refactor task/job executors

* migrate from java's executor impl to spring's abstraction:
let spring handle the bean lifecycle, graceful shutdown etc.

* separate on interface-level between scheduled and async tasks:
we only have 1 use case for scheduled tasks (websocket ping-pongs),
whereas all other usages of ScheduledExecutorService were just async
job submissions. separation might be useful in future, if we want to have
distinct thread pools as well.

Author: goekay

src/main/java/de/rwth/idsg/steve/config/BeanConfiguration.java

@@ -21,7 +21,6 @@
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
-import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.mysql.cj.conf.PropertyKey;
 import com.zaxxer.hikari.HikariConfig;
 import com.zaxxer.hikari.HikariDataSource;
@@ -45,6 +44,7 @@
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
 import org.springframework.scheduling.annotation.EnableScheduling;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 import org.springframework.web.accept.ContentNegotiationManager;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
@@ -55,16 +55,11 @@
 import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.servlet.view.InternalResourceViewResolver;
 
-import jakarta.annotation.PreDestroy;
 import jakarta.validation.Validator;
 
 import javax.sql.DataSource;
 import java.util.List;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.ScheduledThreadPoolExecutor;
-import java.util.concurrent.ThreadFactory;
-import java.util.concurrent.TimeUnit;
+import java.util.concurrent.Executor;
 
 import static de.rwth.idsg.steve.SteveConfiguration.CONFIG;
 
@@ -81,8 +76,6 @@
 @ComponentScan("de.rwth.idsg.steve")
 public class BeanConfiguration implements WebMvcConfigurer {
 
-    private ScheduledThreadPoolExecutor executor;
-
     /**
      * https://github.com/brettwooldridge/HikariCP/wiki/MySQL-Configuration
      */
@@ -144,13 +137,20 @@ public DSLContext dslContext(DataSource dataSource) {
         return DSL.using(conf);
     }
 
-    @Bean
-    public ScheduledExecutorService scheduledExecutorService() {
-        ThreadFactory threadFactory = new ThreadFactoryBuilder().setNameFormat("SteVe-Executor-%d")
-                                                                .build();
+    @Bean(name = "asyncTaskScheduler")
+    public ThreadPoolTaskScheduler asyncTaskScheduler() {
+        ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler();
+        scheduler.setPoolSize(5);
+        scheduler.setThreadNamePrefix("SteVe-Executor-");
+        scheduler.setWaitForTasksToCompleteOnShutdown(true);
+        scheduler.setAwaitTerminationSeconds(30);
+        scheduler.initialize();
+        return scheduler;
+    }
 
-        executor = new ScheduledThreadPoolExecutor(5, threadFactory);
-        return executor;
+    @Bean(name = "asyncTaskExecutor")
+    public Executor asyncTaskExecutor(ThreadPoolTaskScheduler asyncTaskScheduler) {
+        return asyncTaskScheduler;
     }
 
     @Bean
@@ -173,29 +173,6 @@ public ReleaseCheckService releaseCheckService() {
         }
     }
 
-    @PreDestroy
-    public void shutDown() {
-        if (executor != null) {
-            gracefulShutDown(executor);
-        }
-    }
-
-    private void gracefulShutDown(ExecutorService executor) {
-        try {
-            executor.shutdown();
-            executor.awaitTermination(30, TimeUnit.SECONDS);
-
-        } catch (InterruptedException e) {
-            log.error("Termination interrupted", e);
-
-        } finally {
-            if (!executor.isTerminated()) {
-                log.warn("Killing non-finished tasks");
-            }
-            executor.shutdownNow();
-        }
-    }
-
     // -------------------------------------------------------------------------
     // Web config
     // -------------------------------------------------------------------------

src/main/java/de/rwth/idsg/steve/config/WebSocketConfiguration.java

@@ -51,7 +51,7 @@ public class WebSocketConfiguration implements WebSocketConfigurer {
     @Autowired private Ocpp16WebSocketEndpoint ocpp16WebSocketEndpoint;
 
     public static final String PATH_INFIX = "/websocket/CentralSystemService/";
-    public static final long PING_INTERVAL = TimeUnit.MINUTES.toMinutes(15);
+    public static final Duration PING_INTERVAL = Duration.ofMinutes(15);
     public static final Duration IDLE_TIMEOUT = Duration.ofHours(2);
     public static final int MAX_MSG_SIZE = 8_388_608; // 8 MB for max message size
 

src/main/java/de/rwth/idsg/steve/ocpp/soap/MessageHeaderInterceptor.java

@@ -41,7 +41,7 @@
 
 import javax.xml.namespace.QName;
 import java.util.Optional;
-import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.Executor;
 
 import static org.apache.cxf.ws.addressing.JAXWSAConstants.ADDRESSING_PROPERTIES_INBOUND;
 
