resolver

Documentation

Overview

Package resolver defines APIs for name resolution in gRPC. All APIs in this package are experimental.

Index

• func GetDefaultScheme() string
• func Register(b Builder)
• func SetDefaultScheme(scheme string)
• func UnregisterForTesting(scheme string)
• type Address
  • func (a Address) Equal(o Address) bool
  • func (a Address) String() string
• type AddressMap
  • func NewAddressMap() *AddressMap
  • func (a *AddressMap) Delete(addr Address)
  • func (a *AddressMap) Get(addr Address) (value interface{}, ok bool)
  • func (a *AddressMap) Keys() []Address
  • func (a *AddressMap) Len() int
  • func (a *AddressMap) Set(addr Address, value interface{})
  • func (a *AddressMap) Values() []interface{}
• type AddressType
• type BuildOptions
• type Builder
  • func Get(scheme string) Builder
• type ClientConn
• type ResolveNowOptions
• type Resolver
• type State
• type Target
  • func (t Target) Endpoint() string

Functions

func GetDefaultScheme

func GetDefaultScheme() string

GetDefaultScheme gets the default scheme that will be used.

func Register

func Register(b Builder)

Register registers the resolver builder to the resolver map. b.Scheme will be used as the scheme registered with this builder. The registry is case sensitive, and schemes should not contain any uppercase characters.

NOTE: this function must only be called during initialization time (i.e. in an init() function), and is not thread-safe. If multiple Resolvers are registered with the same name, the one registered last will take effect.

func SetDefaultScheme

func SetDefaultScheme(scheme string)

SetDefaultScheme sets the default scheme that will be used. The default default scheme is "passthrough".

NOTE: this function must only be called during initialization time (i.e. in an init() function), and is not thread-safe. The scheme set last overrides previously set values.

func UnregisterForTesting

func UnregisterForTesting(scheme string)

UnregisterForTesting removes the resolver builder with the given scheme from the resolver map. This function is for testing only.

Types

type Address

type Address struct {
	// Addr is the server address on which a connection will be established.
	Addr string

	// ServerName is the name of this address.
	// If non-empty, the ServerName is used as the transport certification authority for
	// the address, instead of the hostname from the Dial target string. In most cases,
	// this should not be set.
	//
	// If Type is GRPCLB, ServerName should be the name of the remote load
	// balancer, not the name of the backend.
	//
	// WARNING: ServerName must only be populated with trusted values. It
	// is insecure to populate it with data from untrusted inputs since untrusted
	// values could be used to bypass the authority checks performed by TLS.
	ServerName string

	// Attributes contains arbitrary data about this address intended for
	// consumption by the SubConn.
	Attributes *attributes.Attributes

	// BalancerAttributes contains arbitrary data about this address intended
	// for consumption by the LB policy.  These attributes do not affect SubConn
	// creation, connection establishment, handshaking, etc.
	BalancerAttributes *attributes.Attributes

	// Type is the type of this address.
	//
	// Deprecated: use Attributes instead.
	Type AddressType

	// Metadata is the information associated with Addr, which may be used
	// to make load balancing decision.
	//
	// Deprecated: use Attributes instead.
	Metadata interface{}
}

Address represents a server the client connects to.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

func (Address) Equal

func (a Address) Equal(o Address) bool

Equal returns whether a and o are identical. Metadata is compared directly, not with any recursive introspection.

func (Address) String

func (a Address) String() string

String returns JSON formatted string representation of the address.

type AddressMap

type AddressMap struct {
	// contains filtered or unexported fields
}

AddressMap is a map of addresses to arbitrary values taking into account Attributes. BalancerAttributes are ignored, as are Metadata and Type. Multiple accesses may not be performed concurrently. Must be created via NewAddressMap; do not construct directly.

func NewAddressMap

func NewAddressMap() *AddressMap

NewAddressMap creates a new AddressMap.

func (*AddressMap) Delete

func (a *AddressMap) Delete(addr Address)

Delete removes addr from the map.

func (*AddressMap) Get

func (a *AddressMap) Get(addr Address) (value interface{}, ok bool)

Get returns the value for the address in the map, if present.

func (*AddressMap) Keys

func (a *AddressMap) Keys() []Address

Keys returns a slice of all current map keys.

func (*AddressMap) Len

func (a *AddressMap) Len() int

Len returns the number of entries in the map.

func (*AddressMap) Set

func (a *AddressMap) Set(addr Address, value interface{})

Set updates or adds the value to the address in the map.

func (*AddressMap) Values

func (a *AddressMap) Values() []interface{}

Values returns a slice of all current map values.

type AddressType

type AddressType uint8

AddressType indicates the address type returned by name resolution.

Deprecated: use Attributes in Address instead.

const (
	// Backend indicates the address is for a backend server.
	//
	// Deprecated: use Attributes in Address instead.
	Backend AddressType = iota
	// GRPCLB indicates the address is for a grpclb load balancer.
	//
	// Deprecated: to select the GRPCLB load balancing policy, use a service
	// config with a corresponding loadBalancingConfig.  To supply balancer
	// addresses to the GRPCLB load balancing policy, set State.Attributes
	// using balancer/grpclb/state.Set.
	GRPCLB
)

type BuildOptions

type BuildOptions struct {
	// DisableServiceConfig indicates whether a resolver implementation should
	// fetch service config data.
	DisableServiceConfig bool
	// DialCreds is the transport credentials used by the ClientConn for
	// communicating with the target gRPC service (set via
	// WithTransportCredentials). In cases where a name resolution service
	// requires the same credentials, the resolver may use this field. In most
	// cases though, it is not appropriate, and this field may be ignored.
	DialCreds credentials.TransportCredentials
	// CredsBundle is the credentials bundle used by the ClientConn for
	// communicating with the target gRPC service (set via
	// WithCredentialsBundle). In cases where a name resolution service
	// requires the same credentials, the resolver may use this field. In most
	// cases though, it is not appropriate, and this field may be ignored.
	CredsBundle credentials.Bundle
	// Dialer is the custom dialer used by the ClientConn for dialling the
	// target gRPC service (set via WithDialer). In cases where a name
	// resolution service requires the same dialer, the resolver may use this
	// field. In most cases though, it is not appropriate, and this field may
	// be ignored.
	Dialer func(context.Context, string) (net.Conn, error)
}

