Package: google.golang.org/grpc/internal/resolver/dns

package dns Import Path google.golang.org/grpc/internal/resolver/dns (on go.dev) Dependency Relation imports 17 packages, and imported by one package

Involved Source Files #d dns_resolver.go Package dns implements a dns resolver to be installed as the default resolver in grpc.

Package-Level Type Names (total 5, none are exported)

/* sort exporteds by: alphabet | popularity */

/* 5 unexporteds ... *//* 5 unexporteds: */

type deadResolver (struct) deadResolver is a resolver that does nothing. Methods (total 2, both are exported) ( deadResolver) Close() ( deadResolver) ResolveNow(resolver.ResolveNowOptions) Implements (at least one exported) deadResolver : google.golang.org/grpc/resolver.Resolver

type dnsBuilder (struct) Methods (total 2, both are exported) (*dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) Build creates and starts a DNS resolver that watches the name resolution of the target. (*dnsBuilder) Scheme() string Scheme returns the naming scheme of this resolver builder, which is "dns". Implements (at least one exported) *dnsBuilder : google.golang.org/grpc/resolver.Builder

type dnsResolver (struct) dnsResolver watches for the name resolution update for a non-IP target. Fields (total 9, none are exported) /* 9 unexporteds ... *//* 9 unexporteds: */ cancel context.CancelFunc cc resolver.ClientConn ctx context.Context disableServiceConfig bool host string port string resolver netResolver rn chan struct{} rn channel is used by ResolveNow() to force an immediate resolution of the target. wg sync.WaitGroup wg is used to enforce Close() to return after the watcher() goroutine has finished. Otherwise, data race will be possible. [Race Example] in dns_resolver_test we replace the real lookup functions with mocked ones to facilitate testing. If Close() doesn't wait for watcher() goroutine finishes, race detector sometimes will warns lookup (READ the lookup function pointers) inside watcher() goroutine has data race with replaceNetFunc (WRITE the lookup function pointers). Methods (total 7, in which 2 are exported) (*dnsResolver) Close() Close closes the dnsResolver. (*dnsResolver) ResolveNow(resolver.ResolveNowOptions) ResolveNow invoke an immediate resolution of the target that this dnsResolver watches. /* 5 unexporteds ... *//* 5 unexporteds: */ (*dnsResolver) lookup() (*resolver.State, error) (*dnsResolver) lookupHost() ([]resolver.Address, error) (*dnsResolver) lookupSRV() ([]resolver.Address, error) (*dnsResolver) lookupTXT() *serviceconfig.ParseResult (*dnsResolver) watcher() Implements (at least one exported) *dnsResolver : google.golang.org/grpc/resolver.Resolver

type netResolver (interface) Methods (total 3, all are exported) ( netResolver) LookupHost(ctx context.Context, host string) (addrs []string, err error) ( netResolver) LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error) ( netResolver) LookupTXT(ctx context.Context, name string) (txts []string, err error) Implemented By (at least one exported) *net.Resolver As Types Of (only one, which is unexported) /* one unexported ... *//* one unexported: */ var defaultResolver

type rawChoice (struct) Fields (total 4, all are exported) ClientHostName *[]string ClientLanguage *[]string Percentage *int ServiceConfig *json.RawMessage

Package-Level Functions (total 8, in which 1 are exported)

func NewBuilder() resolver.Builder NewBuilder creates a dnsBuilder which is used to factory DNS resolvers.

/* 7 unexporteds ... *//* 7 unexporteds: */

func canaryingSC(js string) string

func chosenByPercentage(a *int) bool

func containsString(a *[]string, b string) bool

func formatIP(addr string) (addrIP string, ok bool) formatIP returns ok = false if addr is not a valid textual representation of an IP address. If addr is an IPv4 address, return the addr and ok = true. If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true.

func handleDNSError(err error, lookupType string) error

func init()

func parseTarget(target, defaultPort string) (host, port string, err error) parseTarget takes the user input target string and default port, returns formatted host and port info. If target doesn't specify a port, set the port to be the defaultPort. If target is in IPv6 format and host-name is enclosed in square brackets, brackets are stripped when setting the host. examples: target: "www.google.com" defaultPort: "443" returns host: "www.google.com", port: "443" target: "ipv4-host:80" defaultPort: "443" returns host: "ipv4-host", port: "80" target: "[ipv6-host]" defaultPort: "443" returns host: "ipv6-host", port: "443" target: ":80" defaultPort: "443" returns host: "localhost", port: "80"

Package-Level Variables (total 10, in which 1 are exported)

var EnableSRVLookups bool EnableSRVLookups controls whether the DNS resolver attempts to fetch gRPCLB addresses from SRV records. Must not be changed after init time.

/* 9 unexporteds ... *//* 9 unexporteds: */

var customAuthorityDialler func(authority string) func(ctx context.Context, network string, address string) (net.Conn, error)

var customAuthorityResolver func(authority string) (netResolver, error)

var defaultResolver netResolver

var errEndsWithColon error Addresses ending with a colon that is supposed to be the separator between host and port is not allowed. E.g. "::" is a valid address as it is an IPv6 address (host only) and "[::]:" is invalid as it ends with a colon as the host and port separator

var errMissingAddr error

var logger grpclog.DepthLoggerV2

var minDNSResRate time.Duration To prevent excessive re-resolution, we enforce a rate limit on DNS resolution requests.

var newTimer func(d time.Duration) *time.Timer Globals to stub out in tests. TODO: Perhaps these two can be combined into a single variable for testing the resolver?

var newTimerDNSResRate func(d time.Duration) *time.Timer Globals to stub out in tests. TODO: Perhaps these two can be combined into a single variable for testing the resolver?

Package-Level Constants (total 5, none are exported) /* 5 unexporteds ... *//* 5 unexporteds: */

const defaultDNSSvrPort = "53"

const defaultPort = "443"

const golang = "GO"

const txtAttribute = "grpc_config=" In DNS, service config is encoded in a TXT record via the mechanism described in RFC-1464 using the attribute name grpc_config.

const txtPrefix = "_grpc_config." txtPrefix is the prefix string to be prepended to the host name for txt record lookup.