Crate feldera_samply 

Annotations for Firefox Profiler profiles.

Firefox Profiler can display user-defined annotations for timespans and events, as well as information about network activity and memory use, but only if the profiler added those annotations. The popular samply profiler, however, has only very limited support for adding these annotations. This crate provides a way for a process that is being profiled to record its own annotations and then merge them into profiler output in a postprocessing step.

Use

This crate can be integrated into an existing profiler workflow. For example, the Feldera incremental compute engine runs samply as a subprocess, targeting itself. While samply runs, Feldera uses Capture, Span, LongSpan, and Event to record annotations. After samply completes, Feldera finishes the capture to obtain Annotations, applies them, and then passes the postprocessed output to the user. The annotation step is invisible to the user.

Short of this kind of integration, where a process effectively profiles itself, there must be some way to enable capturing and saving profile data. For example, a command-line option or an environment variable could do the trick. Once the capture is complete, the process needs to somehow save the annotations.

Viewing in Firefox Profiler

Spans and events logged by this module show up in the Marker Chart and Marker Table tabs for a given thread. They are linked to particular threads and the profiler will only show them when those threads are selected.

Spans and events are enabled only when a profile is running. They have minimal overhead otherwise.

Structs

AnnotationOptions

Options for applying annotations.

Annotations

Profile annotation data.

Capture

An in-progress capture of profile annotations.

CaptureOptions

Options for capturing profile annotations.

Event

Annotates an event during a Capture.

LongSpan

A relatively expensive way to annotate a longer timespan during Captures.

LongSpanBuilder

Builds a LongSpan for annotating a long timespan.

Span

Annotates a timespan during a Capture.

Enums

Error

Error returned by Annotations::apply.