Flink 中延时消息处理_在flink sql中延迟写入-优快云博客

该文章探讨了Flink中的ProcessFunction，它是如何处理输入流中的单个元素并允许用户定义状态和定时器的。同时，文章详细解释了Wartermark机制在处理乱序事件中的作用，以及Window如何基于时间或事件进行数据分组和聚合。通过对这两个概念的理解，读者可以更好地掌握Flink的时间语义和流处理能力。

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1 ProcessFunction

public abstract class ProcessFunction<I, O> extends AbstractRichFunction {

    private static final long serialVersionUID = 1L;

    /**
     * Process one element from the input stream.
     *
     * <p>This function can output zero or more elements using the {@link Collector} parameter and
     * also update internal state or set timers using the {@link Context} parameter.
     *
     * @param value The input value.
     * @param ctx A {@link Context} that allows querying the timestamp of the element and getting a
     *     {@link TimerService} for registering timers and querying the time. The context is only
     *     valid during the invocation of this method, do not store it.
     * @param out The collector for returning result values.
     * @throws Exception This method may throw exceptions. Throwing an exception will cause the
     *     operation to fail and may trigger recovery.
     */
    public abstract void processElement(I value, Context ctx, Collector<O> out) throws Exception;

    /**
     * Called when a timer set using {@link TimerService} fires.
     *
     * @param timestamp The timestamp of the firing timer.
     * @param ctx An {@link OnTimerContext} that allows querying the timestamp of the firing timer,
     *     querying the {@link TimeDomain} of the firing timer and getting a {@link TimerService}
     *     for registering timers and querying the time. The context is only valid during the
     *     invocation of this method, do not store it.
     * @param out The collector for returning result values.
     * @throws Exception This method may throw exceptions. Throwing an exception will cause the
     *     operation to fail and may trigger recovery.
     */
    public void onTimer(long timestamp, OnTimerContext ctx, Collector<O> out) throws Exception {}

}

Flink中延时调用设计与实现 - 知乎