github.com/rbisecke/kafka-go@v0.4.27/resolver.go (about)

     1  package kafka
     2  
     3  import (
     4  	"context"
     5  	"net"
     6  )
     7  
     8  // The Resolver interface is used as an abstraction to provide service discovery
     9  // of the hosts of a kafka cluster.
    10  type Resolver interface {
    11  	// LookupHost looks up the given host using the local resolver.
    12  	// It returns a slice of that host's addresses.
    13  	LookupHost(ctx context.Context, host string) (addrs []string, err error)
    14  }
    15  
    16  // BrokerResolver is an interface implemented by types that translate host
    17  // names into a network address.
    18  //
    19  // This resolver is not intended to be a general purpose interface. Instead,
    20  // it is tailored to the particular needs of the kafka protocol, with the goal
    21  // being to provide a flexible mechanism for extending broker name resolution
    22  // while retaining context that is specific to interacting with a kafka cluster.
    23  //
    24  // Resolvers must be safe to use from multiple goroutines.
    25  type BrokerResolver interface {
    26  	// Returns the IP addresses of the broker passed as argument.
    27  	LookupBrokerIPAddr(ctx context.Context, broker Broker) ([]net.IPAddr, error)
    28  }
    29  
    30  // NewBrokerResolver constructs a Resolver from r.
    31  //
    32  // If r is nil, net.DefaultResolver is used instead.
    33  func NewBrokerResolver(r *net.Resolver) BrokerResolver {
    34  	return brokerResolver{r}
    35  }
    36  
    37  type brokerResolver struct {
    38  	*net.Resolver
    39  }
    40  
    41  func (r brokerResolver) LookupBrokerIPAddr(ctx context.Context, broker Broker) ([]net.IPAddr, error) {
    42  	rslv := r.Resolver
    43  	if rslv == nil {
    44  		rslv = net.DefaultResolver
    45  	}
    46  
    47  	ipAddrs, err := r.LookupIPAddr(ctx, broker.Host)
    48  	if err != nil {
    49  		return nil, err
    50  	}
    51  
    52  	if len(ipAddrs) == 0 {
    53  		return nil, &net.DNSError{
    54  			Err:         "no addresses were returned by the resolver",
    55  			Name:        broker.Host,
    56  			IsTemporary: true,
    57  			IsNotFound:  true,
    58  		}
    59  	}
    60  
    61  	return ipAddrs, nil
    62  }