github.com/containerd/containerd@v22.0.0-20200918172823-438c87b8e050+incompatible/namespaces/grpc.go (about)

     1  /*
     2     Copyright The containerd Authors.
     3  
     4     Licensed under the Apache License, Version 2.0 (the "License");
     5     you may not use this file except in compliance with the License.
     6     You may obtain a copy of the License at
     7  
     8         http://www.apache.org/licenses/LICENSE-2.0
     9  
    10     Unless required by applicable law or agreed to in writing, software
    11     distributed under the License is distributed on an "AS IS" BASIS,
    12     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13     See the License for the specific language governing permissions and
    14     limitations under the License.
    15  */
    16  
    17  package namespaces
    18  
    19  import (
    20  	"context"
    21  
    22  	"google.golang.org/grpc/metadata"
    23  )
    24  
    25  const (
    26  	// GRPCHeader defines the header name for specifying a containerd namespace.
    27  	GRPCHeader = "containerd-namespace"
    28  )
    29  
    30  // NOTE(stevvooe): We can stub this file out if we don't want a grpc dependency here.
    31  
    32  func withGRPCNamespaceHeader(ctx context.Context, namespace string) context.Context {
    33  	// also store on the grpc headers so it gets picked up by any clients that
    34  	// are using this.
    35  	nsheader := metadata.Pairs(GRPCHeader, namespace)
    36  	md, ok := metadata.FromOutgoingContext(ctx) // merge with outgoing context.
    37  	if !ok {
    38  		md = nsheader
    39  	} else {
    40  		// order ensures the latest is first in this list.
    41  		md = metadata.Join(nsheader, md)
    42  	}
    43  
    44  	return metadata.NewOutgoingContext(ctx, md)
    45  }
    46  
    47  func fromGRPCHeader(ctx context.Context) (string, bool) {
    48  	// try to extract for use in grpc servers.
    49  	md, ok := metadata.FromIncomingContext(ctx)
    50  	if !ok {
    51  		// TODO(stevvooe): Check outgoing context?
    52  		return "", false
    53  	}
    54  
    55  	values := md[GRPCHeader]
    56  	if len(values) == 0 {
    57  		return "", false
    58  	}
    59  
    60  	return values[0], true
    61  }