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token.go
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token.go
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// Copyright (c) 2015 The gocql Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gocql
import (
"bytes"
"crypto/md5"
"fmt"
"math/big"
"sort"
"strconv"
"strings"
"github.com/gocql/gocql/internal/murmur"
)
// a token partitioner
type partitioner interface {
Name() string
Hash([]byte) token
ParseString(string) token
}
// a token
type token interface {
fmt.Stringer
Less(token) bool
}
// murmur3 partitioner and token
type murmur3Partitioner struct{}
type murmur3Token int64
func (p murmur3Partitioner) Name() string {
return "Murmur3Partitioner"
}
func (p murmur3Partitioner) Hash(partitionKey []byte) token {
h1 := murmur.Murmur3H1(partitionKey)
return murmur3Token(h1)
}
// murmur3 little-endian, 128-bit hash, but returns only h1
func (p murmur3Partitioner) ParseString(str string) token {
val, _ := strconv.ParseInt(str, 10, 64)
return murmur3Token(val)
}
func (m murmur3Token) String() string {
return strconv.FormatInt(int64(m), 10)
}
func (m murmur3Token) Less(token token) bool {
return m < token.(murmur3Token)
}
// order preserving partitioner and token
type orderedPartitioner struct{}
type orderedToken string
func (p orderedPartitioner) Name() string {
return "OrderedPartitioner"
}
func (p orderedPartitioner) Hash(partitionKey []byte) token {
// the partition key is the token
return orderedToken(partitionKey)
}
func (p orderedPartitioner) ParseString(str string) token {
return orderedToken(str)
}
func (o orderedToken) String() string {
return string(o)
}
func (o orderedToken) Less(token token) bool {
return o < token.(orderedToken)
}
// random partitioner and token
type randomPartitioner struct{}
type randomToken big.Int
func (r randomPartitioner) Name() string {
return "RandomPartitioner"
}
// 2 ** 128
var maxHashInt, _ = new(big.Int).SetString("340282366920938463463374607431768211456", 10)
func (p randomPartitioner) Hash(partitionKey []byte) token {
sum := md5.Sum(partitionKey)
val := new(big.Int)
val.SetBytes(sum[:])
if sum[0] > 127 {
val.Sub(val, maxHashInt)
val.Abs(val)
}
return (*randomToken)(val)
}
func (p randomPartitioner) ParseString(str string) token {
val := new(big.Int)
val.SetString(str, 10)
return (*randomToken)(val)
}
func (r *randomToken) String() string {
return (*big.Int)(r).String()
}
func (r *randomToken) Less(token token) bool {
return -1 == (*big.Int)(r).Cmp((*big.Int)(token.(*randomToken)))
}
type hostToken struct {
token token
host *HostInfo
}
func (ht hostToken) String() string {
return fmt.Sprintf("{token=%v host=%v}", ht.token, ht.host.HostID())
}
// a data structure for organizing the relationship between tokens and hosts
type tokenRing struct {
partitioner partitioner
// tokens map token range to primary replica.
// The elements in tokens are sorted by token ascending.
// The range for a given item in tokens starts after preceding range and ends with the token specified in
// token. The end token is part of the range.
// The lowest (i.e. index 0) range wraps around the ring (its preceding range is the one with largest index).
tokens []hostToken
hosts []*HostInfo
}
func newTokenRing(partitioner string, hosts []*HostInfo) (*tokenRing, error) {
tokenRing := &tokenRing{
hosts: hosts,
}
if strings.HasSuffix(partitioner, "Murmur3Partitioner") {
tokenRing.partitioner = murmur3Partitioner{}
} else if strings.HasSuffix(partitioner, "OrderedPartitioner") {
tokenRing.partitioner = orderedPartitioner{}
} else if strings.HasSuffix(partitioner, "RandomPartitioner") {
tokenRing.partitioner = randomPartitioner{}
} else {
return nil, fmt.Errorf("unsupported partitioner '%s'", partitioner)
}
for _, host := range hosts {
for _, strToken := range host.Tokens() {
token := tokenRing.partitioner.ParseString(strToken)
tokenRing.tokens = append(tokenRing.tokens, hostToken{token, host})
}
}
sort.Sort(tokenRing)
return tokenRing, nil
}
func (t *tokenRing) Len() int {
return len(t.tokens)
}
func (t *tokenRing) Less(i, j int) bool {
return t.tokens[i].token.Less(t.tokens[j].token)
}
func (t *tokenRing) Swap(i, j int) {
t.tokens[i], t.tokens[j] = t.tokens[j], t.tokens[i]
}
func (t *tokenRing) String() string {
buf := &bytes.Buffer{}
buf.WriteString("TokenRing(")
if t.partitioner != nil {
buf.WriteString(t.partitioner.Name())
}
buf.WriteString("){")
sep := ""
for i, th := range t.tokens {
buf.WriteString(sep)
sep = ","
buf.WriteString("\n\t[")
buf.WriteString(strconv.Itoa(i))
buf.WriteString("]")
buf.WriteString(th.token.String())
buf.WriteString(":")
buf.WriteString(th.host.ConnectAddress().String())
}
buf.WriteString("\n}")
return string(buf.Bytes())
}
func (t *tokenRing) GetHostForToken(token token) (host *HostInfo, endToken token) {
if t == nil || len(t.tokens) == 0 {
return nil, nil
}
// find the primary replica
p := sort.Search(len(t.tokens), func(i int) bool {
return !t.tokens[i].token.Less(token)
})
if p == len(t.tokens) {
// wrap around to the first in the ring
p = 0
}
v := t.tokens[p]
return v.host, v.token
}