Christian Schwarz
b9b9ad10cf
This PR adds a new field optional field `timestamp_location` that allows the user to specify a timezone different than the default UTC for use in the snapshot suffix. I took @mjasnik 's PR https://github.com/zrepl/zrepl/pull/785 and refactored+extended it as follows: * move all formatting logic into its own package * disallow `dense` and `human` with formats != UTC to protect users from stupidity * document behavior more clearly * regression test for existing users
94 lines
3.0 KiB
Go
94 lines
3.0 KiB
Go
package timestamp
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import (
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"fmt"
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"strconv"
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"strings"
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"time"
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"github.com/pkg/errors"
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)
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type Formatter struct {
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format func(time.Time) string
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location *time.Location
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}
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func New(formatString string, locationString string) (*Formatter, error) {
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location, err := time.LoadLocation(locationString) // no shadow
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if err != nil {
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return nil, errors.Wrapf(err, "load location from string %q", locationString)
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}
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makeFormatFunc := func(formatString string) (func(time.Time) string, error) {
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// NB: we use zfs.EntityNamecheck in higher-level code to filter out all invalid characters.
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// This check here is specifically so that we know for sure that the `+`=>`_` replacement
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// that we do in the returned func replaces exactly the timezone offset `+` and not some other `+`.
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if strings.Contains(formatString, "+") {
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return nil, fmt.Errorf("character '+' is not allowed in ZFS snapshot names and has special handling")
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}
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return func(t time.Time) string {
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res := t.Format(formatString)
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// if the formatString contains a time zone specifier
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// and the location would result in a positive offset to UTC
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// then the result of t.Format would contain a '+' sign.
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if isLocationPositiveOffsetToUTC(location) {
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// the only source of `+` can be the positive time zone offset because we disallowed `+` as a character in the format string
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res = strings.Replace(res, "+", "_", 1)
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}
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if strings.Contains(res, "+") {
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panic(fmt.Sprintf("format produced a string containing illegal character '+' that wasn't the expected case of positive time zone offset: format=%q location=%q unix=%q result=%q", formatString, location, t.Unix(), res))
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}
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return res
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}, nil
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}
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var formatFunc func(time.Time) string
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mustUseUtcError := func() error {
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return fmt.Errorf("format string requires UTC location")
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}
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switch strings.ToLower(formatString) {
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case "dense":
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if location != time.UTC {
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err = mustUseUtcError()
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} else {
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formatFunc, err = makeFormatFunc("20060102_150405_000")
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}
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case "human":
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if location != time.UTC {
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err = mustUseUtcError()
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} else {
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formatFunc, err = makeFormatFunc("2006-01-02_15:04:05")
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}
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case "iso-8601":
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formatFunc, err = makeFormatFunc("2006-01-02T15:04:05.000Z0700")
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case "unix-seconds":
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if location != time.UTC {
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// Technically not required because unix time is by definition in UTC
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// but let's make that clear to confused users...
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err = mustUseUtcError()
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} else {
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formatFunc = func(t time.Time) string {
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return strconv.FormatInt(t.Unix(), 10)
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}
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}
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default:
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formatFunc, err = makeFormatFunc(formatString)
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}
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if err != nil {
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return nil, errors.Wrapf(err, "invalid format string %q or location %q", formatString, locationString)
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}
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return &Formatter{
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format: formatFunc,
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location: location,
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}, nil
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}
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func isLocationPositiveOffsetToUTC(location *time.Location) bool {
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_, offsetSeconds := time.Now().In(location).Zone()
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return offsetSeconds > 0
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}
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func (f *Formatter) Format(t time.Time) string {
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t = t.In(f.location)
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return f.format(t)
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}
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