使用超时用 siddhi 编写 "arrived" 和 "departed" 查询

Question

我希望在我的应用程序中用 Siddhi 替换 Esper。现在的 esper 语句是一个“超时”类型模式，我需要在具有唯一“名称”和“类型”（我可以在传入事件中查找的字符串值）的事件到达和离开时报告。当事件第一次到达我的 firstunique window 时，我知道该事件已经到达，如果我没有看到任何同名事件并在用户定义的超时值中键入，我假设该事件已经结束。这是我的 esper 语句的样子（请注意，实际的 esper 中还有很多内容，我只是为了示例而简化了它）：

create window events_1.std:firstunique(name, type) as NameEvent

insert into events_1 select * from EventCycle[events]

on pattern [every event1=events_1->(timer:interval(4.0 sec) and not events_1(name=event1.name, type=event1.type))]delete from events_1 where name = event1.name AND type=event1.type

然后我 select 来自 events_1 的 irstream 并通过获取传入和删除的事件我然后从 window 获取“到达”和“离开”事件。

对于 siddhi，firstunique window 相当简单（我认为？）：

from EventCycle#window.firstUnique('name')[ type=='type' ] select name, type insert into NameEvent

但我真的对如何用 Siddhi 替换那个 esper “on pattern” 一无所知。我可以为此使用一个“from every”语句吗？还是我需要对 Siddhi 使用不同的方法？

任何帮助我走上正确道路的人都将不胜感激！

Answer 1

实现您的要求的一种方法是检查事件是否发生。恐怕，AFAIK，WSO2 CEP-3.1.0 不支持未发生检查。
然而，它在 WSO2 CEP-4.0.0 中得到支持（我在 2015 年 8 月 24 日撰写本文时尚未发布）。可以参考不发生检测样本[1].

解释：

这里，如果没有唯一事件发生，我们将离开第一个事件 4 秒（这是超时），因为最近的唯一事件已经发生。所以看起来我们需要检查事件是否发生。

在CEP 4.0.0中，您可以通过以下方式实现您的需求：

from EventCycle#window.firstUnique(name)[ type=='type' ] 
select name, type 
insert into NameEvents;     -- Note: I renamed NameEvent in the question to NameEvents

-- After seeing the latest unique event (Query-A), 4 seconds later (Query-B), we're checking if no unique event has occured in between (Query-C and Query-D). 
-- So, we're checking the non-occurance of an event here... See link [1] for a sample.

--Query-A
from EventCycle#window.unique(name)[ type=='type' ] 
select name, type 
insert into latestEvents;

-- Query-B
from latestEvents#window.time(4 seconds)    -- Here, I've taken 4 seconds as the timeout.
select *
insert expired events into timedoutEvents;

-- Query-C
from every latestEvent = latestEvents[ type=='type' ] ->
keepAliveEvent = latestEvents[ latestEvent.name == keepAliveEvent.name and type=='type' ] 
    or timedoutEvent = timedoutEvents[ latestEvent.name == timedoutEvent.name and type=='type' ]
select latestEvent.name as name, keepAliveEvent.name as keepAliveName
insert into filteredEvents;

-- Query-D
from filteredEvents [ isNull(keepAliveName)]  
select name
insert into departedLatestEvents;


-- Since we want the name from the NameEvents stream, we're joining it with the departedLatestEvents stream

from departedLatestEvents#window.length(1) as departedLatestEvent join 
NameEvents#window.length(1) as NameEvent 
on departedLatestEvent.name == NameEvent.name       -- not checking type as both departedLatestEvents and NameEvents have events only with type 'type'  
select NameEvent.name as name, 'type' as type
insert into departedFirstEvents;

Link 代码示例中引用：

1 https://docs.wso2.com/display/CEP400/Sample+0111+-+Detecting+non-occurrences+with+Patterns

希望对您有所帮助！

使用超时用 siddhi 编写 "arrived" 和 "departed" 查询

Writing an "arrived" and "departed" query with siddhi using timeouts

wso2

complex-event-processing

siddhi

wso2cep