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ostore.dispatch
Class Resender

java.lang.Object
  |
  +--ostore.dispatch.Resender
public class Resender
extends Object

A utility class that automatically re-dispatches events.

If an attempt to dispatch an event throws a SinkFullException, the Resender schedules the event for a later attempt and returns a unique, opaque token. That token can be used later to confirm or cancel delivery.

NOTE: A Resender does not guarantee any delivery order for events which are initially delayed. If in-order delivery is important, do not use the automatic re-dispatching features, or avoid this class completely.

Any stage which uses a Resender must Signal.register(int, java.lang.String, seda.sandStorm.api.SinkIF) for Signal.ALRM signals targetted at the name given to the Resender constructor. The Resender will set its own alarms; the stage must catch the resulting AlarmSignals and call process_queues().

Version:
$Id: Resender.java,v 1.14 2004/03/23 03:08:59 hweather Exp $
Author:
Dennis Geels

Constructor Summary
Resender(NodeId node_id, String stage_name)
          Creates a new Resender object that uses the default Classifier for the specified machine.
Resender(NodeId node_id, String stage_name, boolean debug)
          Creates a new Resender object that uses the default Classifier for the specified machine.
 
Method Summary
 QueueElementIF cancel(Object token)
          Cancels the specified event.
 QueueElementIF[] clear(boolean all)
          Cancels all events which have timed out.
 Object dispatch(QueueElementIF event)
          Dispatches an event through the Classifier.
 Object dispatch(QueueElementIF event, int num_retries, long millis)
          Dispatch the specified event, making at most num_retries additional attempts, waiting millis milliseconds in between attempts.
 boolean pending(Object token)
          Checks whether the specified event is scheduled for further attempts.
 void process_queues()
          Processes the queue of pending events, sending any whose deadlines have been reaced.
 Object remember(QueueElementIF event, long millis)
          Waits millis milliseconds, then stores the event in the trash pile.
 Object remember(QueueElementIF event, long millis, Map map, Object key)
          Waits millis milliseconds, then stores the event in the trash pile.
 Object remember(QueueElementIF event, long millis, Map map, Set keys)
          Waits millis milliseconds, then stores the event in the trash pile.
 Object resend(QueueElementIF event, int num_retries, long millis)
          Repeatedly dispatches the specified event, num_retries times, waiting millis milliseconds in between attempts.
 Object resend(QueueElementIF event, int num_retries, long millis, Map map, Object key)
          Repeatedly dispatches the specified event, num_retries times, waiting millis milliseconds in between attempts.
 Object resend(QueueElementIF event, int num_retries, long millis, Map map, Set keys)
          Repeatedly dispatches the specified event, num_retries times, waiting millis milliseconds in between attempts.
 Object send(QueueElementIF event, long millis)
          Dispatches the specified event, waits millis milliseconds, then stores the event in the trash pile.
 Object send(QueueElementIF event, long millis, Map map, Object key)
          Dispatches the specified event, waits millis milliseconds, then stores the event in the trash pile.
 Object send(QueueElementIF event, long millis, Map map, Set keys)
          Dispatches the specified event, waits millis milliseconds, then stores the event in the trash pile.
 boolean timed_out(Object token)
          Checks whether the specified event was been successfully dispatched.
 boolean was_sent(Object token)
          Checks whether the specified event has been successfully dispatched.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Resender

public Resender(NodeId node_id,
                String stage_name)
Creates a new Resender object that uses the default Classifier for the specified machine.

Parameters:
node_id - The ID for this machine - needed to locate the correct Classifier and Signal.
stage_name - The name of the calling stage - needed to address AlarmSignals properly.

Resender

public Resender(NodeId node_id,
                String stage_name,
                boolean debug)
Creates a new Resender object that uses the default Classifier for the specified machine.

Parameters:
node_id - The ID for this machine - needed to locate the correct Classifier and Signal.
stage_name - The name of the calling stage - needed to address AlarmSignals properly.
Method Detail

process_queues

public void process_queues()
Processes the queue of pending events, sending any whose deadlines have been reaced.

This method should be called each time the stage receives an AlarmSignal.

dispatch

public Object dispatch(QueueElementIF event)
Dispatches an event through the Classifier.

