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Add a server for serving Prometheus metrics. Include a configuration block in the config file. Provide HTTP metrics on the API, along with process-level metrics and DB pool metrics.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,120 @@ | ||
| use actix_web::{rt::System, web, App, HttpResponse, HttpServer, Responder}; | ||
| use lemmy_api_common::context::LemmyContext; | ||
| use lemmy_utils::settings::structs::PrometheusConfig; | ||
| use prometheus::{default_registry, Encoder, Gauge, Opts, TextEncoder}; | ||
| use std::{ | ||
| net::{IpAddr, Ipv4Addr}, | ||
| sync::Arc, | ||
| thread, | ||
| }; | ||
|
|
||
| struct PromContext { | ||
| lemmy: LemmyContext, | ||
| db_pool_metrics: DbPoolMetrics, | ||
| } | ||
|
|
||
| struct DbPoolMetrics { | ||
| max_size: Gauge, | ||
| size: Gauge, | ||
| available: Gauge, | ||
| } | ||
|
|
||
| static DEFAULT_BIND: IpAddr = IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)); | ||
| static DEFAULT_PORT: i32 = 10002; | ||
|
|
||
| pub fn serve_prometheus(config: Option<&PrometheusConfig>, lemmy_context: LemmyContext) { | ||
| let context = Arc::new(PromContext { | ||
| lemmy: lemmy_context, | ||
| db_pool_metrics: create_db_pool_metrics(), | ||
| }); | ||
|
|
||
| let (bind, port) = match config { | ||
| Some(config) => ( | ||
| config.bind.unwrap_or(DEFAULT_BIND), | ||
| config.port.unwrap_or(DEFAULT_PORT), | ||
| ), | ||
| None => (DEFAULT_BIND, DEFAULT_PORT), | ||
| }; | ||
|
|
||
| // spawn thread that blocks on handling requests | ||
| // only mapping /metrics to a handler | ||
| thread::spawn(move || { | ||
| let sys = System::new(); | ||
| sys.block_on(async { | ||
| let server = HttpServer::new(move || { | ||
| App::new() | ||
| .app_data(web::Data::new(Arc::clone(&context))) | ||
| .route("/metrics", web::get().to(metrics)) | ||
| }) | ||
| .bind((bind, port as u16)) | ||
| .expect(&format!("Cannot bind to {}:{}", bind, port)) | ||
| .run(); | ||
|
|
||
| if let Err(err) = server.await { | ||
| eprintln!("Prometheus server error: {}", err); | ||
| } | ||
| }) | ||
| }); | ||
| } | ||
|
|
||
| // handler for the /metrics path | ||
| async fn metrics(context: web::Data<Arc<PromContext>>) -> impl Responder { | ||
| // collect metrics | ||
| collect_db_pool_metrics(&context).await; | ||
|
|
||
| let mut buffer = Vec::new(); | ||
| let encoder = TextEncoder::new(); | ||
|
|
||
| // gather metrics from registry and encode in prometheus format | ||
| let metric_families = prometheus::gather(); | ||
| encoder.encode(&metric_families, &mut buffer).unwrap(); | ||
| let output = String::from_utf8(buffer).unwrap(); | ||
|
|
||
| HttpResponse::Ok().body(output) | ||
| } | ||
|
|
||
| // create lemmy_db_pool_* metrics and register them with the default registry | ||
| fn create_db_pool_metrics() -> DbPoolMetrics { | ||
| let metrics = DbPoolMetrics { | ||
| max_size: Gauge::with_opts(Opts::new( | ||
| "lemmy_db_pool_max_connections", | ||
| "Maximum number of connections in the pool", | ||
| )) | ||
| .unwrap(), | ||
| size: Gauge::with_opts(Opts::new( | ||
| "lemmy_db_pool_connections", | ||
| "Current number of connections in the pool", | ||
| )) | ||
| .unwrap(), | ||
| available: Gauge::with_opts(Opts::new( | ||
| "lemmy_db_pool_available_connections", | ||
| "Number of available connections in the pool", | ||
| )) | ||
| .unwrap(), | ||
| }; | ||
|
|
||
| default_registry() | ||
| .register(Box::new(metrics.max_size.clone())) | ||
| .unwrap(); | ||
| default_registry() | ||
| .register(Box::new(metrics.size.clone())) | ||
| .unwrap(); | ||
| default_registry() | ||
| .register(Box::new(metrics.available.clone())) | ||
| .unwrap(); | ||
|
|
||
| return metrics; | ||
| } | ||
|
|
||
| async fn collect_db_pool_metrics(context: &PromContext) { | ||
| let pool_status = context.lemmy.pool().status(); | ||
| context | ||
| .db_pool_metrics | ||
| .max_size | ||
| .set(pool_status.max_size as f64); | ||
| context.db_pool_metrics.size.set(pool_status.size as f64); | ||
| context | ||
| .db_pool_metrics | ||
| .available | ||
| .set(pool_status.available as f64); | ||
| } |