org.lsst.ccs.messaging.util

Class AbstractDispatcher

java.lang.Object

org.lsst.ccs.messaging.util.AbstractDispatcher

All Implemented Interfaces:

Dispatcher

Direct Known Subclasses:

LegacyDispatcher, MultiQueueDispatcher

public abstract class AbstractDispatcher
extends Object
implements Dispatcher

Base class to facilitate implementing Dispatcher.

Functionality provided by this class:

• Handling of listeners. All events (including alerts) are delivered to listeners on a single dedicated thread.
• Registration and raising of alerts.
• Logging.
• Utility for parsing constructor parameters.
• Implementation of Dispatcher.Task that adds access to BusMessage and reference time, as well as empty callback implementation.

Author:

onoprien

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AbstractDispatcher.Task Instrumented Runnable for submission to Dispatcher.

Nested classes/interfaces inherited from interface org.lsst.ccs.messaging.util.Dispatcher

Dispatcher.AlertEvent, Dispatcher.Event, Dispatcher.Listener, Dispatcher.Order, Dispatcher.Stage

Field Summary

Fields

Modifier and Type	Field and Description
protected Map<String,Alert>	alerts Registered alerts.
protected HashMap<String,String>	config Configuration obtained from constructor argument string.
protected ScheduledExecutorService	serviceExec Executor for service tasks, including monitoring and listener notifications.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractDispatcher(String args) Constructs Dispatcher instance in specified configuration.

Method Summary

Modifier and Type	Method and Description
void	addListener(Dispatcher.Listener listener) Registers a listener.
protected void	deliverEvent(Dispatcher.Event event)
void	fireEvent(Dispatcher.Event event) Notifies listeners of the given event.
protected boolean	getBooleanArg(String key) Retrieves boolean configuration parameter value from the constructor argument.
protected int	getIntArg(String key, int defaultValue) Retrieves integer configuration parameter value from the constructor argument.
protected int[]	getIntArrayArg(String key, int[] defaultValue) Retrieves int[] configuration parameter value from the constructor argument.
protected int[]	getIntArrayArg(String key, int defaultValue, int length) Retrieves int[] configuration parameter value from the constructor argument.
Logger	getLogger() Returns a logger to be used for Dispatcher related messages.
List<Alert>	getRegisteredAlerts() Returns a set of alerts registered with this Dispatcher.
void	initialize() Initializes this dispatcher.
void	raiseAlert(Alert alert, AlertState severity, String cause) Notifies listeners by publishing an AlertEvent.
void	raiseAlert(String id, AlertState severity, String cause) Notifies listeners by publishing an AlertEvent.
void	registerAlert(Alert alert) Registers an alert with this Dispatcher.
void	removeListener(Dispatcher.Listener listener) Removes a listener.
void	shutdown() Orderly shuts down this dispatcher.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.lsst.ccs.messaging.util.Dispatcher

in, out

Field Detail

config

protected HashMap<String,String> config

Configuration obtained from constructor argument string. Used by get...Arg(...) methods.

serviceExec

protected final ScheduledExecutorService serviceExec

Executor for service tasks, including monitoring and listener notifications.

alerts

protected final Map<String,Alert> alerts

Registered alerts.

Constructor Detail

AbstractDispatcher

protected AbstractDispatcher(String args)

Constructs Dispatcher instance in specified configuration.

Parameters:

args - Configuration string in key[=value]&...&key[=value] format.

Method Detail

initialize

public void initialize()

Initializes this dispatcher. Empty implementation is provided by this class.

Specified by:

initialize in interface Dispatcher

shutdown

public void shutdown()

Orderly shuts down this dispatcher. Stops accepting tasks, executes previously submitted tasks, delivers events to listeners, then shuts down. The implementation provided by this class drains and shuts down the executor for service tasks.

Specified by:

shutdown in interface Dispatcher

addListener

public void addListener(Dispatcher.Listener listener)

Registers a listener.

Specified by:

addListener in interface Dispatcher

Parameters:

listener - Listener to add.

removeListener

public void removeListener(Dispatcher.Listener listener)

Removes a listener.

Specified by:

removeListener in interface Dispatcher

Parameters:

listener - Listener to remove.

fireEvent

public void fireEvent(Dispatcher.Event event)

Notifies listeners of the given event. This method is public to allow clients publish events through this Dispatcher.

Specified by:

fireEvent in interface Dispatcher

Parameters:

event -

deliverEvent

protected void deliverEvent(Dispatcher.Event event)

raiseAlert

public void raiseAlert(String id,
                       AlertState severity,
                       String cause)

Notifies listeners by publishing an AlertEvent. If an alert with matching id has not been registered, nothing is published.

Specified by:

raiseAlert in interface Dispatcher

Parameters:

id - Alert id.

severity - Alert severity.

cause - Message.

raiseAlert

public void raiseAlert(Alert alert,
                       AlertState severity,
                       String cause)

Notifies listeners by publishing an AlertEvent. An event is published even if an alert with matching id has not been registered.

Specified by:

raiseAlert in interface Dispatcher

Parameters:

alert - Alert instance.

severity - Alert severity.

cause - Message.

getRegisteredAlerts

public List<Alert> getRegisteredAlerts()

Returns a set of alerts registered with this Dispatcher.

Specified by:

getRegisteredAlerts in interface Dispatcher

Returns:

Registered alerts.

registerAlert

public void registerAlert(Alert alert)

Registers an alert with this Dispatcher.

Specified by:

registerAlert in interface Dispatcher

Parameters:

alert - Alert to add.

getLogger

public Logger getLogger()

Returns a logger to be used for Dispatcher related messages.

Specified by:

getLogger in interface Dispatcher

Returns:

Logger associated with this dispatcher.

getIntArg

protected final int getIntArg(String key,
                              int defaultValue)

Retrieves integer configuration parameter value from the constructor argument. This method should only be called inside constructor.

Parameters:

key - Parameter key.

defaultValue - Value to return if the argument strings do not provide value for the specified key.

Returns:

Parameter value.

Throws:

IllegalArgumentException - If the specified key exists but the corresponding value is not integer.

getBooleanArg

protected final boolean getBooleanArg(String key)

Retrieves boolean configuration parameter value from the constructor argument. This method should only be called inside constructor.

Parameters:

key - Parameter key.

Returns:

Parameter value.

getIntArrayArg

protected final int[] getIntArrayArg(String key,
                                     int defaultValue,
                                     int length)

Retrieves int[] configuration parameter value from the constructor argument. If the configuration string passed to the constructor did not contain the specified key, an array of the specified length with all elements equal to defaultValue is returned. This method should only be called inside constructor.

Parameters:

key - Parameter key.

defaultValue - Default value for all array elements.

length - Array length.

Returns:

Parameter value.

Throws:

IllegalArgumentException - If the given key exists but the corresponding value is not an integer array of the specified length.

getIntArrayArg

protected final int[] getIntArrayArg(String key,
                                     int[] defaultValue)

Retrieves int[] configuration parameter value from the constructor argument. If the configuration string passed to the constructor did not contain the specified key, defaultValue is returned. This method should only be called inside constructor.

Parameters:

key - Parameter key.

defaultValue - Default value. If empty, no constraints on the length of the array retrieved from the configuration string are enforced.

Returns:

Parameter value.

Throws:

IllegalArgumentException - If the given key exists but the corresponding value is not an integer array of the same length as defaultValue.