| // Copyright 2016 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 runner |
| |
| import ( |
| "context" |
| "errors" |
| "fmt" |
| |
| "github.com/coreos/etcd/clientv3/concurrency" |
| |
| "github.com/spf13/cobra" |
| ) |
| |
| // NewElectionCommand returns the cobra command for "election runner". |
| func NewElectionCommand() *cobra.Command { |
| cmd := &cobra.Command{ |
| Use: "election [election name (defaults to 'elector')]", |
| Short: "Performs election operation", |
| Run: runElectionFunc, |
| } |
| cmd.Flags().IntVar(&totalClientConnections, "total-client-connections", 10, "total number of client connections") |
| return cmd |
| } |
| |
| func runElectionFunc(cmd *cobra.Command, args []string) { |
| election := "elector" |
| if len(args) == 1 { |
| election = args[0] |
| } |
| if len(args) > 1 { |
| ExitWithError(ExitBadArgs, errors.New("election takes at most one argument")) |
| } |
| |
| rcs := make([]roundClient, totalClientConnections) |
| validatec := make(chan struct{}, len(rcs)) |
| // nextc closes when election is ready for next round. |
| nextc := make(chan struct{}) |
| eps := endpointsFromFlag(cmd) |
| |
| for i := range rcs { |
| v := fmt.Sprintf("%d", i) |
| observedLeader := "" |
| validateWaiters := 0 |
| var rcNextc chan struct{} |
| setRcNextc := func() { |
| rcNextc = nextc |
| } |
| |
| rcs[i].c = newClient(eps, dialTimeout) |
| var ( |
| s *concurrency.Session |
| err error |
| ) |
| for { |
| s, err = concurrency.NewSession(rcs[i].c) |
| if err == nil { |
| break |
| } |
| } |
| |
| e := concurrency.NewElection(s, election) |
| rcs[i].acquire = func() (err error) { |
| ctx, cancel := context.WithCancel(context.Background()) |
| donec := make(chan struct{}) |
| go func() { |
| defer close(donec) |
| for ctx.Err() == nil { |
| if ol, ok := <-e.Observe(ctx); ok { |
| observedLeader = string(ol.Kvs[0].Value) |
| break |
| } |
| } |
| if observedLeader != v { |
| cancel() |
| } |
| }() |
| err = e.Campaign(ctx, v) |
| cancel() |
| <-donec |
| if err == nil { |
| observedLeader = v |
| } |
| if observedLeader == v { |
| validateWaiters = len(rcs) |
| } |
| select { |
| case <-ctx.Done(): |
| return nil |
| default: |
| return err |
| } |
| } |
| rcs[i].validate = func() error { |
| l, err := e.Leader(context.TODO()) |
| if err == nil && string(l.Kvs[0].Value) != observedLeader { |
| return fmt.Errorf("expected leader %q, got %q", observedLeader, l.Kvs[0].Value) |
| } |
| if err != nil { |
| return err |
| } |
| setRcNextc() |
| validatec <- struct{}{} |
| return nil |
| } |
| rcs[i].release = func() error { |
| for validateWaiters > 0 { |
| select { |
| case <-validatec: |
| validateWaiters-- |
| default: |
| return fmt.Errorf("waiting on followers") |
| } |
| } |
| if err := e.Resign(context.TODO()); err != nil { |
| return err |
| } |
| if observedLeader == v { |
| oldNextc := nextc |
| nextc = make(chan struct{}) |
| close(oldNextc) |
| |
| } |
| <-rcNextc |
| observedLeader = "" |
| return nil |
| } |
| } |
| // each client creates 1 key from Campaign() and delete it from Resign() |
| // a round involves in 2*len(rcs) requests. |
| doRounds(rcs, rounds, 2*len(rcs)) |
| } |