esper

Esper: How to configure Esper to connect a Relational Database, through a JDBC, using Esper's configuration API

由 ￡可爱￡侵袭症＋ 提交于 2019-12-13 04:57:56
问题 I would like to know how a java client application that is using Esper's engine (v5.0.0) may configure engine instance so he can to connect to a relation database, say pgSQL. This is essential to write EPL queries capable to join event streams (or data stream) with static/historic data from a database (5.13. Accessing Relational Data via SQL). That is, to Read from a database. (Write to a database requires the usage of a EsperIO adapter.) From Esper's docs I figure out that Configuration and

Esper data loss when inbound threading is enabled

由 不羁岁月 提交于 2019-12-11 15:14:01
问题 I found data loss in Esper (v.7.1.0) in case if inbound thread pool is enabled. Here is simple example that demonstrates this strange behaviour: Configuration config = new Configuration(); // set up concurrent processing config.getEngineDefaults().getThreading().setThreadPoolInbound(true); EPServiceProvider epService = EPServiceProviderManager.getDefaultProvider(config); // simple schema epService.getEPAdministrator().createEPL("create objectarray schema LogLine as (account_name string, value

Esper - detect absence of a certain event

由 ▼魔方 西西 提交于 2019-12-11 14:34:50
问题 is it possible to detect the absence of a certain event type within a given time window without using any other event types in Esper? Thanx ;) 回答1: You can take a look at the solution patterns here for some ideas: http://www.espertech.com/esper/solution-patterns#absence-1 Here is an adapted example of detecting an absence of an event, after it has been fired once: select * from pattern [every EventX -> (timer:interval(10 sec) and not EventX)]; This will fire only once, if after an EventX is

Generating a deduplicated event stream without a window

由 耗尽温柔 提交于 2019-12-11 09:11:11
问题 I'm trying to generate a stream of deduplicated events without specifying any window policy beyond that used for the deduplication. Using an output first every clause on my queries appears to have the desired effect, but not when those queries are inserting directly into a stream. For the example given below, say that I'm trying to detect only the first honk from each car in a 4-hour window. (define-event-type! "CarEvent" {:license_plate java.lang.String}) (define-event-type! "HonkEvent" {

The concept groupwin is like the unaligned windows?

由 守給你的承諾、 提交于 2019-12-11 04:36:30
问题 groupwin I use the meaning in esper: This view groups events into sub-views by the value returned by the specified expression or the combination of values returned by a list of expressions. I think it is that you have the ability to operate by group,not stream(the group by is used to control how aggregations are grouped.) unaligned window In google's dataflow ,unaligned windows means: By unaligned windows, we mean windows which do not span the entirety of a data source, but instead only a

Storm Cluster Duplicate Tuples

由 ↘锁芯ラ 提交于 2019-12-06 10:09:14
问题 Currently I am working on a project where I have setup a Storm cluster across four Unix hosts. The topology itself is as follows: JMS Spout listens to an MQ for new messages JMS Spout parses and then emits the result to an Esper Bolt The Esper Bolt then processes the event and emits a result to a JMS Bolt The JMS Bolt then publishes the message back onto the MQ on a different topic I realize that Storm is a "at least-once" framework. However, if I receive 5 events and pass these onto the

Esper学习笔记四：EPL语法（2）

由 馋奶兔 提交于 2019-12-06 02:53:57
1.select 查询所有属性或特定属性 EPL的select和SQL的select很相近，SQL用*表示查询表的所有字段，而EPL用*表示查询事件流的所有属性值。SQL查询某个字段名，直接在select后跟字段名就ok，EPL也是将要查询的属性名放在select之后。若查多个属性值，则用逗号分割。和SQL一样，EPL查询属性也可以设置别名。 //EPL:查询所有属性 select * from myEvent //在监听器中获取完整对象 MyEvent me = (MyEvent)eb.getUnderlying(); // EPL：查询MyEvent的name和age，age别名为a select name,age as a from myEvent //在监听器中获取查询属性 String name = (String)eb.get("name"); Integer a = (Integer)eb.get("a"); 表达式 除了查询完整对象和属性外，EPL还支持属性值的计算，以计算的值作为结果返回。 // 计算长方形的面积（长乘以宽） select length * width as area from Rectangle 除了简单的加减乘除，还可以利用事件流对象的某个方法 // 计算长方形的面积（长乘以宽） select r.getArea(r.length,r

Esper学习笔记二：进程模型

由 被刻印的时光 ゝ 提交于 2019-12-06 02:53:45
1.UpdateListener UpdaterListener是Esper提供的一个接口，用于监听某个EPL在引擎中的运行情况，即事件进入并产生结果后会通知UpdateListener。 接口如下： package com.espertech.esper.client; import com.espertech.esper.client.EventBean; public interface UpdateListener { public void update(EventBean[] newEvents, EventBean[] oldEvents); } 接口中就包含一个update方法，该方法有两个参数newEvents和oldEvents。两个参数均是EventBean数组。EventBean中有一个最常用的get方法用户获取EPL中字段的值。 //EPL语句 select name,age,avg(age) as avgAge from myEvent eventBean.get("name")//获取name属性 eventBean.get("age")//获取age属性 eventBean.get("avgAge")//获取平均年龄属性 2.Insert 和 Remove insert表示进入引擎，remove表示移除引擎

Esper学习笔记三：EPL语法（1）

由 六眼飞鱼酱① 提交于 2019-12-06 02:53:35
1.EPL语法简介 EPL全称Event Processing Language，是一种类似SQL的语言，包含了SELECT, FROM, WHERE, GROUP BY, HAVING 和 ORDER BY子句，同时用事件流代替了table作为数据源，并且能像SQL那样join，filtering和aggregation。除了select，EPL也有insert into，update，delete，不过含义和SQL并不是很接近。另外还有pattern和output子句，这两个是SQL所没有的。EPL还定义了一个叫view的东西，类似SQL的table，来决定哪些数据是可用的，Esper提供了十多个view，并且保证这些view可以被重复使用。而且用户还可以扩展view成为自定义view来满足需求。在view的基础上，EPL还提供了named window的定义，作用和view类似，但是更加灵活。 2.语法 大部分EPL语句都遵循以下格式 [annotations] [expression_declarations] [context context_name] [insert into insert_into_def] select select_list from stream_def [as name] [, stream_def [as name]] [,...]

Esper学习笔记五：EPL语法（3）

由 纵饮孤独 提交于 2019-12-05 06:47:04
1.Aggregation 类似于SQL中的聚合函数，EPL中聚合函数格式如下： aggregate_function([all|distinct] expression) aggregate_function就是聚合函数的名字，比如avg，sum等。expression通常是事件流的某个属性，也可以是不同事件流的多个属性，或者是属性和常量、函数之间的运算。 // 查询最新5秒的Apple的平均价格 select avg(price) as aPrice from Apple.win:time(5 sec) // 查询最新10个Apple的价格总和的两倍 select sum(price*2) as sPrice from Apple.win:length(10) // 查询最新10个Apple的价格，并用函数计算后再算平均值 select avg(Compute.getResult(price)) from Apple.win:length(10) 函数只能是静态方法，普通方法不可用。即使是事件流里包含的静态方法，也必须用“类名.方法名”的方式进行引用。 可以使用distinct关键字对expression加以约束，表示去掉expression产生的重复的值。默认情况下为all关键字，即所有的expression值都参与聚合运算。 // 查询最新5秒的Apple的平均价格
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