From a64565a10cfa39b09b5f9699f409f198ffdfdc3e Mon Sep 17 00:00:00 2001
From: gjahn <gregor.jahn@bht-berlin.de>
Date: Wed, 20 Dec 2023 00:40:52 +0100
Subject: [PATCH] Add /metrics path supporting Prometheus-compatible Exposition
format
See https://github.com/prometheus/docs/blob/496a6ee5ffea8a08f42f98cc7208256d300be015/content/docs/instrumenting/exposition_formats.md
---
routing/routes.go | 34 ++++++++++++++++++++++++++++++++++
routing/templates.go | 11 +++++++++++
2 files changed, 45 insertions(+)
diff --git a/routing/routes.go b/routing/routes.go
index 3611c33..72ebb06 100644
--- a/routing/routes.go
+++ b/routing/routes.go
@@ -25,6 +25,11 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
return err
}
+ metricsTextTemplate, err := template.New( "metrics" ).Parse( metricsText )
+ if err != nil {
+ return err
+ }
+
if config.LogLevel == "debug" {
router.All( "*", func( c *f.Ctx ) error {
log.Printf( "%s %s mime:%s agent:%s",
@@ -90,6 +95,35 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
})
+ router.Get( "/metrics", func( c *f.Ctx ) error {
+ headers := c.GetReqHeaders()
+ acceptHeader := strings.Join( headers[ "Accept" ], " " )
+ buffer := &bytes.Buffer{}
+
+ if strings.Contains( acceptHeader , "json" ) {
+ // FUTUREWORK: implement https://opentelemetry.io/docs/specs/otlp/#otlphttp
+ return c.SendStatus( http.StatusNotAcceptable )
+ } else {
+ names, err := store.List()
+ if err != nil {
+ return c.SendStatus( http.StatusInternalServerError )
+ }
+
+ data := metricsTextData{
+ Count: len( names ),
+ }
+
+ err = metricsTextTemplate.Execute( buffer, data )
+ if err != nil {
+ return err
+ }
+
+ c.Set( "Content-Type", "text/plain; charset=utf-8" )
+ return c.Send( buffer.Bytes() )
+ }
+ })
+
+
router.Get( "/env", func( c *f.Ctx ) error {
c.Type( "txt", "utf-8" )
diff --git a/routing/templates.go b/routing/templates.go
index 5e06f29..dd99caa 100644
--- a/routing/templates.go
+++ b/routing/templates.go
@@ -20,3 +20,14 @@ type indexHtmlData struct {
Version string
Color string
}
+
+
+const metricsText = `
+ # HELP state_entries_quantity The current number of state entries being stored
+ # TYPE state_entries_quantity gauge
+ state_entries_quantity {{ .Count }}
+`
+
+type metricsTextData struct {
+ Count int
+}
--
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