github.com/hxx258456/ccgo@v0.0.5-0.20230213014102-48b35f46f66f/grpc/xds/internal/balancer/clusterresolver/resource_resolver_dns.go (about)

     1  /*
     2   *
     3   * Copyright 2021 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 clusterresolver
    20  
    21  import (
    22  	"fmt"
    23  
    24  	"github.com/hxx258456/ccgo/grpc/resolver"
    25  	"github.com/hxx258456/ccgo/grpc/serviceconfig"
    26  )
    27  
    28  var (
    29  	newDNS = func(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
    30  		// The dns resolver is registered by the grpc package. So, this call to
    31  		// resolver.Get() is never expected to return nil.
    32  		return resolver.Get("dns").Build(target, cc, opts)
    33  	}
    34  )
    35  
    36  // dnsDiscoveryMechanism watches updates for the given DNS hostname.
    37  //
    38  // It implements resolver.ClientConn interface to work with the DNS resolver.
    39  type dnsDiscoveryMechanism struct {
    40  	target           string
    41  	topLevelResolver *resourceResolver
    42  	r                resolver.Resolver
    43  
    44  	addrs          []string
    45  	updateReceived bool
    46  }
    47  
    48  func newDNSResolver(target string, topLevelResolver *resourceResolver) *dnsDiscoveryMechanism {
    49  	ret := &dnsDiscoveryMechanism{
    50  		target:           target,
    51  		topLevelResolver: topLevelResolver,
    52  	}
    53  	r, err := newDNS(resolver.Target{Scheme: "dns", Endpoint: target}, ret, resolver.BuildOptions{})
    54  	if err != nil {
    55  		select {
    56  		case <-topLevelResolver.updateChannel:
    57  		default:
    58  		}
    59  		topLevelResolver.updateChannel <- &resourceUpdate{err: err}
    60  	}
    61  	ret.r = r
    62  	return ret
    63  }
    64  
    65  func (dr *dnsDiscoveryMechanism) lastUpdate() (interface{}, bool) {
    66  	if !dr.updateReceived {
    67  		return nil, false
    68  	}
    69  	return dr.addrs, true
    70  }
    71  
    72  func (dr *dnsDiscoveryMechanism) resolveNow() {
    73  	dr.r.ResolveNow(resolver.ResolveNowOptions{})
    74  }
    75  
    76  func (dr *dnsDiscoveryMechanism) stop() {
    77  	dr.r.Close()
    78  }
    79  
    80  // dnsDiscoveryMechanism needs to implement resolver.ClientConn interface to receive
    81  // updates from the real DNS resolver.
    82  
    83  func (dr *dnsDiscoveryMechanism) UpdateState(state resolver.State) error {
    84  	dr.topLevelResolver.mu.Lock()
    85  	defer dr.topLevelResolver.mu.Unlock()
    86  	addrs := make([]string, len(state.Addresses))
    87  	for i, a := range state.Addresses {
    88  		addrs[i] = a.Addr
    89  	}
    90  	dr.addrs = addrs
    91  	dr.updateReceived = true
    92  	dr.topLevelResolver.generate()
    93  	return nil
    94  }
    95  
    96  func (dr *dnsDiscoveryMechanism) ReportError(err error) {
    97  	select {
    98  	case <-dr.topLevelResolver.updateChannel:
    99  	default:
   100  	}
   101  	dr.topLevelResolver.updateChannel <- &resourceUpdate{err: err}
   102  }
   103  
   104  func (dr *dnsDiscoveryMechanism) NewAddress(addresses []resolver.Address) {
   105  	dr.UpdateState(resolver.State{Addresses: addresses})
   106  }
   107  
   108  func (dr *dnsDiscoveryMechanism) NewServiceConfig(string) {
   109  	// This method is deprecated, and service config isn't supported.
   110  }
   111  
   112  func (dr *dnsDiscoveryMechanism) ParseServiceConfig(string) *serviceconfig.ParseResult {
   113  	return &serviceconfig.ParseResult{Err: fmt.Errorf("service config not supported")}
   114  }