code: void onSealExclusive(Batch batch, long elapsedTimeMillis)
    {
      try {
        doOnSealExclusive(batch, elapsedTimeMillis);
      }
      catch (Throwable t) {
        try {
          if (!concurrentBatch.compareAndSet(batch, batch.batchNumber)) {
            log.error("Unexpected failure to set currentBatch to the failed Batch.batchNumber");
          }
          log.error(t, "Serious error during onSealExclusive(), set currentBatch to the failed Batch.batchNumber");
        }
        catch (Throwable t2) {
          t.addSuppressed(t2);
        }
        throw t;
      }
    }
docs: Called from {@link Batch} only once for each Batch in existence.