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misc.go
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misc.go
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// Copyright (c) 2014 Couchbase, Inc.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the
// License. You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an "AS
// IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
// express or implied. See the License for the specific language
// governing permissions and limitations under the License.
package cbgt
import (
"bytes"
"encoding/json"
"fmt"
"io"
"math"
"math/rand"
"net/http"
"reflect"
"runtime"
"strconv"
"strings"
"sync/atomic"
"time"
"github.com/rcrowley/go-metrics"
)
func init() {
rand.Seed(time.Now().UTC().UnixNano())
}
// DiagHandler allows modules to provide their own additions in
// response to "diag" or diagnostic information requests.
type DiagHandler struct {
Name string
Handler http.Handler
HandlerFunc http.HandlerFunc
}
// Documentation is used for auto-generated documentation.
type Documentation struct {
Text string // Optional documentation text (markdown).
JSON interface{} // Optional marshall'able to JSON.
}
var EMPTY_BYTES = []byte{}
var JsonNULL = []byte("null")
var JsonOpenBrace = []byte("{")
var JsonCloseBrace = []byte("}")
var JsonCloseBraceComma = []byte("},")
var JsonComma = []byte(",")
// IndentJSON is a helper func that returns indented JSON for its
// interface{} x parameter.
func IndentJSON(x interface{}, prefix, indent string) string {
j, err := json.Marshal(x)
if err != nil {
return fmt.Sprintf("misc: IndentJSON marshal, err: %v", err)
}
var buf bytes.Buffer
err = json.Indent(&buf, j, prefix, indent)
if err != nil {
return fmt.Sprintf("misc: IndentJSON indent, err: %v", err)
}
return buf.String()
}
// ErrorToString is a helper func that returns e.Error(), but also
// returns "" for nil error.
func ErrorToString(e error) string {
if e != nil {
return e.Error()
}
return ""
}
// Compares two dotted versioning strings, like "1.0.1" and "1.2.3".
// Returns true when x >= y.
//
// TODO: Need to handle non-numeric parts?
func VersionGTE(x, y string) bool {
xa := strings.Split(x, ".")
ya := strings.Split(y, ".")
for i := range xa {
if i >= len(ya) {
return true
}
xv, err := strconv.Atoi(xa[i])
if err != nil {
return false
}
yv, err := strconv.Atoi(ya[i])
if err != nil {
return false
}
if xv > yv {
return true
}
if xv < yv {
return false
}
}
return len(xa) >= len(ya)
}
func NewUUID() string {
val1 := rand.Int63()
val2 := rand.Int63()
uuid := fmt.Sprintf("%x%x", val1, val2)
return uuid[0:16]
}
// Calls f() in a loop, sleeping in an exponential backoff if needed.
// The provided f() function should return < 0 to stop the loop; >= 0
// to continue the loop, where > 0 means there was progress which
// allows an immediate retry of f() with no sleeping. A return of < 0
// is useful when f() will never make any future progress.
func ExponentialBackoffLoop(name string,
f func() int,
startSleepMS int,
backoffFactor float32,
maxSleepMS int) {
nextSleepMS := startSleepMS
for {
progress := f()
if progress < 0 {
return
}
if progress > 0 {
// When there was some progress, we can reset nextSleepMS.
nextSleepMS = startSleepMS
} else {
// If zero progress was made this cycle, then sleep.
time.Sleep(time.Duration(nextSleepMS) * time.Millisecond)
// Increase nextSleepMS in case next time also has 0 progress.
nextSleepMS = int(float32(nextSleepMS) * backoffFactor)
if nextSleepMS > maxSleepMS {
nextSleepMS = maxSleepMS
}
}
}
}
// StringsToMap connverts an array of (perhaps duplicated) strings
// into a map with key of those strings and values of true, and is
// useful for simple set-like operations.
func StringsToMap(strsArr []string) map[string]bool {
if strsArr == nil {
return nil
}
strs := map[string]bool{}
for _, str := range strsArr {
strs[str] = true
}
return strs
}
// StringsRemoveDuplicates removes any duplicate strings from the give slice.
