129 lines
4.3 KiB
Go
129 lines
4.3 KiB
Go
/*
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*
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* Copyright 2017 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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// Package resolver defines APIs for name resolution in gRPC.
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// All APIs in this package are experimental.
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package resolver
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var (
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// m is a map from scheme to resolver builder.
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m = make(map[string]Builder)
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// defaultScheme is the default scheme to use.
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defaultScheme string
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)
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// TODO(bar) install dns resolver in init(){}.
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// Register registers the resolver builder to the resolver map.
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// b.Scheme will be used as the scheme registered with this builder.
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func Register(b Builder) {
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m[b.Scheme()] = b
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}
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// Get returns the resolver builder registered with the given scheme.
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// If no builder is register with the scheme, the default scheme will
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// be used.
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// If the default scheme is not modified, "dns" will be the default
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// scheme, and the preinstalled dns resolver will be used.
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// If the default scheme is modified, and a resolver is registered with
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// the scheme, that resolver will be returned.
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// If the default scheme is modified, and no resolver is registered with
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// the scheme, nil will be returned.
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func Get(scheme string) Builder {
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if b, ok := m[scheme]; ok {
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return b
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}
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if b, ok := m[defaultScheme]; ok {
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return b
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}
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return nil
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}
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// SetDefaultScheme sets the default scheme that will be used.
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// The default default scheme is "dns".
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func SetDefaultScheme(scheme string) {
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defaultScheme = scheme
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}
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// AddressType indicates the address type returned by name resolution.
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type AddressType uint8
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const (
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// Backend indicates the address is for a backend server.
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Backend AddressType = iota
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// GRPCLB indicates the address is for a grpclb load balancer.
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GRPCLB
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)
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// Address represents a server the client connects to.
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// This is the EXPERIMENTAL API and may be changed or extended in the future.
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type Address struct {
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// Addr is the server address on which a connection will be established.
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Addr string
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// Type is the type of this address.
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Type AddressType
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// ServerName is the name of this address.
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// It's the name of the grpc load balancer, which will be used for authentication.
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ServerName string
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// Metadata is the information associated with Addr, which may be used
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// to make load balancing decision.
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Metadata interface{}
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}
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// BuildOption includes additional information for the builder to create
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// the resolver.
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type BuildOption struct {
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}
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// ClientConn contains the callbacks for resolver to notify any updates
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// to the gRPC ClientConn.
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type ClientConn interface {
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// NewAddress is called by resolver to notify ClientConn a new list
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// of resolved addresses.
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// The address list should be the complete list of resolved addresses.
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NewAddress(addresses []Address)
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// NewServiceConfig is called by resolver to notify ClientConn a new
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// service config. The service config should be provided as a json string.
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NewServiceConfig(serviceConfig string)
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}
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// Builder creates a resolver that will be used to watch name resolution updates.
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type Builder interface {
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// Build creates a new resolver for the given target.
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//
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// gRPC dial calls Build synchronously, and fails if the returned error is
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// not nil.
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Build(target string, cc ClientConn, opts BuildOption) (Resolver, error)
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// Scheme returns the scheme supported by this resolver.
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// Scheme is defined at https://github.com/grpc/grpc/blob/master/doc/naming.md.
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Scheme() string
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}
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// ResolveNowOption includes additional information for ResolveNow.
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type ResolveNowOption struct{}
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// Resolver watches for the updates on the specified target.
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// Updates include address updates and service config updates.
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type Resolver interface {
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// ResolveNow will be called by gRPC to try to resolve the target name again.
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// It's just a hint, resolver can ignore this if it's not necessary.
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ResolveNow(ResolveNowOption)
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// Close closes the resolver.
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Close()
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}
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