BackgroundTask interrupted when shutting down JabRef

[LoayGhreeb]

I want to close the Lucene IndexWriter when the library is closed or when JabRef shuts down. The index should be closed in the background because writing commits to the disk takes time.

Which method should be used for submitting background tasks? All Lucene indexing runs in the background using org.jabref.gui.util.BackgroundTask, but for closing the index, I used org.jabref.logic.util.HeadlessExecutorService.

• If I use org.jabref.logic.util.HeadlessExecutorService#INSTANCE.execute(), it works without any interruptions, and JabRef waits until the closing task is finished: https://github.com/LoayGhreeb/jabref/blob/ab5388f026e32f860c11f2ff21886a0848f0b0cd/src/main/java/org/jabref/logic/search/indexing/DefaultLinkedFilesIndexer.java#L339-L357
• If I use org.jabref.gui.util.BackgroundTask#executeWith to close the index, the task gets interrupted when it takes some time.

          BackgroundTask.wrap(() -> {
              try {
                  LOGGER.debug("Closing linked files index");
                  searcherManager.close();
                  optimizeIndex();
                  indexWriter.close();
                  indexDirectory.close();
                  LOGGER.debug("Linked files index closed");
                  if (databaseContext.getFulltextIndexPath().getFileName().toString().equals("unsaved")) {
                      LOGGER.debug("Deleting unsaved index directory");
                      FileUtils.deleteDirectory(indexDirectoryPath.toFile());
                  }
              } catch (IOException e) {
                  LOGGER.error("Error while closing linked files index", e);
              }
          }).executeWith(taskExecutor);
      }

Stack trace

``` [pool-2-thread-3] org.jabref.logic.search.indexing.DefaultLinkedFilesIndexer.optimizeIndex() WARN: Could not force merge segments.: java.nio.channels.ClosedChannelException at java.base/sun.nio.ch.FileLockImpl.release(FileLockImpl.java:58) at java.base/java.nio.channels.FileLock.close(FileLock.java:336) at org.apache.lucene.core@9.11.0/org.apache.lucene.store.NativeFSLockFactory$NativeFSLock.close(NativeFSLockFactory.java:195) at org.apache.lucene.core@9.11.0/org.apache.lucene.util.IOUtils.close(IOUtils.java:85) at org.apache.lucene.core@9.11.0/org.apache.lucene.util.IOUtils.close(IOUtils.java:72) at org.apache.lucene.core@9.11.0/org.apache.lucene.index.IndexWriter.rollbackInternalNoCommit(IndexWriter.java:2559) at org.apache.lucene.core@9.11.0/org.apache.lucene.index.IndexWriter.rollbackInternal(IndexWriter.java:2464) at org.apache.lucene.core@9.11.0/org.apache.lucene.index.IndexWriter.maybeCloseOnTragicEvent(IndexWriter.java:5774) at org.apache.lucene.core@9.11.0/org.apache.lucene.index.IndexWriter.doFlush(IndexWriter.java:4321) at org.apache.lucene.core@9.11.0/org.apache.lucene.index.IndexWriter.flush(IndexWriter.java:4255) at org.apache.lucene.core@9.11.0/org.apache.lucene.index.IndexWriter.forceMerge(IndexWriter.java:2128) at org.jabref@100.0.0/org.jabref.logic.search.indexing.DefaultLinkedFilesIndexer.optimizeIndex(DefaultLinkedFilesIndexer.java:332) at org.jabref@100.0.0/org.jabref.logic.search.indexing.DefaultLinkedFilesIndexer.lambda$close$5(DefaultLinkedFilesIndexer.java:344) at org.jabref@100.0.0/org.jabref.gui.util.BackgroundTask$2.call(BackgroundTask.java:91) at org.jabref@100.0.0/org.jabref.gui.util.BackgroundTask$2.call(BackgroundTask.java:88) at org.jabref@100.0.0/org.jabref.gui.util.UiTaskExecutor$1.call(UiTaskExecutor.java:173) at javafx.graphics@22.0.1/javafx.concurrent.Task$TaskCallable.call(Task.java:1399) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) at java.base/java.lang.Thread.run(Thread.java:1583) ```

@koppor, please take a look when you are available. Refs: https://github.com/JabRef/jabref-issue-melting-pot/issues/443

[koppor]

https://github.com/jobrunr/jobrunr could be tried as another framework 😅🙈. Refs https://github.com/JabRef/jabref-issue-melting-pot/issues/460

[koppor]

I want to close the Lucene IndexWriter when the library is closed or when JabRef shuts down. The index should be closed in the background because writing commits to the disk takes time.

And it is OK to not show any progress in the UI?

As far as I understand the PR https://github.com/JabRef/jabref/pull/11385, there was some renaming to distinguish between UI and nonUI (called "headless").

As far as I understand your options and pros and cons, I think, calling HeadlessExecutorService is the right choice? We accept that no progress is shown in the UI. Nevertheless, there should be a LOGGER.info be called at the start and at the end. Sometimes, JabRef hangs during exiting (refs https://github.com/JabRef/jabref/pull/11430) and it should be "easy" to trace which component hangs.