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// Copyright 2017 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 v3election
import (
"context"
"errors"
"go.etcd.io/etcd/client/v3"
"go.etcd.io/etcd/client/v3/concurrency"
epb "go.etcd.io/etcd/server/v3/etcdserver/api/v3election/v3electionpb"
)
// ErrMissingLeaderKey is returned when election API request
// is missing the "leader" field.
var ErrMissingLeaderKey = errors.New(`"leader" field must be provided`)
type electionServer struct {
c *clientv3.Client
}
func NewElectionServer(c *clientv3.Client) epb.ElectionServer {
return &electionServer{c}
}
func (es *electionServer) Campaign(ctx context.Context, req *epb.CampaignRequest) (*epb.CampaignResponse, error) {
s, err := es.session(ctx, req.Lease)
if err != nil {
return nil, err
}
e := concurrency.NewElection(s, string(req.Name))
if err = e.Campaign(ctx, string(req.Value)); err != nil {
return nil, err
}
return &epb.CampaignResponse{
Header: e.Header(),
Leader: &epb.LeaderKey{
Name: req.Name,
Key: []byte(e.Key()),
Rev: e.Rev(),
Lease: int64(s.Lease()),
},
}, nil
}
func (es *electionServer) Proclaim(ctx context.Context, req *epb.ProclaimRequest) (*epb.ProclaimResponse, error) {
if req.Leader == nil {
return nil, ErrMissingLeaderKey
}
s, err := es.session(ctx, req.Leader.Lease)
if err != nil {
return nil, err
}
e := concurrency.ResumeElection(s, string(req.Leader.Name), string(req.Leader.Key), req.Leader.Rev)
if err := e.Proclaim(ctx, string(req.Value)); err != nil {
return nil, err
}
return &epb.ProclaimResponse{Header: e.Header()}, nil
}
func (es *electionServer) Observe(req *epb.LeaderRequest, stream epb.Election_ObserveServer) error {
s, err := es.session(stream.Context(), -1)
if err != nil {
return err
}
e := concurrency.NewElection(s, string(req.Name))
ch := e.Observe(stream.Context())
for stream.Context().Err() == nil {
select {
case <-stream.Context().Done():
case resp, ok := <-ch:
if !ok {
return nil
}
lresp := &epb.LeaderResponse{Header: resp.Header, Kv: resp.Kvs[0]}
if err := stream.Send(lresp); err != nil {
return err
}
}
}
return stream.Context().Err()
}
func (es *electionServer) Leader(ctx context.Context, req *epb.LeaderRequest) (*epb.LeaderResponse, error) {
s, err := es.session(ctx, -1)
if err != nil {
return nil, err
}
l, lerr := concurrency.NewElection(s, string(req.Name)).Leader(ctx)
if lerr != nil {
return nil, lerr
}
return &epb.LeaderResponse{Header: l.Header, Kv: l.Kvs[0]}, nil
}
func (es *electionServer) Resign(ctx context.Context, req *epb.ResignRequest) (*epb.ResignResponse, error) {
if req.Leader == nil {
return nil, ErrMissingLeaderKey
}
s, err := es.session(ctx, req.Leader.Lease)
if err != nil {
return nil, err
}
e := concurrency.ResumeElection(s, string(req.Leader.Name), string(req.Leader.Key), req.Leader.Rev)
if err := e.Resign(ctx); err != nil {
return nil, err
}
return &epb.ResignResponse{Header: e.Header()}, nil
}
func (es *electionServer) session(ctx context.Context, lease int64) (*concurrency.Session, error) {
s, err := concurrency.NewSession(
es.c,
concurrency.WithLease(clientv3.LeaseID(lease)),
concurrency.WithContext(ctx),
)
if err != nil {
return nil, err
}
s.Orphan()
return s, nil
}
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