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forward_index_dice.go
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forward_index_dice.go
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// Copyright (c) 2019 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package storage
import (
"fmt"
"time"
"github.com/m3db/m3/src/x/dice"
)
// forwardIndexDice is a die roll that adds a chance for incoming index writes
// arriving near a block boundary to be duplicated and written to the next block
// index, adding jitter and smoothing index load so that block boundaries do not
// cause a huge influx of new documents that all need to be indexed at once.
type forwardIndexDice struct {
enabled bool
blockSize time.Duration
forwardIndexThreshold time.Duration
forwardIndexDice dice.Dice
}
func newForwardIndexDice(
opts Options,
) (forwardIndexDice, error) {
var (
indexOpts = opts.IndexOptions()
seriesOpts = opts.SeriesOptions()
probability = indexOpts.ForwardIndexProbability()
)
// NB: if not enabled, return a no-op forward index dice.
if probability == 0 {
return forwardIndexDice{}, nil
}
var (
threshold = indexOpts.ForwardIndexThreshold()
retention = seriesOpts.RetentionOptions()
bufferFuture = retention.BufferFuture()
blockSize = retention.BlockSize()
forwardIndexThreshold time.Duration
)
if threshold < 0 || threshold > 1 {
return forwardIndexDice{},
fmt.Errorf("invalid forward write threshold %f", threshold)
}
bufferFragment := float64(bufferFuture) * threshold
forwardIndexThreshold = blockSize - time.Duration(bufferFragment)
dice, err := dice.NewDice(probability)
if err != nil {
return forwardIndexDice{},
fmt.Errorf("cannot create forward write dice: %s", err)
}
return forwardIndexDice{
enabled: true,
blockSize: blockSize,
forwardIndexThreshold: forwardIndexThreshold,
forwardIndexDice: dice,
}, nil
}
// roll decides if a timestamp is eligible for forward index writes.
func (o *forwardIndexDice) roll(timestamp time.Time) bool {
if !o.enabled {
return false
}
threshold := timestamp.Truncate(o.blockSize).Add(o.forwardIndexThreshold)
if !timestamp.Before(threshold) {
return o.forwardIndexDice.Roll()
}
return false
}