yangyichao-mango commented on a change in pull request #12665:
URL: https://github.com/apache/flink/pull/12665#discussion_r456855949
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File path: docs/dev/event_timestamps_watermarks.zh.md
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@@ -175,200 +137,243 @@ withTimestampsAndWatermarks
</div>
</div>
+使用 `WatermarkStrategy` 去获取流并生成带有时间戳的元素和 watermark 的新流时，如果原始流已经具有时间戳或
watermark，则新指定的时间戳分配器将覆盖原有的时间戳和 watermark。
-#### **With Periodic Watermarks**
+## 处理空闲数据源
-`AssignerWithPeriodicWatermarks` assigns timestamps and generates watermarks
periodically (possibly depending
-on the stream elements, or purely based on processing time).
+如果数据源中的某一个分区/分片在一段时间内未发送事件数据，则意味着 `WatermarkGenerator` 也不会获得任何新数据去生成
watermark。我们称这类数据源为*空闲输入*或*空闲源*。在这种情况下，当某些其他分区仍然发送事件数据的时候就会出现问题。由于下游算子
watermark 的计算方式是取所有不同的上游并行数据源 watermark 的最小值，则其 watermark 将不会发生变化。
-The interval (every *n* milliseconds) in which the watermark will be generated
is defined via
-`ExecutionConfig.setAutoWatermarkInterval(...)`. The assigner's
`getCurrentWatermark()` method will be
-called each time, and a new watermark will be emitted if the returned
watermark is non-null and larger than the previous
-watermark.
+为了解决这个问题，你可以使用 `WatermarkStrategy` 来检测空闲输入并将其标记为空闲状态。`WatermarkStrategies`
为此提供了一个工具接口：
-Here we show two simple examples of timestamp assigners that use periodic
watermark generation. Note that Flink ships with a
`BoundedOutOfOrdernessTimestampExtractor` similar to the
`BoundedOutOfOrdernessGenerator` shown below, which you can read about
[here]({{ site.baseurl
}}/dev/event_timestamp_extractors.html#assigners-allowing-a-fixed-amount-of-lateness).
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+{% highlight java %}
+WatermarkStrategies
+ .<Tuple2<Long, String>>forBoundedOutOfOrderness(Duration.ofSeconds(20))
+ .withIdleness(Duration.ofMinutes(1))
+ .build();
+{% endhighlight %}
+</div>
+<div data-lang="scala" markdown="1">
+{% highlight scala %}
+WatermarkStrategies
+ .forBoundedOutOfOrderness[(Long, String)](Duration.ofSeconds(20))
+ .withIdleness(Duration.ofMinutes(1))
+ .build()
+{% endhighlight %}
+</div>
+</div>
+
+
+## 自定义 WatermarkGenerator
+
+`TimestampAssigner` 是一个可以从事件数据中提取时间戳字段的简单函数，我们无需详细查看其实现。但是
`WatermarkGenerator` 的编写相对就要复杂一些了，我们将在接下来的两小节中介绍如何实现此接口。WatermarkGenerator
接口代码如下：
+
+{% highlight java %}
+/**
+ * The {@code WatermarkGenerator} generates watermarks either based on events
or
Review comment:
Hi,
这里的注释也是源码注释。
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