dipper 0.5.3

An out-of-the-box modular dependency injection web application framework.
Documentation 
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use std::time::Instant;

use crate::{
    http::ResBody,
    otel::{
        otel_metrics::{Counter, Histogram},
        semantic_conventions::trace,
        *,
    },
    prelude::*,
};

/// Middleware for metrics with OpenTelemetry.
pub struct Metrics {
    request_count: Counter<u64>,
    error_count: Counter<u64>,
    duration: Histogram<f64>,
}

impl Metrics {
    /// Create `Metrics` middleware with `meter`.
    pub fn new(service_name: String) -> Self {
        let meter = meter(service_name.clone());
        Self {
            request_count: meter
                .u64_counter(service_name.clone() + "_request_count")
                .with_description("total request count (since start of service)")
                .init(),
            error_count: meter
                .u64_counter(service_name.clone() + "_error_count")
                .with_description("failed request count (since start of service)")
                .init(),
            duration: meter
                .f64_histogram(service_name.clone() + "_request_duration_ms")
                .with_unit("milliseconds")
                .with_description("request duration histogram (in milliseconds, since start of service)")
                .init(),
        }
    }
}

#[async_trait]
impl Handler for Metrics {
    async fn handle(&self, req: &mut Request, depot: &mut Depot, res: &mut Response, ctrl: &mut FlowCtrl) {
        let mut labels = Vec::with_capacity(3);
        labels.push(KeyValue::new(trace::HTTP_REQUEST_METHOD, req.method().to_string()));
        labels.push(KeyValue::new(trace::URL_FULL, req.uri().to_string()));

        let s = Instant::now();
        ctrl.call_next(req, depot, res).await;
        let elapsed = s.elapsed();

        let status = res.status_code.unwrap_or(StatusCode::OK);
        labels.push(KeyValue::new(trace::HTTP_RESPONSE_STATUS_CODE, status.as_u16() as i64));
        if status.is_client_error() || status.is_server_error() {
            self.error_count.add(1, &labels);
            let msg = if let ResBody::Error(body) = &res.body {
                body.to_string()
            } else {
                format!("ErrorCode: {}", status.as_u16())
            };
            labels.push(KeyValue::new(trace::EXCEPTION_MESSAGE, msg));
        }

        self.request_count.add(1, &labels);
        self.duration.record(elapsed.as_secs_f64() * 1000.0_f64, &labels);
    }
}