#vulnerable code 
                                @Override
    protected void releaseSub() {
        if (transceiver != null) {
            try {
                transceiver.close();
            } catch (final IOException ioe) {
                LOGGER.error("Attempt to clean up Avro transceiver failed", ioe);
            }
        }
        client = null;
    } 
                            #location 5 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    protected void releaseSub() {
        if (rpcClient != null) {
            try {
                rpcClient.close();
            } catch (final Exception ex) {
                LOGGER.error("Attempt to close RPC client failed", ex);
            }
        }
        rpcClient = null;
    }