shim: add OTEL tracing plugin for trace context propagation

Register a host-side OTel tracing plugin in the shim that configures
a TracerProvider with an OTLP HTTP exporter, enabling end-to-end trace
context propagation across the shim's ttrpc calls.

Signed-off-by: David Scott <dave@recoil.org>

Author: djs55

cmd/containerd-shim-nerdbox-v1/main.go

@@ -26,6 +26,7 @@ import (
 	_ "github.com/containerd/nerdbox/plugins/shim/sandbox"
 	_ "github.com/containerd/nerdbox/plugins/shim/streaming"
 	_ "github.com/containerd/nerdbox/plugins/shim/task"
+	_ "github.com/containerd/nerdbox/plugins/shim/tracing"
 	_ "github.com/containerd/nerdbox/plugins/shim/transfer"
 	_ "github.com/containerd/nerdbox/plugins/vm/libkrun"
 )

plugins/shim/tracing/plugin.go

@@ -0,0 +1,80 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package tracing
+
+import (
+	"context"
+	"time"
+
+	"github.com/containerd/containerd/v2/pkg/shutdown"
+	cplugins "github.com/containerd/containerd/v2/plugins"
+	"github.com/containerd/log"
+	"github.com/containerd/otelttrpc"
+	"github.com/containerd/plugin"
+	"github.com/containerd/plugin/registry"
+	"github.com/containerd/ttrpc"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+
+	"github.com/containerd/nerdbox/internal/tracing"
+	"github.com/containerd/nerdbox/plugins"
+)
+
+func init() {
+	registry.Register(&plugin.Registration{
+		Type: plugins.TTRPCPlugin,
+		ID:   "tracing",
+		Requires: []plugin.Type{
+			cplugins.InternalPlugin,
+		},
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			ctx := ic.Context
+
+			otel.SetTextMapPropagator(propagation.TraceContext{})
+
+			exp := tracing.NewRelayExporter(ctx)
+			if exp == nil {
+				log.G(ctx).Debug("OTEL_EXPORTER_OTLP_ENDPOINT not set, shim tracing disabled")
+				return &interceptor{}, nil
+			}
+
+			tp := sdktrace.NewTracerProvider(
+				sdktrace.WithBatcher(exp,
+					sdktrace.WithBatchTimeout(100*time.Millisecond),
+				),
+			)
+			otel.SetTracerProvider(tp)
+
+			ss, err := ic.GetByID(cplugins.InternalPlugin, "shutdown")
+			if err != nil {
+				return nil, err
+			}
+			ss.(shutdown.Service).RegisterCallback(func(ctx context.Context) error {
+				return tp.Shutdown(ctx)
+			})
+
+			return &interceptor{}, nil
+		},
+	})
+}
+
+type interceptor struct{}
+
+func (i *interceptor) UnaryServerInterceptor() ttrpc.UnaryServerInterceptor {
+	return otelttrpc.UnaryServerInterceptor()
+}