uk.ac.starlink.ttools.cone

Class ConeErrorPolicy

java.lang.Object

uk.ac.starlink.ttools.cone.ConeErrorPolicy

public abstract class ConeErrorPolicy
extends Object

Defines how errors are treated during a multiple cone search operation. It also makes sure that interruptions are checked for, which is important to stop threads continuing to submit requests to remote services after the client no longer has any need for them.

Since:

24 Jan 2007

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static ConeErrorPolicy	ABORT An error during a cone search results in a failure of the task.
static ConeErrorPolicy	IGNORE Errors during cone searches are treated as if the search had returned with no results.
static ConeErrorPolicy	RETRY If an error occurs during a cone search it is retried until a non-error result is obtained.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ConeErrorPolicy(String name) Constructor.

Method Summary

Modifier and Type	Method and Description
static ConeErrorPolicy	createAdviceAbortPolicy(String name, String extraAdvice) Returns a policy like ABORT, except that if an error occurs, the IOException thrown is populated with some custom text.
static ConeErrorPolicy	createRetryPolicy(String name, int nTry) Constructs an error policy which will retry the search a fixed number of times.
abstract StarTable	performConeSearch(ConeSearcher cs, double ra, double dec, double sr) Uses the given cone searcher object to perform an actual cone search.
String	toString() Returns this object's name.

Methods inherited from class java.lang.Object

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

Field Detail

ABORT

public static final ConeErrorPolicy ABORT

An error during a cone search results in a failure of the task.

IGNORE

public static final ConeErrorPolicy IGNORE

Errors during cone searches are treated as if the search had returned with no results.

RETRY

public static final ConeErrorPolicy RETRY

If an error occurs during a cone search it is retried until a non-error result is obtained. Use with care.

Constructor Detail

ConeErrorPolicy

protected ConeErrorPolicy(String name)

Constructor.

Parameters:

name - policy name

Method Detail

toString

public String toString()

Returns this object's name.

Overrides:

toString in class Object

performConeSearch

public abstract StarTable performConeSearch(ConeSearcher cs,
                                            double ra,
                                            double dec,
                                            double sr)
                                     throws IOException,
                                            InterruptedException

Uses the given cone searcher object to perform an actual cone search. This may result in more than one call to the given cone searcher's performSearch method.

Implementations are expected to check for thread interruption status and throw an InterruptedException if interruption has happened. They should do this in such a way that the cone search query is not performed (especially multiple times) following an interruption.

Parameters:

cs - cone searcher providing basic cone search capabilities

ra - right ascension in degrees of search region centre

dec - declination in degrees of search region centre

sr - search radius in degrees

Returns:

table containing records in the given cone, or possibly null if no records are found

Throws:

IOException - if an IO error occurs

InterruptedException - if the thread was interrupted

See Also:

ConeSearcher.performSearch(double, double, double)

createRetryPolicy

public static ConeErrorPolicy createRetryPolicy(String name,
                                                int nTry)

Constructs an error policy which will retry the search a fixed number of times. A backing-off policy applies so that progressively longer delays are introduced between successive attempts following failure.

Parameters:

name - policy name

nTry - maximum number of attempts; if <=0 will retry indefinitely

Returns:

new error policy

createAdviceAbortPolicy

public static ConeErrorPolicy createAdviceAbortPolicy(String name,
                                                      String extraAdvice)

Returns a policy like ABORT, except that if an error occurs, the IOException thrown is populated with some custom text.

Parameters:

name - policy name

extraAdvice - advice to user in case of cone search failure

Returns:

new abort-like policy