server: add ability to record config deprecations

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

plugin/context.go

@@ -127,6 +127,19 @@ func (ps *Set) Get(t Type) (interface{}, error) {
 	return nil, fmt.Errorf("no plugins registered for %s: %w", t, ErrPluginNotFound)
 }
 
+// GetByID returns the plugin of the given type and ID
+func (ps *Set) GetByID(t Type, id string) (*Plugin, error) {
+	typSet, ok := ps.byTypeAndID[t]
+	if !ok || len(typSet) == 0 {
+		return nil, fmt.Errorf("no plugins registered for %s: %w", t, ErrPluginNotFound)
+	}
+	p, ok := typSet[id]
+	if !ok {
+		return nil, fmt.Errorf("no plugins registered for %s %q: %w", t, id, ErrPluginNotFound)
+	}
+	return p, nil
+}
+
 // GetAll returns all initialized plugins
 func (ps *Set) GetAll() []*Plugin {
 	return ps.ordered

services/server/server.go

@@ -34,6 +34,18 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/containerd/log"
+	"github.com/containerd/ttrpc"
+	"github.com/docker/go-metrics"
+	grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware"
+	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
+	v1 "github.com/opencontainers/image-spec/specs-go/v1"
+	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/backoff"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/credentials/insecure"
+
 	csapi "github.com/containerd/containerd/api/services/content/v1"
 	diffapi "github.com/containerd/containerd/api/services/diff/v1"
 	sbapi "github.com/containerd/containerd/api/services/sandbox/v1"
@@ -52,19 +64,9 @@ import (
 	"github.com/containerd/containerd/plugins"
 	sbproxy "github.com/containerd/containerd/sandbox/proxy"
 	srvconfig "github.com/containerd/containerd/services/server/config"
+	"github.com/containerd/containerd/services/warning"
 	ssproxy "github.com/containerd/containerd/snapshots/proxy"
 	"github.com/containerd/containerd/sys"
-	"github.com/containerd/log"
-	"github.com/containerd/ttrpc"
-	"github.com/docker/go-metrics"
-	grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware"
-	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
-	v1 "github.com/opencontainers/image-spec/specs-go/v1"
-	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/backoff"
-	"google.golang.org/grpc/credentials"
-	"google.golang.org/grpc/credentials/insecure"
 )
 
 // CreateTopLevelDirectories creates the top-level root and state directories.
@@ -330,9 +332,33 @@ func New(ctx context.Context, config *srvconfig.Config) (*Server, error) {
 			return nil, err
 		}
 	}
+
+	recordConfigDeprecations(ctx, config, initialized)
 	return s, nil
 }
 
+// recordConfigDeprecations attempts to record use of any deprecated config field.  Failures are logged and ignored.
+func recordConfigDeprecations(ctx context.Context, config *srvconfig.Config, set *plugin.Set) {
+	// record any detected deprecations without blocking server startup
+	plugin, err := set.GetByID(plugins.WarningPlugin, plugins.DeprecationsPlugin)
+	if err != nil {
+		log.G(ctx).WithError(err).Warn("failed to load warning service to record deprecations")
+		return
+	}
+	instance, err := plugin.Instance()
+	if err != nil {
+		log.G(ctx).WithError(err).Warn("failed to load warning service to record deprecations")
+		return
+	}
+	warn, ok := instance.(warning.Service)
+	if !ok {
+		log.G(ctx).WithError(err).Warn("failed to load warning service to record deprecations, unexpected plugin type")
+		return
+	}
+
+	_ = warn // TODO(samuelkarp): placeholder for future use
+}
+
 // Server is the containerd main daemon
 type Server struct {
 	grpcServer  *grpc.Server
@@ -433,7 +459,7 @@ func (s *Server) Wait() {
 // of all plugins.
 func LoadPlugins(ctx context.Context, config *srvconfig.Config) ([]plugin.Registration, error) {
 	// load all plugins into containerd
-	path := config.PluginDir //nolint: staticcheck
+	path := config.PluginDir // nolint: staticcheck
 	if path == "" {
 		path = filepath.Join(config.Root, "plugins")
 	}