In the current implementation, a checkpoint only occurs when the NameNode starts up. Work is in progress to support periodic checkpointing in the near future.

在当前实现中，checkpoint只发生在Namenode启动时，在不久的将来我们将实现支持周期性的checkpoint。

youdao

Only those images that correspond to a consistent snapshot are written to the checkpoint file, and the row shadows allow the currently executing transactions to run unrestricted during checkpointing.

只有那些与一致性快照相符的镜像被写到检查点文件，行影子使当前执行的事务可以在检查点创建期间不受限制地运行。

youdao

This means a checkpoint at the primary server completes only after the checkpoint at the SD server completes.

这意味着只有在SD服务器中的检查点完成后，主服务器中的检查点才能完成。

youdao

On the seventh day of the race, Buser was first out of the checkpoint at Eagle Island, where a single cabin is the only dwelling in the otherwise uninhabited stretch of trail.

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