warning: new service for deprecations

Signed-off-by: Samuel Karp <samuelkarp@google.com>

cmd/containerd/builtins/builtins.go

@@ -46,4 +46,5 @@ import (
 	_ "github.com/containerd/containerd/services/tasks"
 	_ "github.com/containerd/containerd/services/transfer"
 	_ "github.com/containerd/containerd/services/version"
+	_ "github.com/containerd/containerd/services/warning"
 )

plugins/types.go

@@ -65,11 +65,15 @@ const (
 	SandboxControllerPlugin plugin.Type = "io.containerd.sandbox.controller.v1"
 	// ImageVerifierPlugin implements an image verifier service
 	ImageVerifierPlugin plugin.Type = "io.containerd.image-verifier.v1"
+	// WarningPlugin implements a warning service
+	WarningPlugin plugin.Type = "io.containerd.warning.v1"
 )
 
 const (
 	// RuntimeRuncV2 is the runc runtime that supports multiple containers per shim
 	RuntimeRuncV2 = "io.containerd.runc.v2"
+
+	DeprecationsPlugin = "deprecations"
 )
 
 const (

services/warning/service.go

@@ -0,0 +1,95 @@
+/*
+   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 warning
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/containerd/log"
+
+	deprecation "github.com/containerd/containerd/pkg/deprecation"
+	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/plugin/registry"
+	"github.com/containerd/containerd/plugins"
+)
+
+type Service interface {
+	Emit(context.Context, deprecation.Warning)
+	Warnings() []Warning
+}
+
+func init() {
+	registry.Register(&plugin.Registration{
+		Type: plugins.WarningPlugin,
+		ID:   plugins.DeprecationsPlugin,
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			return &service{warnings: make(map[deprecation.Warning]time.Time)}, nil
+		},
+	})
+}
+
+type Warning struct {
+	ID             deprecation.Warning
+	LastOccurrence time.Time
+	Message        string
+}
+
+var _ Service = (*service)(nil)
+
+func init() {
+	registry.Register(&plugin.Registration{
+		Type: plugins.InternalPlugin,
+		ID:   "warning",
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			return &service{warnings: make(map[deprecation.Warning]time.Time)}, nil
+		},
+	})
+}
+
+type service struct {
+	warnings map[deprecation.Warning]time.Time
+	m        sync.RWMutex
+}
+
+func (s *service) Emit(ctx context.Context, warning deprecation.Warning) {
+	if !deprecation.Valid(warning) {
+		log.G(ctx).WithField("warningID", string(warning)).Warn("invalid deprecation warning")
+		return
+	}
+	s.m.Lock()
+	defer s.m.Unlock()
+	s.warnings[warning] = time.Now()
+}
+func (s *service) Warnings() []Warning {
+	s.m.RLock()
+	defer s.m.RUnlock()
+	var warnings []Warning
+	for k, v := range s.warnings {
+		msg, ok := deprecation.Message(k)
+		if !ok {
+			continue
+		}
+		warnings = append(warnings, Warning{
+			ID:             k,
+			LastOccurrence: v,
+			Message:        msg,
+		})
+	}
+	return warnings
+}