[pkg/ottl] add time converter function

[fchikwekwe]

Description: Added a converter function that takes a time string and a format string and converts to a golang time.Time object.

Link to tracking Issue: #22007

Testing: Unit tests to check proper conversion from stringGetter to golang time.Time

Documentation:

[linux-foundation-easycla]

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• ✅ login: fchikwekwe / name: Faith Chikwekwe (93dbc5e, d91a0e4, 92ac9da, cecb1fd, dc5d47d, 4f2d350, 2ec93ca, 6c5d9c7, d4a640a, 8fe9ff7, fbc8843, f29c51e, b99ac6d, 74e6fb4, e057a62, 31efe22, 448e139, 19dc265, ee8cd8a, 437d24e, 7214d9c, 5f6cb4e, a64b301, d7d4f78)

[TylerHelmuth]

Great stuff! Please update the ottlfuncs/README with a new entry for this function.

[TylerHelmuth]

LGTM. Please add a changelog entry by running chlog-new in the root directory of the repo. Also update pkg/ottl/go.mod with the new package dependency. Once you've updated the go.mod file run make gotidy in the root directory of the repo.

[TylerHelmuth]

LGTM!

[TylerHelmuth]

While investigating these tests we found inconsistencies with timezones (it's always timezones). Comparing the time parsing to pkg/stanza/operator/helper TimeParser we found that using only the ctimefmt package was not enough as it did not handle timezones the same way TimeParser does.

Investigating further we found that this was the magic that made TimeParser work as it does:

opentelemetry-collector-contrib/pkg/stanza/operator/helper/time.go

Lines 181 to 204 in d0fe5f3

	result, err := time.ParseInLocation(t.Layout, str, t.location)
	// Depending on the timezone database, we may get a pseudo-matching timezone
	// This is apparent when the zone is not "UTC", but the offset is still 0
	zone, offset := result.Zone()
	if offset != 0 || zone == "UTC" {
	return result, err
	}
	// Manually look up the location based on the zone
	loc, locErr := time.LoadLocation(zone)
	if locErr != nil {
	// can't correct offset, just return what we have
	return result, fmt.Errorf("failed to load location %s: %w", zone, locErr)
	}
	// Reparse the timestamp, with the location
	resultLoc, locErr := time.ParseInLocation(t.Layout, str, loc)
	if locErr != nil {
	// can't correct offset, just return original result
	return result, err
	}
	return resultLoc, locErr

and

opentelemetry-collector-contrib/pkg/stanza/operator/helper/time.go

Lines 113 to 130 in d0fe5f3

	if t.Location != "" {
	// If "location" is specified, it must be in the local timezone database
	loc, err := time.LoadLocation(t.Location)
	if err != nil {
	return fmt.Errorf("failed to load location %s: %w", t.Location, err)
	}
	t.location = loc
	return nil
	}
	if strings.HasSuffix(t.Layout, "Z") {
	// If a timestamp ends with 'Z', it should be interpretted at Zulu (UTC) time
	t.location = time.UTC
	return nil
	}
	t.location = time.Local
	return nil

Handling the time in this way is necessary for a consistent time parsing strategy in the collector. Instead of duplicating these lines we should move the functionality out of stanza and into a shared place. See #23232 for implementation.

Solution changed, needs re-reviewed

[TylerHelmuth]

@evan-bradley can you review this one as well? I'm too close to it after doing the refactor in timeutils to unblock it.

[ptimofee]

Great stuff! Please update the ottlfuncs/README with a new entry for this function.

Not done

[TylerHelmuth]

@ptimofee you are correct, I missed that. It is now being added via #23659