Runtime tracing feature specification

This is the engineering specification for the Tracer abstract type.

Overview

Tracing is a form of logging in which information is recorded about a program's execution. Tracing can be used for debugging code, writing unit tests, and building user interfaces representing the current state of a system.

Tracing can be enabled on a runtime by providing an instance of an object that conforms to the Tracer type.

Runtime

AddTracer and RemoveTracer APIs

The runtime should provide a APIs for adding and removing tracer instances.

Example pseudo-code:

class Runtime {
  function addTracer(Tracer)
  function removeTracer(Tracer)
}

Tracer

Abstract type

Provide an abstract type named Tracer.

Example pseudo-code:

Tracer {
}

didAddPlan: event

The Tracer type can optionally implement a didAddPlan function.

Invoked by the runtime when addPlan is about to return from its execution.

Example pseudo-code:

Tracer {
  optional function didAddPlan(Plan, to: Target)
}

didAddPlan:named: event

The Tracer type can optionally implement a didAddPlan:named: function.

Invoked by the runtime when addPlan:named: is about to return from its execution.

Example pseudo-code:

Tracer {
  optional function didAddPlan(Plan, named: String, to: Target)
}

didRemovePlanNamed: event

The Tracer type can optionally implement a didAddPlan:named: function.

Invoked by the runtime when removePlanNamed is about to return from its execution.

Example pseudo-code:

Tracer {
  optional function didRemovePlanNamed(String, from: Target)
}

didCreatePerformer: event

The Tracer type can optionally implement a didCreatePerformer function.

Invoked by the runtime after a new performer instance has been created.

Example pseudo-code:

Tracer {
  optional function didCreatePerformer(Performer, for: Target)
}