resolver.go

Documentation: go.etcd.io/etcd/client/v3/internal/resolver

     1  // Copyright 2021 The etcd Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package resolver
    16  
    17  import (
    18  	"go.etcd.io/etcd/client/v3/internal/endpoint"
    19  	"google.golang.org/grpc/resolver"
    20  	"google.golang.org/grpc/resolver/manual"
    21  	"google.golang.org/grpc/serviceconfig"
    22  )
    23  
    24  const (
    25  	Schema = "etcd-endpoints"
    26  )
    27  
    28  // EtcdManualResolver is a Resolver (and resolver.Builder) that can be updated
    29  // using SetEndpoints.
    30  type EtcdManualResolver struct {
    31  	*manual.Resolver
    32  	endpoints     []string
    33  	serviceConfig *serviceconfig.ParseResult
    34  }
    35  
    36  func New(endpoints ...string) *EtcdManualResolver {
    37  	r := manual.NewBuilderWithScheme(Schema)
    38  	return &EtcdManualResolver{Resolver: r, endpoints: endpoints, serviceConfig: nil}
    39  }
    40  
    41  // Build returns itself for Resolver, because it's both a builder and a resolver.
    42  func (r *EtcdManualResolver) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
    43  	r.serviceConfig = cc.ParseServiceConfig(`{"loadBalancingPolicy": "round_robin"}`)
    44  	if r.serviceConfig.Err != nil {
    45  		return nil, r.serviceConfig.Err
    46  	}
    47  	res, err := r.Resolver.Build(target, cc, opts)
    48  	if err != nil {
    49  		return nil, err
    50  	}
    51  	// Populates endpoints stored in r into ClientConn (cc).
    52  	r.updateState()
    53  	return res, nil
    54  }
    55  
    56  func (r *EtcdManualResolver) SetEndpoints(endpoints []string) {
    57  	r.endpoints = endpoints
    58  	r.updateState()
    59  }
    60  
    61  func (r EtcdManualResolver) updateState() {
    62  	if r.CC != nil {
    63  		addresses := make([]resolver.Address, len(r.endpoints))
    64  		for i, ep := range r.endpoints {
    65  			addr, serverName := endpoint.Interpret(ep)
    66  			addresses[i] = resolver.Address{Addr: addr, ServerName: serverName}
    67  		}
    68  		state := resolver.State{
    69  			Addresses:     addresses,
    70  			ServiceConfig: r.serviceConfig,
    71  		}
    72  		r.UpdateState(state)
    73  	}
    74  }
    75
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