feat(api): prometheus metrics

lib/libpk/Cargo.toml

@@ -8,6 +8,8 @@ anyhow = { workspace = true }
 config = "0.13.3"
 gethostname = "0.4.1"
 lazy_static = { workspace = true }
+metrics = "0.20.1"
+metrics-exporter-prometheus = { version = "0.11.0", default-features = false, features = ["tokio", "http-listener", "tracing"] }
 serde = { workspace = true }
 tokio = { workspace = true }
 tracing = { workspace = true }

lib/libpk/src/_config.rs

@@ -33,11 +33,18 @@ pub struct ApiConfig {
     pub remote_url: String,
 }
 
+fn _metrics_default() -> bool {
+    false
+}
+
 #[derive(Deserialize, Debug)]
 pub struct PKConfig {
     pub discord: DiscordConfig,
     pub api: ApiConfig,
 
+    #[serde(default = "_metrics_default")]
+    pub run_metrics_server: bool,
+
     pub(crate) gelf_log_url: Option<String>,
 }
 

lib/libpk/src/lib.rs

@@ -1,4 +1,5 @@
 use gethostname::gethostname;
+use metrics_exporter_prometheus::PrometheusBuilder;
 use tracing_subscriber::{prelude::__tracing_subscriber_SubscriberExt, EnvFilter, Registry};
 
 mod _config;
@@ -25,3 +26,12 @@ pub fn init_logging(component: &str) -> anyhow::Result<()> {
 
     Ok(())
 }
+
+pub fn init_metrics() -> anyhow::Result<()> {
+    if config.run_metrics_server {
+        // automatically spawns a http listener at :9000
+        let builder = PrometheusBuilder::new();
+        builder.install()?;
+    }
+    Ok(())
+}