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checksummer.go
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checksummer.go
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package hashring
import (
"bytes"
"sort"
"strconv"
"strings"
"github.com/dgryski/go-farm"
)
// Checksummer computes a checksum for an instance of a HashRing. The
// checksum can be used to compare two rings for equality.
type Checksummer interface {
// Checksum calculates the checksum for the hashring that is passed in.
// Compute will be called while having at least a read-lock on the hashring so
// it is safe to read from the ring, but not safe to change the ring. There
// might be multiple Checksum Computes initiated at the same time, but every
// Checksum will only be called once per hashring at once
Checksum(ring *HashRing) (checksum uint32)
}
type identityChecksummer struct{}
func (i *identityChecksummer) Checksum(ring *HashRing) uint32 {
identitySet := make(map[string]struct{})
ring.tree.root.traverseWhile(func(node *redBlackNode) bool {
identitySet[node.key.(replicaPoint).identity] = struct{}{}
return true
})
identities := make([]string, 0, len(identitySet))
for identity := range identitySet {
identities = append(identities, identity)
}
sort.Strings(identities)
bytes := []byte(strings.Join(identities, ";"))
return farm.Fingerprint32(bytes)
}
type replicaPointChecksummer struct{}
func (r *replicaPointChecksummer) Checksum(ring *HashRing) uint32 {
buffer := bytes.Buffer{}
ring.tree.root.traverseWhile(func(node *redBlackNode) bool {
buffer.WriteString(strconv.Itoa(node.key.(replicaPoint).hash))
buffer.WriteString("-")
buffer.WriteString(node.value.(string))
buffer.WriteString(";")
return true
})
return farm.Fingerprint32(buffer.Bytes())
}