# 🐕 dial9
[dial9] is a Tokio runtime telemetry crate by Russell Cohen and Jess
Izen at AWS. It records poll / wake / scheduling-delay events plus
application-defined events into a binary trace you can analyse offline.
## How rama exposes dial9
Rama crates that emit events or expose runtime boundaries have an opt-in
`dial9` cargo feature. Event-producing crates emit their predefined events at
the matching lifecycle hooks; recording becomes a no-op when no
[`dial9-tokio-telemetry`] `TracedRuntime` is wired into the
application. The `rama` mono-crate has a bundled `dial9` feature that
activates the same on every enabled sub-crate.
Library code that wants its own events alongside rama's predefined
sets can depend on `dial9-trace-format` directly and derive
`TraceEvent` on its types.
The `rama` crate's `dial9` feature also exposes it through
`rama::telemetry::dial9`.
Runtime-owning integrations can use `rama::rt::OwnedRuntime`. Blocking
runtimes resolve `Dial9Config::from_env()` when built if the feature is enabled;
call `with_dial9_config(...)` to replace it or `without_dial9_config()` to opt
out explicitly. Tasks crossing those boundaries remain associated with that
runtime's trace.
### tokio_unstable
Enabling `dial9` on any rama crate requires `--cfg tokio_unstable`
(the standard requirement for [`dial9-tokio-telemetry`]). The rama
workspace sets this in `.cargo/config.toml`. Users who do not enable
`dial9` do not need it.
## Caveats
- macOS only captures runtime-level + application events; Linux gets
kernel scheduling delays and CPU profiling samples too.
- ~1 MiB trace buffer per OS thread.
- dial9 is young — treat it as a diagnostics tool, not a production
metrics replacement.
## Going further
For the design and motivation, see [ Netstack.FM episode 37], the
[Tokio blog post], and the [dial9 README]. A working integration in
the rama tree:
[`ffi/apple/examples/transparent_proxy/`](https://github.com/plabayo/rama/tree/main/ffi/apple/examples/transparent_proxy).
[dial9]: https://github.com/dial9-rs/dial9-tokio-telemetry
[`dial9-tokio-telemetry`]: https://github.com/dial9-rs/dial9-tokio-telemetry
[Netstack.FM episode 37]: https://netstack.fm/#episode-37
[Tokio blog post]: https://tokio.rs/blog/2026-03-18-dial9
[dial9 README]: https://github.com/dial9-rs/dial9-tokio-telemetry