mockforge_observability/prometheus/
exporter.rs

1//! Prometheus metrics exporter
2//!
3//! Provides HTTP endpoints for Prometheus to scrape metrics
4
5use axum::{
6    extract::State,
7    http::StatusCode,
8    response::{IntoResponse, Response},
9    routing::get,
10    Router,
11};
12use prometheus::{Encoder, TextEncoder};
13use std::sync::Arc;
14use tracing::{debug, error};
15
16use super::metrics::MetricsRegistry;
17
18/// Handler for the /metrics endpoint
19pub async fn metrics_handler(
20    State(registry): State<Arc<MetricsRegistry>>,
21) -> Result<impl IntoResponse, MetricsError> {
22    debug!("Serving Prometheus metrics");
23
24    let encoder = TextEncoder::new();
25    let metric_families = registry.registry().gather();
26
27    let mut buffer = Vec::new();
28    encoder.encode(&metric_families, &mut buffer).map_err(|e| {
29        error!("Failed to encode metrics: {}", e);
30        MetricsError::EncodingError(e.to_string())
31    })?;
32
33    let body = String::from_utf8(buffer).map_err(|e| {
34        error!("Failed to convert metrics to UTF-8: {}", e);
35        MetricsError::EncodingError(e.to_string())
36    })?;
37
38    Ok((
39        StatusCode::OK,
40        [("content-type", "text/plain; version=0.0.4; charset=utf-8")],
41        body,
42    ))
43}
44
45/// Health check endpoint for the metrics server
46pub async fn health_handler() -> impl IntoResponse {
47    (StatusCode::OK, "OK")
48}
49
50/// Create a router for the Prometheus metrics endpoint
51pub fn prometheus_router(registry: Arc<MetricsRegistry>) -> Router {
52    Router::new()
53        .route("/metrics", get(metrics_handler))
54        .route("/health", get(health_handler))
55        .with_state(registry)
56}
57
58/// Error type for metrics operations
59#[derive(Debug)]
60pub enum MetricsError {
61    EncodingError(String),
62}
63
64impl IntoResponse for MetricsError {
65    fn into_response(self) -> Response {
66        let (status, message) = match self {
67            MetricsError::EncodingError(msg) => {
68                (StatusCode::INTERNAL_SERVER_ERROR, format!("Encoding error: {}", msg))
69            }
70        };
71
72        (status, message).into_response()
73    }
74}
75
76impl std::fmt::Display for MetricsError {
77    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
78        match self {
79            MetricsError::EncodingError(msg) => write!(f, "Encoding error: {}", msg),
80        }
81    }
82}
83
84impl std::error::Error for MetricsError {}
85
86#[cfg(test)]
87mod tests {
88    use super::*;
89    use crate::prometheus::MetricsRegistry;
90
91    #[tokio::test]
92    async fn test_metrics_handler() {
93        let registry = Arc::new(MetricsRegistry::new());
94
95        // Record some test metrics
96        registry.record_http_request("GET", 200, 0.045);
97        registry.record_http_request("POST", 201, 0.123);
98
99        // Call the handler
100        let result = metrics_handler(State(registry)).await;
101        assert!(result.is_ok());
102    }
103
104    #[tokio::test]
105    async fn test_health_handler() {
106        let response = health_handler().await.into_response();
107        assert_eq!(response.status(), StatusCode::OK);
108    }
109
110    #[test]
111    fn test_prometheus_router_creation() {
112        let registry = Arc::new(MetricsRegistry::new());
113        let _router = prometheus_router(registry);
114        // Router should be created successfully
115    }
116}
mockforge_observability/prometheus/exporter.rs

mockforge_observability/prometheus/
exporter.rs
