[feature] Initial Prometheus metrics implementation (#2334)

* feat: Initial OTEL metrics

* docs: add metrics documentation

* fix: metrics endpoint conditional check

* feat: metrics endpoint basic auth

* fix: make metrics-auth-enabled default false

* fix: go fmt helpers.gen.go

* fix: add metric-related env vars to envparsing.sh

* fix: metrics docs

* fix: metrics related stuff in envparsing.sh

* fix: metrics docs

* chore: metrics docs wording

* fix: metrics stuff in envparsing?

* bump otel versions

---------

Co-authored-by: Tsuribori <user@acertaindebian>
Co-authored-by: Tsuribori <none@example.org>
Co-authored-by: tsmethurst <tobi.smethurst@protonmail.com>

2 files changed, 22 insertions, 1 deletions

diff --git a/cmd/gotosocial/action/server/server.go b/cmd/gotosocial/action/server/server.go
index 2ab8bb7cf..a9896a81c 100644
--- a/cmd/gotosocial/action/server/server.go
+++ b/cmd/gotosocial/action/server/server.go
@@ -33,6 +33,7 @@ import (
 	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
 	"github.com/superseriousbusiness/gotosocial/internal/cleaner"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/metrics"
 	"github.com/superseriousbusiness/gotosocial/internal/middleware"
 	tlprocessor "github.com/superseriousbusiness/gotosocial/internal/processing/timeline"
 	"github.com/superseriousbusiness/gotosocial/internal/timeline"
@@ -81,6 +82,11 @@ var Start action.GTSAction = func(ctx context.Context) error {
 		return fmt.Errorf("error initializing tracing: %w", err)
 	}
 
+	// Initialize Metrics
+	if err := metrics.Initialize(); err != nil {
+		return fmt.Errorf("error initializing metrics: %w", err)
+	}
+
 	// Open connection to the database
 	dbService, err := bundb.NewBunDBService(ctx, &state)
 	if err != nil {
@@ -213,13 +219,18 @@ var Start action.GTSAction = func(ctx context.Context) error {
 	if err != nil {
 		return fmt.Errorf("error creating router: %s", err)
 	}
-
 	middlewares := []gin.HandlerFunc{
 		middleware.AddRequestID(config.GetRequestIDHeader()), // requestID middleware must run before tracing
 	}
+
 	if config.GetTracingEnabled() {
 		middlewares = append(middlewares, tracing.InstrumentGin())
 	}
+
+	if config.GetMetricsEnabled() {
+		middlewares = append(middlewares, metrics.InstrumentGin())
+	}
+
 	middlewares = append(middlewares, []gin.HandlerFunc{
 		// note: hooks adding ctx fields must be ABOVE
 		// the logger, otherwise won't be accessible.
diff --git a/cmd/gotosocial/action/testrig/testrig.go b/cmd/gotosocial/action/testrig/testrig.go
index 452df805c..f08bec609 100644
--- a/cmd/gotosocial/action/testrig/testrig.go
+++ b/cmd/gotosocial/action/testrig/testrig.go
@@ -38,6 +38,7 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/language"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"github.com/superseriousbusiness/gotosocial/internal/metrics"
 	"github.com/superseriousbusiness/gotosocial/internal/middleware"
 	"github.com/superseriousbusiness/gotosocial/internal/oidc"
 	tlprocessor "github.com/superseriousbusiness/gotosocial/internal/processing/timeline"
@@ -68,6 +69,10 @@ var Start action.GTSAction = func(ctx context.Context) error {
 		return fmt.Errorf("error initializing tracing: %w", err)
 	}
 
+	if err := metrics.Initialize(); err != nil {
+		return fmt.Errorf("error initializing metrics: %w", err)
+	}
+
 	// Initialize caches and database
 	state.DB = testrig.NewTestDB(&state)
 
@@ -142,6 +147,11 @@ var Start action.GTSAction = func(ctx context.Context) error {
 	if config.GetTracingEnabled() {
 		middlewares = append(middlewares, tracing.InstrumentGin())
 	}
+
+	if config.GetMetricsEnabled() {
+		middlewares = append(middlewares, metrics.InstrumentGin())
+	}
+
 	middlewares = append(middlewares, []gin.HandlerFunc{
 		middleware.Logger(config.GetLogClientIP()),
 		middleware.UserAgent(),