Fixes issue where Unix crashes when inotify is full

CHANGELOG.md

@@ -88,6 +88,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue where downloaded files would be moved to a directory named after the citationkey when no file directory pattern is specified [#6589](https://github.com/JabRef/jabref/issues/6589)
 - We fixed an issue with the creation of a group of cited entries which incorrectly showed the message that the library had been modified externally whenever saving the library. [#6420](https://github.com/JabRef/jabref/issues/6420)
 - We fixed an issue with the creation of a group of cited entries. Now the file path to an aux file gets validated. [#6585](https://github.com/JabRef/jabref/issues/6585)
+- We fixed an issue on Linux systems where the application would crash upon inotify failure. Now, the user is prompted with a warning, and given the choice to continue the session. [#6073](https://github.com/JabRef/jabref/issues/6073)
 
 ### Removed
 

src/main/java/org/jabref/JabRefGUI.java

@@ -104,6 +104,13 @@ private void openWindow(Stage mainStage) {
             }
         });
         Platform.runLater(this::openDatabases);
+
+        if (!(Globals.getFileUpdateMonitor().isActive())) {
+            this.getMainFrame().getDialogService()
+                    .showErrorDialogAndWait(Localization.lang("Unable to monitor file changes. Please close files " +
+                            "and processes and restart. You may encounter errors if you continue " +
+                            "with this session."));
+        }
     }
 
     private void openDatabases() {

src/main/java/org/jabref/gui/util/DefaultFileUpdateMonitor.java

@@ -7,10 +7,12 @@
 import java.nio.file.WatchEvent;
 import java.nio.file.WatchKey;
 import java.nio.file.WatchService;
-import java.util.Objects;
+import java.util.Optional;
 
+import org.jabref.JabRefException;
 import org.jabref.model.util.FileUpdateListener;
 import org.jabref.model.util.FileUpdateMonitor;
+import org.jabref.model.util.WatchServiceUnavailableException;
 
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.Multimap;
@@ -29,11 +31,14 @@ public class DefaultFileUpdateMonitor implements Runnable, FileUpdateMonitor {
 
     private final Multimap<Path, FileUpdateListener> listeners = ArrayListMultimap.create(20, 4);
     private WatchService watcher;
+    private Optional<JabRefException> filesystemMonitorFailure;
 
     @Override
     public void run() {
         try (WatchService watcher = FileSystems.getDefault().newWatchService()) {
             this.watcher = watcher;
+            filesystemMonitorFailure = Optional.empty();
+
             while (true) {
                 WatchKey key;
                 try {
@@ -59,23 +64,29 @@ public void run() {
                 }
                 Thread.yield();
             }
-        } catch (Throwable e) {
-            LOGGER.error("FileUpdateMonitor has been interrupted.", e);
+        } catch (IOException e) {
+            filesystemMonitorFailure = Optional.of(new WatchServiceUnavailableException(e.getMessage(),
+                    e.getLocalizedMessage(), e.getCause()));
+            LOGGER.warn(filesystemMonitorFailure.get().getLocalizedMessage(), e);
         }
     }
 
+    public boolean isActive() {
+        return filesystemMonitorFailure.isEmpty();
+    }
+
     private void notifyAboutChange(Path path) {
         listeners.get(path).forEach(FileUpdateListener::fileUpdated);
     }
 
     @Override
     public void addListenerForFile(Path file, FileUpdateListener listener) throws IOException {
-        Objects.requireNonNull(watcher, "You need to start the file monitor before watching files");
-
-        // We can't watch files directly, so monitor their parent directory for updates
-        Path directory = file.toAbsolutePath().getParent();
-        directory.register(watcher, StandardWatchEventKinds.ENTRY_MODIFY);
-        listeners.put(file, listener);
+        if (isActive()) {
+            // We can't watch files directly, so monitor their parent directory for updates
+            Path directory = file.toAbsolutePath().getParent();
+            directory.register(watcher, StandardWatchEventKinds.ENTRY_MODIFY);
+            listeners.put(file, listener);
+        }
     }
 
     @Override

src/main/java/org/jabref/model/util/DummyFileUpdateMonitor.java

@@ -1,6 +1,5 @@
 package org.jabref.model.util;
 
-import java.io.IOException;
 import java.nio.file.Path;
 
 /**
@@ -9,12 +8,17 @@
  */
 public class DummyFileUpdateMonitor implements FileUpdateMonitor {
     @Override
-    public void addListenerForFile(Path file, FileUpdateListener listener) throws IOException {
+    public void addListenerForFile(Path file, FileUpdateListener listener) {
 
     }
 
     @Override
     public void removeListener(Path path, FileUpdateListener listener) {
 
     }
+
+    @Override
+    public boolean isActive() {
+        return false;
+    }
 }

src/main/java/org/jabref/model/util/FileUpdateMonitor.java

@@ -18,4 +18,10 @@ public interface FileUpdateMonitor {
      * @param path The path to remove.
      */
     void removeListener(Path path, FileUpdateListener listener);
+
+    /**
+     * Indicates whether or not the native system's file monitor has successfully started.
+     * @return True is process is running; false otherwise.
+     */
+    boolean isActive();
 }

src/main/java/org/jabref/model/util/WatchServiceUnavailableException.java

@@ -0,0 +1,9 @@
+package org.jabref.model.util;
+
+import org.jabref.JabRefException;
+
+public class WatchServiceUnavailableException extends JabRefException {
+    public WatchServiceUnavailableException(final String message, final String localizedMessage, final Throwable cause) {
+        super(message, localizedMessage, cause);
+    }
+}

src/main/resources/l10n/JabRef_en.properties

@@ -1,3 +1,4 @@
+Unable\ to\ monitor\ file\ changes.\ Please\ close\ files\ and\ processes\ and\ restart.\ You\ may\ encounter\ errors\ if\ you\ continue\ with\ this\ session.=Unable to monitor file changes. Please close files and processes and restart. You may encounter errors if you continue with this session.
 %0\ contains\ the\ regular\ expression\ <b>%1</b>=%0 contains the regular expression <b>%1</b>
 
 %0\ contains\ the\ term\ <b>%1</b>=%0 contains the term <b>%1</b>