If the dispatch fails, the event is stored in a trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Parameters:
event - Any event to dispatch
Returns:
a token, used to reference the event later, or null if the object was successfully dispatched.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

dispatch

public Object dispatch(QueueElementIF event,
                       int num_retries,
                       long millis)
Dispatch the specified event, making at most num_retries additional attempts, waiting millis milliseconds in between attempts.

After enough attempts have failed, the event is stored in a trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Parameters:
event - Any event to dispatch
num_retries - The number (>=0) of times to try dispatching the event if the initial attempt fails.
millis - The number of milliseconds to wait after each attempt.
Returns:
a token, used to reference the event later, or null if the object was successfully dispatched on the first try.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF), resend(seda.sandStorm.api.QueueElementIF, int, long), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

resend

public Object resend(QueueElementIF event,
                     int num_retries,
                     long millis)
Repeatedly dispatches the specified event, num_retries times, waiting millis milliseconds in between attempts.

After enough attempts have failed, the event is stored in a trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike dispatch(seda.sandStorm.api.QueueElementIF, int, long), this method resends the event even if it dispatches correctly. It is therefore slightly more expensive and should be used only when these semantics are required.

Parameters:
event - Any event to dispatch
num_retries - The number (>=0) of times to try dispatching the event if the initial attempt fails.
millis - The number of milliseconds to wait after each attempt.
Returns:
a token, used to reference the event later.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

resend

public Object resend(QueueElementIF event,
                     int num_retries,
                     long millis,
                     Map map,
                     Object key)
Repeatedly dispatches the specified event, num_retries times, waiting millis milliseconds in between attempts.

After enough attempts have failed, the event is stored in a trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike dispatch(seda.sandStorm.api.QueueElementIF, int, long), this method resends the event even if it dispatches correctly. It is therefore slightly more expensive and should be used only when these semantics are required.

Parameters:
event - Any event to dispatch
num_retries - The number (>=0) of times to try dispatching the event if the initial attempt fails.
millis - The number of milliseconds to wait after each attempt.
map - Map used to record state by the stage
key - Key to store token in the map.
Returns:
a token, used to reference the event later.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

resend

public Object resend(QueueElementIF event,
                     int num_retries,
                     long millis,
                     Map map,
                     Set keys)
Repeatedly dispatches the specified event, num_retries times, waiting millis milliseconds in between attempts.

After enough attempts have failed, the event is stored in a trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike dispatch(seda.sandStorm.api.QueueElementIF, int, long), this method resends the event even if it dispatches correctly. It is therefore slightly more expensive and should be used only when these semantics are required.

Parameters:
event - Any event to dispatch
num_retries - The number (>=0) of times to try dispatching the event if the initial attempt fails.
millis - The number of milliseconds to wait after each attempt.
map - Map used to record state by the stage
keys - Set of keys to store the same token in the map.
Returns:
a token, used to reference the event later.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

send

public Object send(QueueElementIF event,
                   long millis)
Dispatches the specified event, waits millis milliseconds, then stores the event in the trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike dispatch(seda.sandStorm.api.QueueElementIF, int, long), this method remembers the event even if it dispatches correctly.

Unlike resend(seda.sandStorm.api.QueueElementIF, int, long), this method does not try to resend the event. Use that method instead if the event may be lost (e.g. a NetworkMessage) and duplicate messages are acceptable.

Parameters:
event - Any event to dispatch
millis - The number of milliseconds to wait before trashing the event.
Returns:
a token, used to reference the event later.
See Also:
resend(seda.sandStorm.api.QueueElementIF, int, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

send

public Object send(QueueElementIF event,
                   long millis,
                   Map map,
                   Object key)
Dispatches the specified event, waits millis milliseconds, then stores the event in the trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike dispatch(seda.sandStorm.api.QueueElementIF, int, long), this method remembers the event even if it dispatches correctly.

Unlike resend(seda.sandStorm.api.QueueElementIF, int, long), this method does not try to resend the event. Use that method instead if the event may be lost (e.g. a NetworkMessage) and duplicate messages are acceptable.

