Crate sp_tracing

source ·
Expand description

Substrate tracing primitives and macros.

To trace functions or invidual code in Substrate, this crate provides within_span and enter_span. See the individual docs for how to use these macros.

Note that to allow traces from wasm execution environment there are 2 reserved identifiers for tracing Field recording, stored in the consts: WASM_TARGET_KEY and WASM_NAME_KEY - if you choose to record fields, you must ensure that your identifiers do not clash with either of these.

Additionally, we have a const: WASM_TRACE_IDENTIFIER, which holds a span name used to signal that the ‘actual’ span name and target should be retrieved instead from the associated Fields mentioned above.

Note: The tracing crate requires trace metadata to be static. This does not work for wasm code in substrate, as it is regularly updated with new code from on-chain events. The workaround for this is for the wasm tracing wrappers to put the name and target data in the values map (normally they would be in the static metadata assembled at compile time).


  • Events represent single points in time during the execution of a program.
  • Spans represent periods of time in which a program was executing in a particular context.


  • Constructs an event at the debug level.
  • Constructs a span at the debug level.
  • Enter a span.
  • Constructs an event at the error level.
  • Constructs a span at the error level.
  • Constructs a new Event.
  • Constructs an event at the info level.
  • Constructs a span at the info level.
  • Constructs a new span.
  • Constructs an event at the trace level.
  • Constructs a span at the trace level.
  • Constructs an event at the warn level.
  • Constructs a span at the warn level.
  • Runs given code within a tracing span, measuring it’s execution time.


  • Describes the level of verbosity of a span or event.
  • A handle representing a span, with the capability to enter the span if it exists.
  • Span or Event Attributes
  • The name of a field provided as the argument name when contstructing an event! or span!. Generally generated automaticaly via stringify from an 'static &str. Likely print-able.
  • A list of WasmFieldNames in the order provided
  • Metadata provides generic information about the specifc location of the span! or event! call on the wasm-side.
  • A list of WasmFieldNames with the given WasmValue (if provided) in the order specified.


  • The Tracing Level – the user can filter by this
  • A paramter value provided to the span/event



  • Init a tracing subscriber for logging in tests.
  • Try to init a simple tracing subscriber with log compatibility layer.