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errdefs: centralize error handling

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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>
This commit is contained in:
Stephen J Day
2017-06-28 21:32:15 -07:00
parent 917914fcf5
commit a4fadc596b
42 changed files with 331 additions and 555 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
services/snapshot/client.go
View File

@@ -3,16 +3,12 @@ package snapshot
import (
"context"
"io"
"strings"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
snapshotapi "github.com/containerd/containerd/api/services/snapshot/v1"
"github.com/containerd/containerd/api/types"
"github.com/containerd/containerd/errdefs"
"github.com/containerd/containerd/mount"
"github.com/containerd/containerd/snapshot"
"github.com/pkg/errors"
)
// NewSnapshotterFromClient returns a new Snapshotter which communicates
@@ -30,7 +26,7 @@ type remoteSnapshotter struct {
func (r *remoteSnapshotter) Stat(ctx context.Context, key string) (snapshot.Info, error) {
resp, err := r.client.Stat(ctx, &snapshotapi.StatSnapshotRequest{Key: key})
if err != nil {
return snapshot.Info{}, rewriteGRPCError(err)
return snapshot.Info{}, errdefs.FromGRPC(err)
}
return toInfo(resp.Info), nil
}
@@ -38,7 +34,7 @@ func (r *remoteSnapshotter) Stat(ctx context.Context, key string) (snapshot.Info
func (r *remoteSnapshotter) Usage(ctx context.Context, key string) (snapshot.Usage, error) {
resp, err := r.client.Usage(ctx, &snapshotapi.UsageRequest{Key: key})
if err != nil {
return snapshot.Usage{}, rewriteGRPCError(err)
return snapshot.Usage{}, errdefs.FromGRPC(err)
}
return toUsage(resp), nil
}
@@ -46,7 +42,7 @@ func (r *remoteSnapshotter) Usage(ctx context.Context, key string) (snapshot.Usa
func (r *remoteSnapshotter) Mounts(ctx context.Context, key string) ([]mount.Mount, error) {
resp, err := r.client.Mounts(ctx, &snapshotapi.MountsRequest{Key: key})
if err != nil {
return nil, rewriteGRPCError(err)
return nil, errdefs.FromGRPC(err)
}
return toMounts(resp.Mounts), nil
}
@@ -54,7 +50,7 @@ func (r *remoteSnapshotter) Mounts(ctx context.Context, key string) ([]mount.Mou
func (r *remoteSnapshotter) Prepare(ctx context.Context, key, parent string) ([]mount.Mount, error) {
resp, err := r.client.Prepare(ctx, &snapshotapi.PrepareSnapshotRequest{Key: key, Parent: parent})
if err != nil {
return nil, rewriteGRPCError(err)
return nil, errdefs.FromGRPC(err)
}
return toMounts(resp.Mounts), nil
}
@@ -62,7 +58,7 @@ func (r *remoteSnapshotter) Prepare(ctx context.Context, key, parent string) ([]
func (r *remoteSnapshotter) View(ctx context.Context, key, parent string) ([]mount.Mount, error) {
resp, err := r.client.View(ctx, &snapshotapi.ViewSnapshotRequest{Key: key, Parent: parent})
if err != nil {
return nil, rewriteGRPCError(err)
return nil, errdefs.FromGRPC(err)
}
return toMounts(resp.Mounts), nil
}
@@ -72,18 +68,18 @@ func (r *remoteSnapshotter) Commit(ctx context.Context, name, key string) error
Name: name,
Key: key,
})
return rewriteGRPCError(err)
return errdefs.FromGRPC(err)
}
func (r *remoteSnapshotter) Remove(ctx context.Context, key string) error {
_, err := r.client.Remove(ctx, &snapshotapi.RemoveSnapshotRequest{Key: key})
return rewriteGRPCError(err)
return errdefs.FromGRPC(err)
}
func (r *remoteSnapshotter) Walk(ctx context.Context, fn func(context.Context, snapshot.Info) error) error {
sc, err := r.client.List(ctx, &snapshotapi.ListSnapshotsRequest{})
if err != nil {
rewriteGRPCError(err)
errdefs.FromGRPC(err)
}
for {
resp, err := sc.Recv()
@@ -91,7 +87,7 @@ func (r *remoteSnapshotter) Walk(ctx context.Context, fn func(context.Context, s
if err == io.EOF {
return nil
}
return rewriteGRPCError(err)
return errdefs.FromGRPC(err)
}
if resp == nil {
return nil
@@ -104,25 +100,6 @@ func (r *remoteSnapshotter) Walk(ctx context.Context, fn func(context.Context, s
}
}
func rewriteGRPCError(err error) error {
switch grpc.Code(errors.Cause(err)) {
case codes.AlreadyExists:
return snapshot.ErrSnapshotExist
case codes.NotFound:
return snapshot.ErrSnapshotNotExist
case codes.FailedPrecondition:
desc := grpc.ErrorDesc(errors.Cause(err))
if strings.Contains(desc, snapshot.ErrSnapshotNotActive.Error()) {
return snapshot.ErrSnapshotNotActive
}
if strings.Contains(desc, snapshot.ErrSnapshotNotCommitted.Error()) {
return snapshot.ErrSnapshotNotCommitted
}
}
return err
}
func toKind(kind snapshotapi.Kind) snapshot.Kind {
if kind == snapshotapi.KindActive {
return snapshot.KindActive

