2 files changed, 155 insertions, 2 deletions
diff --git a/internal/observability/gin.go b/internal/observability/gin.go
new file mode 100644
index 000000000..ca74ba06c
--- /dev/null
+++ b/internal/observability/gin.go
@@ -0,0 +1,154 @@
+// 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 (
+	"net/http"
+	"slices"
+	"time"
+
+	"code.superseriousbusiness.org/gotosocial/internal/config"
+	"github.com/gin-gonic/gin"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+	semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
+)
+
+// ginMiddleware returns a middleware that
+// records metrics for incoming requests.
+func ginMiddleware() gin.HandlerFunc {
+	meter := otel.Meter("gin", metric.WithInstrumentationVersion(config.GetSoftwareVersion()))
+
+	activeReqs, _ := meter.Int64UpDownCounter(
+		"http.server.requests_active",
+		metric.WithDescription("Number of requests currently active"),
+	)
+
+	totalReqs, _ := meter.Int64Counter(
+		"http.server.requests",
+		metric.WithDescription("Total number of requests served"),
+	)
+
+	reqSize, _ := meter.Int64Histogram(
+		"http.server.request_size",
+		metric.WithDescription("Request content length (approximate)"),
+		metric.WithUnit("bytes"),
+	)
+
+	respSize, _ := meter.Int64Histogram(
+		"http.server.response_size",
+		metric.WithDescription("Response content length"),
+		metric.WithUnit("bytes"),
+	)
+
+	duration, _ := meter.Int64Histogram(
+		"http.server.duration",
+		metric.WithDescription("Duration of request -> response"),
+		metric.WithUnit("ms"),
+	)
+
+	return func(c *gin.Context) {
+
+		ctx := c.Request.Context()
+		route := c.FullPath()
+		start := time.Now()
+
+		// Generate request attributes.
+		reqAttributes := []attribute.KeyValue{
+			semconv.HTTPServerNameKey.String("GoToSocial"),
+			semconv.HTTPMethodKey.String(c.Request.Method),
+			semconv.HTTPRouteKey.String(route),
+		}
+
+		// Increment active request count,
+		// decrement again when we're finished.
+		activeReqs.Add(ctx, 1, metric.WithAttributes(reqAttributes...))
+		defer activeReqs.Add(ctx, -1, metric.WithAttributes(reqAttributes...))
+
+		// Process request so we can
+		// record response metrics.
+		c.Next()
+
+		// Add HTTP response code to request
+		// attributes to create response attributes.
+		respAttributes := slices.Clone(reqAttributes)
+		respAttributes = append(
+			respAttributes,
+			semconv.HTTPStatusCodeKey.Int(c.Writer.Status()),
+		)
+
+		// Increment total requests.
+		totalReqs.Add(ctx, 1, metric.WithAttributes(respAttributes...))
+
+		// Record request size.
+		reqSize.Record(
+			ctx,
+			computeApproximateRequestSize(c.Request),
+			metric.WithAttributes(respAttributes...),
+		)
+
+		// Record response size.
+		respSize.Record(
+			ctx,
+			int64(c.Writer.Size()),
+			metric.WithAttributes(respAttributes...),
+		)
+
+		// Record req + resp duration.
+		duration.Record(
+			ctx,
+			time.Since(start).Milliseconds(),
+			metric.WithAttributes(respAttributes...),
+		)
+	}
+}
+
+func computeApproximateRequestSize(r *http.Request) (sz int64) {
+	len := func(s string) int64 { return int64(len(s)) }
+
+	// First line
+	sz += len(r.Method)
+	if r.URL != nil {
+		sz += len(r.URL.Path)
+		sz++ // for '?'
+		sz += len(r.URL.RawQuery)
+		sz += len(r.URL.RawFragment)
+	}
+	sz += len(r.Proto)
+	sz += 2 // for '\r\n'
+
+	// Next are lines for request headers.
+	for name, values := range r.Header {
+
+		// Each value on its own line.
+		for _, value := range values {
+			sz += len(name)
+			sz += len(value)
+			sz += 2 // for '\r\n'
+		}
+	}
+
+	// Finally, any request body (if set),
+	// this includes (multipart) form data.
+	sz += max(r.ContentLength, 0)
+
+	return
+}
diff --git a/internal/observability/metrics.go b/internal/observability/metrics.go
index 8df5fd9fb..4bca89c20 100644
--- a/internal/observability/metrics.go
+++ b/internal/observability/metrics.go
@@ -27,7 +27,6 @@ import (
 	"code.superseriousbusiness.org/gotosocial/internal/state"
 
 	"github.com/gin-gonic/gin"
-	"github.com/technologize/otel-go-contrib/otelginmetrics"
 	"go.opentelemetry.io/contrib/exporters/autoexport"
 	"go.opentelemetry.io/contrib/instrumentation/runtime"
 	"go.opentelemetry.io/otel"
@@ -266,5 +265,5 @@ func InitializeMetrics(ctx context.Context, state *state.State) error {
 }
 
 func MetricsMiddleware() gin.HandlerFunc {
-	return otelginmetrics.Middleware(serviceName)
+	return ginMiddleware()
 }