Package org.odpi.openmetadata.adapters.connectors.liskov

Class SurveySchedule

java.lang.Object

org.odpi.openmetadata.adapters.connectors.liskov.SurveySchedule

public class SurveySchedule
extends Object

Decides whether a survey of a data store is due.

A data store that has never been surveyed is surveyed straight away. After that, the interval between surveys starts at the minimum interval and grows by a day each time a survey finds no change since the survey before it, up to the maximum interval. As soon as a survey finds a change, the interval drops back to the minimum and the cycle repeats. With the default limits, a data store that keeps changing is surveyed daily, and one that has stopped changing is surveyed after 1 day, then 2, then 3 and so on up to once a week.

Nothing about the schedule is stored. It is worked out from the survey history each time it is needed, so it survives a restart of the integration daemon. The history is only consulted when the answer depends on it - never before the minimum interval has passed, never once the maximum has, and otherwise only as far back as the time since the latest survey requires.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	SurveySchedule.ChangeDetector	Compares one survey with the survey before it.
static final record	SurveySchedule.Decision	The outcome of decide(java.util.Date, int, org.odpi.openmetadata.adapters.connectors.liskov.SurveySchedule.ChangeDetector, long): whether a survey is due, and why.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_MAXIMUM_INTERVAL_DAYS	The default maximum number of days between surveys.
static final int	DEFAULT_MINIMUM_INTERVAL_DAYS	The default minimum number of days between surveys.

Constructor Summary

Constructors

Constructor	Description
SurveySchedule(int minimumIntervalDays, int maximumIntervalDays)	Constructor.

Method Summary

Modifier and Type	Method	Description
SurveySchedule.Decision	decide(Date latestSurveyTime, int completedSurveyCount, SurveySchedule.ChangeDetector changeDetector, long now)	Determine whether a survey is due, and why - see isSurveyDue(java.util.Date, int, org.odpi.openmetadata.adapters.connectors.liskov.SurveySchedule.ChangeDetector, long).
int	getCompletedSurveysNeeded()	Return the largest number of completed surveys, most recent first, that isSurveyDue(java.util.Date, int, org.odpi.openmetadata.adapters.connectors.liskov.SurveySchedule.ChangeDetector, long) can need to look at.
int	getMaximumIntervalDays()	Return the most days between surveys.
int	getMinimumIntervalDays()	Return the fewest days between surveys.
boolean	isSurveyDue(Date latestSurveyTime, int completedSurveyCount, SurveySchedule.ChangeDetector changeDetector, long now)	Determine whether a survey is due.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_MINIMUM_INTERVAL_DAYS

public static final int DEFAULT_MINIMUM_INTERVAL_DAYS

The default minimum number of days between surveys.

See Also:

• Constant Field Values

DEFAULT_MAXIMUM_INTERVAL_DAYS

public static final int DEFAULT_MAXIMUM_INTERVAL_DAYS

The default maximum number of days between surveys.

See Also:

• Constant Field Values

Constructor Details

SurveySchedule

public SurveySchedule(int minimumIntervalDays,
 int maximumIntervalDays)

Constructor. A negative minimum is treated as zero, and a maximum below the minimum as the minimum.

Parameters:

minimumIntervalDays - fewest days between surveys

maximumIntervalDays - most days between surveys

Method Details

getMinimumIntervalDays

public int getMinimumIntervalDays()

Return the fewest days between surveys.

Returns:

number of days

getMaximumIntervalDays

public int getMaximumIntervalDays()

Return the most days between surveys.

Returns:

number of days

getCompletedSurveysNeeded

public int getCompletedSurveysNeeded()

Return the largest number of completed surveys, most recent first, that isSurveyDue(java.util.Date, int, org.odpi.openmetadata.adapters.connectors.liskov.SurveySchedule.ChangeDetector, long) can need to look at. A caller retrieving the survey history need not retrieve any more than this.

Returns:

number of completed surveys

isSurveyDue

public boolean isSurveyDue(Date latestSurveyTime,
 int completedSurveyCount,
 SurveySchedule.ChangeDetector changeDetector,
 long now)
                    throws InvalidParameterException,
PropertyServerException,
UserNotAuthorizedException

Determine whether a survey is due.

The interval is the minimum plus a day for each of the most recent surveys in a row that found no change, up to the maximum. So with d whole days since the latest survey, the survey is due unless each of the latest (d - minimum + 1) completed surveys found no change since the one before it. The comparisons stop at the first change. A completed survey with no completed survey before it to compare with counts as a change, because there is no evidence yet that the data store is stable.

Parameters:

latestSurveyTime - when the latest survey started - completed or not - or null if there has never been one. Measuring from the latest attempt means a survey that keeps failing is retried at the minimum interval rather than on every refresh.

completedSurveyCount - number of completed surveys available to the change detector

changeDetector - compares a completed survey with the one before it

now - the current time in milliseconds

Returns:

true if a survey should be requested

Throws:

InvalidParameterException - the parameters are invalid

PropertyServerException - problem accessing the property server

UserNotAuthorizedException - user is not authorized to issue this request

decide

public SurveySchedule.Decision decide(Date latestSurveyTime,
 int completedSurveyCount,
 SurveySchedule.ChangeDetector changeDetector,
 long now)
                               throws InvalidParameterException,
PropertyServerException,
UserNotAuthorizedException

Determine whether a survey is due, and why - see isSurveyDue(java.util.Date, int, org.odpi.openmetadata.adapters.connectors.liskov.SurveySchedule.ChangeDetector, long).

Parameters:

latestSurveyTime - when the latest survey started - completed or not - or null if there has never been one

completedSurveyCount - number of completed surveys available to the change detector

changeDetector - compares a completed survey with the one before it

now - the current time in milliseconds

Returns:

decision and the reason for it

Throws:

InvalidParameterException - the parameters are invalid

PropertyServerException - problem accessing the property server

UserNotAuthorizedException - user is not authorized to issue this request