30
services/snapshot/service.go
View File

@@ -6,6 +6,7 @@ import (
eventsapi "github.com/containerd/containerd/api/services/events/v1"
snapshotapi "github.com/containerd/containerd/api/services/snapshot/v1"
"github.com/containerd/containerd/api/types"
"github.com/containerd/containerd/errdefs"
"github.com/containerd/containerd/events"
"github.com/containerd/containerd/log"
"github.com/containerd/containerd/mount"
@@ -14,7 +15,6 @@ import (
protoempty "github.com/golang/protobuf/ptypes/empty"
"golang.org/x/net/context"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
)
func init() {
@@ -60,7 +60,7 @@ func (s *service) Prepare(ctx context.Context, pr *snapshotapi.PrepareSnapshotRe
// TODO: Lookup snapshot id from metadata store
mounts, err := s.snapshotter.Prepare(ctx, pr.Key, pr.Parent)
if err != nil {
return nil, grpcError(err)
return nil, errdefs.ToGRPC(err)
}
if err := s.emit(ctx, "/snapshot/prepare", &eventsapi.SnapshotPrepare{
@@ -80,7 +80,7 @@ func (s *service) View(ctx context.Context, pr *snapshotapi.ViewSnapshotRequest)
// TODO: Lookup snapshot id from metadata store
mounts, err := s.snapshotter.View(ctx, pr.Key, pr.Parent)
if err != nil {
return nil, grpcError(err)
return nil, errdefs.ToGRPC(err)
}
return &snapshotapi.ViewSnapshotResponse{
Mounts: fromMounts(mounts),
@@ -93,7 +93,7 @@ func (s *service) Mounts(ctx context.Context, mr *snapshotapi.MountsRequest) (*s
// TODO: Lookup snapshot id from metadata store
mounts, err := s.snapshotter.Mounts(ctx, mr.Key)
if err != nil {
return nil, grpcError(err)
return nil, errdefs.ToGRPC(err)
}
return &snapshotapi.MountsResponse{
Mounts: fromMounts(mounts),
@@ -105,7 +105,7 @@ func (s *service) Commit(ctx context.Context, cr *snapshotapi.CommitSnapshotRequ
// TODO: Apply namespace
// TODO: Lookup snapshot id from metadata store
if err := s.snapshotter.Commit(ctx, cr.Name, cr.Key); err != nil {
return nil, grpcError(err)
return nil, errdefs.ToGRPC(err)
}
if err := s.emit(ctx, "/snapshot/commit", &eventsapi.SnapshotCommit{
@@ -122,7 +122,7 @@ func (s *service) Remove(ctx context.Context, rr *snapshotapi.RemoveSnapshotRequ
// TODO: Apply namespace
// TODO: Lookup snapshot id from metadata store
if err := s.snapshotter.Remove(ctx, rr.Key); err != nil {
return nil, grpcError(err)
return nil, errdefs.ToGRPC(err)
}
if err := s.emit(ctx, "/snapshot/remove", &eventsapi.SnapshotRemove{
@@ -138,7 +138,7 @@ func (s *service) Stat(ctx context.Context, sr *snapshotapi.StatSnapshotRequest)
// TODO: Apply namespace
info, err := s.snapshotter.Stat(ctx, sr.Key)
if err != nil {
return nil, grpcError(err)
return nil, errdefs.ToGRPC(err)
}
return &snapshotapi.StatSnapshotResponse{Info: fromInfo(info)}, nil
@@ -184,26 +184,12 @@ func (s *service) Usage(ctx context.Context, ur *snapshotapi.UsageRequest) (*sna
// TODO: Apply namespace
usage, err := s.snapshotter.Usage(ctx, ur.Key)
if err != nil {
return nil, grpcError(err)
return nil, errdefs.ToGRPC(err)
}
return fromUsage(usage), nil
}
func grpcError(err error) error {
if snapshot.IsNotExist(err) {
return grpc.Errorf(codes.NotFound, err.Error())
}
if snapshot.IsExist(err) {
return grpc.Errorf(codes.AlreadyExists, err.Error())
}
if snapshot.IsNotActive(err) || snapshot.IsNotCommitted(err) {
return grpc.Errorf(codes.FailedPrecondition, err.Error())
}
return err
}
func fromKind(kind snapshot.Kind) snapshotapi.Kind {
if kind == snapshot.KindActive {
return snapshotapi.KindActive