Observe metrics from the Tokio runtime

Author: sandhose

.cargo/config.toml

@@ -1,4 +1,7 @@
+[build]
+rustflags = ["--cfg", "tokio_unstable"]
+
 # On x86_64, we target the x86-64-v2 psABI, as it is a good compromise between
 # modern CPU instructions and compatibility.
 [target.x86_64-unknown-linux-gnu]
-rustflags = ["-C", "target-cpu=x86-64-v2"]
+rustflags = ["--cfg", "tokio_unstable", "-C", "target-cpu=x86-64-v2"]

crates/cli/build.rs

@@ -6,6 +6,8 @@
 use vergen_gitcl::{Emitter, GitclBuilder, RustcBuilder};
 
 fn main() -> anyhow::Result<()> {
+    println!("cargo::rustc-check-cfg=cfg(tokio_unstable)");
+
     // At build time, we override the version through the environment variable
     // VERGEN_GIT_DESCRIBE. In some contexts, it means this variable is set but
     // empty, so we unset it here.

crates/cli/src/main.rs

@@ -12,6 +12,7 @@ use anyhow::Context;
 use clap::Parser;
 use mas_config::{ConfigurationSection, TelemetryConfig};
 use sentry_tracing::EventFilter;
+use tokio::runtime::{HistogramConfiguration, LogHistogram};
 use tracing_subscriber::{
     EnvFilter, Layer, Registry, filter::LevelFilter, layer::SubscriberExt, util::SubscriberInitExt,
 };
@@ -49,8 +50,19 @@ impl sentry::TransportFactory for SentryTransportFactory {
     }
 }
 
-#[tokio::main]
-async fn main() -> anyhow::Result<ExitCode> {
+fn main() -> anyhow::Result<ExitCode> {
+    let runtime = tokio::runtime::Builder::new_multi_thread()
+        .enable_all()
+        .enable_metrics_poll_time_histogram()
+        .metrics_poll_time_histogram_configuration(HistogramConfiguration::log(
+            LogHistogram::default(),
+        ))
+        .build()?;
+
+    runtime.block_on(async_main())
+}
+
+async fn async_main() -> anyhow::Result<ExitCode> {
     // We're splitting the "fallible" part of main in another function to have a
     // chance to shutdown the telemetry exporters regardless of if there was an
     // error or not

crates/cli/src/telemetry.rs

@@ -4,6 +4,8 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 // Please see LICENSE in the repository root for full details.
 
+mod tokio;
+
 use std::sync::{LazyLock, OnceLock};
 
 use anyhow::Context as _;
@@ -60,6 +62,9 @@ pub fn setup(config: &TelemetryConfig) -> anyhow::Result<()> {
     init_tracer(&config.tracing).context("Failed to configure traces exporter")?;
     init_meter(&config.metrics).context("Failed to configure metrics exporter")?;
 
+    let handle = ::tokio::runtime::Handle::current();
+    self::tokio::observe(handle.metrics());
+
     Ok(())
 }