AgentStatusAggregator (LSST CCS Graphical User Interface 4.2.11 API)

java.lang.Object
- org.lsst.ccs.gconsole.services.aggregator.AgentStatusAggregator

```
public class AgentStatusAggregator
extends Object
```
Collects status data from local and remote agents and notifies clients of relevant changes. A singleton instance of this class is created by the graphical console.
For each Agent present on the buses, this aggregator obtains data dictionary and compiles the complete list of AgentChannel. Published data not present in the dictionary is ignored. If there are any listeners interested in a specific Agent, all channels for that Agent are kept up to date. If there are no such listeners, only "infrequently updated channels" are updated.
Listeners registered with this aggregator are notified of any changes in the channels they requested. See addListener(AgentStatusListener listener, AgentChannelsFilter filter) and addListener(AgentStatusListener listener, Collection agents, Collection channels) method descriptions for explanation of how filters, as well as explicit lists of agents and channels, are used to determine what events are delivered to each listener.
The aggregator modifies its state (in response to status messages received on the buses) and notifies listeners on a single dedicated thread. No new messages will be processed, and the aggregator state will not change, until all listeners process the current event. Listeners that need to perform any time consuming or potentially blocking operations should do that on other threads to avoid clogging the aggregator.
Methods that retrieve current status of agents and channels can be called on any thread - they are guaranteed to report consistent information that reflects the aggregator state that existed at some point between processing two consecutive status messages. There is no guarantee, however, that the aggregator will remain in that state by the time these methods return. There is also no guarantee that the state of the aggregator reflects the actual current state of an Agent, due to the asynchronous nature of message delivery and delays in processing.

Author:

onoprien

Constructor Summary

Constructors
Constructor and Description

AgentStatusAggregator()

Constructors
Constructor and Description
`AgentStatusAggregator()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addListener(AgentStatusListener listener, AgentChannelsFilter filter)` Adds a listener to be notified of changes in agents and channels specified by the filter.
`void`	`addListener(AgentStatusListener listener, Collection<String> agents, Collection<String> channels)` Adds a listener to be notified of changes in specified agents and data channels.
`org.lsst.ccs.bus.data.AgentInfo`	`getAgent(String agentName)` Return `AgentInfo` instance for the specified `Agent`.
`List<org.lsst.ccs.bus.data.AgentInfo>`	`getAgents()` Lists currently connected agents.
`org.lsst.ccs.bus.states.StateBundle`	`getAgentState(String agentName)` Returns the current state of the specified `Agent`.
`AgentChannel`	`getChannel(String path)` Returns the channel specified by the given path.
`List<AgentChannel>`	`getDictionaryChannels(List<String> agents, List<String> channelSelectors)` Returns a list of channels identified by the specified selectors.
`boolean`	`hasAgent(String agentName)` Returns `true` if the specified localAgent is present on the buses.
`void`	`initialize()` Initializes this status aggregator.
`void`	`removeListener(AgentStatusListener listener)` Removes the specified listener.
`void`	`shutdown()` Shuts down this status aggregator.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - AgentStatusAggregator
```
public AgentStatusAggregator()
```
- Method Detail
  - initialize
```
public void initialize()
```
    Initializes this status aggregator.
  - shutdown
```
public void shutdown()
```
    Shuts down this status aggregator. Once shut down, the aggregator cannot be restarted (this restriction can be removed in future versions if necessary).
  - getAgents
```
public List<org.lsst.ccs.bus.data.AgentInfo> getAgents()
```
    Lists currently connected agents.
    
    Returns:
    
    List of connected agents.
  - getAgent
```
public org.lsst.ccs.bus.data.AgentInfo getAgent(String agentName)
```
    Return AgentInfo instance for the specified Agent.
    
    Parameters:
    
    agentName - Name of the localAgent.
    
    Returns:
    
    AgentInfo instance, or null is no localAgent with the specified name is connected to the buses.
  - hasAgent
```
public boolean hasAgent(String agentName)
```
    Returns true if the specified localAgent is present on the buses.
    
    Parameters:
    
    agentName - Agent name.
    
