Expose All Metrics in tokio::runtime::RuntimeMetrics?

[AlJohri]

I've made the mistake a few times now of thinking a metric doesn't exist and finding it is in tokio::runtime::RuntimeMetrics rather than this crate.

Some examples of this are:

• active_tasks_count
• num_blocking_threads
• num_idle_blocking_threads
• blocking_queue_depth
• io_driver_fd_registered_count
• io_driver_fd_deregistered_count

Is there a way to expose all of the available tokio metrics here and keep them in sync?

Currently we use tokio-metrics for most metrics and then manually get the missing ones from the runtime handle:

struct AdditionalTokioRuntimeMetrics {
    active_tasks_count: usize,
    num_blocking_threads: usize,
    num_idle_blocking_threads: usize,
    blocking_queue_depth: usize,
}

// NOTE: some metrics are not available from `tokio_metrics::RuntimeMetrics` so instead we
// get it from `tokio::runtime::RuntimeMetrics`
fn get_additional_tokio_metrics(
    runtime: tokio::runtime::RuntimeMetrics,
) -> AdditionalTokioRuntimeMetrics {
    AdditionalTokioRuntimeMetrics {
        active_tasks_count: runtime.active_tasks_count(),
        num_blocking_threads: runtime.num_blocking_threads(),
        num_idle_blocking_threads: runtime.num_idle_blocking_threads(),
        blocking_queue_depth: runtime.blocking_queue_depth(),
    }
}

Hoping to remove this snippet of code and rely exclusively on tokio-metrics.

[AlJohri]

Related: https://github.com/tokio-rs/tokio-metrics/pull/49/files

[mox692]

I don't see any harm in adding these metrics as well.

Note that some of these metrics are not stabilized yet, so the they could be changed or removed. (See also tokio-rs/tokio#6546.)