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Event time #84

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becketqin
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@JasonSongHoho
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你好，已经看过贵翻译，基本表述出了原文的意思。但部分语句还不够通顺和准确，麻烦参考以下两篇博客修改下吧（他们翻译和理解的也不一定准确）。
1.https://www.jianshu.com/p/68ab40c7f347
2.https://blog.csdn.net/yanghua_kobe/article/details/72953921

@becketqin
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@JasonSongHoho 谢谢review。可否在你觉得有问题的具体地方加comments？笼统的对几篇文章对比可操作性有点低。

@xccui
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xccui commented Nov 9, 2018

hello，刚好我也在看这篇译文，有些comments还在斟酌，稍候会给出

xccui
xccui reviewed Nov 9, 2018
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非常感谢@becketqin老师的翻译，评论里分享了一些个人的想法，不当之处请秦老师指出。

dev/event_time.md Outdated
在实际情况中，可能会出现有一些记录在水印标记到达后才到达，这意味着即便一个标记时间戳为t的水印watermark(t)到达后，
还会有时间戳t’（t’ <= t）的记录到达。事实上，在很多现实设定中，某些记录可能会在任意晚的时间到达，对这些记录，就不
可能给定一个保证所有记录都已到达的水印时间，此外，即便迟到的程度有上限，延迟太长时间发送一个水印通常都不是用户想要
看到的，因为这会导致一个窗口的计算结果也被延迟很长时间。
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因为这会导致时间窗口被延迟很久才触发计算？

dev/event_time.md Outdated
arrive after the system's event time clock (as signaled by the watermarks) has already passed the time of the late element's
timestamp. See [Allowed Lateness]({{ site.baseurl }}/dev/stream/operators/windows.html#allowed-lateness) for more information on how to work
with late elements in event time windows.
由于这个原因，流处理总是会预期一些迟到的记录，也就是那些在系统事件时间（以水印为记号）已经过了记录中的事件时间。在
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预期->收到？

dev/event_time.md Outdated


## Debugging Watermarks
## 定位水印问题
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定位->调试？

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Please refer to the [Debugging Windows & Event Time]({{ site.baseurl }}/monitoring/debugging_event_time.html) section for debugging
watermarks at runtime.
请参考定位[窗口和事件时间](https://github.com/flink-china/1.6.0/blob/master/monitoring/debugging_event_time.md)的部分以了解更多关于如何
在运行时定位水印的内容。
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->调试水印相关问题？

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<img src="{{ site.baseurl }}/fig/parallel_streams_watermarks.svg" alt="Parallel data streams and operators with events and watermarks" class="center" width="80%" />
下图展示了算子是如何根据在数据流中流经的事件和水印来更新其事件时间时钟的。
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parallel没体现出来？

dev/event_time.md Outdated

Internally, *ingestion time* is treated much like *event time*, but with automatic timestamp assignment and
automatic watermark generation.
下面这个例子展示了一个以每小时作为时间窗对事件进行聚合的Flink程序。其中时间窗的行为适应于时间特性。
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其中时间窗口的行为取决于设置的时间特性？

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注意为了使用事件时间，这个程序要么需要直接定义事件时间并且自己发出水印，要么需要在数据源后植入一个时间戳指定器和
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注意后面加个逗号？
这个程序->上述程序？

dev/event_time.md Outdated
that directly define event time for the data and emit watermarks themselves, or the program must
inject a *Timestamp Assigner & Watermark Generator* after the sources. Those functions describe how to access
the event timestamps, and what degree of out-of-orderness the event stream exhibits.
下面的这个部分表述了一个在时间戳和水印背后的通用机制。关于如何使用Flink DataStream API打时间戳以及生成水印，
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表述->介绍？

dev/event_time.md Outdated
For example, a window operator that builds hourly windows needs to be notified when event time has passed beyond the
end of an hour, so that the operator can close the window in progress.
一个支持*事件时间*的流处理器需要一种能够衡量*事件时间*进度的方法。比如一个基于小时的时间窗口操作，它需要在*事件
时间*处理超过了一个小时的结束时刻被通知，这样它才能据此关闭正在进行的时间窗口。
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时间窗口操作->时间窗口算子？
*事件时间*处理超过了一个小时的结束时刻被通知，这样它才能……->*事件时间*一小时结束后收到通知，并据此关闭……

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<img src="{{ site.baseurl }}/fig/stream_watermark_in_order.svg" alt="A data stream with events (in order) and watermarks" class="center" width="65%" />
下图展示了一个带有逻辑时间戳的事件流，其中含有水印。这个例子中所有的事件都是有序的（根据时间戳排序），也就是说水印
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下图展示了一个带有逻辑时间戳的事件流，其中含有水印->下图展示了一个带有逻辑时间戳和包含水印的事件流？

@JasonSongHoho
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这篇文章是流计算比较核心的概念，两位大佬辛苦了👍

@becketqin
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@xccui 谢谢这么仔细的review。修改以后的确通顺多了。

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@becketqin @JasonSongHoho @xccui