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shardset.go
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shardset.go
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// Copyright (c) 2016 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 sharding
import (
"errors"
"math"
"github.com/m3db/m3/src/cluster/shard"
"github.com/m3db/m3/src/x/ident"
"github.com/spaolacci/murmur3"
)
var (
// ErrDuplicateShards returned when shard set is empty
ErrDuplicateShards = errors.New("duplicate shards")
// ErrInvalidShardID is returned on an invalid shard ID
ErrInvalidShardID = errors.New("no shard with given ID")
)
type shardSet struct {
shards []shard.Shard
ids []uint32
shardMap map[uint32]shard.Shard
fn HashFn
}
// NewShardSet creates a new sharding scheme with a set of shards
func NewShardSet(shards []shard.Shard, fn HashFn) (ShardSet, error) {
if err := validateShards(shards); err != nil {
return nil, err
}
return newValidatedShardSet(shards, fn), nil
}
// NewEmptyShardSet creates a new sharding scheme with an empty set of shards
func NewEmptyShardSet(fn HashFn) ShardSet {
return newValidatedShardSet(nil, fn)
}
func newValidatedShardSet(shards []shard.Shard, fn HashFn) ShardSet {
ids := make([]uint32, len(shards))
shardMap := make(map[uint32]shard.Shard, len(shards))
for i, shard := range shards {
ids[i] = shard.ID()
shardMap[shard.ID()] = shard
}
return &shardSet{
shards: shards,
ids: ids,
shardMap: shardMap,
fn: fn,
}
}
func (s *shardSet) Lookup(identifier ident.ID) uint32 {
return s.fn(identifier)
}
func (s *shardSet) LookupStateByID(shardID uint32) (shard.State, error) {
hostShard, ok := s.shardMap[shardID]
if !ok {
return shard.State(0), ErrInvalidShardID
}
return hostShard.State(), nil
}
func (s *shardSet) All() []shard.Shard {
return s.shards[:]
}
func (s *shardSet) AllIDs() []uint32 {
return s.ids[:]
}
func (s *shardSet) Min() uint32 {
min := uint32(math.MaxUint32)
for _, shard := range s.ids {
if shard < min {
min = shard
}
}
return min
}
func (s *shardSet) Max() uint32 {
max := uint32(0)
for _, shard := range s.ids {
if shard > max {
max = shard
}
}
return max
}
func (s *shardSet) HashFn() HashFn {
return s.fn
}
// NewShards returns a new slice of shards with a specified state
func NewShards(ids []uint32, state shard.State) []shard.Shard {
shards := make([]shard.Shard, len(ids))
for i, id := range ids {
shards[i] = shard.NewShard(id).SetState(state)
}
return shards
}
// IDs returns a new slice of shard IDs for a set of shards
func IDs(shards []shard.Shard) []uint32 {
ids := make([]uint32, len(shards))
for i := range ids {
ids[i] = shards[i].ID()
}
return ids
}
func validateShards(shards []shard.Shard) error {
uniqueShards := make(map[uint32]struct{}, len(shards))
for _, s := range shards {
if _, exist := uniqueShards[s.ID()]; exist {
return ErrDuplicateShards
}
uniqueShards[s.ID()] = struct{}{}
}
return nil
}
// DefaultHashFn generates a HashFn based on murmur32
func DefaultHashFn(length int) HashFn {
return NewHashFn(length, 0)
}
// NewHashGenWithSeed generates a HashFnGen based on murmur32 with a given seed
func NewHashGenWithSeed(seed uint32) HashGen {
return func(length int) HashFn {
return NewHashFn(length, seed)
}
}
// NewHashFn generates a HashFN based on murmur32 with a given seed
func NewHashFn(length int, seed uint32) HashFn {
return func(id ident.ID) uint32 {
return murmur3.Sum32WithSeed(id.Bytes(), seed) % uint32(length)
}
}