Created
April 16, 2023 07:48
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Proxy differ using containerd default applier
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/* | |
Copyright The containerd Authors. | |
Licensed under the Apache License, Version 2.0 (the "License"); | |
you may not use this file except in compliance with the License. | |
You may obtain a copy of the License at | |
http://www.apache.org/licenses/LICENSE-2.0 | |
Unless required by applicable law or agreed to in writing, software | |
distributed under the License is distributed on an "AS IS" BASIS, | |
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
See the License for the specific language governing permissions and | |
limitations under the License. | |
*/ | |
package main | |
import ( | |
"context" | |
"os" | |
"sync" | |
"sync/atomic" | |
"github.com/containerd/containerd" | |
diffapi "github.com/containerd/containerd/api/services/diff/v1" | |
"github.com/containerd/containerd/contrib/diffservice" | |
"github.com/containerd/containerd/defaults" | |
"github.com/containerd/containerd/diff" | |
"github.com/containerd/containerd/diff/apply" | |
"github.com/containerd/containerd/log" | |
"github.com/containerd/containerd/mount" | |
"github.com/containerd/containerd/namespaces" | |
"github.com/containerd/containerd/sys" | |
grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware" | |
ocispec "github.com/opencontainers/image-spec/specs-go/v1" | |
"google.golang.org/grpc" | |
) | |
func main() { | |
serverOpts := []grpc.ServerOption{ | |
grpc.StreamInterceptor(grpc_middleware.ChainStreamServer( | |
streamNamespaceInterceptor, | |
)), | |
grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer( | |
unaryNamespaceInterceptor, | |
)), | |
} | |
s := grpc.NewServer(serverOpts...) | |
diffapi.RegisterDiffServer(s, diffservice.FromApplierAndComparer(&applierService{address: defaults.DefaultAddress}, nil)) | |
path := "proxy.sock" | |
if len(os.Args) == 2 { | |
path = os.Args[1] | |
} | |
l, err := sys.GetLocalListener(path, os.Getuid(), os.Getgid()) | |
if err != nil { | |
log.L.WithError(err).Fatalf("unable to listen on %s", path) | |
} | |
defer l.Close() | |
if err := s.Serve(l); err != nil { | |
log.L.WithError(err).Fatal("serve GRPC") | |
} | |
} | |
func unaryNamespaceInterceptor(ctx context.Context, req interface{}, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) { | |
if ns, ok := namespaces.Namespace(ctx); ok { | |
// The above call checks the *incoming* metadata, this makes sure the outgoing metadata is also set | |
ctx = namespaces.WithNamespace(ctx, ns) | |
} | |
return handler(ctx, req) | |
} | |
func streamNamespaceInterceptor(srv interface{}, ss grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error { | |
ctx := ss.Context() | |
if ns, ok := namespaces.Namespace(ctx); ok { | |
// The above call checks the *incoming* metadata, this makes sure the outgoing metadata is also set | |
ctx = namespaces.WithNamespace(ctx, ns) | |
ss = &wrappedSSWithContext{ctx: ctx, ServerStream: ss} | |
} | |
return handler(srv, ss) | |
} | |
type wrappedSSWithContext struct { | |
grpc.ServerStream | |
ctx context.Context | |
} | |
func (w *wrappedSSWithContext) Context() context.Context { | |
return w.ctx | |
} | |
type applierService struct { | |
address string | |
applier diff.Applier | |
loaded uint32 | |
loadM sync.Mutex | |
diffapi.UnimplementedDiffServer | |
} | |
func (a *applierService) getApplier() (diff.Applier, error) { | |
if atomic.LoadUint32(&a.loaded) == 1 { | |
return a.applier, nil | |
} | |
a.loadM.Lock() | |
defer a.loadM.Unlock() | |
if a.loaded == 1 { | |
return a.applier, nil | |
} | |
client, err := containerd.New(a.address) | |
if err != nil { | |
return nil, nil | |
} | |
defer atomic.StoreUint32(&a.loaded, 1) | |
a.applier = apply.NewFileSystemApplier(client.ContentStore()) | |
return a.applier, nil | |
} | |
func (a *applierService) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []mount.Mount, opts ...diff.ApplyOpt) (d ocispec.Descriptor, err error) { | |
applier, err := a.getApplier() | |
if err != nil { | |
return d, err | |
} | |
log.G(ctx).WithField("digest", desc.Digest).Info("applying diff") | |
return applier.Apply(ctx, desc, mounts, opts...) | |
} |
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