metrics: Remove legacy Prometheus metrics

OpenTelemetry now covers the server and worker metrics previously exposed through Prometheus. Remove the private endpoint, legacy instruments and request updates, endpoint configuration, and the unused Prometheus dependency while retaining the database snapshot used by the OpenTelemetry collector.

Author: Turbo87

Cargo.lock

@@ -147,7 +147,6 @@ p256 = "=0.14.0"
 parking_lot = "=0.12.5"
 paste = "=1.0.15"
 postgres-native-tls = "=0.5.3"
-prometheus = { version = "=0.14.0", default-features = false }
 rand = "=0.10.2"
 regex = "=1.13.1"
 reqwest = { version = "=0.13.5", features = ["gzip", "json", "stream"] }

Cargo.toml

@@ -6,7 +6,7 @@ use std::collections::HashMap;
 use std::sync::Arc;
 
 use crate::email::Emails;
-use crate::metrics::{InstanceMetrics, ServerMetrics, ServiceMetrics};
+use crate::metrics::ServerMetrics;
 use crate::rate_limiter::{LimitedAction, RateLimiter, RateLimiterConfig};
 use crate::storage::{Storage, StorageConfig};
 use axum::extract::{FromRef, FromRequestParts, State};
@@ -59,14 +59,6 @@ pub struct App {
     /// Storage backend for crate files and other large objects.
     pub storage: Arc<Storage>,
 
-    /// Metrics related to the service as a whole
-    #[builder(default = ServiceMetrics::new().expect("could not initialize service metrics"))]
-    pub service_metrics: ServiceMetrics,
-
-    /// Metrics related to this specific instance of the service
-    #[builder(default = InstanceMetrics::new().expect("could not initialize instance metrics"))]
-    pub instance_metrics: InstanceMetrics,
-
     /// OpenTelemetry metrics recorded by the HTTP server
     pub metrics: ServerMetrics,
 
@@ -195,12 +187,6 @@ impl App {
 
             // Replica is not available, but primary might be available
             Err(error) => {
-                let _ = self
-                    .instance_metrics
-                    .database_fallback_used
-                    .get_metric_with_label_values(&["follower"])
-                    .map(|metric| metric.inc());
-
                 self.metrics.db_fallback("replica");
 
                 warn!("Replica is unavailable, falling back to primary ({error})");
@@ -224,12 +210,6 @@ impl App {
 
             // Primary is not available, but replica might be available
             Err(error) => {
-                let _ = self
-                    .instance_metrics
-                    .database_fallback_used
-                    .get_metric_with_label_values(&["primary"])
-                    .map(|metric| metric.inc());
-
                 self.metrics.db_fallback("primary");
 
                 warn!("Primary is unavailable, falling back to replica ({error})");

src/app.rs

@@ -1,5 +1,4 @@
 use crates_io_env_vars::var;
-use secrecy::SecretString;
 
 #[derive(Debug, Default)]
 pub struct MetricsConfig {
@@ -8,24 +7,14 @@ pub struct MetricsConfig {
     /// Selected when either `OTEL_EXPORTER_OTLP_ENDPOINT` or
     /// `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT` is present.
     pub otlp_enabled: bool,
-
-    /// Authorization token needed to query the metrics endpoints. If missing,
-    /// querying metrics is completely disabled.
-    ///
-    /// Read from the `METRICS_AUTHORIZATION_TOKEN` environment variable.
-    pub authorization_token: Option<SecretString>,
 }
 
 impl MetricsConfig {
     pub fn from_env() -> anyhow::Result<Self> {
         let otlp_endpoint = var("OTEL_EXPORTER_OTLP_ENDPOINT")?;
         let metrics_endpoint = var("OTEL_EXPORTER_OTLP_METRICS_ENDPOINT")?;
         let otlp_enabled = otlp_endpoint.is_some() || metrics_endpoint.is_some();
-        let authorization_token = var("METRICS_AUTHORIZATION_TOKEN")?.map(Into::into);
 
-        Ok(Self {
-            otlp_enabled,
-            authorization_token,
-        })
+        Ok(Self { otlp_enabled })
     }
 }

src/config/metrics.rs

@@ -8,7 +8,6 @@ pub mod git;
 pub mod github;
 pub mod keyword;
 pub mod krate;
-pub mod metrics;
 pub mod session;
 pub mod site_metadata;
 pub mod summary;