package raft import ( "bytes" crand "crypto/rand" "fmt" "math" "math/big" "math/rand" "time" "github.com/hashicorp/go-msgpack/codec" ) func init() { // Ensure we use a high-entropy seed for the pseudo-random generator rand.Seed(newSeed()) } // returns an int64 from a crypto random source // can be used to seed a source for a math/rand. func newSeed() int64 { r, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64)) if err != nil { panic(fmt.Errorf("failed to read random bytes: %v", err)) } return r.Int64() } // randomTimeout returns a value that is between the minVal and 2x minVal. func randomTimeout(minVal time.Duration) <-chan time.Time { if minVal == 0 { return nil } extra := (time.Duration(rand.Int63()) % minVal) return time.After(minVal + extra) } // min returns the minimum. func min(a, b uint64) uint64 { if a <= b { return a } return b } // max returns the maximum. func max(a, b uint64) uint64 { if a >= b { return a } return b } // generateUUID is used to generate a random UUID. func generateUUID() string { buf := make([]byte, 16) if _, err := crand.Read(buf); err != nil { panic(fmt.Errorf("failed to read random bytes: %v", err)) } return fmt.Sprintf("%08x-%04x-%04x-%04x-%12x", buf[0:4], buf[4:6], buf[6:8], buf[8:10], buf[10:16]) } // asyncNotifyCh is used to do an async channel send // to a single channel without blocking. func asyncNotifyCh(ch chan struct{}) { select { case ch <- struct{}{}: default: } } // drainNotifyCh empties out a single-item notification channel without // blocking, and returns whether it received anything. func drainNotifyCh(ch chan struct{}) bool { select { case <-ch: return true default: return false } } // asyncNotifyBool is used to do an async notification // on a bool channel. func asyncNotifyBool(ch chan bool, v bool) { select { case ch <- v: default: } } // overrideNotifyBool is used to notify on a bool channel // but override existing value if value is present. // ch must be 1-item buffered channel. // // This method does not support multiple concurrent calls. func overrideNotifyBool(ch chan bool, v bool) { select { case ch <- v: // value sent, all done case <-ch: // channel had an old value select { case ch <- v: default: panic("race: channel was sent concurrently") } } } // Decode reverses the encode operation on a byte slice input. func decodeMsgPack(buf []byte, out interface{}) error { r := bytes.NewBuffer(buf) hd := codec.MsgpackHandle{} dec := codec.NewDecoder(r, &hd) return dec.Decode(out) } // Encode writes an encoded object to a new bytes buffer. func encodeMsgPack(in interface{}) (*bytes.Buffer, error) { buf := bytes.NewBuffer(nil) hd := codec.MsgpackHandle{} enc := codec.NewEncoder(buf, &hd) err := enc.Encode(in) return buf, err } // backoff is used to compute an exponential backoff // duration. Base time is scaled by the current round, // up to some maximum scale factor. func backoff(base time.Duration, round, limit uint64) time.Duration { power := min(round, limit) for power > 2 { base *= 2 power-- } return base } // Needed for sorting []uint64, used to determine commitment type uint64Slice []uint64 func (p uint64Slice) Len() int { return len(p) } func (p uint64Slice) Less(i, j int) bool { return p[i] < p[j] } func (p uint64Slice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }