github.com/m3db/m3@v1.5.0/src/cmd/services/m3coordinator/downsample/leader_local.go (about)

     1  // Copyright (c) 2018 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package downsample
    22  
    23  import (
    24  	"errors"
    25  	"fmt"
    26  	"sync"
    27  
    28  	"github.com/m3db/m3/src/cluster/services"
    29  	"github.com/m3db/m3/src/cluster/services/leader/campaign"
    30  )
    31  
    32  // localLeaderService provides a mocked out local leader service so that
    33  // we do not need to rely on using an etcd cluster just to elect a leader
    34  // for aggregation in-process (which doesn't need leader election at all,
    35  // however it is simpler to keep the current aggregator code structured the
    36  // way it is which is most natural for accommodating the distributed and
    37  // non-in-process aggregation use case).
    38  type localLeaderService struct {
    39  	sync.Mutex
    40  	id        services.ServiceID
    41  	elections map[string]chan campaign.Status
    42  	leaders   map[string]string
    43  }
    44  
    45  func newLocalLeaderService(id services.ServiceID) services.LeaderService {
    46  	l := &localLeaderService{id: id}
    47  	l.reset()
    48  	return l
    49  }
    50  
    51  func (l *localLeaderService) reset() {
    52  	l.Lock()
    53  	defer l.Unlock()
    54  	l.elections = make(map[string]chan campaign.Status)
    55  	l.leaders = make(map[string]string)
    56  }
    57  
    58  func (l *localLeaderService) Campaign(
    59  	electionID string,
    60  	opts services.CampaignOptions,
    61  ) (<-chan campaign.Status, error) {
    62  	l.Lock()
    63  	defer l.Unlock()
    64  
    65  	campaignCh, ok := l.elections[electionID]
    66  	if !ok {
    67  		campaignCh = make(chan campaign.Status, 1)
    68  		campaignCh <- campaign.Status{State: campaign.Leader}
    69  		l.elections[electionID] = campaignCh
    70  		l.leaders[electionID] = l.id.String()
    71  	}
    72  	return campaignCh, nil
    73  }
    74  
    75  func (l *localLeaderService) push(id string, status campaign.Status) error {
    76  	l.Lock()
    77  	defer l.Unlock()
    78  
    79  	campaignCh, ok := l.elections[id]
    80  	if !ok {
    81  		return fmt.Errorf("no such campaign: %s", id)
    82  	}
    83  
    84  	campaignCh <- status
    85  	return nil
    86  }
    87  
    88  func (l *localLeaderService) Resign(electionID string) error {
    89  	return l.push(electionID, campaign.Status{State: campaign.Follower})
    90  }
    91  
    92  func (l *localLeaderService) Leader(electionID string) (string, error) {
    93  	l.Lock()
    94  	defer l.Unlock()
    95  
    96  	leader, ok := l.leaders[electionID]
    97  	if !ok {
    98  		return "", fmt.Errorf("no such campaign: %s", electionID)
    99  	}
   100  	return leader, nil
   101  }
   102  
   103  func (l *localLeaderService) Observe(electionID string) (<-chan string, error) {
   104  	return nil, errors.New("unimplemented")
   105  }
   106  
   107  func (l *localLeaderService) Close() error {
   108  	l.reset()
   109  	return nil
   110  }