GH-145 - Make sure the async ApplicationModulesRuntime bootstrap doesn't prevent shutdown.

We now use an AsyncTaskExecutor to bootstrap the ApplicationModules instance at startup asynchronously and - at the same time - do not block an explicit application shutdown. This also more idiomatic compared to using an ExecutorService directly.

spring-modulith-runtime/src/main/java/org/springframework/modulith/runtime/autoconfigure/SpringModulithRuntimeAutoConfiguration.java

@@ -16,7 +16,6 @@
 package org.springframework.modulith.runtime.autoconfigure;
 
 import java.util.List;
-import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.function.Supplier;
 
@@ -31,6 +30,8 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Role;
+import org.springframework.core.task.AsyncTaskExecutor;
+import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.modulith.ApplicationModuleInitializer;
 import org.springframework.modulith.core.ApplicationModule;
 import org.springframework.modulith.core.ApplicationModules;
@@ -49,6 +50,7 @@ import org.springframework.util.Assert;
 class SpringModulithRuntimeAutoConfiguration {
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(SpringModulithRuntimeAutoConfiguration.class);
+	private final AsyncTaskExecutor executor = new SimpleAsyncTaskExecutor();
 
 	@Bean
 	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
@@ -63,7 +65,7 @@ class SpringModulithRuntimeAutoConfiguration {
 	ApplicationModulesRuntime modulesRuntime(ApplicationRuntime runtime) {
 
 		var mainClass = runtime.getMainApplicationClass();
-		var modules = Executors.newFixedThreadPool(1)
+		var modules = executor
 				.submit(() -> ApplicationModulesBootstrap.initializeApplicationModules(mainClass));
 
 		return new ApplicationModulesRuntime(toSupplier(modules), runtime);

spring-modulith-runtime/src/main/resources/logback.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+	
+	<include resource="org/springframework/boot/logging/logback/defaults.xml"/>
+	<include resource="org/springframework/boot/logging/logback/console-appender.xml" />
+	
+	<root level="INFO">
+		<appender-ref ref="CONSOLE" />
+	</root>
+	
+	<logger name="org.springframework.modulith" level="DEBUG"/>
+	<logger name="example" level="INFO" />
+	
+</configuration>