68 lines
1.3 KiB
Go
68 lines
1.3 KiB
Go
// Package main provides simple consistenthash commandline utility.
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/*
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Demo:
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$ seq -f node-%.f 1 100 > /tmp/nodes
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$ consistenthash < /tmp/nodes apple
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node-42
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$ consistenthash < /tmp/nodes banana
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node-48
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$ consistenthash < /tmp/nodes chocolate
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node-2
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Modify /tmp/nodes and confirm that the result rarely changes.
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*/
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package main
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import (
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"fmt"
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"io/ioutil"
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"os"
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"strings"
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"github.com/pkg/errors"
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"github.com/serialx/hashring"
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"github.com/sirupsen/logrus"
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)
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func main() {
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if err := xmain(); err != nil {
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logrus.Fatal(err)
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}
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}
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func xmain() error {
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if len(os.Args) != 2 {
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fmt.Fprintf(os.Stderr, "Usage: %s KEY\nNode list needs to be provided via stdin\n", os.Args[0])
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os.Exit(1)
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return errors.New("should not reach here")
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}
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key := os.Args[1]
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stdin, err := ioutil.ReadAll(os.Stdin)
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if err != nil {
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return err
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}
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var nodes []string
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for _, s := range strings.Split(string(stdin), "\n") {
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s = strings.TrimSpace(s)
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if s != "" {
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nodes = append(nodes, s)
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}
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}
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chosen, err := doConsistentHash(nodes, key)
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if err != nil {
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return err
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}
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fmt.Println(chosen)
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return nil
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}
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func doConsistentHash(nodes []string, key string) (string, error) {
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ring := hashring.New(nodes)
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x, ok := ring.GetNode(key)
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if !ok {
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return "", errors.Errorf("no node found for key %q", key)
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}
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return x, nil
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}
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