Add /metrics endpoint for Prometheus (#724)

Cargo.lock

@@ -284,6 +284,19 @@ dependencies = [
  "syn 1.0.109",
 ]
 
+[[package]]
+name = "actix-web-prom"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f23f332a652836b8f3a6876103c70c9ed436d0e69fa779ab5d7f57b1d5c8d488"
+dependencies = [
+ "actix-web",
+ "futures-core",
+ "pin-project-lite",
+ "prometheus",
+ "regex",
+]
+
 [[package]]
 name = "actix-ws"
 version = "0.2.5"
@@ -2234,6 +2247,7 @@ dependencies = [
  "actix-multipart",
  "actix-rt",
  "actix-web",
+ "actix-web-prom",
  "actix-ws",
  "argon2",
  "async-trait",
@@ -3139,6 +3153,20 @@ dependencies = [
  "rustc_version 0.2.3",
 ]
 
+[[package]]
+name = "prometheus"
+version = "0.13.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "449811d15fbdf5ceb5c1144416066429cf82316e2ec8ce0c1f6f8a02e7bbcf8c"
+dependencies = [
+ "cfg-if 1.0.0",
+ "fnv",
+ "lazy_static",
+ "memchr",
+ "parking_lot 0.12.1",
+ "thiserror",
+]
+
 [[package]]
 name = "ptr_meta"
 version = "0.1.4"

Cargo.toml

@@ -18,6 +18,7 @@ actix-multipart = "0.6.0"
 actix-cors = "0.6.4"
 actix-ws = "0.2.5"
 actix-files = "0.6.2"
+actix-web-prom = "0.7.0"
 
 tokio = { version = "1.29.1", features = ["sync"] }
 tokio-stream = "0.1.14"
@@ -37,7 +38,7 @@ hyper-tls = "0.5.0"
 serde_json = "1.0"
 serde = { version = "1.0", features = ["derive"] }
 serde_with = "3.0.0"
-chrono = { version = "0.4.26", features = ["serde"]}
+chrono = { version = "0.4.26", features = ["serde"] }
 yaserde = "0.8.0"
 yaserde_derive = "0.8.0"
 xml-rs = "0.8.15"
@@ -72,9 +73,21 @@ log = "0.4.19"
 env_logger = "0.10.0"
 thiserror = "1.0.41"
 
-sqlx = { version = "0.6.3", features = ["offline", "runtime-tokio-rustls", "postgres", "chrono", "macros", "migrate", "decimal", "json"] }
-rust_decimal = { version = "1.30.0", features = ["serde-with-float", "serde-with-str"] }
-redis = { version = "0.23.0", features = ["tokio-comp", "ahash", "r2d2"]}
+sqlx = { version = "0.6.3", features = [
+    "offline",
+    "runtime-tokio-rustls",
+    "postgres",
+    "chrono",
+    "macros",
+    "migrate",
+    "decimal",
+    "json",
+] }
+rust_decimal = { version = "1.30.0", features = [
+    "serde-with-float",
+    "serde-with-str",
+] }
+redis = { version = "0.23.0", features = ["tokio-comp", "ahash", "r2d2"] }
 deadpool-redis = "0.12.0"
 clickhouse = { version = "0.11.2", features = ["uuid", "time"] }
 uuid = { version = "1.2.2", features = ["v4", "fast-rng", "serde"] }

src/main.rs

@@ -1,4 +1,5 @@
 use actix_web::{App, HttpServer};
+use actix_web_prom::PrometheusMetricsBuilder;
 use env_logger::Env;
 use labrinth::database::redis::RedisPool;
 use labrinth::file_hosting::S3Host;
@@ -88,6 +89,11 @@ async fn main() -> std::io::Result<()> {
 
     let store = MemoryStore::new();
 
+    let prometheus = PrometheusMetricsBuilder::new("labrinth")
+        .endpoint("/metrics")
+        .build()
+        .expect("Failed to create prometheus metrics middleware");
+
     info!("Starting Actix HTTP server!");
 
     let labrinth_config = labrinth::app_setup(
@@ -101,6 +107,7 @@ async fn main() -> std::io::Result<()> {
     // Init App
     HttpServer::new(move || {
         App::new()
+            .wrap(prometheus.clone())
             .wrap(actix_web::middleware::Compress::default())
             .wrap(
                 RateLimiter::new(MemoryStoreActor::from(store.clone()).start())