IfFlapping (Resin 4.0.s170329)

java.lang.Object
- com.caucho.health.predicate.AbstractHealthPredicate
- - com.caucho.health.predicate.AbstractScheduledHealthPredicate
  - - com.caucho.health.predicate.AbstractHealthCheckPredicate
    - - com.caucho.health.predicate.IfFlapping

All Implemented Interfaces:

HealthPredicate
```
@Configurable
public class IfFlapping
extends AbstractHealthCheckPredicate
```
Qualifies an action to match only when the health check status is flapping.
Flapping occurs when a health check changes state too frequently. This can serve as convenient filter for nuisance actions, as well as a useful indicator of real issues that would otherwise be hard to detect.
IfFlapping scans recent historical data for state changes to calculate a weighted percent change. By default, recent state changes are weighted more than older changes. This predicate matches if the overall weighted percent change exceeds a threshold.
Note: Use <health:Not> predicate for filtering.
```
 <health:HttpStatusHealthCheck ee:Named="httpStatusCheck">
   <url>http://localhost:8080/test-ping.jsp</url>
 </health:HttpStatusHealthCheck>
 
 <health:Restart>
   <health:IfHealthCritical healthCheck="${httpStatusCheck}"/>
   <health:Not>
    <health:IfFlapping healthCheck="${httpStatusHealthCheck}"/>
  </health:Not>
 </health:Restart> 
 
```

Constructor Summary

Constructors
Constructor and Description

IfFlapping()

IfFlapping(HealthCheck healthCheck)

Constructors
Constructor and Description
`IfFlapping()`
`IfFlapping(HealthCheck healthCheck)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`static double`	`calculatePercentChange(StatServiceValue[] data, double lowWeight, double highWeight)`
`double`	`getHighWeight()` Returns the high weight (most recent)
`double`	`getLowWeight()` Returns the low weight (least recent)
`int`	`getSampleSize()` Returns the minimum sample size before attempting to detect flapping.
`double`	`getThreshold()` Returns the weighted percent change that must be exceeded to detect flapping, as a floating point number between 0 and 1.
`void`	`init()`
`protected boolean`	`isFlapping(HealthService healthService, HealthCheck healthCheck, long sampleId)`
`boolean`	`isMatch(HealthEvent healthEvent)` Match if calculated weighted percent change exceeds the threshold
`void`	`setHighWeight(double highWeight)` Newer state changes can be weighted more than older changes.
`void`	`setLowWeight(double lowWeight)` Older state changes can be weighted less than more recent changes.
`void`	`setSampleSize(int sampleSize)` The minimum number of samples required before attempting to detect flapping.
`void`	`setThreshold(double threshold)` Flapping is detected when the calculated weighted percent change exceeds this threshold,

Methods inherited from class com.caucho.health.predicate.AbstractHealthCheckPredicate
getHealthCheck, getLastResult, setHealthCheck, toString

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - IfFlapping
```
public IfFlapping()
```
  - IfFlapping
```
public IfFlapping(HealthCheck healthCheck)
```
- Method Detail
  - init
```
@PostConstruct
public void init()
```
  - getSampleSize
```
public int getSampleSize()
```
    Returns the minimum sample size before attempting to detect flapping.
  - setSampleSize
```
@Configurable
public void setSampleSize(int sampleSize)
```
    The minimum number of samples required before attempting to detect flapping. Assuming the default health system check period of 5 minutes, a minimum of 1 hour and 45 minutes of data collection is required.
    
    Parameters:
    
    sampleSize - minimum number of samples, default 21
  - getThreshold
```
public double getThreshold()
```
    Returns the weighted percent change that must be exceeded to detect flapping, as a floating point number between 0 and 1.
  - setThreshold
```
@Configurable
public void setThreshold(double threshold)
```
    Flapping is detected when the calculated weighted percent change exceeds this threshold,
    
    Parameters:
    
    threshold - percent change threshold as a floating point number between 0 and 1, default 0.5 (approximate 50% of samples, adjusted depending on weight)
  - getLowWeight
```
public double getLowWeight()
```
    Returns the low weight (least recent)
  - setLowWeight
```
@Configurable
public void setLowWeight(double lowWeight)
```
    Older state changes can be weighted less than more recent changes.
    
    Parameters:
    
    lowWeight - The starting weight (least recent), default .75
  - getHighWeight
```
public double getHighWeight()
```
    Returns the high weight (most recent)
  - setHighWeight
```
@Configurable
public void setHighWeight(double highWeight)
```
    Newer state changes can be weighted more than older changes.
    
    Parameters:
    
    highWeight - The ending weight, default 1.25
  - isMatch
```
public boolean isMatch(HealthEvent healthEvent)
```
    Match if calculated weighted percent change exceeds the threshold
    
    Specified by:
    
    isMatch in interface HealthPredicate
    
    Overrides:
    
    isMatch in class AbstractScheduledHealthPredicate
  - isFlapping
```
protected boolean isFlapping(HealthService healthService,
                             HealthCheck healthCheck,
                             long sampleId)
```
  - calculatePercentChange
```
public static double calculatePercentChange(StatServiceValue[] data,
                                            double lowWeight,
                                            double highWeight)
```

Class IfFlapping

Constructor Summary

Method Summary

Methods inherited from class com.caucho.health.predicate.AbstractHealthCheckPredicate

Methods inherited from class java.lang.Object

Constructor Detail

IfFlapping

IfFlapping

Method Detail

init

getSampleSize

setSampleSize

getThreshold

setThreshold

getLowWeight

setLowWeight

getHighWeight

setHighWeight

isMatch

isFlapping

calculatePercentChange