DockerCLI/vendor/google.golang.org/grpc/resolver/resolver.go

333 lines
13 KiB
Go

/*
*
* Copyright 2017 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
// Package resolver defines APIs for name resolution in gRPC.
// All APIs in this package are experimental.
package resolver
import (
"context"
"fmt"
"net"
"net/url"
"strings"
"google.golang.org/grpc/attributes"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/internal"
"google.golang.org/grpc/serviceconfig"
)
var (
// m is a map from scheme to resolver builder.
m = make(map[string]Builder)
// defaultScheme is the default scheme to use.
defaultScheme = "passthrough"
)
// TODO(bar) install dns resolver in init(){}.
// 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 Register(b Builder) {
m[b.Scheme()] = b
}
// Get returns the resolver builder registered with the given scheme.
//
// If no builder is register with the scheme, nil will be returned.
func Get(scheme string) Builder {
if b, ok := m[scheme]; ok {
return b
}
return nil
}
// SetDefaultScheme sets the default scheme that will be used. The default
// scheme is initially set to "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 SetDefaultScheme(scheme string) {
defaultScheme = scheme
internal.UserSetDefaultScheme = true
}
// GetDefaultScheme gets the default scheme that will be used by grpc.Dial. If
// SetDefaultScheme is never called, the default scheme used by grpc.NewClient is "dns" instead.
func GetDefaultScheme() string {
return defaultScheme
}
// Address represents a server the client connects to.
//
// # Experimental
//
// Notice: This type is EXPERIMENTAL and may be changed or removed in a
// later release.
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
}
// 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 (a Address) Equal(o Address) bool {
return a.Addr == o.Addr && a.ServerName == o.ServerName &&
a.Attributes.Equal(o.Attributes) &&
a.BalancerAttributes.Equal(o.BalancerAttributes) &&
a.Metadata == o.Metadata
}
// String returns JSON formatted string representation of the address.
func (a Address) String() string {
var sb strings.Builder
sb.WriteString(fmt.Sprintf("{Addr: %q, ", a.Addr))
sb.WriteString(fmt.Sprintf("ServerName: %q, ", a.ServerName))
if a.Attributes != nil {
sb.WriteString(fmt.Sprintf("Attributes: %v, ", a.Attributes.String()))
}
if a.BalancerAttributes != nil {
sb.WriteString(fmt.Sprintf("BalancerAttributes: %v", a.BalancerAttributes.String()))
}
sb.WriteString("}")
return sb.String()
}
// BuildOptions includes additional information for the builder to create
// the resolver.
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)
// Authority is the effective authority of the clientconn for which the
// resolver is built.
Authority string
}
// An Endpoint is one network endpoint, or server, which may have multiple
// addresses with which it can be accessed.
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
}
// State contains the current Resolver state relevant to the ClientConn.
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
}
// 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 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
}
// 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.
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
}
// Endpoint retrieves endpoint without leading "/" from either `URL.Path`
// or `URL.Opaque`. The latter is used when the former is empty.
func (t Target) Endpoint() string {
endpoint := t.URL.Path
if endpoint == "" {
endpoint = t.URL.Opaque
}
// For targets of the form "[scheme]://[authority]/endpoint, the endpoint
// value returned from url.Parse() contains a leading "/". Although this is
// in accordance with RFC 3986, we do not want to break existing resolver
// implementations which expect the endpoint without the leading "/". So, we
// end up stripping the leading "/" here. But this will result in an
// incorrect parsing for something like "unix:///path/to/socket". Since we
// own the "unix" resolver, we can workaround in the unix resolver by using
// the `URL` field.
return strings.TrimPrefix(endpoint, "/")
}
// String returns the canonical string representation of Target.
func (t Target) String() string {
return t.URL.Scheme + "://" + t.URL.Host + "/" + t.Endpoint()
}
// Builder creates a resolver that will be used to watch name resolution updates.
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
}
// ResolveNowOptions includes additional information for ResolveNow.
type ResolveNowOptions struct{}
// Resolver watches for the updates on the specified target.
// Updates include address updates and service config updates.
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()
}
// AuthorityOverrider is implemented by Builders that wish to override the
// default authority for the ClientConn.
// By default, the authority used is target.Endpoint().
type AuthorityOverrider interface {
// OverrideAuthority returns the authority to use for a ClientConn with the
// given target. The implementation must generate it without blocking,
// typically in line, and must keep it unchanged.
OverrideAuthority(Target) string
}