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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
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21
services/tasks/service.go
View File

@@ -16,6 +16,7 @@ import (
"github.com/containerd/containerd/archive"
"github.com/containerd/containerd/containers"
"github.com/containerd/containerd/content"
"github.com/containerd/containerd/errdefs"
"github.com/containerd/containerd/events"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/log"
@@ -36,6 +37,9 @@ var (
empty = &google_protobuf.Empty{}
)
// TODO(stevvooe): Clean up error mapping to avoid double mapping certain
// errors within helper methods.
func init() {
plugin.Register(&plugin.Registration{
Type: plugin.GRPCPlugin,
@@ -114,14 +118,7 @@ func (s *Service) Create(ctx context.Context, r *api.CreateTaskRequest) (*api.Cr
container, err := s.getContainer(ctx, r.ContainerID)
if err != nil {
switch {
case metadata.IsNotFound(err):
return nil, grpc.Errorf(codes.NotFound, "container %v not found", r.ContainerID)
case metadata.IsExists(err):
return nil, grpc.Errorf(codes.AlreadyExists, "container %v already exists", r.ContainerID)
}
return nil, err
return nil, errdefs.ToGRPC(err)
}
opts := plugin.CreateOpts{
@@ -491,7 +488,7 @@ func (s *Service) getContainer(ctx context.Context, id string) (containers.Conta
container, err = store.Get(ctx, id)
return err
}); err != nil {
return containers.Container{}, err
return containers.Container{}, errdefs.ToGRPC(err)
}
return container, nil
@@ -500,12 +497,12 @@ func (s *Service) getContainer(ctx context.Context, id string) (containers.Conta
func (s *Service) getTask(ctx context.Context, id string) (plugin.Task, error) {
container, err := s.getContainer(ctx, id)
if err != nil {
return nil, grpc.Errorf(codes.InvalidArgument, "task %v not found: %s", id, err.Error())
return nil, err
}
runtime, err := s.getRuntime(container.Runtime.Name)
if err != nil {
return nil, grpc.Errorf(codes.NotFound, "task %v not found: %s", id, err.Error())
return nil, errdefs.ToGRPCf(err, "runtime for task %v", id)
}
t, err := runtime.Get(ctx, id)
@@ -519,7 +516,7 @@ func (s *Service) getTask(ctx context.Context, id string) (plugin.Task, error) {
func (s *Service) getRuntime(name string) (plugin.Runtime, error) {
runtime, ok := s.runtimes[name]
if !ok {
return nil, fmt.Errorf("unknown runtime %q", name)
return nil, grpc.Errorf(codes.NotFound, "unknown runtime %q", name)
}
return runtime, nil
}