/usr/share/gocode/src/github.com/hashicorp/serf/vendor/github.com/hashicorp/memberlist/util.go is in golang-github-hashicorp-serf-dev 0.8.1+git20171021.c20a0b1~ds1-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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import (
"bytes"
"compress/lzw"
"encoding/binary"
"fmt"
"io"
"math"
"math/rand"
"strings"
"time"
"github.com/hashicorp/go-msgpack/codec"
"github.com/sean-/seed"
)
// pushPullScale is the minimum number of nodes
// before we start scaling the push/pull timing. The scale
// effect is the log2(Nodes) - log2(pushPullScale). This means
// that the 33rd node will cause us to double the interval,
// while the 65th will triple it.
const pushPullScaleThreshold = 32
const (
// Constant litWidth 2-8
lzwLitWidth = 8
)
func init() {
seed.Init()
}
// Decode reverses the encode operation on a byte slice input
func decode(buf []byte, out interface{}) error {
r := bytes.NewReader(buf)
hd := codec.MsgpackHandle{}
dec := codec.NewDecoder(r, &hd)
return dec.Decode(out)
}
// Encode writes an encoded object to a new bytes buffer
func encode(msgType messageType, in interface{}) (*bytes.Buffer, error) {
buf := bytes.NewBuffer(nil)
buf.WriteByte(uint8(msgType))
hd := codec.MsgpackHandle{}
enc := codec.NewEncoder(buf, &hd)
err := enc.Encode(in)
return buf, err
}
// Returns a random offset between 0 and n
func randomOffset(n int) int {
if n == 0 {
return 0
}
return int(rand.Uint32() % uint32(n))
}
// suspicionTimeout computes the timeout that should be used when
// a node is suspected
func suspicionTimeout(suspicionMult, n int, interval time.Duration) time.Duration {
nodeScale := math.Max(1.0, math.Log10(math.Max(1.0, float64(n))))
// multiply by 1000 to keep some precision because time.Duration is an int64 type
timeout := time.Duration(suspicionMult) * time.Duration(nodeScale*1000) * interval / 1000
return timeout
}
// retransmitLimit computes the limit of retransmissions
func retransmitLimit(retransmitMult, n int) int {
nodeScale := math.Ceil(math.Log10(float64(n + 1)))
limit := retransmitMult * int(nodeScale)
return limit
}
// shuffleNodes randomly shuffles the input nodes using the Fisher-Yates shuffle
func shuffleNodes(nodes []*nodeState) {
n := len(nodes)
for i := n - 1; i > 0; i-- {
j := rand.Intn(i + 1)
nodes[i], nodes[j] = nodes[j], nodes[i]
}
}
// pushPushScale is used to scale the time interval at which push/pull
// syncs take place. It is used to prevent network saturation as the
// cluster size grows
func pushPullScale(interval time.Duration, n int) time.Duration {
// Don't scale until we cross the threshold
if n <= pushPullScaleThreshold {
return interval
}
multiplier := math.Ceil(math.Log2(float64(n))-math.Log2(pushPullScaleThreshold)) + 1.0
return time.Duration(multiplier) * interval
}
// moveDeadNodes moves nodes that are dead and beyond the gossip to the dead interval
// to the end of the slice and returns the index of the first moved node.
func moveDeadNodes(nodes []*nodeState, gossipToTheDeadTime time.Duration) int {
numDead := 0
n := len(nodes)
for i := 0; i < n-numDead; i++ {
if nodes[i].State != stateDead {
continue
}
// Respect the gossip to the dead interval
if time.Since(nodes[i].StateChange) <= gossipToTheDeadTime {
continue
}
// Move this node to the end
nodes[i], nodes[n-numDead-1] = nodes[n-numDead-1], nodes[i]
numDead++
i--
}
return n - numDead
}
// kRandomNodes is used to select up to k random nodes, excluding any nodes where
// the filter function returns true. It is possible that less than k nodes are
// returned.
