holoscan::PubSubContext

Beta

Pub/Sub NetworkContext class for topic-based inter-fragment communication.

PubSubContext provides topic-based publish/subscribe messaging for distributed Holoscan applications. It wraps the GXF nvidia::gxf::PubSubContext component, which is backend-agnostic and supports different discovery and transport implementations.

#include <holoscan/pubsub_context.hpp>

Inherits from: holoscan::gxf::GXFNetworkContext (public)

Constructors

PubSubContext

Move

Default

inlineexplicit

template <typename ArgT,
          typename... ArgsT,
          typename = std::enable_if_t<   !std::is_base_of_v<::holoscan::NetworkContext, std::decay_t<ArgT>> &&   (std::is_same_v<::holoscan::Arg, std::decay_t<ArgT>> ||   std::is_same_v<::holoscan::ArgList, std::decay_t<ArgT>>)>>
holoscan::PubSubContext::PubSubContext(holoscan::PubSubContext::PubSubContext(
    ArgT &&arg,
    ArgsT &&... args
)

Methods

gxf_typename

const char * holoscan::PubSubContext::gxf_typename() const override

Get the type name of the GXF network context.

The returned string is the type name of the GXF network context and is used to create the GXF network context.

Example: “nvidia::holoscan::UcxContext”

Returns: The type name of the GXF network context.

setup

void holoscan::PubSubContext::setup(
    ComponentSpec &spec
) override

Define the network context specification.

Parameters

spec

ComponentSpec &

The reference to the component specification.

initialize

void holoscan::PubSubContext::initialize() override

Initialize the network context.

This function is called after the network context is created by holoscan::Fragment::make_network_context().

clock

std::shared_ptr<Clock> holoscan::PubSubContext::clock() overridestd::shared_ptr<Clock> holoscan::PubSubContext::clock() override

Get the Clock used by the network context.

Returns: The Clock used by the network context, or nullptr if not applicable.

get

nvidia::gxf::PubSubContext * holoscan::PubSubContext::get() constnvidia::gxf::PubSubContext * holoscan::PubSubContext::get() const

Get the underlying GXF PubSubContext component.

Returns: Pointer to the GXF PubSubContext, or nullptr if not initialized.

node_name

std::string holoscan::PubSubContext::node_name() const

Get the node name for this context.

Returns: The node name string.

get_topics

std::vector<nvidia::gxf::TopicInfo> holoscan::PubSubContext::get_topics() const

Get information about all known topics.

Returns: Vector of TopicInfo structures.

get_publisher_count

size_t holoscan::PubSubContext::get_publisher_count(
    const std::string &topic
) const

Get number of publishers on a topic.

Returns: Number of publishers.

Parameters

topic

const std::string &

Topic name to query.

get_subscriber_count

size_t holoscan::PubSubContext::get_subscriber_count(
    const std::string &topic
) const

Get number of subscribers on a topic.

Returns: Number of subscribers.

Parameters

topic

const std::string &

Topic name to query.

registered_publisher_gids

std::vector<nvidia::gxf::Gid> holoscan::PubSubContext::registered_publisher_gids() const

Get the GIDs of all locally registered publishers.

Returns: Vector of publisher GIDs (snapshot under lock).

registered_subscriber_gids

std::vector<nvidia::gxf::Gid> holoscan::PubSubContext::registered_subscriber_gids() const

Get the GIDs of all locally registered subscribers.

Returns: Vector of subscriber GIDs (snapshot under lock).

get_publisher_transmitter

nvidia::gxf::Expected<nvidia::gxf::Handle<nvidia::gxf::Transmitter>> holoscan::PubSubContext::get_publisher_transmitter(nvidia::gxf::Expected<nvidia::gxf::Handle<nvidia::gxf::Transmitter>> holoscan::PubSubContext::get_publisher_transmitter(
    const nvidia::gxf::Gid &gid
) const

Look up the transmitter Handle for a registered publisher.

Returns: Handle to the Transmitter, or Unexpected with GXF_ENTITY_NOT_FOUND.

Parameters

gid

const nvidia::gxf::Gid &

Publisher GID.

get_subscriber_receiver

nvidia::gxf::Expected<nvidia::gxf::Handle<nvidia::gxf::Receiver>> holoscan::PubSubContext::get_subscriber_receiver(nvidia::gxf::Expected<nvidia::gxf::Handle<nvidia::gxf::Receiver>> holoscan::PubSubContext::get_subscriber_receiver(
    const nvidia::gxf::Gid &gid
) const

Look up the receiver Handle for a registered subscriber.

Returns: Handle to the Receiver, or Unexpected with GXF_ENTITY_NOT_FOUND.

Parameters

gid

const nvidia::gxf::Gid &

Subscriber GID.

to_yaml_node

YAML::Node holoscan::PubSubContext::to_yaml_node() const override

Get a YAML representation of the network context.

