Add metrics to legacy api

Author: TymanWasTaken

src/api/common/metrics.rs

@@ -16,6 +16,7 @@ use prometheus_client::{
 
 use crate::api::{
 	common::{caching::CacheLabels, data::ApiData},
+	legacy::metrics::ApiLegacyMetrics,
 	v1::metrics::ApiV1Metrics
 };
 
@@ -50,6 +51,8 @@ pub struct AppMetrics {
 	pub registry: Registry,
 	/// All of the global (application-wide) metrics
 	pub global: GlobalMetrics,
+	/// All of the legacy API metrics
+	pub legacy: ApiLegacyMetrics,
 	/// All of the API v1 metrics
 	pub v1: ApiV1Metrics
 }
@@ -60,6 +63,7 @@ impl AppMetrics {
 
 		AppMetrics {
 			global: GlobalMetrics::init_metrics(&mut registry),
+			legacy: ApiLegacyMetrics::init_metrics(&mut registry),
 			v1: ApiV1Metrics::init_metrics(&mut registry),
 			registry
 		}

src/api/legacy/metrics.rs

@@ -0,0 +1,118 @@
+use std::fmt::Write;
+
+use actix_web::{
+	body::MessageBody,
+	dev::{ServiceRequest, ServiceResponse},
+	http::header,
+	middleware::Next,
+	web
+};
+use documented::DocumentedFields;
+use prometheus_client::{
+	encoding::{EncodeLabelSet, EncodeLabelValue},
+	metrics::{counter::Counter, family::Family},
+	registry::Registry
+};
+use serde::{Deserialize, Serialize};
+
+use crate::{
+	api::common::{data::ApiData, metrics::MetricsGroup},
+	make_api_metric
+};
+
+macro_rules! impl_serde_variant_as_label_value {
+	($enum:ty) => {
+		impl EncodeLabelValue for $enum {
+			fn encode(
+				&self,
+				encoder: &mut prometheus_client::encoding::LabelValueEncoder
+			) -> Result<(), std::fmt::Error> {
+				encoder.write_str(
+					serde_variant::to_variant_name(self).map_err(|_| std::fmt::Error)?
+				)
+			}
+		}
+	};
+}
+
+#[derive(Serialize, Deserialize, Debug, Hash, PartialEq, Eq, Clone)]
+#[serde(rename_all = "lowercase")]
+pub enum UserAgentType {
+	Loader,
+	Wrapper,
+	Unknown
+}
+
+#[derive(Serialize, Deserialize, Debug, Hash, PartialEq, Eq, Clone, EncodeLabelSet)]
+pub struct OneConfigRequest {
+	pub version: String,
+	pub loader: String,
+	pub user_agent_type: UserAgentType
+}
+
+impl_serde_variant_as_label_value!(UserAgentType);
+
+/// A struct containing all of the metrics state for the API
+#[derive(DocumentedFields)]
+pub struct ApiLegacyMetrics {
+	/// The amount of OneConfig requests, by version, loader, and user agent
+	/// type
+	oneconfig_requests: Family<OneConfigRequest, Counter>
+}
+
+impl MetricsGroup for ApiLegacyMetrics {
+	fn init_metrics(registry: &mut Registry) -> Self {
+		let registry = registry.sub_registry_with_prefix("legacy");
+
+		make_api_metric!(registry, Self, oneconfig_requests);
+
+		Self { oneconfig_requests }
+	}
+}
+
+/// A middleware to increment all metrics per-request
+pub async fn middleware(
+	mut service_request: ServiceRequest,
+	next: Next<impl MessageBody>
+) -> Result<ServiceResponse<impl MessageBody>, actix_web::Error> {
+	let data = service_request.extract::<web::Data<ApiData>>().await?;
+
+	#[allow(clippy::single_match)]
+	match service_request
+		.match_pattern()
+		.unwrap_or("default".to_string())
+		.as_str()
+	{
+		"/oneconfig/{version}-{loader}" => 'inner: {
+			let Some((version, loader)) = service_request.uri().path()
+				[(const { "/oneconfig/".len() })..]
+				.split_once('-')
+			else {
+				break 'inner;
+			};
+
+			data.metrics
+				.legacy
+				.oneconfig_requests
+				.get_or_create(&OneConfigRequest {
+					version: version.to_owned(),
+					loader: loader.to_owned(),
+					user_agent_type: match service_request
+						.headers()
+						.get(header::USER_AGENT)
+						.and_then(|v| v.to_str().ok())
+					{
+						Some(s) if s.contains("OneConfigLoader") => UserAgentType::Loader,
+						Some(s) if s.contains("OneConfigWrapper") =>
+							UserAgentType::Wrapper,
+						Some(_) | None => UserAgentType::Unknown
+					}
+				})
+				.inc();
+		}
+		_ => ()
+	};
+
+	// Let the real request handler continue
+	next.call(service_request).await
+}

src/api/legacy/mod.rs

@@ -1,7 +1,11 @@
 use actix_web::web::ServiceConfig;
 
 pub mod endpoint;
+pub mod metrics;
 pub mod types;
 pub mod utils;
 
-pub fn configure(config: &mut ServiceConfig) { config.service(endpoint::oneconfig); }
+pub fn configure(config: &mut ServiceConfig) {
+	config.service(endpoint::oneconfig);
+	// Metrics middleware in main.rs due to github.com/actix/actix-web#414
+}

src/main.rs

@@ -52,13 +52,19 @@ async fn main() {
 
 	let mut server = HttpServer::new(move || {
 		App::new()
+			// Register app state
 			.app_data(data.clone())
+			// Register legacy routes and middleware
 			.configure(api::legacy::configure)
+			.wrap(actix_web::middleware::from_fn(api::legacy::metrics::middleware))
+			// Register v1 routes and middleware
 			.configure(api::v1::configure)
-			.configure(api::common::metrics::configure)
+			// Register caching middleware
 			.wrap(actix_web::middleware::from_fn(
 				api::common::caching::middleware
 			))
+			// Register metrics routes and middleware
+			.configure(api::common::metrics::configure)
 			.wrap(actix_web::middleware::from_fn(
 				api::common::metrics::middleware
 			))