How do I register custom metrics?

[DFINITYManu]

I've tried

lazy_static! {
    static ref CACHE_HIT_COUNTER: IntCounterVec = register_int_counter_vec!(
        "http_cache_hits_total",
        "Number of HTTP cache hits",
        &["http_response_status_code"]
    )
    .unwrap();
    static ref CACHE_MISS_COUNTER: IntCounterVec = register_int_counter_vec!(
        "http_cache_misses_total",
        "Number of HTTP cache misses",
        &["http_response_status_code"]
    )
    .unwrap();
}

but these metrics aren't getting registered in the registry that the HttpMetricsLayerBuilder creates and assigns to the HttpMetricsLayer my system uses.

How do I obtain a reference to the registry such that my code can use register_int_counter_vec_with_registry? Alternatively, how do I instruct the HttpMetricsLayerBuilder to use the default prometheus crate registry?

Thanks in advance.

[DFINITYManu]

I think what I am asking is more probably how do I add custom metrics that will be exporter by axum-otel-metrics in general. I'm stuck and I'm not sure how to do this. The documentation does not mention this.

[DFINITYManu]

I also tried this:

use opentelemetry::global;
use opentelemetry::metrics::Counter;

#[derive(Clone)]
pub struct CustomMetrics {
    pub http_cache_misses: Counter<u64>,
    pub http_cache_hits: Counter<u64>,
}

impl CustomMetrics {
    pub fn new() -> Self {
        let meter = global::meter("axum-app");
        // Create two instruments.
        let http_cache_misses = meter
            .u64_counter("http.cache.misses")
            .with_description("Total number of HTTP cache misses")
            .init();
        let http_cache_hits = meter
            .u64_counter("http.cache.hits")
            .with_description("Total number of HTTP cache hits")
            .init();
        CustomMetrics {
            http_cache_misses,
            http_cache_hits,
        }
    }
}

but nothing seems to have happened. Metrics are not served, despite me initializing the struct, and calling the .add() methods on each call.

[DFINITYManu]

Oh mang, I got it to work! Thanks for your software.