github.com/m3db/m3@v1.5.0/src/cluster/kv/util/runtime/value.go (about)

     1  // Copyright (c) 2017 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 runtime
    22  
    23  import (
    24  	"fmt"
    25  
    26  	"github.com/m3db/m3/src/cluster/kv"
    27  	"github.com/m3db/m3/src/x/watch"
    28  
    29  	"go.uber.org/zap"
    30  )
    31  
    32  // Value is a value that can be updated during runtime.
    33  type Value interface {
    34  	watch.Value
    35  
    36  	// Key is the key associated with value.
    37  	Key() string
    38  }
    39  
    40  // UnmarshalFn unmarshals a kv value and extracts its payload.
    41  type UnmarshalFn func(value kv.Value) (interface{}, error)
    42  
    43  // ProcessFn processes a value.
    44  type ProcessFn func(value interface{}) error
    45  
    46  type value struct {
    47  	watch.Value
    48  
    49  	key         string
    50  	store       kv.Store
    51  	opts        Options
    52  	log         *zap.Logger
    53  	unmarshalFn UnmarshalFn
    54  	processFn   ProcessFn
    55  	updateFn    watch.ProcessFn
    56  
    57  	currValue kv.Value
    58  }
    59  
    60  // NewValue creates a new value.
    61  func NewValue(
    62  	key string,
    63  	opts Options,
    64  ) Value {
    65  	v := &value{
    66  		key:         key,
    67  		store:       opts.KVStore(),
    68  		opts:        opts,
    69  		log:         opts.InstrumentOptions().Logger(),
    70  		unmarshalFn: opts.UnmarshalFn(),
    71  		processFn:   opts.ProcessFn(),
    72  	}
    73  	v.updateFn = v.update
    74  	v.initValue()
    75  	return v
    76  }
    77  
    78  func (v *value) initValue() {
    79  	valueOpts := watch.NewOptions().
    80  		SetInstrumentOptions(v.opts.InstrumentOptions()).
    81  		SetInitWatchTimeout(v.opts.InitWatchTimeout()).
    82  		SetNewUpdatableFn(v.newUpdatableFn).
    83  		SetGetUpdateFn(v.getUpdateFn).
    84  		SetProcessFn(v.updateFn).
    85  		SetKey(v.key).
    86  		SetInterruptedCh(v.opts.InterruptedCh())
    87  	v.Value = watch.NewValue(valueOpts)
    88  }
    89  
    90  func (v *value) Key() string { return v.key }
    91  
    92  func (v *value) newUpdatableFn() (watch.Updatable, error) {
    93  	return v.store.Watch(v.key)
    94  }
    95  
    96  func (v *value) getUpdateFn(updatable watch.Updatable) (interface{}, error) {
    97  	return updatable.(kv.ValueWatch).Get(), nil
    98  }
    99  
   100  func (v *value) update(value interface{}) error {
   101  	update := value.(kv.Value)
   102  	if v.currValue != nil && !update.IsNewer(v.currValue) {
   103  		v.log.Warn("ignore kv update with version which is not newer than the version of the current value",
   104  			zap.Int("new version", update.Version()),
   105  			zap.Int("current version", v.currValue.Version()))
   106  		return nil
   107  	}
   108  	v.log.Info("received kv update",
   109  		zap.Int("version", update.Version()),
   110  		zap.String("key", v.key))
   111  	latest, err := v.unmarshalFn(update)
   112  	if err != nil {
   113  		return fmt.Errorf("error unmarshalling value for version %d: %v", update.Version(), err)
   114  	}
   115  	if err := v.processFn(latest); err != nil {
   116  		return err
   117  	}
   118  	v.currValue = update
   119  	return nil
   120  }