    Returns:
    
    true if the localAgent is connected.
  - getDictionaryChannels
```
public List<AgentChannel> getDictionaryChannels(List<String> agents,
                                                List<String> channelSelectors)
```
    Returns a list of channels identified by the specified selectors.
    This method returns all matching channels found in data dictionaries of remote agents, regardless of whether there are any listeners watching those channels. Unwatched channels can only be used to retrieve their paths and static attributes. Current values and metadata may be not set or outdated.
    
    Parameters:
    
    agents - Subsystem names.
    
    channelSelectors - Channel selectors.
    
    Returns:
    
    List of matching channels.
  - getChannel
```
public AgentChannel getChannel(String path)
```
    Returns the channel specified by the given path.
    
    Parameters:
    
    path - Data channel path.
    
    Returns:
    
    Requested channel, or null if the channel is not being watched by this aggregator.
  - getAgentState
```
public org.lsst.ccs.bus.states.StateBundle getAgentState(String agentName)
```
    Returns the current state of the specified Agent.
    
    Parameters:
    
    agentName - Name of the localAgent.
    
    Returns:
    
    State of the specified localAgent.
  - addListener
```
public void addListener(AgentStatusListener listener,
                        AgentChannelsFilter filter)
```
    Adds a listener to be notified of changes in agents and channels specified by the filter.
    The listener is added with the lists of agents and channels returned by the filter's getAgents() and getOriginChannels() methods, respectively. No reference to the filter is kept, no filter methods are called when processing messages.
    
    Parameters:
    
    listener - Listener to be added.
    
    filter - Channels filter.
    
    Throws:
    
    NullPointerException - if either argument is null.
  - addListener
```
public void addListener(AgentStatusListener listener,
                        Collection<String> agents,
                        Collection<String> channels)
```
    Adds a listener to be notified of changes in specified agents and data channels. Note that calling this method with both agents and channels arguments equal to null forces this aggregator to watch all channels from all agents.
    The list of channels passed to this method may contain:
    - Complete channel paths.
    - Path templates in the "[Agent]/[partial path][/]" format. Templates that omit the Agent name are expanded against all agents whose names are in the agents list (or all agents present on the buses if that list is null). Templates that end with "/" match all channels that start with "Agent/partial path/".
    - Selector strings in the "[agent.name=value&][agent.type=value&][agent.key[=value]&…&agent.key[=value]&][key[=value]&…&key[=value]]" format, where key and value are names and values of Agent properties or static channel attributes. If value is omitted, the existence of the attribute is checked. Note that templates and selectors are only applied to channels and their attributes as listed in the agent channels dictionary. Any channels not appearing in the dictionary are ignored, as are attribute changes.
    The listener is notified of agent connection, configuration, and disconnection events if the agent name is in the supplied list of channels, or the list is null, or the Agent name is explicitly contained in any of the templates and selectors.
    The listener is notified of value changes in data channels if:
    - The channel path is contained in the supplied list of channels.
    - The channel path matches any of the supplied templates.
    - The channel satisfies any of the supplied selectors.
    Unless the agent list is null, templates and selectors that do not explicitly specify agent names are only applied to agents whose names are on the Agent list.
    Parameters:
    
    listener - Listener to be added.
    
    agents - Names of agents the listener is interested in. If null, the listener will be notified of changes in all agents.
    
    channels - Paths, templates, and selectors specifying channels the listener is interested in. If null, the listener is notified of changes in all channels from the specified agents. Supplying an empty list ensures that the listener is only notified of agent connections and disconnections.
    
    Throws:
    
    NullPointerException - if the listener argument is null.
  - removeListener
```
public void removeListener(AgentStatusListener listener)
```
    Removes the specified listener. Also stops watching channels that were only watched because of this listener.
    
    Parameters:
    
    listener - Listener to be removed.

Class AgentStatusAggregator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

AgentStatusAggregator

Method Detail

initialize

shutdown

getAgents

getAgent

hasAgent

getDictionaryChannels

getChannel

getAgentState

addListener

addListener

removeListener