Parameters:
event - Any event to dispatch
millis - The number of milliseconds to wait before trashing the event.
map - Map used to record state by the stage
key - Key to store token in the map.
Returns:
a token, used to reference the event later.
See Also:
resend(seda.sandStorm.api.QueueElementIF, int, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

send

public Object send(QueueElementIF event,
                   long millis,
                   Map map,
                   Set keys)
Dispatches the specified event, waits millis milliseconds, then stores the event in the trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike dispatch(seda.sandStorm.api.QueueElementIF, int, long), this method remembers the event even if it dispatches correctly.

Unlike resend(seda.sandStorm.api.QueueElementIF, int, long), this method does not try to resend the event. Use that method instead if the event may be lost (e.g. a NetworkMessage) and duplicate messages are acceptable.

Parameters:
event - Any event to dispatch
millis - The number of milliseconds to wait before trashing the event.
map - Map used to record state by the stage
keys - Set of keys to store same token in the map.
Returns:
a token, used to reference the event later.
See Also:
resend(seda.sandStorm.api.QueueElementIF, int, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

remember

public Object remember(QueueElementIF event,
                       long millis)
Waits millis milliseconds, then stores the event in the trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike the other methods, this one never tries to send the event. It is provided as a convenient interface to the internal timeout support.

Parameters:
event - Any event to remember
millis - The number of milliseconds to wait before trashing the event.
Returns:
a token, used to reference the event later.
See Also:
resend(seda.sandStorm.api.QueueElementIF, int, long), send(seda.sandStorm.api.QueueElementIF, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

remember

public Object remember(QueueElementIF event,
                       long millis,
                       Map map,
                       Object key)
Waits millis milliseconds, then stores the event in the trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike the other methods, this one never tries to send the event. It is provided as a convenient interface to the internal timeout support.

Parameters:
event - Any event to remember
millis - The number of milliseconds to wait before trashing the event.
map - Map used to record state by the stage
key - Key to store token in the map.
Returns:
a token, used to reference the event later.
See Also:
resend(seda.sandStorm.api.QueueElementIF, int, long), send(seda.sandStorm.api.QueueElementIF, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

remember

public Object remember(QueueElementIF event,
                       long millis,
                       Map map,
                       Set keys)
Waits millis milliseconds, then stores the event in the trash pile. Events on the trash pile can be recovered by the clear(boolean) method.

Unlike the other methods, this one never tries to send the event. It is provided as a convenient interface to the internal timeout support.

Parameters:
event - Any event to remember
millis - The number of milliseconds to wait before trashing the event.
map - Map used to record state by the stage
keys - Set of keys to store the same token in the map.
Returns:
a token, used to reference the event later.
See Also:
resend(seda.sandStorm.api.QueueElementIF, int, long), send(seda.sandStorm.api.QueueElementIF, long), cancel(Object), Classifier.dispatch(seda.sandStorm.api.QueueElementIF)

cancel

public QueueElementIF cancel(Object token)
Cancels the specified event. All state relating to the pending event is removed from the Resender. If the event has already dispatched successfully, this method does nothing.

Parameters:
token - A token returned by dispatch(seda.sandStorm.api.QueueElementIF).
Returns:
the event, if it has not yet been dispatched successfully, otherwise null.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long)

timed_out

public boolean timed_out(Object token)
Checks whether the specified event was been successfully dispatched.

Parameters:
token - A token returned by dispatch(seda.sandStorm.api.QueueElementIF).
Returns:
true iff the event has timed out.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long)

pending

public boolean pending(Object token)
Checks whether the specified event is scheduled for further attempts.

Parameters:
token - A token returned by dispatch(seda.sandStorm.api.QueueElementIF).
Returns:
true iff the event is on the queue for another attempted dispatch.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long)

was_sent

public boolean was_sent(Object token)
Checks whether the specified event has been successfully dispatched.

Equivalent to ( !pending(token) && !timed_out(token) ).

Parameters:
token - A token returned by dispatch(seda.sandStorm.api.QueueElementIF).
Returns:
true iff the Resender no longer has any memory of the token, which implies that the event was previously dispatched.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long)

clear

public QueueElementIF[] clear(boolean all)
Cancels all events which have timed out. If all == true, also cancels all pending events.

Parameters:
all - true iff pending events should also be cancelled.
Returns:
an array containing all cancelled events.
See Also:
dispatch(seda.sandStorm.api.QueueElementIF, int, long), cancel(java.lang.Object)
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