func StringsRemoveDuplicates(strsArr []string) []string {
if len(strsArr) <= 1 {
return strsArr
}
rv := make([]string, 0, len(strsArr))
lookup := make(map[string]struct{}, len(strsArr))
for _, str := range strsArr {
if _, ok := lookup[str]; !ok {
lookup[str] = struct{}{}
rv = append(rv, str)
}
}
return rv
}
// StringsRemoveStrings returns a copy of stringArr, but with some
// strings removed, keeping the same order as stringArr.
func StringsRemoveStrings(stringArr, removeArr []string) []string {
removeMap := StringsToMap(removeArr)
rv := make([]string, 0, len(stringArr))
for _, s := range stringArr {
if !removeMap[s] {
rv = append(rv, s)
}
}
return rv
}
// StringsIntersectStrings returns a brand new array that has the
// intersection of a and b.
func StringsIntersectStrings(a, b []string) []string {
bMap := StringsToMap(b)
rMap := map[string]bool{}
rv := make([]string, 0, len(a))
for _, s := range a {
if bMap[s] && !rMap[s] {
rMap[s] = true
rv = append(rv, s)
}
}
return rv
}
// TimeoutCancelChan creates a channel that closes after a given
// timeout in milliseconds.
func TimeoutCancelChan(timeout int64) <-chan bool {
if timeout > 0 {
cancelCh := make(chan bool, 1)
go func() {
time.Sleep(time.Duration(timeout) * time.Millisecond)
close(cancelCh)
}()
return cancelCh
}
return nil
}
// Time invokes a func f and updates the totalDuration, totalCount and
// maxDuration metrics. See also Timer() for a metrics based
// alternative.
func Time(f func() error,
totalDuration, totalCount, maxDuration *uint64) error {
startTime := time.Now()
err := f()
duration := uint64(time.Since(startTime))
atomic.AddUint64(totalDuration, duration)
if totalCount != nil {
atomic.AddUint64(totalCount, 1)
}
if maxDuration != nil {
retry := true
for retry {
retry = false
md := atomic.LoadUint64(maxDuration)
if md < duration {
retry = !atomic.CompareAndSwapUint64(maxDuration, md, duration)
}
}
}
return err
}
// Timer updates a metrics.Timer. Unlike metrics.Timer.Time(), this
// version also captures any error return value.
func Timer(f func() error, t metrics.Timer) error {
var err error
t.Time(func() {
err = f()
})
return err
}
// AtomicCopyMetrics copies uint64 metrics from s to r (from source to
// result), and also applies an optional fn function to each metric.
// The fn is invoked with metrics from s and r, and can be used to
// compute additions, subtractions, etc. When fn is nil, AtomicCopyTo
// defaults to just a straight copier.
func AtomicCopyMetrics(s, r interface{},
fn func(sv uint64, rv uint64) uint64) {
// Using reflection rather than a whole slew of explicit
// invocations of atomic.LoadUint64()/StoreUint64()'s.
if fn == nil {
fn = func(sv uint64, rv uint64) uint64 { return sv }
}
rve := reflect.ValueOf(r).Elem()
sve := reflect.ValueOf(s).Elem()
svet := sve.Type()
for i := 0; i < svet.NumField(); i++ {
rvef := rve.Field(i)
svef := sve.Field(i)
if rvef.CanAddr() && svef.CanAddr() {
rvefp := rvef.Addr().Interface()
svefp := svef.Addr().Interface()
rv := atomic.LoadUint64(rvefp.(*uint64))
sv := atomic.LoadUint64(svefp.(*uint64))
atomic.StoreUint64(rvefp.(*uint64), fn(sv, rv))
}
}
}
// StructChanges uses reflection to compare the fields of two structs,
// which must the same type, and returns info on the changes of field
// values.
func StructChanges(a1, a2 interface{}) (rv []string) {
if a1 == nil || a2 == nil {
return nil
}
v1 := reflect.ValueOf(a1)
v2 := reflect.ValueOf(a2)
if v1.Type() != v2.Type() {
return nil
}
if v1.Kind() != v2.Kind() ||
v1.Kind() != reflect.Struct {
return nil
}
for i := 0; i < v1.NumField(); i++ {
v1f := v1.Field(i)
v2f := v2.Field(i)
if v1f.Kind() == v2f.Kind() &&
v1f.Kind() == reflect.Int {
if v1f.Int() != v2f.Int() {
rv = append(rv, fmt.Sprintf("%s: %d -> %d",
v2.Type().Field(i).Name, v1f.Int(), v2f.Int()))
}
}
}
return rv
}
var timerPercentiles = []float64{0.5, 0.75, 0.95, 0.99, 0.999}
// WriteTimerJSON writes a metrics.Timer instance as JSON to a
// io.Writer.
