4 files changed, 403 insertions, 0 deletions
diff --git a/internal/observability/bun.go b/internal/observability/bun.go
new file mode 100644
index 000000000..4baf786e4
--- /dev/null
+++ b/internal/observability/bun.go
@@ -0,0 +1,42 @@
+// 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 (
+	"github.com/uptrace/bun"
+	"github.com/uptrace/bun/extra/bunotel"
+	metricnoop "go.opentelemetry.io/otel/metric/noop"
+	tracenoop "go.opentelemetry.io/otel/trace/noop"
+)
+
+func InstrumentBun(traces bool, metrics bool) bun.QueryHook {
+	opts := []bunotel.Option{
+		bunotel.WithFormattedQueries(true),
+	}
+	if !traces {
+		opts = append(opts, bunotel.WithTracerProvider(tracenoop.NewTracerProvider()))
+	}
+	if !metrics {
+		opts = append(opts, bunotel.WithMeterProvider(metricnoop.NewMeterProvider()))
+	}
+	return bunotel.NewQueryHook(
+		opts...,
+	)
+}
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)
+}
diff --git a/internal/observability/no_otel.go b/internal/observability/no_otel.go
new file mode 100644
index 000000000..122d7a897
--- /dev/null
+++ b/internal/observability/no_otel.go
@@ -0,0 +1,46 @@
+// 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 (
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+
+	"github.com/gin-gonic/gin"
+	"github.com/uptrace/bun"
+)
+
+func InitializeMetrics(db db.DB) error {
+	return nil
+}
+func InitializeTracing() error {
+	return nil
+}
+
+func MetricsMiddleware() gin.HandlerFunc {
+	return nil
+}
+
+func TracingMiddleware() gin.HandlerFunc {
+	return nil
+}
+
+func InstrumentBun(traces bool, metrics bool) bun.QueryHook {
+	return nil
+}
diff --git a/internal/observability/tracing.go b/internal/observability/tracing.go
new file mode 100644
index 000000000..7827004a3
--- /dev/null
+++ b/internal/observability/tracing.go
@@ -0,0 +1,182 @@
+// 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"
+	"fmt"
+
+	"codeberg.org/gruf/go-kv"
+	"github.com/gin-gonic/gin"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/resource"
+	"go.opentelemetry.io/otel/sdk/trace"
+	"go.opentelemetry.io/otel/semconv/v1.20.0/httpconv"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+	oteltrace "go.opentelemetry.io/otel/trace"
+
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+)
+
+const (
+	tracerKey  = "gotosocial-server-tracer"
+	tracerName = "github.com/superseriousbusiness/gotosocial/internal/observability"
+)
+
+func InitializeTracing() error {
+	if !config.GetTracingEnabled() {
+		return nil
+	}
+
+	insecure := config.GetTracingInsecureTransport()
+
+	var tpo trace.TracerProviderOption
+	switch config.GetTracingTransport() {
+	case "grpc":
+		opts := []otlptracegrpc.Option{
+			otlptracegrpc.WithEndpoint(config.GetTracingEndpoint()),
+		}
+		if insecure {
+			opts = append(opts, otlptracegrpc.WithInsecure())
+		}
+		exp, err := otlptracegrpc.New(context.Background(), opts...)
+		if err != nil {
+			return fmt.Errorf("building tracing exporter: %w", err)
+		}
+		tpo = trace.WithBatcher(exp)
+	case "http":
+		opts := []otlptracehttp.Option{
+			otlptracehttp.WithEndpoint(config.GetTracingEndpoint()),
+		}
+		if insecure {
+			opts = append(opts, otlptracehttp.WithInsecure())
+		}
+		exp, err := otlptracehttp.New(context.Background(), opts...)
+		if err != nil {
+			return fmt.Errorf("building tracing exporter: %w", err)
+		}
+		tpo = trace.WithBatcher(exp)
+	default:
+		return fmt.Errorf("invalid tracing transport: %s", config.GetTracingTransport())
+	}
+	r, err := resource.Merge(
+		resource.Default(),
+		resource.NewSchemaless(
+			semconv.ServiceName("GoToSocial"),
+			semconv.ServiceVersion(config.GetSoftwareVersion()),
+		),
+	)
+	if err != nil {
+		// this can happen if semconv versioning is out-of-sync
+		return fmt.Errorf("building tracing resource: %w", err)
+	}
+
+	tp := trace.NewTracerProvider(
+		tpo,
+		trace.WithResource(r),
+	)
+	otel.SetTracerProvider(tp)
+	propagator := propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+	otel.SetTextMapPropagator(propagator)
+	log.Hook(func(ctx context.Context, kvs []kv.Field) []kv.Field {
+		span := oteltrace.SpanFromContext(ctx)
+		if span != nil && span.SpanContext().HasTraceID() {
+			return append(kvs, kv.Field{K: "traceID", V: span.SpanContext().TraceID().String()})
+		}
+		return kvs
+	})
+	return nil
+}
+
+// InstrumentGin is a middleware injecting tracing information based on the
+// otelgin implementation found at
+// https://github.com/open-telemetry/opentelemetry-go-contrib/blob/main/instrumentation/github.com/gin-gonic/gin/otelgin/gintrace.go
+func TracingMiddleware() gin.HandlerFunc {
+	provider := otel.GetTracerProvider()
+	tracer := provider.Tracer(
+		tracerName,
+		oteltrace.WithInstrumentationVersion(config.GetSoftwareVersion()),
+	)
+	propagator := otel.GetTextMapPropagator()
+	return func(c *gin.Context) {
+		spanName := c.FullPath()
+		// Do not trace a request if it didn't match a route. This doesn't omit
+		// all 404s as a request matching /:user for a user that doesn't exist
+		// still matches the route
+		if spanName == "" {
+			c.Next()
+			return
+		}
+
+		c.Set(tracerKey, tracer)
+		savedCtx := c.Request.Context()
+		defer func() {
+			c.Request = c.Request.WithContext(savedCtx)
+		}()
+		ctx := propagator.Extract(savedCtx, propagation.HeaderCarrier(c.Request.Header))
+		opts := []oteltrace.SpanStartOption{
+			oteltrace.WithAttributes(httpconv.ServerRequest(config.GetHost(), c.Request)...),
+			oteltrace.WithSpanKind(oteltrace.SpanKindServer),
+		}
+
+		rAttr := semconv.HTTPRoute(spanName)
+		opts = append(opts, oteltrace.WithAttributes(rAttr))
+		id := gtscontext.RequestID(c.Request.Context())
+		if id != "" {
+			opts = append(opts, oteltrace.WithAttributes(attribute.String("requestID", id)))
+		}
+		ctx, span := tracer.Start(ctx, spanName, opts...)
+		defer span.End()
+
+		// pass the span through the request context
+		c.Request = c.Request.WithContext(ctx)
+
+		// serve the request to the next middleware
+		c.Next()
+
+		status := c.Writer.Status()
+		span.SetStatus(httpconv.ServerStatus(status))
+		if status > 0 {
+			span.SetAttributes(semconv.HTTPResponseStatusCode(status))
+		}
+		if len(c.Errors) > 0 {
+			span.SetAttributes(attribute.String("gin.errors", c.Errors.String()))
+		}
+	}
+}
+
+func InjectRequestID() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		id := gtscontext.RequestID(c.Request.Context())
+		if id != "" {
+			span := oteltrace.SpanFromContext(c.Request.Context())
+			span.SetAttributes(attribute.String("requestID", id))
+		}
+	}
+}