fix wrong ClassLoader for Delayed-Restart Thread, which has caused an ClassLoader leak.

Also added system properties to configure shutdown only, wait between stop and start and possibility to disable gc.

scm-webapp/src/main/java/sonia/scm/event/LegmanScmEventBus.java

@@ -90,8 +90,12 @@ public class LegmanScmEventBus extends ScmEventBus
   @Override
   public void post(Object event)
   {
-    logger.debug("post {} to event bus {}", event, name);
-    eventBus.post(event);
+    if (eventBus != null) {
+      logger.debug("post {} to event bus {}", event, name);
+      eventBus.post(event);
+    } else {
+      logger.error("failed to post event {}, because event bus is shutdown", event);
+    }
   }
 
   /**
@@ -104,9 +108,12 @@ public class LegmanScmEventBus extends ScmEventBus
   @Override
   public void register(Object object)
   {
-    logger.trace("register {} to event bus {}", object, name);
-    eventBus.register(object);
-
+    if (eventBus != null) {
+      logger.trace("register {} to event bus {}", object, name);
+      eventBus.register(object);
+    } else {
+      logger.error("failed to register {}, because eventbus is shutdown", object);
+    }
   }
 
   /**
@@ -118,22 +125,37 @@ public class LegmanScmEventBus extends ScmEventBus
   @Override
   public void unregister(Object object)
   {
-    logger.trace("unregister {} from event bus {}", object, name);
-    
-    try
-    {
-      eventBus.unregister(object);
+    if (eventBus != null) {
+      logger.trace("unregister {} from event bus {}", object, name);
+
+      try {
+        eventBus.unregister(object);
+      } catch (IllegalArgumentException ex) {
+        logger.trace("object {} was not registered", object);
+      }
+    } else {
+      logger.error("failed to unregister object {}, because event bus is shutdown", object);
     }
-    catch (IllegalArgumentException ex)
-    {
-      logger.trace("object {} was not registered", object);
+  }
+
+  @Subscribe(async = false)
+  public void shutdownEventBus(ShutdownEventBusEvent shutdownEventBusEvent) {
+    if (eventBus != null) {
+      logger.info("shutdown event bus executor for {}, because of received ShutdownEventBusEvent", name);
+      eventBus.shutdown();
+      eventBus = null;
+    } else {
+      logger.warn("event bus was already shutdown");
     }
   }
 
   @Subscribe(async = false)
   public void recreateEventBus(RecreateEventBusEvent recreateEventBusEvent) {
-    logger.info("shutdown event bus executor for {}", name);
-    eventBus.shutdown();
+    if (eventBus != null) {
+      logger.info("shutdown event bus executor for {}, because of received RecreateEventBusEvent", name);
+      eventBus.shutdown();
+    }
+    logger.info("recreate event bus because of received RecreateEventBusEvent");
     eventBus = create();
   }
 

scm-webapp/src/main/java/sonia/scm/event/ShutdownEventBusEvent.java

@@ -0,0 +1,4 @@
+package sonia.scm.event;
+
+public class ShutdownEventBusEvent {
+}

scm-webapp/src/main/java/sonia/scm/lifecycle/BootstrapContextFilter.java

@@ -58,13 +58,16 @@ public class BootstrapContextFilter extends GuiceFilter {
 
   private final BootstrapContextListener listener = new BootstrapContextListener();
 
+  private ClassLoader webAppClassLoader;
+
   /** Field description */
   private FilterConfig filterConfig;
 
   @Override
   public void init(FilterConfig filterConfig) throws ServletException {
     this.filterConfig = filterConfig;
-
+    // store webapp classloader for delayed restarts
+    webAppClassLoader = Thread.currentThread().getContextClassLoader();
     initializeContext();
   }
 
@@ -97,7 +100,7 @@ public class BootstrapContextFilter extends GuiceFilter {
     if (filterConfig == null) {
       LOG.error("filter config is null, scm-manager is not initialized");
     } else {
-      RestartStrategy restartStrategy = RestartStrategy.get();
+      RestartStrategy restartStrategy = RestartStrategy.get(webAppClassLoader);
       restartStrategy.restart(new GuiceInjectionContext());
     }
   }

scm-webapp/src/main/java/sonia/scm/lifecycle/InjectionContextRestartStrategy.java

