gistfile1.txt

  @Test
  public void testTransactionIsCanceledAfterServerUpdate()
      throws InterruptedException, ExecutionException {
    // This test reproduces https://github.com/firebase/firebase-admin-java/issues/178:
    //
    // If we run two transactions (one at "path/nested1" and one at "path"), the SDK did not
    // correctly re-run the "path" transaction if it got an update from the server for
    // "path/nested2". This caused the "path" transaction to succeed on the server
    // (our hash included the update from the server), merging stale data.
    final DatabaseReference ref = IntegrationTestUtils.getRandomNode(masterApp);
    ref.getDatabase().goOffline();

    // Write data to the backend from a secondary instance. The primary instance receives this data
    // when it goes online during the first transaction.
    FirebaseApp secondaryApp = IntegrationTestUtils.initApp("secondaryApp");
    DatabaseReference initialData =
        FirebaseDatabase.getInstance(secondaryApp).getReference(ref.getKey());
    initialData.setValueAsync(new MapBuilder().put("a", "a").build()).get();
    secondaryApp.delete();

    final Semaphore semaphore = new Semaphore(0);

    ref.child("b").runTransaction(new Handler() {
      @Override
      public Result doTransaction(MutableData currentData) {
        ref.getDatabase().goOnline();
        currentData.setValue("b");
        return Transaction.success(currentData);
      }

      @Override
      public void onComplete(DatabaseError error, boolean committed, DataSnapshot currentData) {
        Assert.assertTrue(committed);
        semaphore.release();
      }
    });

    ref.runTransaction(new Handler() {
      @Override
      public Result doTransaction(MutableData currentData) {
        currentData.child("c").setValue("c");
        return Transaction.success(currentData);
      }

      @Override
      public void onComplete(DatabaseError error, boolean committed, DataSnapshot currentData) {
        Assert.assertTrue(committed);
        semaphore.release();
      }
    });

    TestHelpers.waitFor(semaphore, 2);

    DataSnapshot dataSnapshot = TestHelpers.getSnap(ref);
    assertEquals(3, dataSnapshot.getChildrenCount());
  }