SPL File changeover.spl

com.ibm.streamsx.plumbing > com.ibm.streamsx.plumbing 1.0.0 > com.ibm.streamsx.plumbing.switches > changeover.spl

Content

Operators

• Changeover: Changeover switch.
• ControlledChangeover: Controlled changeover switch.

Composites

composite Changeover(output CLOSE, OPEN; input IN, CONTROL)

Changeover switch. Changeover has the same control api as the Switch operator in the SPL standard toolkit, but delivers tuples and punctuation to a second output port OPEN when the switch is open, instead of blocking.

Parameters

• initialState: This is an optional parameter of type boolean, which specifies if the this operator starts in the open (false -> submits tuples to output port OPEN) or closed (true -> submits tuples to output port CLOSE). If not specified, the default is false (tuples are submitted to OPEN).
• status: This is a mandatory parameter of type boolean, which specifies if the Switch is open or closed. The expression is evaluated each time a tuple arrives on the second (CONTROL) port. If the expression evaluates to true, the switch will flow tuples to CLOSED. If the expression evaluates to false, the switch will flow tuples to OPEN.

Input Ports

• IN: Input stream to be switched.
• CONTROL: Stream to control switching of IN.

Output Ports

• CLOSE: Output port tuples and punctuation are submitted to when the switch is closed.
• OPEN: Output port tuples and punctuation are submitted to when the switch is open.

SPL Source Code

 public composite Changeover (input IN, CONTROL; output CLOSE, OPEN) {
     param expression<boolean> $initialState : false; 
      expression<boolean> $status;
    graph
    (stream<IN> CLOSE; stream<IN> OPEN) as SPDT = Custom(IN ; CONTROL) {
      logic
      
      state: {mutable boolean closed = $initialState;}
      
      onTuple IN: if (closed) submit(IN, CLOSE);  else submit(IN, OPEN);
      onTuple CONTROL: closed = $status;
      onPunct IN:  if (closed) submit(currentPunct(), CLOSE); else submit(currentPunct(), OPEN);
    }
 }

   

composite ControlledChangeover(output CLOSE, OPEN; input IN)

Controlled changeover switch.

A controlled version of Changeover.

Operator invocations in the same job register an interest in controlling this switch by calling registerSwitch(rstring, boolean) passing the name of this switch. Then the state of this switch is changed by calling setSwitchState(rstring, boolean).

A boolean control variable named name is created in the Job Control Plane which provides notifications and operations to control if the switch is open or closed.

Multiple invocations of ControlledChangeover can share the same name and will then be controlled by the same control variable. Any call to setSwitchState(rstring, boolean) sets the state of all switches with the same name.

In the case of failure the state of the switch is retained by the Job Control Plane.

Any application that invokes this operator must include a single invocation of the spl.control::JobControlPlane operator.

Parameters

• name: Name of the switch.
• initialState: This is an optional parameter of type boolean, which specifies if the this operator starts in the open (false -> submits tuples to output port OPEN) or closed (true -> submits tuples to output port CLOSE). If not specified, the default is false (tuples are submitted to OPEN).

Input Ports

• IN: Input stream to be switched

Output Ports

• CLOSE: Output port tuples and punctuation are submitted to when the switch is closed.
• OPEN: Output port tuples and punctuation are submitted to when the switch is open.

SPL Source Code

 public composite ControlledChangeover(input IN; output CLOSE, OPEN)
 {
    param
         expression<rstring> $name;
         expression<boolean> $initialState : false;
     graph
 
         (stream<IN> CLOSE; stream<IN> OPEN) as CtrlSPDT = Changeover(IN ; SwitchControl)
         {
             param
                 status : getSwitchState($name) ;
                 initialState: __initChangeover($name, $initialState);
             config placement: partitionColocation(getThisCompositeInstanceName());
         }
         // this issues an attribute change notification which is then
         // sent to the Changeover's control port. This will then call
         // getSwitchState() to set the switch to its correct state.
         stream<MBeanNotificationBase> SwitchControl = ControlVariableChange()
         {
             param
                 name : $name;
             config placement: partitionColocation(getThisCompositeInstanceName());
         }
 }