BoxStore: also print threads where objectbox appears in a class name #258

Author: greenrobot-team

objectbox-java/src/main/java/io/objectbox/BoxStore.java

@@ -82,6 +82,8 @@ public class BoxStore implements Closeable {
 
     /** The ObjectBox database version this Java library is known to work with. */
     private static final String VERSION = "4.3.1-2025-08-02";
+
+    private static final String OBJECTBOX_PACKAGE_NAME = "objectbox";
     private static BoxStore defaultStore;
 
     /** Currently used DB dirs with values from {@link #getCanonicalPath(File)}. */
@@ -753,28 +755,43 @@ private void checkThreadTermination() {
             if (!internalThreadPool().awaitTermination(1, TimeUnit.SECONDS)) {
                 getErrorOutput().println("ObjectBox thread pool not terminated in time." +
                         " Ensure all async calls have completed and subscriptions are cancelled before closing the Store." +
-                        "\nPrinting pool threads...");
+                        "\nDumping stack traces of threads on the pool and any using ObjectBox APIs:" +
+                        "\n=== BEGIN OF DUMP ===");
                 // Note: this may not print any pool threads if other threads are started while enumerating
                 // (and the pool threads do not make it into the threads array).
                 Thread[] threads = new Thread[Thread.activeCount()];
                 int count = Thread.enumerate(threads);
                 for (int i = 0; i < count; i++) {
                     Thread thread = threads[i];
-                    if (thread.getName().startsWith(ObjectBoxThreadPool.THREAD_NAME_PREFIX)) {
+                    if (shouldDumpThreadStackTrace(thread)) {
                         getErrorOutput().println("Thread: " + thread.getName());
                         StackTraceElement[] trace = thread.getStackTrace();
                         for (StackTraceElement traceElement : trace) {
                             getErrorOutput().println("\tat " + traceElement);
                         }
                     }
                 }
-                getErrorOutput().println("Printing pool threads...DONE");
+                getErrorOutput().println("=== END OF DUMP ===");
             }
         } catch (InterruptedException e) {
             e.printStackTrace(getErrorOutput());
         }
     }
 
+    private boolean shouldDumpThreadStackTrace(Thread thread) {
+        // Dump any threads of the internal thread pool
+        if (thread.getName().startsWith(ObjectBoxThreadPool.THREAD_NAME_PREFIX)) return true;
+
+        // Any other thread might be blocking a thread on the internal pool, so also dump any that appear to use
+        // ObjectBox APIs.
+        StackTraceElement[] trace = thread.getStackTrace();
+        for (StackTraceElement traceElement : trace) {
+            if (traceElement.getClassName().contains(OBJECTBOX_PACKAGE_NAME)) return true;
+        }
+
+        return false;
+    }
+
     /**
      * Danger zone! This will delete all data (files) of this BoxStore!
      * You must call {@link #close()} before and read the docs of that method carefully!

tests/objectbox-java-test/src/test/java/io/objectbox/BoxStoreLogTest.java

@@ -28,6 +28,7 @@
 
 
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 /**
  * Sets a custom error output stream to assert log messages of {@link BoxStore}.
@@ -65,13 +66,23 @@ public void close_activeThreadPool_printsError() throws UnsupportedEncodingExcep
 
         String errOutput = this.errOutput.toString("UTF-8");
         assertTrue(errOutput.contains("ObjectBox thread pool not terminated in time"));
-        assertTrue(errOutput.contains("Printing pool threads..."));
-        assertTrue(errOutput.contains("Printing pool threads...DONE"));
-        // Check that only ObjectBox threads are printed
+        assertTrue(errOutput.contains("=== BEGIN OF DUMP ==="));
+        assertTrue(errOutput.contains("=== END OF DUMP ==="));
+        // Check that only pool threads or threads with stack traces that contain the objectbox package are printed
         String[] lines = errOutput.split("\n");
+        String checkStackTrace = null;
         for (String line : lines) {
             if (line.startsWith("Thread:")) {
-                assertTrue("Expected thread name to start with 'ObjectBox-' but was: " + line, line.contains("ObjectBox-"));
+                if (checkStackTrace != null) {
+                    fail("Expected stack trace to contain class in objectbox package");
+                }
+                if (!line.contains("ObjectBox-")) {
+                    checkStackTrace = line;
+                }
+            } else if (checkStackTrace != null) {
+                if (line.contains("objectbox")) {
+                    checkStackTrace = null;
+                }
             }
         }
     }