unix.go

Documentation: google.golang.org/grpc/internal/resolver/unix

     1  /*
     2   *
     3   * Copyright 2020 gRPC authors.
     4   *
     5   * Licensed under the Apache License, Version 2.0 (the "License");
     6   * you may not use this file except in compliance with the License.
     7   * You may obtain a copy of the License at
     8   *
     9   *     http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   *
    17   */
    18  
    19  // Package unix implements a resolver for unix targets.
    20  package unix
    21  
    22  import (
    23  	"fmt"
    24  
    25  	"google.golang.org/grpc/internal/transport/networktype"
    26  	"google.golang.org/grpc/resolver"
    27  )
    28  
    29  const unixScheme = "unix"
    30  const unixAbstractScheme = "unix-abstract"
    31  
    32  type builder struct {
    33  	scheme string
    34  }
    35  
    36  func (b *builder) Build(target resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (resolver.Resolver, error) {
    37  	if target.URL.Host != "" {
    38  		return nil, fmt.Errorf("invalid (non-empty) authority: %v", target.URL.Host)
    39  	}
    40  
    41  	// gRPC was parsing the dial target manually before PR #4817, and we
    42  	// switched to using url.Parse() in that PR. To avoid breaking existing
    43  	// resolver implementations we ended up stripping the leading "/" from the
    44  	// endpoint. This obviously does not work for the "unix" scheme. Hence we
    45  	// end up using the parsed URL instead.
    46  	endpoint := target.URL.Path
    47  	if endpoint == "" {
    48  		endpoint = target.URL.Opaque
    49  	}
    50  	addr := resolver.Address{Addr: endpoint}
    51  	if b.scheme == unixAbstractScheme {
    52  		// We can not prepend \0 as c++ gRPC does, as in Golang '@' is used to signify we do
    53  		// not want trailing \0 in address.
    54  		addr.Addr = "@" + addr.Addr
    55  	}
    56  	cc.UpdateState(resolver.State{Addresses: []resolver.Address{networktype.Set(addr, "unix")}})
    57  	return &nopResolver{}, nil
    58  }
    59  
    60  func (b *builder) Scheme() string {
    61  	return b.scheme
    62  }
    63  
    64  func (b *builder) OverrideAuthority(resolver.Target) string {
    65  	return "localhost"
    66  }
    67  
    68  type nopResolver struct {
    69  }
    70  
    71  func (*nopResolver) ResolveNow(resolver.ResolveNowOptions) {}
    72  
    73  func (*nopResolver) Close() {}
    74  
    75  func init() {
    76  	resolver.Register(&builder{scheme: unixScheme})
    77  	resolver.Register(&builder{scheme: unixAbstractScheme})
    78  }
    79
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