holoscan::HoloscanEntityData | Holoscan SDK Documentation

source_operator: Tracing/debugging (identifies the publishing operator)
timestamp_ns: <a class="fern-mdx-link" href="/holoscan/sdk-user-guide/api-reference/cpp/holoscan/classes/message">Message timestamping (for latency measurement, ordering)

DDS data type for Holoscan pub/sub messages.

This structure is used for two kinds of DDS messages:

Main-topic messages: serialized_data carries a CodecRegistry-serialized Holoscan Entity (which may reference GPU tensors). The metadata fields contains_gpu_tensors and gpu_device_id describe the entity payload. descriptor_format_version is 0 and protocol_name / publisher_gid are empty.
Sidecar messages (native buffer descriptors): serialized_data carries native-descriptor bytes produced by FastDdsTransport::send_native_descriptor(). descriptor_format_version (> 0) and protocol_name identify the wire format, and publisher_gid associates the descriptor with a main-topic publisher.

Common metadata fields:

#include <holoscan/fastdds_holoscan_entity_type_support.hpp>

Member variables

Name	Type	Description
`serialized_data`	`std::vector< uint8_t >`	Message payload bytes.
`source_operator`	`std::string`	Name of the operator that produced this message.
`timestamp_ns`	`int64_t`	Timestamp in nanoseconds (typically from std::chrono::steady_clock).
`contains_gpu_tensors`	`bool`	True if serialized_data contains GPU tensor references that need staging.
`gpu_device_id`	`int32_t`	GPU device ID where tensors originated (for device affinity).
`publisher_gid`	`std::string`	GID of the main-topic publisher (hex string, e.g.
`descriptor_format_version`	`uint8_t`	Native descriptor wire format version (0 for regular/main-topic payloads).
`protocol_name`	`std::string`	Native descriptor protocol identifier (empty for regular/main-topic payloads).