RTC::ExecutionContext Interface Reference

ExecutionContext. More...

import "RTC.idl";

Inheritance diagram for RTC::ExecutionContext:
RTC::ExecutionContextService OpenRTM::ExtTrigExecutionContextService

List of all members.

Public Member Functions

boolean is_running ()
 is_running
ReturnCode_t start ()
 start
ReturnCode_t stop ()
 stop
double get_rate ()
 get_rate
ReturnCode_t set_rate (in double rate)
 set_rate
ReturnCode_t add_component (in LightweightRTObject comp)
 add_component
ReturnCode_t remove_component (in LightweightRTObject comp)
 remove_component
ReturnCode_t activate_component (in LightweightRTObject comp)
 activate_component
ReturnCode_t deactivate_component (in LightweightRTObject comp)
 deactivate_component
ReturnCode_t reset_component (in LightweightRTObject comp)
 reset_component
LifeCycleState get_component_state (in LightweightRTObject comp)
 get_component_state
ExecutionKind get_kind ()
 get_kind

Detailed Description

ExecutionContext.

Description

An ExecutionContext allows the business logic of an RTC to be decoupled from the thread of control in which it is executed. The context represents a logical thread of control and is provided to RTCs at runtime as an argument to various operations, allowing them to query and modify their own state, and that of other RTCs executing within the same context, in the lifecycle. This separation of concerns is important for two primary reasons:

Semantics

The state machine of an ExecutionContext has two parts. The behavior of the ExecutionContext itself is defined by the upper region in the above figure. The behavior of the RTCs that participate in the context is defined by the lower region. The contents of that region are displayed in more detail in Figure 5.5 in Section 5.2.2.2. Ownership and Participation Each execution context is owned by a single RTC and may be used to execute that RTC and the RTCs contained within it, directly or indirectly. An RTC that owns one or more execution contexts is known as an autonomous RTC. An autonomous RTC and some subset of the RTCs within it (to be defined by the application developer) shall be executed by the infrastructure according to the context¡Ç s execution kind, which defines when each RTC¡Çs operations will be invoked when and in which order. These RTCs are said to participate in the context. The available execution kinds are described in Section 5.2.2.7. The relationship between RTCs and execution contexts may be many-to-many in the general case: multiple RTCs may be invoked from the same execution context, and a single RTC may be invoked from multiple contexts. In the case where multiple RTCs are invoked from the same context, starting or stopping the context shall result in the corresponding lifecycle transitions for all of those components.

and Physical Threads

Although an execution context represents a logical thread of control, the choice of how it maps to a physical thread shall be left to the application¡Çs deployment environment. Implementations may elect to associate contexts with threads with a one-to-one mapping, to serve multiple contexts from a single thread, or by any other means. In the case where a given RTC may be invoked from multiple contexts, concurrency management is implementation-dependent.


Member Function Documentation

ReturnCode_t RTC::ExecutionContext::activate_component ( in LightweightRTObject  comp  ) 

activate_component

Description

The given participant RTC is Inactive and is therefore not being invoked according to the execution context¡Çs execution kind. This operation shall cause the RTC to transition to the Active state such that it may subsequently be invoked in this execution context.

Semantics

The callback on_activate shall be called as a result of calling this operation. This operation shall not return until the callback has returned, and shall result in an error if the callback does. The following figure is a non-normative example sequence diagram for activate_component.

Constraints

  • An execution context can only activate its participant components. If the given RTC is not participating in the execution context, this operation shall fail with ReturnCode_t::BAD_PARAMETER.
  • An RTC that is in the Error state cannot be activated until after it has been reset. If the given RTC is in the Error state, this operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET.
  • This operation shall fail with ReturnCode_t::BAD_PARAMETER if the given component is not in its Alive state.
ReturnCode_t RTC::ExecutionContext::add_component ( in LightweightRTObject  comp  ) 

add_component

Description

The operation causes the given RTC to begin participating in the execution context.

Semantics

The newly added RTC will receive a call to LightweightRTComponent::attach_context (see Section 5.2.2.2.5) and then enter the Inactive state.

Constraints

  • If the ExecutionKind of this context is PERIODIC, the RTC must be a data flow component (see Section 5.3.1.1). Otherwise, this operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET.
  • If the ExecutionKind of this context is EVENT_DRIVEN, the RTC must be an FSM participant (see Section 5.3.2.3). Otherwise, this operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET.
ReturnCode_t RTC::ExecutionContext::deactivate_component ( in LightweightRTObject  comp  ) 

deactivate_component

Description

The given RTC is Active in the execution context. Cause it to transition to the Inactive state such that it will not be subsequently invoked from the context unless and until it is activated again.

Semantics

The callback on_deactivate shall be called as a result of calling this operation. This operation shall not return until the callback has returned, and shall result in an error if the callback does. The following figure is a non-normative example sequence diagram for deactivate_component.

