reminder-bot/src/metrics.rs

use axum::{routing::get, Router};
use lazy_static::lazy_static;
use log::warn;
use prometheus::{IntCounterVec, Opts, Registry};

lazy_static! {
    pub static ref REGISTRY: Registry = Registry::new();
    pub static ref REQUEST_COUNTER: IntCounterVec =
        IntCounterVec::new(Opts::new("requests", "Web requests"), &["method", "status", "route"])
            .unwrap();
    pub static ref REMINDER_COUNTER: IntCounterVec =
        IntCounterVec::new(Opts::new("reminders_sent", "Reminders sent"), &["channel"]).unwrap();
    pub static ref REMINDER_FAIL_COUNTER: IntCounterVec = IntCounterVec::new(
        Opts::new("reminders_failed", "Reminders failed"),
        &["channel", "error"]
    )
    .unwrap();
    pub static ref COMMAND_COUNTER: IntCounterVec =
        IntCounterVec::new(Opts::new("commands", "Commands used"), &["command"]).unwrap();
}

pub fn init_metrics() {
    REGISTRY.register(Box::new(REQUEST_COUNTER.clone())).unwrap();
    REGISTRY.register(Box::new(REMINDER_COUNTER.clone())).unwrap();
    REGISTRY.register(Box::new(REMINDER_FAIL_COUNTER.clone())).unwrap();
    REGISTRY.register(Box::new(COMMAND_COUNTER.clone())).unwrap();
}

pub async fn serve() {
    let app = Router::new().route("/metrics", get(metrics));

    let listener = tokio::net::TcpListener::bind("localhost:31756").await.unwrap();
    axum::serve(listener, app).await.unwrap();
}

async fn metrics() -> String {
    let encoder = prometheus::TextEncoder::new();
    let res_custom = encoder.encode_to_string(&REGISTRY.gather());

    res_custom.unwrap_or_else(|e| {
        warn!("Error encoding metrics: {:?}", e);

        String::new()
    })
}