github.com/m3db/m3@v1.5.0/src/cluster/placement/storage/watch.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 storage
    22  
    23  import (
    24  	"errors"
    25  
    26  	"github.com/m3db/m3/src/cluster/kv"
    27  	"github.com/m3db/m3/src/cluster/placement"
    28  )
    29  
    30  var (
    31  	errPlacementNotAvailable            = errors.New("placement is not available")
    32  	errStagedPlacementNoActivePlacement = errors.New("staged placement with no active placement")
    33  )
    34  
    35  type w struct {
    36  	kv.ValueWatch
    37  	opts placement.Options
    38  }
    39  
    40  func newPlacementWatch(vw kv.ValueWatch, opts placement.Options) placement.Watch {
    41  	return &w{ValueWatch: vw, opts: opts}
    42  }
    43  
    44  func (w *w) Get() (placement.Placement, error) {
    45  	v := w.ValueWatch.Get()
    46  	if v == nil {
    47  		return nil, errPlacementNotAvailable
    48  	}
    49  
    50  	if w.opts.IsStaged() {
    51  		ps, err := placementsFromValue(v)
    52  		if err != nil {
    53  			return nil, err
    54  		}
    55  
    56  		latest := ps.Latest()
    57  		latest.SetVersion(v.Version())
    58  
    59  		return latest, nil
    60  	}
    61  
    62  	return placementFromValue(v)
    63  }