tapir:perf_trace
Write the last closed perf session as a Chrome Trace JSON file and print only its path.
On this page
The file opens as is in ui.perfetto.dev and chrome://tracing.
Synopsis#
dart run tapir tapir:perf_trace --out=<file> [--token=<perf-1>]
tapir:perf_trace requires a running session (CommandBoot.connected) and calls ext.tapir.perf_trace. The trace runs to thousands of events, which is why it goes to a file: the path is all an agent needs to hand on.
| Flag | Default | Meaning |
|---|---|---|
--out |
required | The file to write. Parent directories are created. |
--token |
none | The session's sessionToken. Only the most recent closed session is kept; a token naming any other is refused. |
The file carries traceEvents, displayTimeUnit and otherData (the session token, its window and the event counts). What goes into it, and why the frames must be exported before the next perf_begin, is on the perf trace page.
| Exit code | Meaning |
|---|---|
0 |
Written; stdout is the absolute path. |
1 |
--out missing. |
| non-zero | The extension refused: no closed session, a stale token, or a session still open. |