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tstime: write Parse3339 parse that doesn't use time.Parse

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It doesn't allocate and it's half the time of time.Parse (which
allocates), and 2/3rds the time of time.ParseInLocation (which
doesn't).

Go with a UTC time:

BenchmarkGoParse3339/Z-8                 2200995               534 ns/op               0 B/op          0 allocs/op
BenchmarkGoParse3339/Z-8                 2254816               554 ns/op               0 B/op          0 allocs/op
BenchmarkGoParse3339/Z-8                 2159504               522 ns/op               0 B/op          0 allocs/op

Go allocates with a "-08:00" suffix instead of ending in "Z":

BenchmarkGoParse3339/TZ-8                1276491               884 ns/op             144 B/op          3 allocs/op
BenchmarkGoParse3339/TZ-8                1355858               942 ns/op             144 B/op          3 allocs/op
BenchmarkGoParse3339/TZ-8                1385484               911 ns/op             144 B/op          3 allocs/op

Go doesn't allocate if you use time.ParseInLocation, but then you need
to parse the string to find the location anyway, so might as well go
all the way (below).

BenchmarkGoParse3339InLocation-8         1912254               597 ns/op               0 B/op          0 allocs/op
BenchmarkGoParse3339InLocation-8         1980043               612 ns/op               0 B/op          0 allocs/op
BenchmarkGoParse3339InLocation-8         1891366               612 ns/op               0 B/op          0 allocs/op

Parsing RFC3339 ourselves, UTC:

BenchmarkParse3339/Z-8                   3889220               307 ns/op               0 B/op          0 allocs/op
BenchmarkParse3339/Z-8                   3718500               309 ns/op               0 B/op          0 allocs/op
BenchmarkParse3339/Z-8                   3621231               303 ns/op               0 B/op          0 allocs/op

Parsing RFC3339 ourselves, with timezone (w/ *time.Location fetched
from sync.Map)

BenchmarkParse3339/TZ-8                  3019612               418 ns/op               0 B/op          0 allocs/op
BenchmarkParse3339/TZ-8                  2921618               401 ns/op               0 B/op          0 allocs/op
BenchmarkParse3339/TZ-8                  3031671               408 ns/op               0 B/op          0 allocs/op

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2020-04-05 21:47:47 -07:00 committed by Brad Fitzpatrick
parent 02948d2c86
commit febdac0499
2 changed files with 154 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

80
tstime/tstime.go
View File

@ -6,16 +6,20 @@
package tstime
import (
"errors"
"fmt"
"strconv"
"strings"
"sync"
"time"
)
// zoneOf returns the RFC3339 zone suffix, or the empty string
// if it's invalid or not something we want to cache.
// zoneOf returns the RFC3339 zone suffix (either "Z" or like
// "+08:30"), or the empty string if it's invalid or not something we
// want to cache.
func zoneOf(s string) string {
if strings.HasSuffix(s, "Z") {
return ""
return "Z"
}
if len(s) < len("2020-04-05T15:56:00+08:00") {
// Too short, invalid? Let time.Parse fail on it.
@ -36,23 +40,75 @@ func zoneOf(s string) string {
// *time.Location (from FixedLocation).
var locCache sync.Map
func getLocation(zone, timeValue string) (*time.Location, error) {
if zone == "Z" {
return time.UTC, nil
}
if loci, ok := locCache.Load(zone); ok {
return loci.(*time.Location), nil
}
// TODO(bradfitz): just parse it and call time.FixedLocation.
// For now, just have time.Parse do it once:
t, err := time.Parse(time.RFC3339Nano, timeValue)
if err != nil {
return nil, err
}
loc := t.Location()
locCache.LoadOrStore(zone, loc)
return loc, nil
}
// Parse3339 is a wrapper around time.Parse(time.RFC3339Nano, s) that caches
// timezone Locations for future parses.
func Parse3339(s string) (time.Time, error) {
zone := zoneOf(s)
if zone == "" {
// Invalid or weird timezone offset. Use slow path,
// which'll probably return an error.
return time.Parse(time.RFC3339Nano, s)
}
loci, ok := locCache.Load(zone)
if ok {
// TODO(bradfitz): just rewrite this do the trivial parsing by hand
// which will be faster than Go's format-driven one. RFC3339 is trivial.
return time.ParseInLocation(time.RFC3339Nano, s, loci.(*time.Location))
}
t, err := time.Parse(time.RFC3339Nano, s)
loc, err := getLocation(zone, s)
if err != nil {
return time.Time{}, err
}
locCache.LoadOrStore(zone, t.Location())
return t, nil
s = s[:len(s)-len(zone)] // remove zone suffix
var year, mon, day, hr, min, sec, nsec int
const baseLen = len("2020-04-05T15:56:00")
if len(s) < baseLen ||
!parseInt(s[:4], &year) ||
s[4] != '-' ||
!parseInt(s[5:7], &mon) ||
s[7] != '-' ||
!parseInt(s[8:10], &day) ||
s[10] != 'T' ||
!parseInt(s[11:13], &hr) ||
s[13] != ':' ||
!parseInt(s[14:16], &min) ||
s[16] != ':' ||
!parseInt(s[17:19], &sec) {
return time.Time{}, errors.New("invalid time")
}
nsStr := s[baseLen:]
if nsStr != "" {
if nsStr[0] != '.' {
return time.Time{}, errors.New("invalid optional nanosecond prefix")
}
if !parseInt(nsStr[1:], &nsec) {
return time.Time{}, fmt.Errorf("invalid optional nanosecond number %q", nsStr[1:])
}
for i := 0; i < len("999999999")-(len(nsStr)-1); i++ {
nsec *= 10
}
}
return time.Date(year, time.Month(mon), day, hr, min, sec, nsec, loc), nil
}
func parseInt(s string, dst *int) bool {
n, err := strconv.ParseInt(s, 10, 0)
if err != nil || n < 0 {
return false
}
*dst = int(n)
return true
}

