[Fix #722] Close executor service if created

Signed-off-by: fjtirado <[email protected]>

Author: fjtirado

impl/core/src/main/java/io/serverlessworkflow/impl/DefaultExecutorServiceFactory.java

@@ -17,23 +17,37 @@
 
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 public class DefaultExecutorServiceFactory implements ExecutorServiceFactory {
 
-  private static final ExecutorServiceFactory instance = new DefaultExecutorServiceFactory();
+  private ExecutorService service;
+  private Lock serviceLock = new ReentrantLock();
 
   public static ExecutorServiceFactory instance() {
-    return instance;
-  }
-
-  private static class ExecutorServiceHolder {
-    private static ExecutorService instance = Executors.newCachedThreadPool();
+    return new DefaultExecutorServiceFactory();
   }
 
   @Override
   public ExecutorService get() {
-    return ExecutorServiceHolder.instance;
+    try {
+      serviceLock.lock();
+      if (service == null) {
+        service = Executors.newCachedThreadPool();
+      }
+    } finally {
+      serviceLock.unlock();
+    }
+    return service;
   }
 
   private DefaultExecutorServiceFactory() {}
+
+  @Override
+  public void close() {
+    if (service != null) {
+      service.shutdown();
+    }
+  }
 }

impl/core/src/main/java/io/serverlessworkflow/impl/ExecutorServiceFactory.java

@@ -18,5 +18,6 @@
 import java.util.concurrent.ExecutorService;
 import java.util.function.Supplier;
 
-@FunctionalInterface
-public interface ExecutorServiceFactory extends Supplier<ExecutorService> {}
+public interface ExecutorServiceFactory extends Supplier<ExecutorService>, AutoCloseable {
+  void close();
+}

impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowApplication.java

@@ -39,7 +39,6 @@
 import java.util.ServiceLoader.Provider;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
 import java.util.stream.Collectors;
 
 public class WorkflowApplication implements AutoCloseable {
@@ -137,7 +136,7 @@ public SchemaValidator getValidator(SchemaInline inline) {
     private SchemaValidatorFactory schemaValidatorFactory;
     private WorkflowPositionFactory positionFactory = () -> new QueueWorkflowPosition();
     private WorkflowIdFactory idFactory = () -> UlidCreator.getMonotonicUlid().toString();
-    private ExecutorServiceFactory executorFactory = () -> Executors.newCachedThreadPool();
+    private ExecutorServiceFactory executorFactory = DefaultExecutorServiceFactory.instance();
     private EventConsumer<?, ?> eventConsumer = InMemoryEvents.get();
     private EventPublisher eventPublisher = InMemoryEvents.get();
     private RuntimeDescriptorFactory descriptorFactory =
@@ -236,6 +235,7 @@ public WorkflowDefinition workflowDefinition(Workflow workflow) {
 
   @Override
   public void close() {
+    executorFactory.close();
     for (WorkflowDefinition definition : definitions.values()) {
       definition.close();
     }