From 4ca2521937bc57bda4b6e45080dcd497687d8ec0 Mon Sep 17 00:00:00 2001
From: Jef Roosens <roosensjef@gmail.com>
Date: Wed, 28 Dec 2022 17:39:45 +0100
Subject: [PATCH] feat(server): ability to disable metrics

---
 CHANGELOG.md             |  2 ++
 src/server/api_metrics.v | 13 ++++++++-----
 src/server/cli.v         |  1 +
 src/server/server.v      |  8 +++++++-
 src/web/web.v            |  9 ++++++---
 vieter.toml              |  1 +
 6 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e4e228..72c5440 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://git.rustybever.be/vieter-v/vieter/src/branch/dev)
 
+* Metrics endpoint for Prometheus integration
+
 ## [0.5.0](https://git.rustybever.be/vieter-v/vieter/src/tag/0.5.0)
 
 ### Added
diff --git a/src/server/api_metrics.v b/src/server/api_metrics.v
index af1b134..8d6f654 100644
--- a/src/server/api_metrics.v
+++ b/src/server/api_metrics.v
@@ -3,14 +3,17 @@ module server
 import metrics
 import web
 
-['/api/v1/metrics'; get]
+// v1_metrics serves a Prometheus-compatible metrics endpoint.
+['/api/v1/metrics'; get; markused]
 fn (mut app App) v1_metrics() web.Result {
+	if !app.conf.collect_metrics {
+		return app.status(.not_found)
+	}
+
 	mut exporter := metrics.new_prometheus_exporter([0.01, 0.05, 0.1, 0.5, 1, 100])
 	exporter.load(app.collector)
-	
+
 	// TODO stream to connection instead
-	body := exporter.export_to_string() or {
-		return app.status(.internal_server_error)
-	}
+	body := exporter.export_to_string() or { return app.status(.internal_server_error) }
 	return app.body(.ok, 'text/plain', body)
 }
diff --git a/src/server/cli.v b/src/server/cli.v
index 21fb15e..9a8b144 100644
--- a/src/server/cli.v
+++ b/src/server/cli.v
@@ -15,6 +15,7 @@ pub:
 	base_image           string = 'archlinux:base-devel'
 	max_log_age          int    [empty_default]
 	log_removal_schedule string = '0 0'
+	collect_metrics      bool   [empty_default]
 }
 
 // cmd returns the cli submodule that handles starting the server
diff --git a/src/server/server.v b/src/server/server.v
index 9571b7b..76e7ad6 100644
--- a/src/server/server.v
+++ b/src/server/server.v
@@ -101,14 +101,20 @@ pub fn server(conf Config) ! {
 		util.exit_with_message(1, 'Failed to initialize database: $err.msg()')
 	}
 
+	collector := if conf.collect_metrics {
+		&metrics.MetricsCollector(metrics.new_default_collector())
+	} else {
+		&metrics.MetricsCollector(metrics.new_null_collector())
+	}
+
 	mut app := &App{
 		logger: logger
 		api_key: conf.api_key
 		conf: conf
 		repo: repo
 		db: db
+		collector: collector
 		job_queue: build.new_job_queue(global_ce, conf.base_image)
-		collector: metrics.new_default_collector()
 	}
 	app.init_job_queue() or {
 		util.exit_with_message(1, 'Failed to inialize job queue: $err.msg()')
diff --git a/src/web/web.v b/src/web/web.v
index 95c91ed..c44057e 100644
--- a/src/web/web.v
+++ b/src/web/web.v
@@ -148,6 +148,7 @@ pub fn (ctx &Context) is_authenticated() bool {
 	return false
 }
 
+// body sends the given body as an HTTP response.
 pub fn (mut ctx Context) body(status http.Status, content_type string, body string) Result {
 	ctx.status = status
 	ctx.content_type = content_type
@@ -334,11 +335,13 @@ fn handle_conn<T>(mut conn net.TcpConn, mut app T, routes map[string]Route) {
 		labels := [
 			['method', app.req.method.str()]!,
 			['path', app.req.url]!,
-			['status', app.status.int().str()]!
+			['status', app.status.int().str()]!,
 		]
 		app.collector.counter_increment(name: 'http_requests_total', labels: labels)
-		app.collector.histogram_record(time.ticks() - app.page_gen_start, name: 'http_requests_time_ms', labels: labels)
-		/* app.collector.histogram_ */
+		app.collector.histogram_record(time.ticks() - app.page_gen_start,
+			name: 'http_requests_time_ms'
+			labels: labels
+		)
 
 		unsafe {
 			free(app)
diff --git a/vieter.toml b/vieter.toml
index 1f839f0..31eadc0 100644
--- a/vieter.toml
+++ b/vieter.toml
@@ -13,3 +13,4 @@ api_update_frequency = 2
 image_rebuild_frequency = 1
 max_concurrent_builds = 3
 max_log_age = 64
+collect_metrics = true