120
tstime/tstime_test.go
View File

@ -9,6 +9,51 @@ import (
"time"
)
func TestParse3339(t *testing.T) {
tests := []string{
"2020-04-05T15:56:00Z",
"2020-04-05T15:56:00.1234Z",
"2020-04-05T15:56:00+08:00",
"2020-04-05T15:56:00.1+08:00",
"2020-04-05T15:56:00.12+08:00",
"2020-04-05T15:56:00.012+08:00",
"2020-04-05T15:56:00.0012+08:00",
"2020-04-05T15:56:00.148487491+08:00",
"2020x04-05T15:56:00.1234+08:00",
"2020-04x05T15:56:00.1234+08:00",
"2020-04-05x15:56:00.1234+08:00",
"2020-04-05T15x56:00.1234+08:00",
"2020-04-05T15:56x00.1234+08:00",
"2020-04-05T15:56:00x1234+08:00",
}
for _, s := range tests {
t.Run(s, func(t *testing.T) {
goTime, goErr := time.Parse(time.RFC3339Nano, s)
Parse3339(s) // prime the tz cache so next parse use fast path
got, err := Parse3339(s)
if (err == nil) != (goErr == nil) {
t.Errorf("for %q, go err = %v; our err = %v", s, goErr, err)
return
}
if err != nil {
return
}
if !goTime.Equal(got) {
t.Errorf("for %q, times not Equal: we got %v, want go's %v", s, got, goTime)
}
if goStr, ourStr := goTime.Format(time.RFC3339Nano), got.Format(time.RFC3339Nano); goStr != ourStr {
t.Errorf("for %q, strings not equal: we got %q, want go's %q", s, ourStr, goStr)
}
})
}
}
func TestZoneOf(t *testing.T) {
tests := []struct {
in, want string
@ -16,17 +61,14 @@ func TestZoneOf(t *testing.T) {
{"2020-04-05T15:56:00+08:00", "+08:00"},
{"2020-04-05T15:56:00-08:00", "-08:00"},
{"2020-04-05T15:56:00.12345-08:00", "-08:00"},
// don't cache weird offsets, only 00 15, 30:
{"2020-04-05T15:56:00.12345-08:00", "-08:00"},
{"2020-04-05T15:56:00.12345-08:30", "-08:30"},
{"2020-04-05T15:56:00.12345-08:15", "-08:15"},
{"2020-04-05T15:56:00.12345-08:17", ""},
// don't cache UTC:
{"2020-04-05T15:56:00.12345Z", ""},
{"2020-04-05T15:56:00Z", ""},
// too short:
{"123+08:00", ""},
{"+08:00", ""},
{"2020-04-05T15:56:00.12345-08:17", ""}, // don't cache weird offsets
{"2020-04-05T15:56:00.12345Z", "Z"},
{"2020-04-05T15:56:00Z", "Z"},
{"123+08:00", ""}, // too short
{"+08:00", ""}, // too short
}
for _, tt := range tests {
if got := zoneOf(tt.in); got != tt.want {
@ -36,14 +78,19 @@ func TestZoneOf(t *testing.T) {
}
func BenchmarkGoParse3339(b *testing.B) {
b.ReportAllocs()
const in = `2020-04-05T15:56:00.148487491+08:00`
for i := 0; i < b.N; i++ {
_, err := time.Parse(time.RFC3339Nano, in)
if err != nil {
b.Fatal(err)
run := func(in string) func(*testing.B) {
return func(b *testing.B) {
b.ReportAllocs()
for i := 0; i < b.N; i++ {
_, err := time.Parse(time.RFC3339Nano, in)
if err != nil {
b.Fatal(err)
}
}
}
}
b.Run("Z", run("2020-04-05T15:56:00.148487491Z"))
b.Run("TZ", run("2020-04-05T15:56:00.148487491+08:00"))
}
func BenchmarkGoParse3339InLocation(b *testing.B) {
@ -76,29 +123,34 @@ func BenchmarkGoParse3339InLocation(b *testing.B) {
}
func BenchmarkParse3339(b *testing.B) {
b.ReportAllocs()
const in = `2020-04-05T15:56:00.148487491+08:00`
run := func(in string) func(*testing.B) {
return func(b *testing.B) {
b.ReportAllocs()
t, err := time.Parse(time.RFC3339Nano, in)
if err != nil {
b.Fatal(err)
}
t, err := time.Parse(time.RFC3339Nano, in)
if err != nil {
b.Fatal(err)
}
t2, err := Parse3339(in)
if err != nil {
b.Fatal(err)
}
if !t.Equal(t2) {
b.Fatal("not equal")
}
if s1, s2 := t.Format(time.RFC3339Nano), t2.Format(time.RFC3339Nano); s1 != s2 {
b.Fatalf("times don't stringify the same: %q vs %q", s1, s2)
}
t2, err := Parse3339(in)
if err != nil {
b.Fatal(err)
}
if !t.Equal(t2) {
b.Fatal("not equal")
}
if s1, s2 := t.Format(time.RFC3339Nano), t2.Format(time.RFC3339Nano); s1 != s2 {
b.Fatalf("times don't stringify the same: %q vs %q", s1, s2)
}
for i := 0; i < b.N; i++ {
_, err := Parse3339(in)
if err != nil {
b.Fatal(err)
for i := 0; i < b.N; i++ {
_, err := Parse3339(in)
if err != nil {
b.Fatal(err)
}
}
}
}
b.Run("Z", run("2020-04-05T15:56:00.148487491Z"))
b.Run("TZ", run("2020-04-05T15:56:00.148487491+08:00"))
}