pool.java

private ConcurrentHashMap<String, TNonblockingTransport> open_connections = new ConcurrentHashMap<String, TNonblockingTransport>();
private ConcurrentHashMap<String, KeyValueService.AsyncClient> open_clients = new ConcurrentHashMap<String, KeyValueService.AsyncClient>();

private TNonblockingTransport getConnection(Integer server) throws TException, IOException {
    String threadKey = server.toString() + Thread.currentThread().getId();
    if(open_connections.containsKey(threadKey))
        return open_connections.get(threadKey);

    String host = StorageNode.hosts.get(server);
    Integer port = StorageNode.ports.get(server);

    TNonblockingTransport transport = new TNonblockingSocket(host, port);

    open_connections.put(threadKey, transport);
    return transport;
}

private KeyValueService.AsyncClient getClient(Integer server, TNonblockingTransport transport) throws IOException {
    String threadKey = server.toString() + Thread.currentThread().getId();
    if(open_clients.containsKey(threadKey))
        return open_clients.get(threadKey);

    TAsyncClientManager clientManager = new TAsyncClientManager();
    TProtocolFactory protocolFactory = new TBinaryProtocol.Factory();
    KeyValueService.AsyncClient client = new KeyValueService.AsyncClient(protocolFactory, clientManager, transport);

    open_clients.put(threadKey, client);
    return client;
}

// somewhere else
try {
    // use the client
} catch { // client is dead
    // remove client from open_clients
}