134 lines
2.9 KiB
Go
134 lines
2.9 KiB
Go
package raft
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import (
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"bytes"
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crand "crypto/rand"
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"fmt"
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"math"
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"math/big"
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"math/rand"
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"time"
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"github.com/hashicorp/go-msgpack/codec"
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)
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func init() {
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// Ensure we use a high-entropy seed for the psuedo-random generator
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rand.Seed(newSeed())
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}
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// returns an int64 from a crypto random source
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// can be used to seed a source for a math/rand.
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func newSeed() int64 {
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r, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
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if err != nil {
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panic(fmt.Errorf("failed to read random bytes: %v", err))
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}
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return r.Int64()
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}
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// randomTimeout returns a value that is between the minVal and 2x minVal.
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func randomTimeout(minVal time.Duration) <-chan time.Time {
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if minVal == 0 {
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return nil
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}
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extra := (time.Duration(rand.Int63()) % minVal)
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return time.After(minVal + extra)
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}
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// min returns the minimum.
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func min(a, b uint64) uint64 {
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if a <= b {
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return a
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}
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return b
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}
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// max returns the maximum.
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func max(a, b uint64) uint64 {
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if a >= b {
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return a
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}
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return b
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}
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// generateUUID is used to generate a random UUID.
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func generateUUID() string {
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buf := make([]byte, 16)
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if _, err := crand.Read(buf); err != nil {
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panic(fmt.Errorf("failed to read random bytes: %v", err))
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}
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return fmt.Sprintf("%08x-%04x-%04x-%04x-%12x",
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buf[0:4],
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buf[4:6],
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buf[6:8],
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buf[8:10],
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buf[10:16])
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}
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// asyncNotifyCh is used to do an async channel send
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// to a single channel without blocking.
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func asyncNotifyCh(ch chan struct{}) {
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select {
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case ch <- struct{}{}:
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default:
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}
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}
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// drainNotifyCh empties out a single-item notification channel without
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// blocking, and returns whether it received anything.
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func drainNotifyCh(ch chan struct{}) bool {
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select {
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case <-ch:
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return true
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default:
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return false
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}
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}
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// asyncNotifyBool is used to do an async notification
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// on a bool channel.
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func asyncNotifyBool(ch chan bool, v bool) {
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select {
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case ch <- v:
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default:
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}
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}
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// Decode reverses the encode operation on a byte slice input.
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func decodeMsgPack(buf []byte, out interface{}) error {
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r := bytes.NewBuffer(buf)
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hd := codec.MsgpackHandle{}
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dec := codec.NewDecoder(r, &hd)
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return dec.Decode(out)
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}
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// Encode writes an encoded object to a new bytes buffer.
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func encodeMsgPack(in interface{}) (*bytes.Buffer, error) {
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buf := bytes.NewBuffer(nil)
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hd := codec.MsgpackHandle{}
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enc := codec.NewEncoder(buf, &hd)
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err := enc.Encode(in)
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return buf, err
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}
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// backoff is used to compute an exponential backoff
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// duration. Base time is scaled by the current round,
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// up to some maximum scale factor.
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func backoff(base time.Duration, round, limit uint64) time.Duration {
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power := min(round, limit)
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for power > 2 {
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base *= 2
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power--
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}
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return base
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}
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// Needed for sorting []uint64, used to determine commitment
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type uint64Slice []uint64
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func (p uint64Slice) Len() int { return len(p) }
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func (p uint64Slice) Less(i, j int) bool { return p[i] < p[j] }
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func (p uint64Slice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
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