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

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/*
*
* 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"
"net"
"google.golang.org/grpc/attributes"
"google.golang.org/grpc/credentials"
"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.
//
// 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
// 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 SetDefaultScheme(scheme string) {
defaultScheme = scheme
}
// GetDefaultScheme gets the default scheme that will be used.
func GetDefaultScheme() string {
return defaultScheme
}
// AddressType indicates the address type returned by name resolution.
//
// Deprecated: use Attributes in Address instead.
type AddressType uint8
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: use Attributes in Address instead.
GRPCLB
)
// Address represents a server the client connects to.
// This is the EXPERIMENTAL API and may be changed or extended in the future.
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 load balancing policy.
Attributes *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{}
}
// 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)
}
// State contains the current Resolver state relevant to the ClientConn.
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
}
// 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.
UpdateState(State)
// 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
}
// 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. e.g. "dns://some_authority/foo.bar" will be parsed
// into &Target{Scheme: "dns", Authority: "some_authority", Endpoint: "foo.bar"}
//
// If the target does not contain a scheme, we will apply the default scheme, and set the Target to
// be the full target string. e.g. "foo.bar" will be parsed into
// &Target{Scheme: resolver.GetDefaultScheme(), Endpoint: "foo.bar"}.
//
// If the parsed scheme is not registered (i.e. no corresponding resolver available to resolve the
// endpoint), we set the Scheme to be the default scheme, and set the Endpoint to be the full target
// string. e.g. target string "unknown_scheme://authority/endpoint" will be parsed into
// &Target{Scheme: resolver.GetDefaultScheme(), Endpoint: "unknown_scheme://authority/endpoint"}.
type Target struct {
Scheme string
Authority string
Endpoint string
}
// 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.
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()
}
// UnregisterForTesting removes the resolver builder with the given scheme from the
// resolver map.
// This function is for testing only.
func UnregisterForTesting(scheme string) {
delete(m, scheme)
}