Dispatcher (LSST CCS - Messaging Layer 6.0.3 API)

All Known Implementing Classes:

AbstractDispatcher, LegacyDispatcher, MultiQueueDispatcher
```
public interface Dispatcher
```
Task dispatcher that decouples MessagingLayer implementation (currently, JGroups) from CCS messaging framework. MessagingLayer submits executable tasks (either message processing or disconnection notifications) through the in(...) method. CCS framework submits message sending tasks through the out(...) method.
All implementations should provide public constructor that takes String[] parameter. This is a way to supply configuration parameters through the protocol string passed to TransportManager. Implementations should be thread-safe, methods of this interface can be called on any thread.
Dispatcher collects statistics on task processing that can be retrieved thorough its getters. Some implementations might not provide all types of statistics. In that case, corresponding getters will return 0.

Author:

onoprien

Nested Class Summary

Nested Classes
Modifier and Type	Interface and Description
`static class`	`Dispatcher.Order` Enumeration of order of execution and capacity control policies.
`static class`	`Dispatcher.Stage` Enumeration of task execution stages for which statistical data can be reported.
`static class`	`Dispatcher.Stat` Enumeration of statistics.
`static interface`	`Dispatcher.Status`
`static interface`	`Dispatcher.StatusListener` Interface to be implemented by classes that should by notified of status changes.
`static interface`	`Dispatcher.Task`

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`void`	`addStatusListener(Dispatcher.StatusListener listener)` Registers status listener.
`Dispatcher.Status`	`getStatus()` Returns statistics and diagnostic data on the current state of this `Dispatcher`.
`void`	`in(Runnable task, Bus bus, String... agents)` Submits a task to process an incoming message or disconnection notification.
`default void`	`initialize()` Initializes this dispatcher.
`void`	`out(Runnable task, Bus bus, Dispatcher.Order order)` Submits a task to process an outgoing message.
`void`	`removeStatusListener(Dispatcher.StatusListener listener)` Removes status listener.
`default void`	`shutdown()` Orderly shuts down this dispatcher.

- Method Detail
  - initialize
```
default void initialize()
```
    Initializes this dispatcher.
  - shutdown
```
default void shutdown()
```
    Orderly shuts down this dispatcher. The MessagingLayer will not be closed until this method returns.
  - in
```
void in(Runnable task,
        Bus bus,
        String... agents)
```
    Submits a task to process an incoming message or disconnection notification. Depending on the implementation, this method may return immediately or after the task has been executed.
    If one or more agent names are given, the task if guaranteed to be executed after any previously submitted tasks for the same bus and agent. If no agents are specified, the task is independent of other tasks, subject to capacity controls imposed by the implementation of this service. If the agents argument is null, the task is independent of other tasks, not subject to capacity controls.
    Calling this method has no effect if this Dispatcher has not been initialized or it has been shut down. No exceptions are thrown in this case.
    
    Parameters:
    
    task - Task to be executed.
    
    bus - Bus (LOG, STATUS, or COMMAND).
    
    agents - Names of affected agents (source or disconnected).
    
    Throws:
    
    TransportStateException - If this Dispatcher is unable to accept the request for reasons other than being uninitialized or shut down.
  - out
```
void out(Runnable task,
         Bus bus,
         Dispatcher.Order order)
```
    Submits a task to process an outgoing message. Depending on the implementation, this method may return immediately or after the task has been executed.
    Tasks submitted with outOfBand equal to false for the same bus are guaranteed to be processed in the order of submission. If outOfBand equals true, the task is executed independently of others, subject to capacity controls imposed by the implementation of this service. If outOfBand equals null, the task is independent, not subject to capacity controls.
    
    Parameters:
    
    task - Task to be executed.
    
    bus - Bus (LOG, STATUS, or COMMAND).
    
    order - Order of execution and capacity control policies.
    
    Throws:
    
    TransportStateException - If this Dispatcher is unable to accept the request, typically either because it has not been initialized or because it has been shut down.
  - getStatus
```
Dispatcher.Status getStatus()
```
    Returns statistics and diagnostic data on the current state of this Dispatcher. Implementations of Status returned by specific implementations of Dispatcher may provide additional data. The object returned by this method should be treated as immutable. It reflects the latest recorded state and will not be updated.
    
    Returns:
    
    Dispatcher status, or null if not available.
  - addStatusListener
```
void addStatusListener(Dispatcher.StatusListener listener)
```
    Registers status listener. The listener will be notified whenever an updated status becomes available.
    
    Parameters:
    
    listener - Listener to add.
  - removeStatusListener
```
void removeStatusListener(Dispatcher.StatusListener listener)
```
    Removes status listener.
    
    Parameters:
    
    listener - Listener to remove.

Interface Dispatcher

Nested Class Summary

Method Summary

Method Detail

initialize

shutdown

in

out

getStatus

addStatusListener

removeStatusListener