BuildOptions includes additional information for the builder to create the resolver.

type Builder

type Builder interface {
	// Build creates a new resolver for the given target.
	//
	// gRPC dial calls Build synchronously, and fails if the returned error is
	// not nil.
	Build(target Target, cc ClientConn, opts BuildOptions) (Resolver, error)
	// Scheme returns the scheme supported by this resolver.  Scheme is defined
	// at https://github.com/grpc/grpc/blob/master/doc/naming.md.  The returned
	// string should not contain uppercase characters, as they will not match
	// the parsed target's scheme as defined in RFC 3986.
	Scheme() string
}

Builder creates a resolver that will be used to watch name resolution updates.

func Get

func Get(scheme string) Builder

Get returns the resolver builder registered with the given scheme.

If no builder is register with the scheme, nil will be returned.

type ClientConn

type ClientConn interface {
	// UpdateState updates the state of the ClientConn appropriately.
	//
	// If an error is returned, the resolver should try to resolve the
	// target again. The resolver should use a backoff timer to prevent
	// overloading the server with requests. If a resolver is certain that
	// reresolving will not change the result, e.g. because it is
	// a watch-based resolver, returned errors can be ignored.
	//
	// If the resolved State is the same as the last reported one, calling
	// UpdateState can be omitted.
	UpdateState(State) error
	// ReportError notifies the ClientConn that the Resolver encountered an
	// error.  The ClientConn will notify the load balancer and begin calling
	// ResolveNow on the Resolver with exponential backoff.
	ReportError(error)
	// NewAddress is called by resolver to notify ClientConn a new list
	// of resolved addresses.
	// The address list should be the complete list of resolved addresses.
	//
	// Deprecated: Use UpdateState instead.
	NewAddress(addresses []Address)
	// NewServiceConfig is called by resolver to notify ClientConn a new
	// service config. The service config should be provided as a json string.
	//
	// Deprecated: Use UpdateState instead.
	NewServiceConfig(serviceConfig string)
	// ParseServiceConfig parses the provided service config and returns an
	// object that provides the parsed config.
	ParseServiceConfig(serviceConfigJSON string) *serviceconfig.ParseResult
}

ClientConn contains the callbacks for resolver to notify any updates to the gRPC ClientConn.

This interface is to be implemented by gRPC. Users should not need a brand new implementation of this interface. For the situations like testing, the new implementation should embed this interface. This allows gRPC to add new methods to this interface.

type ResolveNowOptions

type ResolveNowOptions struct{}

ResolveNowOptions includes additional information for ResolveNow.

type Resolver

type Resolver interface {
	// ResolveNow will be called by gRPC to try to resolve the target name
	// again. It's just a hint, resolver can ignore this if it's not necessary.
	//
	// It could be called multiple times concurrently.
	ResolveNow(ResolveNowOptions)
	// Close closes the resolver.
	Close()
}

Resolver watches for the updates on the specified target. Updates include address updates and service config updates.

type State

type State struct {
	// Addresses is the latest set of resolved addresses for the target.
	Addresses []Address

	// ServiceConfig contains the result from parsing the latest service
	// config.  If it is nil, it indicates no service config is present or the
	// resolver does not provide service configs.
	ServiceConfig *serviceconfig.ParseResult

	// Attributes contains arbitrary data about the resolver intended for
	// consumption by the load balancing policy.
	Attributes *attributes.Attributes
}

State contains the current Resolver state relevant to the ClientConn.

type Target

type Target struct {
	// Deprecated: use URL.Scheme instead.
	Scheme string
	// Deprecated: use URL.Host instead.
	Authority string
	// URL contains the parsed dial target with an optional default scheme added
	// to it if the original dial target contained no scheme or contained an
	// unregistered scheme. Any query params specified in the original dial
	// target can be accessed from here.
	URL url.URL
}

Target represents a target for gRPC, as specified in: https://github.com/grpc/grpc/blob/master/doc/naming.md. It is parsed from the target string that gets passed into Dial or DialContext by the user. And gRPC passes it to the resolver and the balancer.

If the target follows the naming spec, and the parsed scheme is registered with gRPC, we will parse the target string according to the spec. If the target does not contain a scheme or if the parsed scheme is not registered (i.e. no corresponding resolver available to resolve the endpoint), we will apply the default scheme, and will attempt to reparse it.

Examples:

• "dns://some_authority/foo.bar" Target{Scheme: "dns", Authority: "some_authority", Endpoint: "foo.bar"}
• "foo.bar" Target{Scheme: resolver.GetDefaultScheme(), Endpoint: "foo.bar"}
• "unknown_scheme://authority/endpoint" Target{Scheme: resolver.GetDefaultScheme(), Endpoint: "unknown_scheme://authority/endpoint"}

func (Target) Endpoint

func (t Target) Endpoint() string

Endpoint retrieves endpoint without leading "/" from either `URL.Path` or `URL.Opaque`. The latter is used when the former is empty.