func kRandomNodes(k int, nodes []*nodeState, filterFn func(*nodeState) bool) []*nodeState {
n := len(nodes)
kNodes := make([]*nodeState, 0, k)
OUTER:
// Probe up to 3*n times, with large n this is not necessary
// since k << n, but with small n we want search to be
// exhaustive
for i := 0; i < 3*n && len(kNodes) < k; i++ {
// Get random node
idx := randomOffset(n)
node := nodes[idx]
// Give the filter a shot at it.
if filterFn != nil && filterFn(node) {
continue OUTER
}
// Check if we have this node already
for j := 0; j < len(kNodes); j++ {
if node == kNodes[j] {
continue OUTER
}
}
// Append the node
kNodes = append(kNodes, node)
}
return kNodes
}
// makeCompoundMessage takes a list of messages and generates
// a single compound message containing all of them
func makeCompoundMessage(msgs [][]byte) *bytes.Buffer {
// Create a local buffer
buf := bytes.NewBuffer(nil)
// Write out the type
buf.WriteByte(uint8(compoundMsg))
// Write out the number of message
buf.WriteByte(uint8(len(msgs)))
// Add the message lengths
for _, m := range msgs {
binary.Write(buf, binary.BigEndian, uint16(len(m)))
}
// Append the messages
for _, m := range msgs {
buf.Write(m)
}
return buf
}
// decodeCompoundMessage splits a compound message and returns
// the slices of individual messages. Also returns the number
// of truncated messages and any potential error
func decodeCompoundMessage(buf []byte) (trunc int, parts [][]byte, err error) {
if len(buf) < 1 {
err = fmt.Errorf("missing compound length byte")
return
}
numParts := uint8(buf[0])
buf = buf[1:]
// Check we have enough bytes
if len(buf) < int(numParts*2) {
err = fmt.Errorf("truncated len slice")
return
}
// Decode the lengths
lengths := make([]uint16, numParts)
for i := 0; i < int(numParts); i++ {
lengths[i] = binary.BigEndian.Uint16(buf[i*2 : i*2+2])
}
buf = buf[numParts*2:]
// Split each message
for idx, msgLen := range lengths {
if len(buf) < int(msgLen) {
trunc = int(numParts) - idx
return
}
// Extract the slice, seek past on the buffer
slice := buf[:msgLen]
buf = buf[msgLen:]
parts = append(parts, slice)
}
return
}
// Given a string of the form "host", "host:port",
// "ipv6::addr" or "[ipv6::address]:port",
// return true if the string includes a port.
func hasPort(s string) bool {
last := strings.LastIndex(s, ":")
if last == -1 {
return false
}
if s[0] == '[' {
return s[last-1] == ']'
}
return strings.Index(s, ":") == last
}
// compressPayload takes an opaque input buffer, compresses it
// and wraps it in a compress{} message that is encoded.
func compressPayload(inp []byte) (*bytes.Buffer, error) {
var buf bytes.Buffer
compressor := lzw.NewWriter(&buf, lzw.LSB, lzwLitWidth)
_, err := compressor.Write(inp)
if err != nil {
return nil, err
}
// Ensure we flush everything out
if err := compressor.Close(); err != nil {
return nil, err
}
// Create a compressed message
c := compress{
Algo: lzwAlgo,
Buf: buf.Bytes(),
}
return encode(compressMsg, &c)
}
// decompressPayload is used to unpack an encoded compress{}
// message and return its payload uncompressed
func decompressPayload(msg []byte) ([]byte, error) {
// Decode the message
var c compress
if err := decode(msg, &c); err != nil {
return nil, err
}
return decompressBuffer(&c)
}
// decompressBuffer is used to decompress the buffer of
// a single compress message, handling multiple algorithms
func decompressBuffer(c *compress) ([]byte, error) {
// Verify the algorithm
if c.Algo != lzwAlgo {
return nil, fmt.Errorf("Cannot decompress unknown algorithm %d", c.Algo)
}
// Create a uncompressor
uncomp := lzw.NewReader(bytes.NewReader(c.Buf), lzw.LSB, lzwLitWidth)
defer uncomp.Close()
// Read all the data
var b bytes.Buffer
_, err := io.Copy(&b, uncomp)
if err != nil {
return nil, err
}
// Return the uncompressed bytes
return b.Bytes(), nil
}
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