- 在client 1.5之前，由于kudu客户端链接的token有效时间是7天，当时间大于7天的时候token失效，客户端不会主动去刷新token，导致写入数据报错；
解决办法：kudu-client 版本使用1.5以上的版本
- kudu数据flush的模式问题
AUTO_FLUSH_BACKGROUND：异步刷新可能会导致写入的时候乱序，因此有严格的顺序的写入操作可能要使用AUTO_FLUSH_SYNC模式
具体说明如下：
/**
* Each {@link KuduSession#apply KuduSession.apply()} call will return only after being
* flushed to the server automatically. No batching will occur.
*
* <p>In this mode, the {@link KuduSession#flush} call never has any effect, since each
* {@link KuduSession#apply KuduSession.apply()} has already flushed the buffer before
* returning.
*
* <p><strong>This is the default flush mode.</strong>
* 使用该模式的时候调用apply以后就直接flush，不回有批量flush的情况，该模式为默认模式
*/
AUTO_FLUSH_SYNC,
/**
* {@link KuduSession#apply KuduSession.apply()} calls will return immediately, but the writes
* will be sent in the background, potentially batched together with other writes from
* the same session. If there is not sufficient buffer space, then
* {@link KuduSession#apply KuduSession.apply()} may block for buffer space to be available.
*
* <p>Because writes are applied in the background, any errors will be stored
* in a session-local buffer. Call {@link #countPendingErrors() countPendingErrors()} or
* {@link #getPendingErrors() getPendingErrors()} to retrieve them.
*
* <p><strong>Note:</strong> The {@code AUTO_FLUSH_BACKGROUND} mode may result in
* out-of-order writes to Kudu. This is because in this mode multiple write
* operations may be sent to the server in parallel.
* See <a href="https://issues.apache.org/jira/browse/KUDU-1767">KUDU-1767</a> for more
* information.
*
* <p>The {@link KuduSession#flush()} call can be used to block until the buffer is empty.
* 1. 在该模式下，调用apply以后自动返回，写入是在后台异步进行。有可能会和同一个session里面其他的写入操作一起批量提交，如果buffer的
* 空间不够用的话apply会被阻塞直到有可用空间。
* 2.由于写入是后台异步操作，可以使用countPendingErrors（）或者getPendingErrors()来检索错误。
* 3. AUTO_FLUSH_BACKGROUND可能会导致写入的结果是乱序的，因为这个模式可能会并行写入服务器中。
*/
AUTO_FLUSH_BACKGROUND,
/**
* {@link KuduSession#apply KuduSession.apply()} calls will return immediately, but the writes
* will not be sent until the user calls {@link KuduSession#flush()}. If the buffer runs past
* the configured space limit, then {@link KuduSession#apply KuduSession.apply()} will return
* an error.
* apply以后会立即返回，写操作会在flush以后执行。如果缓冲超过了配置的大小，apply则会 报错 */ MANUAL_FLUSH