Returns: YAML node including type, specs, resources of the network context in addition to the base component properties.

reset_backend_objects

void holoscan::PubSubContext::reset_backend_objects() override

Reset any backend-specific objects.

set_parameters

void holoscan::PubSubContext::set_parameters() override

Set the parameters based on defaults (sets GXF parameters for GXF operators).

id

Mutable

Const

NetworkContext & holoscan::NetworkContext::id(NetworkContext & holoscan::NetworkContext::id(
    int64_t id
)

Set the NetworkContext ID.

Returns: The reference to this network context.

Parameters

int64_t

The ID of the network context.

name

Set the name of the network context (1)

Set the name of the network context (2)

Const

NetworkContext & holoscan::NetworkContext::name(NetworkContext & holoscan::NetworkContext::name(
    const std::string &name
) &

Set the name of the network context.

Returns: The reference to the network context.

Parameters

name

const std::string &

The name of the network context.

fragment

Set the fragment of the network context

Get a pointer to Fragment object

Const

NetworkContext & holoscan::NetworkContext::fragment(NetworkContext & holoscan::NetworkContext::fragment(
    Fragment *fragment
)

Set the fragment of the network context.

Returns: The reference to the network context.

Parameters

fragment

Fragment *

The pointer to the fragment of the network context.

spec

Overload 1

Overload 2

NetworkContext & holoscan::NetworkContext::spec(NetworkContext & holoscan::NetworkContext::spec(
    const std::shared_ptr<ComponentSpec> &spec
)

Set the component specification to the network context.

Returns: The reference to the network context.

Parameters

spec

const std::shared_ptr<ComponentSpec> &

The component specification.

spec_shared

std::shared_ptr<ComponentSpec> holoscan::NetworkContext::spec_shared()

Get the shared pointer to the component spec.

Returns: The shared pointer to the component spec.

add_arg

Add a resource to the network context (1)

Add a resource to the network context (2)

Add an argument to the component (1)

Add an argument to the component (2)

Add a list of arguments to the component (1)

Add a list of arguments to the component (2)

void holoscan::NetworkContext::add_arg(
    const std::shared_ptr<Resource> &arg
)

Add a resource to the network context.

Parameters

arg

const std::shared_ptr<Resource> &

The resource to add.

resources

std::unordered_map<std::string, std::shared_ptr<Resource>> & holoscan::NetworkContext::resources()

Get the resources of the network context.

Returns: The resources of the network context.

args

std::vector<Arg> & holoscan::ComponentBase::args()

Get the list of arguments.

Returns: The vector of arguments.

description

std::string holoscan::ComponentBase::description() const

Get a description of the component.

Returns: YAML string.

See also: to_yaml_node()

service

template <typename ServiceT = DefaultFragmentService>
std::shared_ptr<ServiceT> holoscan::ComponentBase::service(
    std::string_view id = ""
) const

Retrieve a registered fragment service or resource.

Retrieves a previously registered fragment service or resource by its type and optional identifier. Returns nullptr if no service/resource is found with the specified type and identifier.

Note that any changes to the service retrieval logic in this method should be synchronized with the implementation in Fragment::service() method to maintain consistency.

Returns: The shared pointer to the service/resource, or nullptr if not found or if type casting fails.

Template parameters

ServiceT

typename

The type of the service/resource to retrieve. Must inherit from either Resource or FragmentService. Defaults to DefaultFragmentService if not specified.

Parameters

std::string_viewDefaults to ""

The identifier of the service/resource. If empty, retrieves by type only.

get_service_by_type_info

std::shared_ptr<FragmentService> holoscan::ComponentBase::get_service_by_type_info(
    const std::type_info &service_type,
    std::string_view id = ""
) const

Retrieve a registered fragment service or resource for Python bindings.

This is a helper method for Python bindings to retrieve a service by its C++ type info.

Returns: The shared pointer to the base service, or nullptr if not found.

Parameters

service_type

const std::type_info &

The type info of the service/resource to retrieve.

std::string_viewDefaults to ""

The identifier of the service/resource. If empty, retrieves by type only.

gxf_context

Mutable

Const

void holoscan::gxf::GXFComponent::gxf_context(
    gxf_context_t gxf_context
)

gxf_eid

Mutable

Const

void holoscan::gxf::GXFComponent::gxf_eid(
    gxf_uid_t gxf_eid
)

gxf_tid

Mutable

Const

void holoscan::gxf::GXFComponent::gxf_tid(
    gxf_tid_t gxf_tid
)

gxf_cid

Mutable

Const

void holoscan::gxf::GXFComponent::gxf_cid(
    gxf_uid_t gxf_cid
)

gxf_cname

Overload 1

Overload 2

std::string & holoscan::gxf::GXFComponent::gxf_cname()

gxf_graph_entity

Overload 1

Overload 2

std::shared_ptr<nvidia::gxf::GraphEntity> holoscan::gxf::GXFComponent::gxf_graph_entity()

gxf_entity_group_name

std::string holoscan::gxf::GXFComponent::gxf_entity_group_name()

