errdefs: centralize error handling

Now that we have most of the services required for use with containerd,
it was found that common patterns were used throughout services. By
defining a central `errdefs` package, we ensure that services will map
errors to and from grpc consistently and cleanly. One can decorate an
error with as much context as necessary, using `pkg/errors` and still
have the error mapped correctly via grpc.

We make a few sacrifices. At this point, the common errors we use across
the repository all map directly to grpc error codes. While this seems
positively crazy, it actually works out quite well. The error conditions
that were specific weren't super necessary and the ones that were
necessary now simply have better context information. We lose the
ability to add new codes, but this constraint may not be a bad thing.

Effectively, as long as one uses the errors defined in `errdefs`, the
error class will be mapped correctly across the grpc boundary and
everything will be good. If you don't use those definitions, the error
maps to "unknown" and the error message is preserved.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

services/containers/helpers.go

@@ -3,13 +3,8 @@ package containers
 import (
 	api "github.com/containerd/containerd/api/services/containers/v1"
 	"github.com/containerd/containerd/containers"
-	"github.com/containerd/containerd/identifiers"
-	"github.com/containerd/containerd/metadata"
-	"github.com/containerd/containerd/namespaces"
 	"github.com/gogo/protobuf/types"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/codes"
 )
 
 func containersToProto(containers []containers.Container) []api.Container {
@@ -52,18 +47,3 @@ func containerFromProto(containerpb *api.Container) containers.Container {
 		RootFS: containerpb.RootFS,
 	}
 }
-
-func mapGRPCError(err error, id string) error {
-	switch {
-	case metadata.IsNotFound(err):
-		return grpc.Errorf(codes.NotFound, "container %v not found", id)
-	case metadata.IsExists(err):
-		return grpc.Errorf(codes.AlreadyExists, "container %v already exists", id)
-	case namespaces.IsNamespaceRequired(err):
-		return grpc.Errorf(codes.InvalidArgument, "namespace required, please set %q header", namespaces.GRPCHeader)
-	case identifiers.IsInvalid(err):
-		return grpc.Errorf(codes.InvalidArgument, err.Error())
-	}
-
-	return err
-}

services/containers/service.go

@@ -5,6 +5,7 @@ import (
 	api "github.com/containerd/containerd/api/services/containers/v1"
 	eventsapi "github.com/containerd/containerd/api/services/events/v1"
 	"github.com/containerd/containerd/containers"
+	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/events"
 	"github.com/containerd/containerd/metadata"
 	"github.com/containerd/containerd/plugin"
@@ -49,31 +50,30 @@ func (s *Service) Register(server *grpc.Server) error {
 func (s *Service) Get(ctx context.Context, req *api.GetContainerRequest) (*api.GetContainerResponse, error) {
 	var resp api.GetContainerResponse
 
-	return &resp, s.withStoreView(ctx, func(ctx context.Context, store containers.Store) error {
+	return &resp, errdefs.ToGRPC(s.withStoreView(ctx, func(ctx context.Context, store containers.Store) error {
 		container, err := store.Get(ctx, req.ID)
 		if err != nil {
-			return mapGRPCError(err, req.ID)
+			return err
 		}
 		containerpb := containerToProto(&container)
 		resp.Container = containerpb
 
 		return nil
-	})
+	}))
 }
 
 func (s *Service) List(ctx context.Context, req *api.ListContainersRequest) (*api.ListContainersResponse, error) {
 	var resp api.ListContainersResponse
 
-	return &resp, s.withStoreView(ctx, func(ctx context.Context, store containers.Store) error {
+	return &resp, errdefs.ToGRPC(s.withStoreView(ctx, func(ctx context.Context, store containers.Store) error {
 		containers, err := store.List(ctx, req.Filter)
 		if err != nil {
-			return mapGRPCError(err, "")
+			return err
 		}
 
 		resp.Containers = containersToProto(containers)
 		return nil
-	})
-
+	}))
 }
 
 func (s *Service) Create(ctx context.Context, req *api.CreateContainerRequest) (*api.CreateContainerResponse, error) {
@@ -84,14 +84,14 @@ func (s *Service) Create(ctx context.Context, req *api.CreateContainerRequest) (
 
 		created, err := store.Create(ctx, container)
 		if err != nil {
-			return mapGRPCError(err, req.Container.ID)
+			return err
 		}
 
 		resp.Container = containerToProto(&created)
 
 		return nil
 	}); err != nil {
-		return &resp, err
+		return &resp, errdefs.ToGRPC(err)
 	}
 	if err := s.emit(ctx, "/containers/create", &eventsapi.ContainerCreate{
 		ContainerID: resp.Container.ID,
@@ -115,7 +115,7 @@ func (s *Service) Update(ctx context.Context, req *api.UpdateContainerRequest) (
 
 		current, err := store.Get(ctx, container.ID)
 		if err != nil {
-			return mapGRPCError(err, container.ID)
+			return err
 		}
 
 		if current.ID != container.ID {
@@ -150,14 +150,14 @@ func (s *Service) Update(ctx context.Context, req *api.UpdateContainerRequest) (
 
 		created, err := store.Update(ctx, container)
 		if err != nil {
-			return mapGRPCError(err, req.Container.ID)
+			return err
 		}
 
 		resp.Container = containerToProto(&created)
 
 		return nil
 	}); err != nil {
-		return &resp, err
+		return &resp, errdefs.ToGRPC(err)
 	}
 
 	if err := s.emit(ctx, "/containers/update", &eventsapi.ContainerUpdate{
@@ -174,9 +174,9 @@ func (s *Service) Update(ctx context.Context, req *api.UpdateContainerRequest) (
 
 func (s *Service) Delete(ctx context.Context, req *api.DeleteContainerRequest) (*empty.Empty, error) {
 	if err := s.withStoreUpdate(ctx, func(ctx context.Context, store containers.Store) error {
-		return mapGRPCError(store.Delete(ctx, req.ID), req.ID)
+		return store.Delete(ctx, req.ID)
 	}); err != nil {
-		return &empty.Empty{}, mapGRPCError(err, req.ID)
+		return &empty.Empty{}, errdefs.ToGRPC(err)
 	}
 
 	if err := s.emit(ctx, "/containers/delete", &eventsapi.ContainerDelete{