在项目中memcache服务之间缓存同步时出现阻塞的原因

public boolean delete(String key, Integer hashCode, Date expiry,boolean isReply) {

        if (key == null) {
            log.error("null value for key passed to delete()");
            return false;
        }

        try {
            key = sanitizeKey(key);
        } catch (UnsupportedEncodingException e) {

            // if we have an errorHandler, use its hook
            if (errorHandler != null)
                errorHandler.handleErrorOnDelete(this, e, key);

            log.error("failed to sanitize your key!", e);
            return false;
        }

        // get SockIO obj from hash or from key
        SchoonerSockIO sock = pool.getSock(key, hashCode);

        // return false if unable to get SockIO obj
        if (sock == null) {
            if (errorHandler != null)
                errorHandler.handleErrorOnDelete(this, new IOException("no socket to server available"), key);
            return false;
        }

        // build command
        StringBuilder command = new StringBuilder("delete ").append(key);
        if (expiry != null)
            command.append(" " + expiry.getTime() / 1000);
       
        /**如果不要需要用到服务器返回的结果最好是加上noreply
         * 这样服务器之间同步缓存的时候就不会出现线程阻塞的情况**/
        if(!isReply){
            command.append(" noreply");
        }
        command.append("\r\n");

        try {
            sock.write(command.toString().getBytes());
           
            //判断是否需要服务器返回结果
            if(!isReply){
                return true;
            }
           
            // if we get appropriate response back, then we return true
            // get result code
            String line = new SockInputStream(sock, Integer.MAX_VALUE).getLine();
            if (DELETED.equals(line)) { // successful
                if (log.isDebugEnabled())
                    log.debug(new StringBuffer().append("++++ deletion of key: ").append(key)
                            .append(" from cache was a success").toString());
                return true;
            } else if (NOTFOUND.equals(line)) { // key not found
                if (log.isDebugEnabled())
                    log.debug(new StringBuffer().append("++++ deletion of key: ").append(key)
                            .append(" from cache failed as the key was not found").toString());
            } else { // other error information
                log.error(new StringBuffer().append("++++ error deleting key: ").append(key).toString());
                log.error(new StringBuffer().append("++++ server response: ").append(line).toString());
            }
        } catch (IOException e) {

            // if we have an errorHandler, use its hook
            if (errorHandler != null)
                errorHandler.handleErrorOnDelete(this, e, key);

            // exception thrown
            log.error("++++ exception thrown while writing bytes to server on delete");
            log.error(e.getMessage(), e);

            try {
                sock.sockets.invalidateObject(sock);
            } catch (Exception e1) {
                log.error("++++ failed to close socket : " + sock.toString());
            }

            sock = null;
        } finally {
            if (sock != null) {
                sock.close();
                sock = null;
            }
        }

        return false;
    }