Tokio metrics collector for Prometheus

Provides utilities for collecting Prometheus-compatible metrics from Tokio runtime and tasks.

[dependencies]
tokio-metrics-collector = { version = "0.3.1" }

Documentation:

• API reference (docs.rs)

QuickStart

use prometheus::Encoder;

#[tokio::main]
async fn main() {
    // register global runtime collector
    prometheus::default_registry()
        .register(Box::new(
            tokio_metrics_collector::default_runtime_collector(),
        ))
        .unwrap();

    // register global task collector
    let task_collector = tokio_metrics_collector::default_task_collector();
    prometheus::default_registry()
        .register(Box::new(task_collector))
        .unwrap();

    // construct a TaskMonitor
    let monitor = tokio_metrics_collector::TaskMonitor::new();
    // add this monitor to task collector with label 'simple_task'
    // NOTE: duplicate labels in multiple monitors cause incorrect data aggregation.
    // It is recommended to use unique labels for each monitor and
    // instrument multiple tasks by the `instrument` function.
    task_collector.add("simple_task", monitor.clone());

    // spawn a background task and instrument
    tokio::spawn(monitor.instrument(async {
        loop {
            // do something
            tokio::time::sleep(tokio::time::Duration::from_millis(500)).await;
        }
    }));

    // print metrics every tick
    for _ in 0..5 {
        tokio::time::sleep(tokio::time::Duration::from_secs(1)).await;

        let encoder = prometheus::TextEncoder::new();
        let mut buffer = Vec::new();
        encoder
            .encode(&prometheus::default_registry().gather(), &mut buffer)
            .unwrap();
        let data = String::from_utf8(buffer.clone()).unwrap();

        println!("{}", data);
    }
}

And a http server example, you can find in examples/server.rs.

Runtime Metrics

This unstable functionality requires tokio_unstable, and the rt crate feature. To enable tokio_unstable, the --cfg tokio_unstable must be passed to rustc when compiling. You can do this by setting the RUSTFLAGS environment variable before compiling your application; e.g.:

RUSTFLAGS="--cfg tokio_unstable" cargo build

Or, by creating the file .cargo/config.toml in the root directory of your crate. If you're using a workspace, put this file in the root directory of your workspace instead.

[build]
rustflags = ["--cfg", "tokio_unstable"]
rustdocflags = ["--cfg", "tokio_unstable"]

• [workers_count] | type: Gauge
  The number of worker threads used by the runtime.
• [total_park_count] | type: Counter
  The number of times worker threads parked.
• [total_noop_count] | type: Counter
  The number of times worker threads unparked but performed no work before parking again.
• [total_steal_count] | type: Counter
  The number of tasks worker threads stole from another worker thread.
• [total_steal_operations] | type: Counter
  The number of times worker threads stole tasks from another worker thread.
• [num_remote_schedules] | type: Counter
  The number of tasks scheduled from outside of the runtime.
• [total_local_schedule_count] | type: Counter
  The number of tasks scheduled from worker threads.
• [total_overflow_count] | type: Counter
  The number of times worker threads saturated their local queues.
• [total_polls_count] | type: Counter
  The number of tasks that have been polled across all worker threads.
• [total_busy_duration] | type: Counter
  The amount of time worker threads were busy.
• [total_global_queue_depth] | type: Gauge
  The number of tasks currently scheduled in the runtime’s global queue.
• [total_local_queue_depth] | type: Gauge
  The total number of tasks currently scheduled in workers' local queues.
• [elapsed] | type: Counter
  Total amount of time elapsed since observing runtime metrics.
• [budget_forced_yield_count] | type: Counter
  The number of times that a task was forced to yield because it exhausted its budget.
• [io_driver_ready_count] | type: Counter The number of ready events received from the I/O driver.

Task Metrics

• [instrumented_count] | type: Gauge
  The number of tasks instrumented in the interval.
• [dropped_count] | type: Gauge The number of tasks dropped in the interval.
• [first_poll_count] | type: Gauge
  The number of tasks polled for the first time in the interval.
• [total_first_poll_delay] | type: Counter The total duration elapsed between the instant tasks are instrumented, and the instant they are first polled.
• [total_idled_count] | type: Counter The total number of times that tasks idled, waiting to be awoken.
• [total_idle_duration] | type: Counter The total duration that tasks idled.
• [total_scheduled_count] | type: Counter The total number of times that tasks were awoken (and then, presumably, scheduled for execution).
• [total_scheduled_duration] | type: Counter The total duration that tasks spent waiting to be polled after awakening.
• [total_poll_count] | type: Counter The total number of times that tasks were polled.
• [total_poll_duration] | type: Counter The total duration elapsed during polls.
• [total_fast_poll_count] | type: Counter The total number of times that polling tasks completed swiftly.
• [total_fast_poll_duration] | type: Counter The total duration of fast polls.
• [total_slow_poll_count] | type: Counter The total number of times that polling tasks completed slowly.
• [total_slow_poll_duration] | type: Counter The total duration of slow polls.
• [total_short_delay_count] | type: Counter The total count of short scheduling delays.
• [total_short_delay_duration] | type: Counter The total duration of short scheduling delays.
• [total_long_delay_count] | type: Counter The total count of long scheduling delays.
• [total_long_delay_duration] | type: Counter The total duration of long scheduling delays.
• [tokio_task_total_first_poll_count] | type: Counter The total number of tasks polled for the first time.

License

tokio-metrics-collector is distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-APACHE and LICENSE-MIT, and COPYRIGHT for details.