fixes #332

main/frontend-webdav/src/main/java/org/cryptomator/frontend/webdav/Tarpit.java

@@ -7,8 +7,10 @@ package org.cryptomator.frontend.webdav;
 
 import static java.lang.Math.max;
 import static java.lang.System.currentTimeMillis;
+import static java.util.Collections.synchronizedSet;
 
 import java.io.Serializable;
+import java.util.Collection;
 import java.util.HashSet;
 import java.util.Optional;
 import java.util.Set;
@@ -27,18 +29,15 @@ class Tarpit implements Serializable {
 	private static final Logger LOG = LoggerFactory.getLogger(Tarpit.class);
 	private static final long DELAY_MS = 10000;
 
-	private final Set<FrontendId> validFrontendIds = new HashSet<>();
+	private final Set<FrontendId> validFrontendIds = synchronizedSet(new HashSet<>());
 
 	@Inject
-	public Tarpit() {
-	}
+	public Tarpit() {}
 
-	public void register(FrontendId frontendId) {
-		validFrontendIds.add(frontendId);
-	}
-
-	public void unregister(FrontendId frontendId) {
-		validFrontendIds.remove(frontendId);
+	public void setValidFrontendIds(Collection<FrontendId> validFrontendIds) {
+		this.validFrontendIds.retainAll(validFrontendIds);
+		this.validFrontendIds.addAll(validFrontendIds);
+		validFrontendIds.forEach(System.out::println);
 	}
 
 	public void handle(HttpServletRequest req) {

main/frontend-webdav/src/main/java/org/cryptomator/frontend/webdav/WebDavFrontend.java

@@ -24,15 +24,13 @@ class WebDavFrontend implements Frontend {
 	private final WebDavMounterProvider webdavMounterProvider;
 	private final ServletContextHandler handler;
 	private final URI uri;
-	private final Runnable afterClose;
 
 	private WebDavMount mount;
 
-	public WebDavFrontend(WebDavMounterProvider webdavMounterProvider, ServletContextHandler handler, URI uri, Runnable afterUnmount) throws FrontendCreationFailedException {
+	public WebDavFrontend(WebDavMounterProvider webdavMounterProvider, ServletContextHandler handler, URI uri) throws FrontendCreationFailedException {
 		this.webdavMounterProvider = webdavMounterProvider;
 		this.handler = handler;
 		this.uri = uri;
-		this.afterClose = afterUnmount;
 		try {
 			handler.start();
 		} catch (Exception e) {
@@ -42,12 +40,8 @@ class WebDavFrontend implements Frontend {
 
 	@Override
 	public void close() throws Exception {
-		try {
-			unmount();
-			handler.stop();
-		} finally {
-			afterClose.run();
-		}
+		unmount();
+		handler.stop();
 	}
 
 	@Override

main/frontend-webdav/src/main/java/org/cryptomator/frontend/webdav/WebDavServer.java

@@ -12,6 +12,7 @@ import static java.lang.String.format;
 
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.util.Collection;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 
@@ -117,9 +118,12 @@ public class WebDavServer implements FrontendFactory {
 			throw new IllegalStateException(e);
 		}
 		final ServletContextHandler handler = addServlet(root, uri);
-		tarpit.register(id);
 		LOG.info("Servlet available under " + uri);
-		return new WebDavFrontend(webdavMounterProvider, handler, uri, () -> tarpit.unregister(id));
+		return new WebDavFrontend(webdavMounterProvider, handler, uri);
+	}
+	
+	public void setValidFrontendIds(Collection<FrontendId> validFrontendIds) {
+		tarpit.setValidFrontendIds(validFrontendIds);
 	}
 
 }