using ObservableGauge instrument with non trivial callback function (aync / blocking)

[pitoniak32]

I am looking to use the InstrumentKind::ObservableGauge to register some http requests, and record the results of them as a measurement. I was hoping I am missing something and there is an easy work around for this.

I think this is related to: #1437

this is the closest I have gotten:

let healthcheck = HealthCheck {
    url: "http://localhost:3000/_manage/health".to_string(),
    metadata: HealthCheckMetaData {
        team: "mine".to_string(),
        feature: "test".to_string(),
    },
};

meter.u64_observable_gauge("health_check").with_callback(move |observer| {
    let check = healthcheck.clone();
    tokio::task::spawn_blocking(move ||{
        let res = reqwest::blocking::get(&check.url)
            .unwrap()
            .json::<HealthCheckResult>()
            .unwrap();
        println!("{res:?}");
        let code = match res.status {
            HealthCheckStatus::Down => 0,
            HealthCheckStatus::Up => 1,
            HealthCheckStatus::Degraded => 2,
            HealthCheckStatus::Unknown => 3,
        };
    });
    observer.observe(
        1, // code,
        &[
            KeyValue::new("team", check.metadata.team.clone()),
            KeyValue::new("feature", check.metadata.feature.clone()),
        ],
    );
});

The issue I run into is allowing the observer to run in the async block / getting the result of the http response. If I remove the tokio::task::spawn_blocking(...) I get a runtime error for dropping the async runtime.

Thank you in advance!!

[pitoniak32]

Update:

I got it "working", this will run the callbacks on the periodic metric interval and the results show correctly in my backend. But it feels really dirty, and hoping someone might be able to point to a cleaner option 😅

let healthcheck = HealthCheck {
    url: "http://localhost:3000/_manage/health".to_string(),
    metadata: HealthCheckMetaData {
        team: "mine".to_string(),
        feature: "test".to_string(),
    },
};

meter
  .u64_observable_gauge("health_check")
  .with_callback(move |observer| {
      let check = healthcheck.clone();
      let url = healthcheck.url.clone();
      let (tx, rx) = std::sync::mpsc::channel();
      tokio::task::spawn_blocking(move || {
          let res = reqwest::blocking::get(url)
              .unwrap()
              .json::<HealthCheckResult>()
              .unwrap();
          tx.send(res).unwrap();
      });
      let code = match rx.recv().unwrap().status {
          HealthCheckStatus::Down => 0,
          HealthCheckStatus::Up => 1,
          HealthCheckStatus::Degraded => 2,
          HealthCheckStatus::OutOfService => 3,
          HealthCheckStatus::Unknown => 4,
      };
      println!("recording [{code}] - {} : {}", check.metadata.feature, check.url);
      observer.observe(
          code,
          &[
              KeyValue::new("team", check.metadata.team.clone()),
              KeyValue::new("feature", check.metadata.feature.clone()),
          ],
      );
  }).init()