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)
• 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 any, ok bool)
  • func (a *AddressMap) Keys() []Address
  • func (a *AddressMap) Len() int
  • func (a *AddressMap) Set(addr Address, value any)
  • func (a *AddressMap) Values() []any
• type BuildOptions
• type Builder
  • func Get(scheme string) Builder
• type ClientConn
• type Endpoint
• type EndpointMap
  • func NewEndpointMap() *EndpointMap
  • func (em *EndpointMap) Delete(e Endpoint)
  • func (em *EndpointMap) Get(e Endpoint) (value any, ok bool)
  • func (em *EndpointMap) Keys() []Endpoint
  • func (em *EndpointMap) Len() int
  • func (em *EndpointMap) Set(e Endpoint, value any)
  • func (em *EndpointMap) Values() []any
• type ResolveNowOptions
• type Resolver
• type State
• type Target
  • func (t Target) Endpoint() string
  • func (t Target) String() 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.

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.
	//
	// 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.
	//
	// Deprecated: when an Address is inside an Endpoint, this field should not
	// be used, and it will eventually be removed entirely.
	BalancerAttributes *attributes.Attributes

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

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.

This method compares all fields of the address. When used to tell apart addresses during subchannel creation or connection establishment, it might be more appropriate for the caller to implement custom equality logic.

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 any, 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 any)

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

func (*AddressMap) Values

func (a *AddressMap) Values() []any

Values returns a slice of all current map values.

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)
	// 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 Endpoint

type Endpoint struct {
	// Addresses contains a list of addresses used to access this endpoint.
	Addresses []Address

	// Attributes contains arbitrary data about this endpoint intended for
	// consumption by the LB policy.
	Attributes *attributes.Attributes
}

An Endpoint is one network endpoint, or server, which may have multiple addresses with which it can be accessed.

type EndpointMap

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

EndpointMap is a map of endpoints to arbitrary values keyed on only the unordered set of address strings within an endpoint. This map is not thread safe, thus it is unsafe to access concurrently. Must be created via NewEndpointMap; do not construct directly.

func NewEndpointMap

func NewEndpointMap() *EndpointMap

NewEndpointMap creates a new EndpointMap.

func (*EndpointMap) Delete

func (em *EndpointMap) Delete(e Endpoint)

Delete removes the specified endpoint from the map.

func (*EndpointMap) Get

func (em *EndpointMap) Get(e Endpoint) (value any, ok bool)

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

func (*EndpointMap) Keys

func (em *EndpointMap) Keys() []Endpoint

Keys returns a slice of all current map keys, as endpoints specifying the addresses present in the endpoint keys, in which uniqueness is determined by the unordered set of addresses. Thus, endpoint information returned is not the full endpoint data (drops duplicated addresses and attributes) but can be used for EndpointMap accesses.

func (*EndpointMap) Len

func (em *EndpointMap) Len() int

Len returns the number of entries in the map.

func (*EndpointMap) Set

func (em *EndpointMap) Set(e Endpoint, value any)

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

func (*EndpointMap) Values

func (em *EndpointMap) Values() []any

Values returns a slice of all current map values.

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.
	//
	// If a resolver sets Addresses but does not set Endpoints, one Endpoint
	// will be created for each Address before the State is passed to the LB
	// policy.  The BalancerAttributes of each entry in Addresses will be set
	// in Endpoints.Attributes, and be cleared in the Endpoint's Address's
	// BalancerAttributes.
	//
	// Soon, Addresses will be deprecated and replaced fully by Endpoints.
	Addresses []Address

	// Endpoints is the latest set of resolved endpoints for the target.
	//
	// If a resolver produces a State containing Endpoints but not Addresses,
	// it must take care to ensure the LB policies it selects will support
	// Endpoints.
	Endpoints []Endpoint

	// 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 {
	// 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.

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.

func (Target) String

func (t Target) String() string

String returns a string representation of Target.