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resolver.go
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resolver.go
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// Copyright 2021 The etcd 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 etcd
import (
"context"
"sync"
"github.com/starfork/stargo/naming"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/resolver"
"google.golang.org/grpc/status"
clientv3 "go.etcd.io/etcd/client/v3"
"go.etcd.io/etcd/client/v3/naming/endpoints"
)
type Resolver struct {
c *clientv3.Client
//target string
cc resolver.ClientConn
wch endpoints.WatchChannel
ctx context.Context
cancel context.CancelFunc
conf *naming.Config
wg sync.WaitGroup
}
// type builder struct {
// c *clientv3.Client
// }
// NewResolver creates a resolver builder.
func NewResolver(conf *naming.Config) resolver.Builder {
client := newClient(conf)
r := &Resolver{c: client, conf: conf}
resolver.Register(r)
return r
}
func (e *Resolver) key(name string) string {
return e.conf.Org + "/" + name
}
func (e *Resolver) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
// Refer to https://github.com/grpc/grpc-go/blob/16d3df80f029f57cff5458f1d6da6aedbc23545d/clientconn.go#L1587-L1611
key := e.key(target.URL.Host)
// r := &Resolver{
// //c: b.c,
// target: key,
// cc: cc,
// }
e.cc = cc
e.ctx, e.cancel = context.WithCancel(context.Background())
em, err := endpoints.NewManager(e.c, key)
if err != nil {
return nil, status.Errorf(codes.InvalidArgument, "resolver: failed to new endpoint manager: %s", err)
}
e.wch, err = em.NewWatchChannel(e.ctx)
if err != nil {
return nil, status.Errorf(codes.Internal, "resolver: failed to new watch channer: %s", err)
}
e.wg.Add(1)
go e.watch()
return e, nil
}
func (b *Resolver) Scheme() string {
return "etcd"
}
func (e *Resolver) watch() {
defer e.wg.Done()
allUps := make(map[string]*endpoints.Update)
for {
select {
case <-e.ctx.Done():
return
case ups, ok := <-e.wch:
if !ok {
return
}
for _, up := range ups {
switch up.Op {
case endpoints.Add:
allUps[up.Key] = up
case endpoints.Delete:
delete(allUps, up.Key)
}
}
addrs := convertToGRPCAddress(allUps)
e.cc.UpdateState(resolver.State{Addresses: addrs})
}
}
}
func convertToGRPCAddress(ups map[string]*endpoints.Update) []resolver.Address {
var addrs []resolver.Address
for _, up := range ups {
addr := resolver.Address{
Addr: up.Endpoint.Addr,
Metadata: up.Endpoint.Metadata,
}
addrs = append(addrs, addr)
}
return addrs
}
// ResolveNow is a no-op here.
// It's just a hint, resolver can ignore this if it's not necessary.
func (r *Resolver) ResolveNow(resolver.ResolveNowOptions) {}
func (r *Resolver) Close() {
r.cancel()
r.wg.Wait()
}