/software/amazon/lambda/powertools/idempotency/persistence/dynamodb/DynamoDBPersistenceStore.java

@@ -30,6 +30,7 @@
 import software.amazon.awssdk.services.dynamodb.model.GetItemResponse;
 import software.amazon.awssdk.services.dynamodb.model.PutItemRequest;
 import software.amazon.awssdk.services.dynamodb.model.UpdateItemRequest;
+import software.amazon.lambda.powertools.common.internal.ClassPreLoader;
 import software.amazon.lambda.powertools.common.internal.UserAgentConfigurator;
 import software.amazon.lambda.powertools.idempotency.Constants;
 import software.amazon.lambda.powertools.idempotency.exceptions.IdempotencyItemAlreadyExistsException;
@@ -123,7 +124,13 @@ private DynamoDBPersistenceStore(String tableName,
      */
     @Override
     public void beforeCheckpoint(org.crac.Context<? extends Resource> context) throws Exception {
+        // Skip priming if DynamoDB client is not available
+        if (dynamoDbClient == null) {
+            return;
+        }
+
         try {
+            // Invoke priming - exercise DynamoDB SDK paths
             String primingRecordKey = "__invoke_prime__";
             Instant now = Instant.now();
             long expiry = now.plus(3600, ChronoUnit.SECONDS).getEpochSecond();
@@ -137,8 +144,12 @@ public void beforeCheckpoint(org.crac.Context<? extends Resource> context) throw
             putRecord(primingDataRecord, Instant.now());
             getRecord(primingRecordKey);
             deleteRecord(primingRecordKey);
-        } catch (Exception unknown) {
-            // This is unexpected but we must continue without any interruption
+
+            // Automatic priming - preload classes from classesloaded.txt
+            ClassPreLoader.preloadClasses();
+        } catch (Exception e) {
+            // Log the exception for debugging but continue to ensure checkpoint succeeds
+            LOG.warn("Priming failed during checkpoint, continuing anyway", e);
         }
     }