java - Drools:在一段时间内为组中的每个事实触发一个事件

Question

我正在尝试实现以下用例:如果具有相同属性的多个警报在 30 秒的时间间隔内到达，则需要触发单一根本原因警报。

我编写了代码，但它有两个缺点:

1. 它为组中计数 > 1 的每个到达的警报触发警报

2. 规则仅有效一次。如果我在一分钟后发送警报，规则不会触发。

   rule "fire rca when at least 2 events arrive in timeWindow"
   when
     $alert: AlertEvent(type == Type.RAISE, 
                  this.isPropertySet("elementSystemID"), 
                  ElementSystemID: alertProperties["elementSystemID"]
                  )
     accumulate(
       $a: AlertEvent(type == Type.RAISE,
             alertProperties["elementSystemID"] == ElementSystemID,
       ) over window:time(30s);
       $cnt: count($a);
       $cnt > 1 
     )
   then
     HashMap<String,Object> props = new HashMap<String,Object>();
   
     props.put(AlertConstants.DISPLAY_NAME, "RCA on port");
     props.put(AlertConstants.PERCEIVED_SEVERITY, 6);
     props.put(AlertConstants.ELEMENT_ID, $alert.getProperty("SystemID"));
   
     ruleActions.raiseAlert(props, "Alert raised");
   end
   

Answer 1

最好避免 window:time 并累积。

这是一个实用程序类:

public class Monitor {
    private final static long INTERVAL = 30*1000;
    private int sysId;
    private Date startTime;
    private int count = 1;
    public Monitor( int sysId, Date startTime ){
        this.sysId = sysId;
        this.startTime = startTime;
    }
    public int getSysId(){ return sysId; }
    public Date getStartTime(){ return startTime; }
    public void reset( Date startTime ){
        this.startTime = startTime;
        count = 1;
    }
    public int getCount(){ return count; }
    public void incCount(){ count++; }
    public boolean inInterval( Date t ){
        return (t.getTime() - startTime.getTime()) < INTERVAL;
    }
}

以下是规则 - 它们应该是不言自明的。

rule "new id"
when
    $ae: AlertEvent( $id: sysId )
    not Monitor( sysId == $id )
then
    retract( $ae );
    insert( new Monitor( $id, new Date() ) );
end

rule "same id, within interval, second"
when
    $ae: AlertEvent( $id: sysId, $ts: timestamp )
    $m: Monitor( sysId == $id, count == 1,
                 eval( $m.inInterval( $ts ) ) )
then
    retract( $ae );
    modify( $m ){ incCount() }
    System.out.println( "alarm for " + $id );
end

// This rule is redundant - just in case.
rule "same id, within interval, third or more"
when
    $ae: AlertEvent( $id: sysId, $ts: timestamp )
    $m:  Monitor( sysId == $id, count > 1,
                  eval( $m.inInterval( $ts ) ) )
then
    retract( $ae );
    modify( $m ){ incCount() }
end

rule "same id, not within interval"
when
    $ae: AlertEvent( $id: sysId, $ts: timestamp )
    $m: Monitor( sysId == $id,
                 eval( ! $m.inInterval( $ts ) ) )
then
    retract( $ae );
    modify( $m ){ reset( new Date() ) }
end