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Name

CStateMonitorBase -- Base class for state monitor classess

Synopsis


        
#include <CStateMonitor.h>
    
       CStateMonitorBase
      
  CStateMonitorBase(std::string transitionRequestUri, std::string statePublisherUri, CStateMonitorBase::InitCallback cb)
          throws ;
      
   std::string requestTransition(std::string transitionName)
          throws ;
          void run()
          throws ;
          CZMQEventLoop& getEventLoop()
          throws ;
          zmq::context_t* getContext()
          throws ;
          std::string getState()
          throws ;
protected:
        virtual  void initialState(std::string state)
          throws ;
        virtual  void transition(std::string newState)
          throws ;

DESCRIPTION

This class is intended to be used as a base class for programs that must monitor the state of the state manager program. The methods initialState and transition are intended to be overidden by the actual application, as these methods are the ones that are called when state are entered. See also CStateMonitor which is a good concrete example of a derived class.

This object contains a CZMQEventLoop which can also be obtained by the application software.

METHODS

CStateMonitorBase(std::string transitionRequestUri, std::string statePublisherUri, CStateMonitorBase::InitCallback cb) throws ;

Constructs the object. The transitionRequestUri is the URI that specifies the end point on which the state manager is listening for transition requests. This is normally constructed by looking up the StateRequest service in the system that is running the state manager to get the port number. The form of the URI is tcp://hostname:portnum

Similarly, statePublisherUri is the URI of the endpoint on which the state manager periodically publishes it state and publishes state transitions. It can usually be found by using the port manager to look up the StatePublish service in the host that is running the state manager.

std::string requestTransition(std::string transitionName) throws ;

Requests that the state transition perform the state transition indicated by transitionName the function retuns the reply from the state manager. This is a string that is either OK if the transition could be performed or FAIL followed by human readable text that indicates why the state transition could not be performed.

void run() throws ;

Runs the event loop. The event loop runs until the program exits. If you need more complex behavior you can invoke getEventLoop to obtain the event loop and use either its poll or pollForever with a callback to achieve that.

CZMQEventLoop& getEventLoop() throws ;

Returns a reference to the event loop that will be used to monitor the state manager. This event loop is the one that is used by the run method above.

zmq::context_t* getContext() throws ;

Returns a pointer to the ZeroMQ context object that is used by the CStateMonitor to create zmq::socket_t objects. If you will create your own sockets, it is best to use this context rather than creating a new one.

std::string getState() throws ;

Returns the current state of the state manager. If that is not yet known, the function returns an empty string.

virtual void initialState(std::string state) throws ;

This method is called when the event loop either gets a state broadcast or when the state manager makes a state transition when the state is not yet known. Derived classes that override this should invoke this base class method at some meaningful point in their initial state processing.

In the base class implementation: The current state is set to state, and the subscription for state broacasts is removed. From this point on, only state transitions will activate us.

virtual void transition(std::string newState) throws ;

This method is called when the evetn loop gets a state transition message from the state manager. If you override this method in a derived class you should invoke this method at some point during your processing of state transitions.

If the prior state is not known, initialState is invoked. Otherwise, the new state (newState) is memorized by the function, so that getState will return it.

TYPES

InitCallback

This is a pointer to a function that takes as a single parameter a pointer to the CStateMonitorBase that is being constructed.

When called, any of the CStateMonitorBase methods can be safely called. The intent is that this callback might need to obtain the event loop and register callbacks for other objects besides the sockets registered with the state and transition publications.

The callback might also obtain the ZeroMQ context and use it to create additional ZeroMQ sockets.

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