@@ -5,6 +5,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import sonia.scm.event.RecreateEventBusEvent;
 import sonia.scm.event.ScmEventBus;
+import sonia.scm.event.ShutdownEventBusEvent;
 
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -13,20 +14,47 @@ import java.util.concurrent.atomic.AtomicLong;
  */
 public class InjectionContextRestartStrategy implements RestartStrategy {
 
+  private static final String DISABLE_RESTART_PROPERTY = "sonia.scm.restart.disable";
+  private static final String WAIT_PROPERTY = "sonia.scm.restart.wait";
+  private static final String DISABLE_GC_PROPERTY = "sonia.scm.restart.disable-gc";
+
   private static final AtomicLong INSTANCE_COUNTER = new AtomicLong();
   private static final Logger LOG = LoggerFactory.getLogger(InjectionContextRestartStrategy.class);
 
-  private long waitInMs = 250L;
+  private boolean restartEnabled = !Boolean.getBoolean(DISABLE_RESTART_PROPERTY);
+  private long waitInMs = Integer.getInteger(WAIT_PROPERTY, 250);
+  private boolean gcEnabled = !Boolean.getBoolean(DISABLE_GC_PROPERTY);
+
+  private final ClassLoader webAppClassLoader;
+
+  InjectionContextRestartStrategy(ClassLoader webAppClassLoader) {
+    this.webAppClassLoader = webAppClassLoader;
+  }
 
   @VisibleForTesting
   void setWaitInMs(long waitInMs) {
     this.waitInMs = waitInMs;
   }
 
+  @VisibleForTesting
+  void setGcEnabled(boolean gcEnabled) {
+    this.gcEnabled = gcEnabled;
+  }
+
   @Override
   public void restart(InjectionContext context) {
-    LOG.warn("destroy injection context");
-    context.destroy();
+    stop(context);
+    if (restartEnabled) {
+      start(context);
+    } else {
+      LOG.warn("restarting context is disabled");
+    }
+  }
+
+  @SuppressWarnings("squid:S1215") // suppress explicit gc call warning
+  private void start(InjectionContext context) {
+    LOG.debug("use WebAppClassLoader as ContextClassLoader, to avoid ClassLoader leaks");
+    Thread.currentThread().setContextClassLoader(webAppClassLoader);
 
     LOG.warn("send recreate eventbus event");
     ScmEventBus.getInstance().post(new RecreateEventBusEvent());
@@ -34,6 +62,12 @@ public class InjectionContextRestartStrategy implements RestartStrategy {
     // restart context delayed, to avoid timing problems
     new Thread(() -> {
       try {
+        if (gcEnabled){
+          LOG.info("call gc to clean up memory from old instances");
+          System.gc();
+        }
+
+        LOG.info("wait {}ms before re starting the context", waitInMs);
         Thread.sleep(waitInMs);
 
         LOG.warn("reinitialize injection context");
@@ -45,6 +79,15 @@ public class InjectionContextRestartStrategy implements RestartStrategy {
         LOG.error("failed to restart", ex);
       }
     }, "Delayed-Restart-" + INSTANCE_COUNTER.incrementAndGet()).start();
+  }
 
+  private void stop(InjectionContext context) {
+    LOG.warn("destroy injection context");
+    context.destroy();
+
+    if (!restartEnabled) {
+      // shutdown eventbus, but do this only if restart is disabled
+      ScmEventBus.getInstance().post(new ShutdownEventBusEvent());
+    }
   }
 }

scm-webapp/src/main/java/sonia/scm/lifecycle/RestartStrategy.java

@@ -13,7 +13,6 @@ public interface RestartStrategy {
      * Initialize the injection context.
      */
     void initialize();
-
     /**
      * Destroys the injection context.
      */
@@ -31,8 +30,8 @@ public interface RestartStrategy {
    *
    * @return configured strategy
    */
-  static RestartStrategy get() {
-    return new InjectionContextRestartStrategy();
+  static RestartStrategy get(ClassLoader webAppClassLoader) {
+    return new InjectionContextRestartStrategy(webAppClassLoader);
   }
 
 }