The name of the entity group this component belongs to.

gxf_entity_group_id

gxf_uid_t holoscan::gxf::GXFComponent::gxf_entity_group_id()

The group id of the entity group this component belongs to.

gxf_cptr

void * holoscan::gxf::GXFComponent::gxf_cptr()

gxf_component

nvidia::gxf::Handle<nvidia::gxf::Component> holoscan::gxf::GXFComponent::gxf_component()

gxf_initialize

void holoscan::gxf::GXFComponent::gxf_initialize()

set_gxf_parameter

void holoscan::gxf::GXFComponent::set_gxf_parameter(
    const std::string &component_name,
    const std::string &key,
    ParameterWrapper &param_wrap
)

Set a given parameter on the underlying GXF component.

reset_gxf_graph_entity

void holoscan::gxf::GXFComponent::reset_gxf_graph_entity()

setup_backend

virtual void holoscan::PubSubContext::setup_backend()

Set up the PubSub backend (discovery, transport, serializer).

Called automatically from initialize() after the GXF component is created and get() returns a valid pointer.

The default implementation is a no-op. Subclasses should override this to create backend components and inject them into the GXF PubSubContext:

Example

void setup_backend() override {
  auto* gxf_ctx = get();
  gxf_ctx->set_discovery(std::make_shared<MyDiscovery>(...));
  gxf_ctx->set_transport(std::make_shared<MyTransport>(...));
  gxf_ctx->set_serializer(std::make_shared<MySerializer>(...));
  gxf_ctx->initialize();
  gxf_ctx->init_context();
}

See also: DDSPubSubNetworkContext for the FastDDS backend implementation.

update_params_from_args

Update parameters based on the specified arguments

Update parameters based on the specified arguments (with params)

void holoscan::Component::update_params_from_args()

Update parameters based on the specified arguments.

service_provider

void holoscan::ComponentBase::service_provider(
    FragmentServiceProvider *provider
)

Set the service provider that owns this component.

Static methods

register_converter

template <typename typeT>
static void holoscan::ComponentBase::register_converter()

If an operator or resource has an argument with a custom type, the argument setter must be registered using this method.

The argument setter is used to set the value of the argument from the YAML configuration.

This method can be called in the initialization phase of the operator/resource (e.g., initialize()). The example below shows how to register the argument setter for the custom type (Vec3):

It is assumed that YAML::convert<T>::encode and YAML::convert<T>::decode are implemented for the given type. You need to specialize the YAML::convert<> template class.

For example, suppose that you had a Vec3 class with the following members:

You can define the YAML::convert<Vec3> as follows in a ‘.cpp’ file:

Please refer to the yaml-cpp documentation for more details.

Template parameters

typeT

typename

The type of the argument to register.

Example

void MyOp::initialize() {
  register_converter<Vec3>();
}

Example

struct Vec3 {
  // make sure you have overloaded operator==() for the comparison
  double x, y, z;
};

Example

namespace YAML {
template<>
struct convert<Vec3> {
  static Node encode(const Vec3& rhs) {
    Node node;
    node.push_back(rhs.x);
    node.push_back(rhs.y);
    node.push_back(rhs.z);
    return node;
  }
  static bool decode(const Node& node, Vec3& rhs) {
    if(!node.IsSequence() || node.size() != 3) {
      return false;
    }
    rhs.x = node[0].as<double>();
    rhs.y = node[1].as<double>();
    rhs.z = node[2].as<double>();
    return true;
  }
};
}

register_argument_setter

template <typename typeT>
void holoscan::ComponentBase::register_argument_setter()

Please refer to the documentation of register_converter() for more details.

Template parameters

typeT

typename

The type of the argument to register.

Member variables

Name	Type	Description
`node_name_`	`Parameter< std::string >`
`clock_`	`Parameter< std::shared_ptr< gxf::Clock > >`
`resources_`	`std::unordered_map< std::string, std::shared_ptr< Resource > >`	The resources used by the network context.
`spec_`	`std::shared_ptr< ComponentSpec >`	The component specification.
`id_`	`int64_t`	The ID of the component.
`name_`	`std::string`	Name of the component.
`fragment_`	`Fragment *`	Pointer to the fragment that owns this component.
`args_`	`std::vector< Arg >`	List of arguments.
`service_provider_`	`FragmentServiceProvider *`	Pointer to the service provider.
`gxf_context_`	`gxf_context_t`
`gxf_eid_`	`gxf_uid_t`
`gxf_tid_`	`gxf_tid_t`
`gxf_cid_`	`gxf_uid_t`
`gxf_graph_entity_`	`std::shared_ptr< nvidia::gxf::GraphEntity >`
`gxf_cname_`	`std::string`
`gxf_component_`	`nvidia::gxf::Handle< nvidia::gxf::Component >`
`gxf_cptr_`	`void *`