144 lines
4.7 KiB
Go
144 lines
4.7 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
|
|
|
|
var (
|
|
// m is a map from scheme to resolver builder.
|
|
m = make(map[string]Builder)
|
|
// defaultScheme is the default scheme to use.
|
|
defaultScheme string
|
|
)
|
|
|
|
// 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.
|
|
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, the default scheme will
|
|
// be used.
|
|
// If the default scheme is not modified, "dns" will be the default
|
|
// scheme, and the preinstalled dns resolver will be used.
|
|
// If the default scheme is modified, and a resolver is registered with
|
|
// the scheme, that resolver will be returned.
|
|
// If the default scheme is modified, and no resolver is registered with
|
|
// the scheme, nil will be returned.
|
|
func Get(scheme string) Builder {
|
|
if b, ok := m[scheme]; ok {
|
|
return b
|
|
}
|
|
if b, ok := m[defaultScheme]; ok {
|
|
return b
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// SetDefaultScheme sets the default scheme that will be used.
|
|
// The default default scheme is "dns".
|
|
func SetDefaultScheme(scheme string) {
|
|
defaultScheme = scheme
|
|
}
|
|
|
|
// AddressType indicates the address type returned by name resolution.
|
|
type AddressType uint8
|
|
|
|
const (
|
|
// Backend indicates the address is for a backend server.
|
|
Backend AddressType = iota
|
|
// GRPCLB indicates the address is for a grpclb load balancer.
|
|
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
|
|
// Type is the type of this address.
|
|
Type AddressType
|
|
// ServerName is the name of this address.
|
|
// It's the name of the grpc load balancer, which will be used for authentication.
|
|
ServerName string
|
|
// Metadata is the information associated with Addr, which may be used
|
|
// to make load balancing decision.
|
|
Metadata interface{}
|
|
}
|
|
|
|
// BuildOption includes additional information for the builder to create
|
|
// the resolver.
|
|
type BuildOption struct {
|
|
}
|
|
|
|
// ClientConn contains the callbacks for resolver to notify any updates
|
|
// to the gRPC ClientConn.
|
|
type ClientConn interface {
|
|
// 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.
|
|
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.
|
|
NewServiceConfig(serviceConfig string)
|
|
}
|
|
|
|
// Target represents a target for gRPC, as specified in:
|
|
// https://github.com/grpc/grpc/blob/master/doc/naming.md.
|
|
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 BuildOption) (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
|
|
}
|
|
|
|
// ResolveNowOption includes additional information for ResolveNow.
|
|
type ResolveNowOption 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.
|
|
ResolveNow(ResolveNowOption)
|
|
// 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)
|
|
}
|