Class CallbackGroup

Class Documentation

class CallbackGroup

Public Functions

explicit CallbackGroup(CallbackGroupType group_type, bool automatically_add_to_executor_with_node = true)

Constructor for CallbackGroup.

Callback Groups have a type, either ‘Mutually Exclusive’ or ‘Reentrant’ and when creating one the type must be specified.

Callbacks in Reentrant Callback Groups must be able to:

  • run at the same time as themselves (reentrant)

  • run at the same time as other callbacks in their group

  • run at the same time as other callbacks in other groups

Callbacks in Mutually Exclusive Callback Groups:

  • will not be run multiple times simultaneously (non-reentrant)

  • will not be run at the same time as other callbacks in their group

  • but must run at the same time as callbacks in other groups

Additionally, callback groups have a property which determines whether or not they are added to an executor with their associated node automatically. When creating a callback group the automatically_add_to_executor_with_node argument determines this behavior, and if true it will cause the newly created callback group to be added to an executor with the node when the Executor::add_node method is used. If false, this callback group will not be added automatically and would have to be added to an executor manually using the Executor::add_callback_group method.

Whether the node was added to the executor before creating the callback group, or after, is irrelevant; the callback group will be automatically added to the executor in either case.

Parameters:

  • group_type – [in] The type of the callback group.

  • automatically_add_to_executor_with_node – [in] A boolean that determines whether a callback group is automatically added to an executor with the node with which it is associated.

explicit CallbackGroup(CallbackGroupType group_type, rclcpp::Context::WeakPtr context, bool automatically_add_to_executor_with_node = true)

Constructor for CallbackGroup.

Callback Groups have a type, either ‘Mutually Exclusive’ or ‘Reentrant’ and when creating one the type must be specified.

Callbacks in Reentrant Callback Groups must be able to:

  • run at the same time as themselves (reentrant)

  • run at the same time as other callbacks in their group

  • run at the same time as other callbacks in other groups

Callbacks in Mutually Exclusive Callback Groups:

  • will not be run multiple times simultaneously (non-reentrant)

  • will not be run at the same time as other callbacks in their group

  • but must run at the same time as callbacks in other groups

Additionally, callback groups have a property which determines whether or not they are added to an executor with their associated node automatically. When creating a callback group the automatically_add_to_executor_with_node argument determines this behavior, and if true it will cause the newly created callback group to be added to an executor with the node when the Executor::add_node method is used. If false, this callback group will not be added automatically and would have to be added to an executor manually using the Executor::add_callback_group method.

Whether the node was added to the executor before creating the callback group, or after, is irrelevant; the callback group will be automatically added to the executor in either case.

Parameters:

  • group_type – [in] The type of the callback group.

  • context – [in] A weak pointer to the context associated with this callback group.

  • automatically_add_to_executor_with_node – [in] A boolean that determines whether a callback group is automatically added to an executor with the node with which it is associated.

~CallbackGroup()

Default destructor.

template<typename Function>
inline rclcpp::SubscriptionBase::SharedPtr find_subscription_ptrs_if(Function func) const
template<typename Function>
inline rclcpp::TimerBase::SharedPtr find_timer_ptrs_if(Function func) const
template<typename Function>
inline rclcpp::ServiceBase::SharedPtr find_service_ptrs_if(Function func) const
template<typename Function>
inline rclcpp::ClientBase::SharedPtr find_client_ptrs_if(Function func) const
template<typename Function>
inline rclcpp::Waitable::SharedPtr find_waitable_ptrs_if(Function func) const
size_t size() const

Get the total number of entities in this callback group.

Returns:

the number of entities in the callback group.

std::atomic_bool &can_be_taken_from()

Return a reference to the ‘can be taken’ atomic boolean.

The resulting bool will be true in the case that no executor is currently using an executable entity from this group. The resulting bool will be false in the case that an executor is currently using an executable entity from this group, and the group policy doesn’t allow a second take (eg mutual exclusion)

Returns:

a reference to the flag

const CallbackGroupType &type() const

Get the group type.

Returns:

the group type

void collect_all_ptrs(std::function<void(const rclcpp::SubscriptionBase::SharedPtr&)> sub_func, std::function<void(const rclcpp::ServiceBase::SharedPtr&)> service_func, std::function<void(const rclcpp::ClientBase::SharedPtr&)> client_func, std::function<void(const rclcpp::TimerBase::SharedPtr&)> timer_func, std::function<void(const rclcpp::Waitable::SharedPtr&)> waitable_func) const

Collect all of the entity pointers contained in this callback group.

Parameters:

  • sub_func – [in] Function to execute for each subscription

  • service_func – [in] Function to execute for each service

  • client_func – [in] Function to execute for each client

  • timer_func – [in] Function to execute for each timer

  • waitable_fuinc – [in] Function to execute for each waitable

std::atomic_bool &get_associated_with_executor_atomic()

Return a reference to the ‘associated with executor’ atomic boolean.

When a callback group is added to an executor this boolean is checked to ensure it has not already been added to another executor. If it has not been, then this boolean is set to true to indicate it is now associated with an executor.

When the callback group is removed from the executor, this atomic boolean is set back to false.

Returns:

the ‘associated with executor’ atomic boolean

bool automatically_add_to_executor_with_node() const

Return true if this callback group should be automatically added to an executor by the node.

Returns:

boolean true if this callback group should be automatically added to an executor when the associated node is added, otherwise false.

rclcpp::GuardCondition::SharedPtr get_notify_guard_condition()

Retrieve the guard condition used to signal changes to this callback group.

Returns:

guard condition if it is valid, otherwise nullptr.

void trigger_notify_guard_condition()

Trigger the notify guard condition.

Protected Functions

void add_publisher(const rclcpp::PublisherBase::SharedPtr publisher_ptr)
void add_subscription(const rclcpp::SubscriptionBase::SharedPtr subscription_ptr)
void add_timer(const rclcpp::TimerBase::SharedPtr timer_ptr)
void add_service(const rclcpp::ServiceBase::SharedPtr service_ptr)
void add_client(const rclcpp::ClientBase::SharedPtr client_ptr)
void add_waitable(const rclcpp::Waitable::SharedPtr waitable_ptr)
void remove_waitable(const rclcpp::Waitable::SharedPtr waitable_ptr) noexcept

Protected Attributes

CallbackGroupType type_
mutable std::mutex mutex_
std::atomic_bool associated_with_executor_
std::vector<rclcpp::SubscriptionBase::WeakPtr> subscription_ptrs_
std::vector<rclcpp::TimerBase::WeakPtr> timer_ptrs_
std::vector<rclcpp::ServiceBase::WeakPtr> service_ptrs_
std::vector<rclcpp::ClientBase::WeakPtr> client_ptrs_
std::vector<rclcpp::Waitable::WeakPtr> waitable_ptrs_
std::atomic_bool can_be_taken_from_
const bool automatically_add_to_executor_with_node_
std::shared_ptr<rclcpp::GuardCondition> notify_guard_condition_ = nullptr
std::recursive_mutex notify_guard_condition_mutex_
rclcpp::Context::WeakPtr context_

Friends

friend class rclcpp::node_interfaces::NodeServices
friend class rclcpp::node_interfaces::NodeTimers
friend class rclcpp::node_interfaces::NodeTopics
friend class rclcpp::node_interfaces::NodeWaitables