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Add support for multiple differs

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Updates the differ service to support calling and configuring
multiple differs. The differs are configured as an ordered list
of differs which will each be attempting until a supported differ
is called.

Additionally a not supported error type was added to allow differs
to be selective of whether the differ arguments are supported by
the differ. This error type corresponds to the GRPC unimplemented error.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>
This commit is contained in:
Derek McGowan
2017-08-18 11:19:08 -07:00
parent b2ee0ab34e
commit 2fa366d6af
4 changed files with 98 additions and 29 deletions
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63
services/diff/service.go
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@@ -6,10 +6,22 @@ import (
"github.com/containerd/containerd/errdefs"
"github.com/containerd/containerd/mount"
"github.com/containerd/containerd/plugin"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
"golang.org/x/net/context"
"google.golang.org/grpc"
)
type config struct {
// Order is the order of preference in which to try diff algorithms, the
// first differ which is supported is used.
// Note when multiple differs may be supported, this order will be
// respected for which is choosen. Each differ should return the same
// correct output, allowing any ordering to be used to prefer
// more optimimal implementations.
Order []string `toml:"default,omitempty"`
}
func init() {
plugin.Register(&plugin.Registration{
Type: plugin.GRPCPlugin,
@@ -17,20 +29,34 @@ func init() {
Requires: []plugin.PluginType{
plugin.DiffPlugin,
},
Config: &config{
Order: []string{"walking"},
},
Init: func(ic *plugin.InitContext) (interface{}, error) {
d, err := ic.Get(plugin.DiffPlugin)
differs, err := ic.GetAll(plugin.DiffPlugin)
if err != nil {
return nil, err
}
orderedNames := ic.Config.(*config).Order
ordered := make([]plugin.Differ, len(orderedNames))
for i, n := range orderedNames {
differ, ok := differs[n]
if !ok {
return nil, errors.Errorf("needed differ not loaded: %s", n)
}
ordered[i] = differ.(plugin.Differ)
}
return &service{
diff: d.(plugin.Differ),
differs: ordered,
}, nil
},
})
}
type service struct {
diff plugin.Differ
differs []plugin.Differ
}
func (s *service) Register(gs *grpc.Server) error {
@@ -39,12 +65,20 @@ func (s *service) Register(gs *grpc.Server) error {
}
func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi.ApplyResponse, error) {
desc := toDescriptor(er.Diff)
// TODO: Check for supported media types
var (
ocidesc ocispec.Descriptor
err error
desc = toDescriptor(er.Diff)
mounts = toMounts(er.Mounts)
)
mounts := toMounts(er.Mounts)
for _, differ := range s.differs {
ocidesc, err = differ.Apply(ctx, desc, mounts)
if !errdefs.IsNotSupported(err) {
break
}
}
ocidesc, err := s.diff.Apply(ctx, desc, mounts)
if err != nil {
return nil, errdefs.ToGRPC(err)
}
@@ -56,10 +90,19 @@ func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi
}
func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.DiffResponse, error) {
aMounts := toMounts(dr.Left)
bMounts := toMounts(dr.Right)
var (
ocidesc ocispec.Descriptor
err error
aMounts = toMounts(dr.Left)
bMounts = toMounts(dr.Right)
)
ocidesc, err := s.diff.DiffMounts(ctx, aMounts, bMounts, dr.MediaType, dr.Ref)
for _, differ := range s.differs {
ocidesc, err = differ.DiffMounts(ctx, aMounts, bMounts, dr.MediaType, dr.Ref)
if !errdefs.IsNotSupported(err) {
break
}
}
if err != nil {
return nil, errdefs.ToGRPC(err)
}