@@ -62,7 +62,7 @@ public class MessageHeaderInterceptor extends AbstractPhaseInterceptor<Message>
 
     @Autowired private OcppServerRepository ocppServerRepository;
     @Autowired private ChargePointHelperService chargePointHelperService;
-    @Autowired private ScheduledExecutorService executorService;
+    @Autowired private Executor asyncTaskExecutor;
 
     private static final String BOOT_OPERATION_NAME = "BootNotification";
     private static final String CHARGEBOX_ID_HEADER = "ChargeBoxIdentity";
@@ -93,7 +93,7 @@ public void handleMessage(Message message) throws Fault {
         // 2. update endpoint
         // -------------------------------------------------------------------------
 
-        executorService.execute(() -> {
+        asyncTaskExecutor.execute(() -> {
             try {
                 String endpointAddress = getEndpointAddress(message);
                 if (endpointAddress != null) {

src/main/java/de/rwth/idsg/steve/ocpp/ws/AbstractWebSocketEndpoint.java

@@ -31,6 +31,7 @@
 import org.joda.time.DateTime;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.web.socket.BinaryMessage;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.PongMessage;
@@ -39,14 +40,13 @@
 import org.springframework.web.socket.WebSocketMessage;
 import org.springframework.web.socket.WebSocketSession;
 
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Deque;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
-import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 
 /**
@@ -55,7 +55,7 @@
  */
 public abstract class AbstractWebSocketEndpoint extends ConcurrentWebSocketHandler implements SubProtocolCapable {
 
-    @Autowired private ScheduledExecutorService service;
+    @Autowired private ThreadPoolTaskScheduler asyncTaskScheduler;
     @Autowired private OcppServerRepository ocppServerRepository;
     @Autowired private FutureResponseContextStore futureResponseContextStore;
     @Autowired private ApplicationEventPublisher applicationEventPublisher;
@@ -131,11 +131,11 @@ public void onOpen(WebSocketSession session) throws Exception {
 
         // Just to keep the connection alive, such that the servers do not close
         // the connection because of a idle timeout, we ping-pong at fixed intervals.
-        ScheduledFuture pingSchedule = service.scheduleAtFixedRate(
+        ScheduledFuture pingSchedule = asyncTaskScheduler.scheduleAtFixedRate(
                 new PingTask(chargeBoxId, session),
-                WebSocketConfiguration.PING_INTERVAL,
-                WebSocketConfiguration.PING_INTERVAL,
-                TimeUnit.MINUTES);
+                Instant.now().plus(WebSocketConfiguration.PING_INTERVAL),
+                WebSocketConfiguration.PING_INTERVAL
+        );
 
         futureResponseContextStore.addSession(session);
 

src/main/java/de/rwth/idsg/steve/service/BackgroundService.java

@@ -23,7 +23,7 @@
 import lombok.RequiredArgsConstructor;
 
 import java.util.List;
-import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executor;
 import java.util.function.Consumer;
 
 /**
@@ -32,10 +32,10 @@
  */
 @RequiredArgsConstructor
 public class BackgroundService {
-    private final ExecutorService executorService;
+    private final Executor asyncTaskExecutor;
 
-    public static BackgroundService with(ExecutorService executorService) {
-        return new BackgroundService(executorService);
+    public static BackgroundService with(Executor asyncTaskExecutor) {
+        return new BackgroundService(asyncTaskExecutor);
     }
 
     public Runner forFirst(List<ChargePointSelect> list) {
@@ -56,7 +56,7 @@ private class BackgroundSingleRunner implements Runner {
 
         @Override
         public void execute(Consumer<ChargePointSelect> consumer) {
-            executorService.execute(() -> consumer.accept(cps));
+            asyncTaskExecutor.execute(() -> consumer.accept(cps));
         }
     }
 
@@ -66,7 +66,7 @@ private class BackgroundListRunner implements Runner {
 
         @Override
         public void execute(Consumer<ChargePointSelect> consumer) {
-            executorService.execute(() -> list.forEach(consumer));
+            asyncTaskExecutor.execute(() -> list.forEach(consumer));
         }
     }
 }