Constraints

  • An execution context can only deactivate its participant components. If the given RTC is not participating in the execution context, this operation shall fail with ReturnCode_t::BAD_PARAMETER.
  • This operation shall fail with ReturnCode_t::BAD_PARAMETER if the given component is not in its Alive state.
LifeCycleState RTC::ExecutionContext::get_component_state ( in LightweightRTObject  comp  ) 

get_component_state

Description

This operation shall report the LifeCycleState of the given participant RTC.

Constraints

  • The given RTC must be Alive.
  • The given RTC must be a participant in the target execution context.
  • The LifeCycleState returned by this operation shall be one of LifeCycleState::INACTIVE, ACTIVE, or ERROR.
ExecutionKind RTC::ExecutionContext::get_kind (  ) 

get_kind

Description

This operation shall report the execution kind of the execution context.

double RTC::ExecutionContext::get_rate (  ) 

get_rate

Description

This operation shall return the rate (in hertz) at which its Active participating RTCs are being invoked.

Semantics

An implementation is permitted to perform some periodic or quasi-periodic processing within an execution context with an ExecutionKind other than PERIODIC. In such a case, the result of this operation is implementation-defined. If no periodic processing of any kind is taking place within the context, this operation shall fail as described in Section 5.2.1.

Constraints

  • If the context has an ExecutionKind of PERIODIC, this operation shall return a rate greater than zero.
boolean RTC::ExecutionContext::is_running (  ) 

is_running

Description

This operation shall return true if the context is in the Running state.

Semantics

While the context is Running, all Active RTCs participating in the context shall be executed according to the context¡Çs execution kind.

ReturnCode_t RTC::ExecutionContext::remove_component ( in LightweightRTObject  comp  ) 

remove_component

Description

This operation causes a participant RTC to stop participating in the execution context.

Semantics

The removed RTC will receive a call to LightweightRTComponent::detach_context (see Section 5.2.2.2.6).

Constraints

  • If the given RTC is not currently participating in the execution context, this operation shall fail with ReturnCode_t::BAD_PARAMETER.
  • An RTC must be deactivated before it can be removed from an execution context. If the given RTC is participating in the execution context but is still in the Active state, this operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET.
ReturnCode_t RTC::ExecutionContext::reset_component ( in LightweightRTObject  comp  ) 

reset_component

Description

Attempt to recover the RTC when it is in Error.

Semantics

The ComponentAction::on_reset callback shall be invoked. This operation shall not return until the callback has returned, and shall result in an error if the callback does. If possible, the RTC developer should implement that callback such that the RTC may be returned to a valid state. * If this operation fails, the RTC will remain in Error.

Constraints

  • An RTC may only be reset in an execution context in which it is in error. If the RTC is not in Error in the identified context, this operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET. However, that failure shall not cause the RTC to enter the Error state.
  • An RTC may not be reset while in the Created state. Any attempt to invoke this operation while the RTC is in that state shall fail with ReturnCode_t::PRECONDITION_NOT_MET. However, that failure shall not cause the RTC to enter the Error state.
ReturnCode_t RTC::ExecutionContext::set_rate ( in double  rate  ) 

set_rate

Description

This operation shall set the rate (in hertz) at which this context¡Çs Active participating RTCs are being called.

Semantics

If the execution kind of the context is PERIODIC, a rate change shall result in the invocation of on_rate_changed on any RTCs realizing DataFlowComponentAction that are registered with any RTCs participating in the context. An implementation is permitted to perform some periodic or quasi-periodic processing within an execution context with an ExecutionKind other than PERIODIC. If such is the case, and the implementation reports a rate from get_rate, this operation shall set that rate successfully provided that the given rate is valid. If no periodic processing of any kind is taking place within the context, this operation shall fail with ReturnCode_t::UNSUPPORTED.

Constraints

  • The given rate must be greater than zero. Otherwise, this operation shall fail with ReturnCode_t::BAD_PARAMETER.
ReturnCode_t RTC::ExecutionContext::start (  ) 

start

Description

Request that the context enter the Running state. Once the state transition occurs, the ComponentAction::on_startup operation (see Section 5.2.2.4.3) will be invoked.

Description

Semantics

An execution context may not be started until the RT components that participate in it have been initialized. An execution context may be started and stopped multiple times.

Constraints

  • This operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET if the context is not in the Stopped state.
  • This operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET if any of the participating components are not in their Alive state.
ReturnCode_t RTC::ExecutionContext::stop (  ) 

stop

Description

Request that the context enter the Stopped state. Once the transition occurs, the ComponentAction::on_shutdown operation (see Section 5.2.2.4.4) will be invoked.

Semantics

An execution context must be stopped before the RT components that participate in it are finalized.

An execution context may be started and stopped multiple times.

Constraints

  • This operation shall fail with ReturnCode_t::PRECONDITION_NOT_MET if the context is not in the Running state.

The documentation for this interface was generated from the following file:
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