| // Copyright 2016 Google LLC. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package internal |
| |
| import ( |
| "errors" |
| |
| "google.golang.org/grpc/naming" |
| ) |
| |
| // PoolResolver provides a fixed list of addresses to load balance between |
| // and does not provide further updates. |
| type PoolResolver struct { |
| poolSize int |
| dialOpt *DialSettings |
| ch chan []*naming.Update |
| } |
| |
| // NewPoolResolver returns a PoolResolver |
| // This is an EXPERIMENTAL API and may be changed or removed in the future. |
| func NewPoolResolver(size int, o *DialSettings) *PoolResolver { |
| return &PoolResolver{poolSize: size, dialOpt: o} |
| } |
| |
| // Resolve returns a Watcher for the endpoint defined by the DialSettings |
| // provided to NewPoolResolver. |
| func (r *PoolResolver) Resolve(target string) (naming.Watcher, error) { |
| if r.dialOpt.Endpoint == "" { |
| return nil, errors.New("no endpoint configured") |
| } |
| addrs := make([]*naming.Update, 0, r.poolSize) |
| for i := 0; i < r.poolSize; i++ { |
| addrs = append(addrs, &naming.Update{Op: naming.Add, Addr: r.dialOpt.Endpoint, Metadata: i}) |
| } |
| r.ch = make(chan []*naming.Update, 1) |
| r.ch <- addrs |
| return r, nil |
| } |
| |
| // Next returns a static list of updates on the first call, |
| // and blocks indefinitely until Close is called on subsequent calls. |
| func (r *PoolResolver) Next() ([]*naming.Update, error) { |
| return <-r.ch, nil |
| } |
| |
| // Close releases resources associated with the pool and causes Next to unblock. |
| func (r *PoolResolver) Close() { |
| close(r.ch) |
| } |