func WriteTimerJSON(w io.Writer, timer metrics.Timer) {
t := timer.Snapshot()
p := t.Percentiles(timerPercentiles)
fmt.Fprintf(w, `{"count":%9d,`, t.Count())
fmt.Fprintf(w, `"min":%9d,`, t.Min())
fmt.Fprintf(w, `"max":%9d,`, t.Max())
mean := t.Mean()
if !isNanOrInf(mean) {
fmt.Fprintf(w, `"mean":%12.2f,`, mean)
}
stddev := t.StdDev()
if !isNanOrInf(stddev) {
fmt.Fprintf(w, `"stddev":%12.2f,`, stddev)
}
fPrintFloatMap(w, "percentiles", map[string]float64{
"median": p[0],
"75%": p[1],
"95%": p[2],
"99%": p[3],
"99.9%": p[4],
})
fmt.Fprintf(w, `,`)
fPrintFloatMap(w, "rates", map[string]float64{
"1-min": t.Rate1(),
"5-min": t.Rate5(),
"15-min": t.Rate15(),
"mean": t.RateMean(),
})
fmt.Fprintf(w, `}`)
}
// a helper to safely print a json map with string keys and float64 values
// if +/-Inf or NaN values are encountered, that k/v pair is omitted
// if there are no valid values in the map, the named map is still emitted
// with no contents, ie:
// "name":{}
func fPrintFloatMap(w io.Writer, name string, vals map[string]float64) {
fmt.Fprintf(w, `"%s":{`, name)
first := true
for k, v := range vals {
if !isNanOrInf(v) {
if !first {
fmt.Fprintf(w, `,`)
}
fmt.Fprintf(w, `"%s":%12.2f`, k, v)
first = false
}
}
fmt.Fprintf(w, `}`)
}
func isNanOrInf(v float64) bool {
if math.IsNaN(v) || math.IsInf(v, 0) {
return true
}
return false
}
// CalcMovingPartitionsCount attempts to compute the number of
// moving partitions during a rebalance, given few node count
// statistics of the cluster
func CalcMovingPartitionsCount(numKeepNodes, numRemoveNodes, numNewNodes,
numPrevNodes, totalPartitions int) int {
// figure out the per node partitions to move during cases like
// scaleOut, scaleIn and constant nodecount in cluster
partitionsPerNode := 0
if numRemoveNodes == numNewNodes && numKeepNodes > 0 {
partitionsPerNode = totalPartitions / numKeepNodes
} else if numRemoveNodes > numNewNodes && numPrevNodes > 0 {
partitionsPerNode = totalPartitions / numPrevNodes
} else if numRemoveNodes < numNewNodes && numKeepNodes > 0 {
partitionsPerNode = totalPartitions / numKeepNodes
}
// adjust the partitionsPerNode for the rebalance scenario
// where both node additions and removals happen at the same time
delta := numRemoveNodes
if numRemoveNodes > 0 && numNewNodes > 0 {
delta = int(math.Abs(float64(numRemoveNodes - numNewNodes)))
}
return partitionsPerNode * (delta + numNewNodes)
}
var maxCallerStackDepth = 50
const panicCallStack = "panic callstack: \n"
// ReadableStackTrace tries to capture the caller stack frame
// for the calling function in a panic scenario.
func ReadableStackTrace() string {
callers := make([]uintptr, maxCallerStackDepth)
length := runtime.Callers(3, callers[:])
callers = callers[:length]
var result bytes.Buffer
frames := callersToFrames(callers)
for _, frame := range frames {
result.WriteString(fmt.Sprintf("%s:%d (%#x)\n\t%s\n",
frame.File, frame.Line, frame.PC, frame.Function))
}
return panicCallStack + result.String()
}
func callersToFrames(callers []uintptr) []runtime.Frame {
frames := make([]runtime.Frame, 0, len(callers))
framesPtr := runtime.CallersFrames(callers)
for {
frame, more := framesPtr.Next()
frames = append(frames, frame)
if !more {
return frames
}
}
}