1 files changed, 133 insertions, 0 deletions
diff --git a/internal/observability/metrics.go b/internal/observability/metrics.go
new file mode 100644
index 000000000..f2ff2ac0d
--- /dev/null
+++ b/internal/observability/metrics.go
@@ -0,0 +1,133 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build !nootel
+
+package observability
+
+import (
+	"context"
+	"errors"
+
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+
+	"github.com/gin-gonic/gin"
+	"github.com/technologize/otel-go-contrib/otelginmetrics"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/prometheus"
+	"go.opentelemetry.io/otel/metric"
+	sdk "go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
+	"go.opentelemetry.io/otel/sdk/resource"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+)
+
+const (
+	serviceName = "GoToSocial"
+)
+
+func InitializeMetrics(db db.DB) error {
+	if !config.GetMetricsEnabled() {
+		return nil
+	}
+
+	if config.GetMetricsAuthEnabled() {
+		if config.GetMetricsAuthPassword() == "" || config.GetMetricsAuthUsername() == "" {
+			return errors.New("metrics-auth-username and metrics-auth-password must be set when metrics-auth-enabled is true")
+		}
+	}
+
+	r, _ := resource.Merge(
+		resource.Default(),
+		resource.NewSchemaless(
+			semconv.ServiceName(serviceName),
+			semconv.ServiceVersion(config.GetSoftwareVersion()),
+		),
+	)
+
+	prometheusExporter, err := prometheus.New()
+	if err != nil {
+		return err
+	}
+
+	meterProvider := sdk.NewMeterProvider(
+		sdk.WithExemplarFilter(exemplar.AlwaysOffFilter),
+		sdk.WithResource(r),
+		sdk.WithReader(prometheusExporter),
+	)
+
+	otel.SetMeterProvider(meterProvider)
+
+	meter := meterProvider.Meter(serviceName)
+
+	thisInstance := config.GetHost()
+
+	_, err = meter.Int64ObservableGauge(
+		"gotosocial.instance.total_users",
+		metric.WithDescription("Total number of users on this instance"),
+		metric.WithInt64Callback(func(c context.Context, o metric.Int64Observer) error {
+			userCount, err := db.CountInstanceUsers(c, thisInstance)
+			if err != nil {
+				return err
+			}
+			o.Observe(int64(userCount))
+			return nil
+		}),
+	)
+	if err != nil {
+		return err
+	}
+
+	_, err = meter.Int64ObservableGauge(
+		"gotosocial.instance.total_statuses",
+		metric.WithDescription("Total number of statuses on this instance"),
+		metric.WithInt64Callback(func(c context.Context, o metric.Int64Observer) error {
+			statusCount, err := db.CountInstanceStatuses(c, thisInstance)
+			if err != nil {
+				return err
+			}
+			o.Observe(int64(statusCount))
+			return nil
+		}),
+	)
+	if err != nil {
+		return err
+	}
+
+	_, err = meter.Int64ObservableGauge(
+		"gotosocial.instance.total_federating_instances",
+		metric.WithDescription("Total number of other instances this instance is federating with"),
+		metric.WithInt64Callback(func(c context.Context, o metric.Int64Observer) error {
+			federatingCount, err := db.CountInstanceDomains(c, thisInstance)
+			if err != nil {
+				return err
+			}
+			o.Observe(int64(federatingCount))
+			return nil
+		}),
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func MetricsMiddleware() gin.HandlerFunc {
+	return otelginmetrics.Middleware(serviceName)
+}