FLINK CEP（Java 8）通过匹配模式持久化“身份”

Question

我试图使用FLINK-CEP来衡量市场中的出价从BidState.OPEN到BidState.Closed所花费的时间。我收到了一个带有ID和状态的投标数据流，目前我正在将所有“开放”投标与所有“关闭”投标进行匹配

我在patternStream.process中有一个条件，它只允许使用相同ID的开标和收盘报价配对，就像它们应该配对一样。但这感觉是错误的，因为匹配的数量以这种方式以难以置信的速度增长，我有一种感觉，这可以通过模式来完成。那么，有没有办法确保“开始”和“结束”对象具有相同的ID

AfterMatchSkipStrategy skipStrategy = AfterMatchSkipStrategy.noSkip();
//Is it possible to make sure that start.BidID == end.BidID in the pattern?
Pattern<BidEvent, ?> pattern = Pattern.<BidEvent>begin("start", skipStrategy).where(
        new SimpleCondition<BidEvent>() {
            @Override
            public boolean filter(BidEvent value) {
                return value.getState() == BidState.OPENED;
            }
        }).followedByAny("end").where(
        new SimpleCondition<BidEvent>() {
            @Override
            public boolean filter(BidEvent value) throws Exception {
                return value.getState() == BidState.CLOSED; // && value.getBidID == start.getBidID?
            }
        }).within(timeout);

PatternStream<BidEvent> patternStream = CEP.pattern(BidEventDataStream, pattern);

patternStream.process(new PatternProcessFunction<BidEvent, MatchingDuration>() {
    @Override
    public void processMatch(Map<String
            , List<BidEvent>> map
            , Context context
            , Collector<MatchingDuration> collector) {

        BidEvent start = map.get("start").get(0);
        BidEvent end = map.get("end").get(0);
        if (start.getBidId() == end.getBidId()){ // Make sure opening and closing bid is the same. Can this be done in the pattern?
            collector.collect(new MatchingDuration(start.getBidId(), (end.getTimestamp() - start.getTimestamp())));
        }
    }
}).addSink(matchingDurationSinkFunction);

Answer 1

我想出了如何获得我想要的行为：必须为BidEventDataStream设置键，以便在具有相同键的对象上进行模式匹配。问题中的代码无需更改，但必须编辑BidEventDataStream以捕获BidEvent.getBidId()：

BidEventDataStream.keyBy(new KeySelector<BidEvent, Long>() {
                    @Override
                    public Long getKey(BidEventvalue) {
                        return value.getBidId();
                    }
                })