> For clean Markdown of any page, append .md to the page URL. > For a complete documentation index, see https://docs.nvidia.com/holoscan/sdk-user-guide/llms.txt. > For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.nvidia.com/holoscan/sdk-user-guide/_mcp/server. # holoscan::MessageLabel > Class to define a MessageLabel that is attached to every GXF Entity being communicated as a message between Operators in Holoscan, for Data Frame Flow Tracking. Class to define a `MessageLabel` that is attached to every GXF Entity being communicated as a message between Operators in Holoscan, for Data Frame Flow Tracking. A `MessageLabel` has a vector of paths, where each path is a vector of [Operator](operator) references and their publish and receive timestamps. It also stores frame numbers for root operators. ```cpp showLineNumbers={false} #include ``` --- ## Constructors ### MessageLabel \[#messagelabel] #### Default ```cpp showLineNumbers={false} holoscan::MessageLabel::MessageLabel() ``` #### Copy (with m) ```cpp showLineNumbers={false} holoscan::MessageLabel::MessageLabel( const MessageLabel &m ) ``` #### Copy (with m paths) explicit ```cpp showLineNumbers={false} holoscan::MessageLabel::MessageLabel( const std::vector &m_paths ) ``` Construct a new [Message](message) Label object from a vector of TimestampedPaths. This constructor automatically fills the message\_path\_operators vector from the argument of the constructor. **Parameters** **`m_paths`** `const std::vector &` The vector of TimestampedPaths to create the `MessageLabel` from. --- --- ## Assignment operators ### operator= \[#operator\_assign] ```cpp showLineNumbers={false} MessageLabel & holoscan::MessageLabel::operator=( const MessageLabel &m ) ``` --- ## Methods ### num\_paths \[#numpaths] ```cpp showLineNumbers={false} int holoscan::MessageLabel::num_paths() const ``` Get the number of paths in a `MessageLabel`. **Returns:** The number of paths in a `MessageLabel`. ### get\_all\_path\_names \[#getallpathnames] ```cpp showLineNumbers={false} std::vector holoscan::MessageLabel::get_all_path_names() ``` Get all the names of the path in formatted string, which is comma-separated values of the [Operator](operator) names. **Returns:** std::vector\ The vector of strings, where each string is a path name. ### paths \[#paths] #### Mutable ```cpp showLineNumbers={false} std::vector & holoscan::MessageLabel::paths() ``` #### Const const ```cpp showLineNumbers={false} const std::vector & holoscan::MessageLabel::paths() const ``` ### get\_e2e\_latency \[#gete2elatency] ```cpp showLineNumbers={false} int64_t holoscan::MessageLabel::get_e2e_latency( int index ) ``` Get the current end-to-end latency of a path in microseconds. `MessageLabel` and the whole Data Flow Tracking component tracks the latency in microseconds, which is sufficient for our use-cases. **Returns:** int64\_t The current end-to-end latency of the index path in microseconds **Parameters** **`index`** `int` The index of the path for which to get the latency --- ### get\_e2e\_latency\_ms \[#gete2elatencyms] ```cpp showLineNumbers={false} double holoscan::MessageLabel::get_e2e_latency_ms( int index ) ``` Get the current end-to-end latency of a path in milliseconds. **Returns:** double The current end-to-end latency of the index path in milliseconds. **Parameters** **`index`** `int` The index of the path for which to get the latency. --- ### get\_path \[#getpath] ```cpp showLineNumbers={false} TimestampedPath holoscan::MessageLabel::get_path( int index ) ``` Get the Timestamped path at the given index. **Returns:** TimestampedPath& The timestamped path at the given index **Parameters** **`index`** `int` The index of the path to get --- ### get\_path\_name \[#getpathname] ```cpp showLineNumbers={false} std::string holoscan::MessageLabel::get_path_name( int index ) ``` Get the path name string which is comma-separated values of the operator names. **Returns:** The path name string **Parameters** **`index`** `int` The index of the path to get --- ### get\_operator \[#getoperator] ```cpp showLineNumbers={false} OperatorTimestampLabel & holoscan::MessageLabel::get_operator( int path_index, int op_index ) ``` Get the [OperatorTimestampLabel](../structs/operatortimestamplabel) at the given path and operator index. **Returns:** [OperatorTimestampLabel](../structs/operatortimestamplabel)& The [Operator](operator) reference at the given path and operator index **Parameters** **`path_index`** `int` The path index of the [OperatorTimestampLabel](../structs/operatortimestamplabel) to get --- **`op_index`** `int` The [Operator](operator) index of the [OperatorTimestampLabel](../structs/operatortimestamplabel) to get --- ### set\_operator\_pub\_timestamp \[#setoperatorpubtimestamp] ```cpp showLineNumbers={false} void holoscan::MessageLabel::set_operator_pub_timestamp( int path_index, int op_index, int64_t pub_timestamp ) ``` Set an [Operator](operator)'s pub\_timestamp. **Parameters** **`path_index`** `int` The path index of the [Operator](operator) --- **`op_index`** `int` The index of the [Operator](operator) in the path --- **`pub_timestamp`** `int64_t` The new pub\_timestamp to set --- ### set\_operator\_rec\_timestamp \[#setoperatorrectimestamp] ```cpp showLineNumbers={false} void holoscan::MessageLabel::set_operator_rec_timestamp( int path_index, int op_index, int64_t rec_timestamp ) ``` Set an [Operator](operator)'s pub\_timestamp. **Parameters** **`path_index`** `int` The path index of the [Operator](operator) --- **`op_index`** `int` The index of the [Operator](operator) in the path --- **`rec_timestamp`** `int64_t` The new rec\_timestamp to set --- ### has\_operator \[#hasoperator] ```cpp showLineNumbers={false} std::vector holoscan::MessageLabel::has_operator( const std::string &op_name ) const ``` Check if an operator is present in the `MessageLabel`. Returns an empty vector if the operator is not present in any path. **Returns:** List of path indexes where the operator is present **Parameters** **`op_name`** `const std::string &` The name of the operator to check --- ### set\_frame\_number \[#setframenumber] ```cpp showLineNumbers={false} void holoscan::MessageLabel::set_frame_number( const std::string &operator_name, const std::string &port_name, uint64_t frame_number ) ``` Set frame number for a specific root operator and port. **Parameters** **`operator_name`** `const std::string &` The name of the root operator --- **`port_name`** `const std::string &` The name of the output port --- **`frame_number`** `uint64_t` The frame number to set --- ### get\_frame\_numbers \[#getframenumbers] ```cpp showLineNumbers={false} FrameNumberMap holoscan::MessageLabel::get_frame_numbers() const ``` Get all frame numbers as a map. **Returns:** Copy of the frame number map (thread-safe) ### add\_new\_op\_timestamp \[#addnewoptimestamp] ```cpp showLineNumbers={false} void holoscan::MessageLabel::add_new_op_timestamp( const holoscan::OperatorTimestampLabel &o_timestamp ) ``` Add a new [Operator](operator) timestamp to all the paths in a message label. **Parameters** **`o_timestamp`** `const holoscan::OperatorTimestampLabel &` The new operator timestamp to be added --- ### update\_last\_op\_publish \[#updatelastoppublish] ```cpp showLineNumbers={false} void holoscan::MessageLabel::update_last_op_publish() ``` Update the publish timestamp of the last operator in all the paths in a message label. ### add\_new\_path \[#addnewpath] #### Add a new path to the \`MessageLabel\` ```cpp showLineNumbers={false} void holoscan::MessageLabel::add_new_path( const TimestampedPath &path ) ``` Add a new path to the `MessageLabel`. **Parameters** **`path`** `const TimestampedPath &` The path to be added. --- #### Overload 2 ```cpp showLineNumbers={false} void holoscan::MessageLabel::add_new_path( TimestampedPath &&path ) ``` Add a new path to the `MessageLabel` using move semantics. **Parameters** **`path`** `TimestampedPath &&` The path to be moved into the `MessageLabel`. --- ### to\_string \[#tostring] ```cpp showLineNumbers={false} std::string holoscan::MessageLabel::to_string() const ``` Convert the `MessageLabel` to a string. **Returns:** std::string The formatted string representing the `MessageLabel` with all the paths and the Operators with their publish and receive timestamps. ### print\_all \[#printall] ```cpp showLineNumbers={false} void holoscan::MessageLabel::print_all() ``` Print the to\_string() in the standard output with a heading for the `MessageLabel`. --- ## Static methods ### get\_path\_e2e\_latency\_ms \[#getpathe2elatencyms] ```cpp showLineNumbers={false} static double holoscan::MessageLabel::get_path_e2e_latency_ms( const TimestampedPath &path ) ``` Get the end-to-end latency of a TimestampedPath in microseconds. It is a utility function in the class and not dependent on the object of this class. Therefore, it's a static function. **Returns:** The end-to-end latency of the path in ms **Parameters** **`path`** `const TimestampedPath &` The path for which to get the latency --- ### to\_string \[#tostring] ```cpp showLineNumbers={false} static std::string holoscan::MessageLabel::to_string( const TimestampedPath &path ) ``` --- ## Types ### Typedefs | Name | Definition | | ----------------- | --------------------------------------- | | `TimestampedPath` | `std::vector< OperatorTimestampLabel >` | | `PathOperators` | `std::unordered_set< std::string >` | | `FrameNumberMap` | `std::map< std::string, uint64_t >` | --- ## Member variables | Name | Type | Description | | ------------------------ | -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------- | | `message_paths` | `std::vector< TimestampedPath >` | | | `message_path_operators` | `std::vector< PathOperators >` | List of paths where each path is a set of name of the operators This variable is used to quickly check whether an operator is in a path. | | `frame_numbers_` | `FrameNumberMap` | [Map](map) of root operator-port combinations to their frame numbers Keys are in format "operatorname-portname" to track frame numbers per output port. | | `frame_numbers_mutex_` | `std::mutex` | Mutex to protect concurrent access to frame\_numbers\_. |