IndexWriter iw = new IndexWriter(indexDir.getAbsolutePath(), analyzer, false);

DataNode aNode = ... ;
synchronized (LOCK) {
    try {
        indexWriter = createFulltextIndexWriter();
                ... do modifications and save node, update index
        indexWriter.close();

    } finally {
        try {
            indexWriter.close();
        } catch (Throwable e2) {
        }
    }
}

private static final Object LOCK = new Object();