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100 lines
2.8 KiB
Go
100 lines
2.8 KiB
Go
// Copyright (c) 2015-2021 MinIO, Inc.
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//
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// This file is part of MinIO Object Storage stack
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package main
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import (
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"encoding/binary"
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"flag"
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"fmt"
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"hash/crc32"
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"log"
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"github.com/dchest/siphash"
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"github.com/google/uuid"
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)
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// hashes the key returning an integer based on the input algorithm.
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// This function currently supports
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// - SIPMOD
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func sipHashMod(key string, cardinality int, id [16]byte) int {
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if cardinality <= 0 {
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return -1
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}
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// use the faster version as per siphash docs
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// https://github.com/dchest/siphash#usage
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k0, k1 := binary.LittleEndian.Uint64(id[0:8]), binary.LittleEndian.Uint64(id[8:16])
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sum64 := siphash.Hash(k0, k1, []byte(key))
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return int(sum64 % uint64(cardinality))
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}
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// hashOrder - hashes input key to return consistent
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// hashed integer slice. Returned integer order is salted
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// with an input key. This results in consistent order.
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// NOTE: collisions are fine, we are not looking for uniqueness
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// in the slices returned.
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func hashOrder(key string, cardinality int) []int {
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if cardinality <= 0 {
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// Returns an empty int slice for cardinality < 0.
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return nil
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}
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nums := make([]int, cardinality)
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keyCrc := crc32.Checksum([]byte(key), crc32.IEEETable)
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start := int(keyCrc % uint32(cardinality))
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for i := 1; i <= cardinality; i++ {
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nums[i-1] = 1 + ((start + i) % cardinality)
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}
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return nums
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}
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var (
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object, deploymentID string
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setCount, shards int
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)
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func main() {
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flag.StringVar(&object, "object", "", "Select an object")
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flag.StringVar(&deploymentID, "deployment-id", "", "MinIO deployment ID, obtained from 'format.json'")
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flag.IntVar(&setCount, "set-count", 0, "Total set count")
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flag.IntVar(&shards, "shards", 0, "Total shards count")
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flag.Parse()
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if object == "" {
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log.Fatalln("object name is mandatory")
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}
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if deploymentID == "" {
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log.Fatalln("deployment ID is mandatory")
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}
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if setCount == 0 {
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log.Fatalln("set count cannot be zero")
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}
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if shards == 0 {
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log.Fatalln("total shards cannot be zero")
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}
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id := uuid.MustParse(deploymentID)
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fmt.Println("Erasure distribution for the object", hashOrder(object, shards))
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fmt.Println("Erasure setNumber for the object", sipHashMod(object, setCount, id)+1)
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}
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