ARTEMIS-2837 Bursts of open files under high load

This would prevent to push a new opened file if there
is already one available to be consumed

artemis-journal/src/main/java/org/apache/activemq/artemis/core/journal/impl/JournalFilesRepository.java

@@ -88,6 +88,8 @@ public class JournalFilesRepository {
    private final Runnable pushOpenRunnable = new Runnable() {
       @Override
       public void run() {
+         // if there's already an opened file there is no need to push a new one
+         if (openedFiles.isEmpty()) {
             try {
                pushOpenedFile();
             } catch (Exception e) {
@@ -95,6 +97,7 @@ public class JournalFilesRepository {
                fileFactory.onIOError(e, "unable to open ", null);
             }
          }
+      }
    };
 
    public JournalFilesRepository(final SequentialFileFactory fileFactory,
@@ -444,12 +447,12 @@ public class JournalFilesRepository {
          pushOpen();
 
          nextFile = openedFiles.poll(journalFileOpenTimeout, TimeUnit.SECONDS);
-      }
-
+      } else {
          if (openedFiles.isEmpty()) {
             // if empty, push to open one.
             pushOpen();
          }
+      }
 
       if (nextFile == null) {
 

tests/unit-tests/src/test/java/org/apache/activemq/artemis/tests/unit/core/journal/impl/JournalImplTestUnit.java

@@ -117,6 +117,31 @@ public abstract class JournalImplTestUnit extends JournalImplTestBase {
       stopJournal();
    }
 
+   @Test
+   public void testFlushAppendsAndDeletes() throws Exception {
+      setup(10, 10 * 1024, true);
+      createJournal();
+      startJournal();
+      load();
+      byte[] record = new byte[1000];
+      for (int i = 0; i < record.length; i++) {
+         record[i] = (byte) 'a';
+      }
+      // Appending records after restart should be valid (not throwing any
+      // exceptions)
+      for (int i = 0; i < 10_000; i++) {
+         journal.appendAddRecord(i, (byte) 1, new SimpleEncoding(2, (byte) 'a'), false);
+         journal.appendDeleteRecord(i, false);
+      }
+      stopJournal();
+
+      List<String> files = fileFactory.listFiles(fileExtension);
+
+      // I am allowing one extra as a possible race with pushOpenFiles. I have not seen it happening on my test
+      // but it wouldn't be a problem if it happened
+      Assert.assertTrue("Supposed to have up to 10 files", files.size() <= 11);
+   }
+
    @Test
    public void testParams() throws Exception {
       try {