Class PubSubContext

• Defined in File pubsub_context.hpp

Base Type

• public holoscan::gxf::GXFNetworkContext (Class GXFNetworkContext)

class PubSubContext : public holoscan::gxf::GXFNetworkContext

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.

Public Functions

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>>)>>
inline explicit PubSubContext(ArgT &&arg, ArgsT&&... args)

PubSubContext() = default

inline virtual const char *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.

virtual void setup(ComponentSpec &spec) override

Define the network context specification.

Parameters

spec – The reference to the component specification.

virtual void initialize() override

Initialize the network context.

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

virtual std::shared_ptr<Clock> clock() override

Get the Clock used by the network context.

Returns

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

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

Get the underlying GXF PubSubContext component.

Returns

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

std::string node_name() const

Get the node name for this context.

Returns

The node name string.

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

Get information about all known topics.

Returns

Vector of TopicInfo structures.

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

Get number of publishers on a topic.

Parameters

topic – Topic name to query.

Returns

Number of publishers.

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

Get number of subscribers on a topic.

Parameters

topic – Topic name to query.

Returns

Number of subscribers.

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

Get the GIDs of all locally registered publishers.

Returns

Vector of publisher GIDs (snapshot under lock).

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

Get the GIDs of all locally registered subscribers.

Returns

Vector of subscriber GIDs (snapshot under lock).

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

Look up the transmitter Handle for a registered publisher.

Parameters

gid – Publisher GID.

Returns

Handle to the Transmitter, or Unexpected with GXF_ENTITY_NOT_FOUND.

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

Look up the receiver Handle for a registered subscriber.

Parameters

gid – Subscriber GID.

Returns

Handle to the Receiver, or Unexpected with GXF_ENTITY_NOT_FOUND.

Protected Functions

virtual void 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:

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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.