fix ts with no trailing zeros

[chaochn47]

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

2024-06-02T01:49:05.536Z should be 2024-06-02T01:49:05.536000Z, so precision won't be dropped and it's easier to use string compare when sorting the timestamp. For example 2024-06-02T01:49:05.536Z should be bigger than 2024-06-02T01:49:05.535123Z but the former appears first when sorting the strings.

The RFC3339Nano format removes trailing zeros from the seconds field and thus may not sort correctly once formatted.

A comma or decimal point followed by one or more zeros represents a fractional second, printed to the given number of decimal places. A comma or decimal point followed by one or more nines represents a fractional second, printed to the given number of decimal places, with trailing zeros removed. For example "15:04:05,000" or "15:04:05.000" formats or parses with millisecond precision.

https://pkg.go.dev/time

package main

import (
	"fmt"
	"time"
)

func main() {
	// Define the time in Go's reference format
	t := time.Date(2024, time.June, 2, 1, 49, 5, 536000000, time.UTC)

	formattedOmittedZerosTime := t.Format("2006-01-02T15:04:05.999999Z0700")

	fmt.Println(formattedOmittedZerosTime) // Outputs: 2024-06-02T01:49:05.536Z

	formattedWithTrailingZerosTime := t.Format("2006-01-02T15:04:05.000000Z0700")
	fmt.Println(formattedWithTrailingZerosTime) // Outputs: 2024-06-02T01:49:05.536000Z
}

xref:

1. Regression in timestamp resolution #15236
2. Adjust time resolution to microseconds #15239

[serathius]

Please add a unit test.

[chaochn47]

Please add a unit test.

Done.

Before

dev-dsk-chaochn-2c-a26acd76 % stress ./logutil.test -test.run=TestEncodeTimePrecisionToMicroSeconds
/tmp/go-stress-20240607T001548-3505485664
--- FAIL: TestEncodeTimePrecisionToMicroSeconds (0.00s)
    zap_test.go:57:
        	Error Trace:	/home/chaochn/workplace/EKS-etcd/src/EKS-etcd/client/pkg/logutil/zap_test.go:57
        	Error:      	Not equal:
        	            	expected: 6
        	            	actual  : 5
        	Test:       	TestEncodeTimePrecisionToMicroSeconds
        	Messages:   	unexpected timestamp 2024-06-07T00:15:49.48821Z
FAIL


ERROR: exit status 1


/tmp/go-stress-20240607T001548-935680383
--- FAIL: TestEncodeTimePrecisionToMicroSeconds (0.00s)
    zap_test.go:57:
        	Error Trace:	/home/chaochn/workplace/EKS-etcd/src/EKS-etcd/client/pkg/logutil/zap_test.go:57
        	Error:      	Not equal:
        	            	expected: 6
        	            	actual  : 4
        	Test:       	TestEncodeTimePrecisionToMicroSeconds
        	Messages:   	unexpected timestamp 2024-06-07T00:15:49.4881Z
FAIL


ERROR: exit status 1


/tmp/go-stress-20240607T001548-48431470
--- FAIL: TestEncodeTimePrecisionToMicroSeconds (0.00s)
    zap_test.go:57:
        	Error Trace:	/home/chaochn/workplace/EKS-etcd/src/EKS-etcd/client/pkg/logutil/zap_test.go:57
        	Error:      	Not equal:
        	            	expected: 6
        	            	actual  : 5
        	Test:       	TestEncodeTimePrecisionToMicroSeconds
        	Messages:   	unexpected timestamp 2024-06-07T00:15:49.49074Z
FAIL


ERROR: exit status 1

After

dev-dsk-chaochn-2c-a26acd76 % stress ./logutil.test -test.run=TestEncodeTimePrecisionToMicroSeconds
5s: 13273 runs so far, 0 failures
10s: 27055 runs so far, 0 failures
15s: 40982 runs so far, 0 failures
20s: 54810 runs so far, 0 failures
25s: 68705 runs so far, 0 failures
30s: 82586 runs so far, 0 failures
35s: 96406 runs so far, 0 failures
40s: 110097 runs so far, 0 failures
45s: 123984 runs so far, 0 failures
50s: 137534 runs so far, 0 failures
55s: 151337 runs so far, 0 failures
1m0s: 165105 runs so far, 0 failures

[jmhbnz]

LGTM - Retaining precision for ease of formatting/sorting/viewing makes sense. Thanks for adding a unit test @chaochn47

[serathius]

On second thought, it might be a better idea to expand e2e logging tests in ./tests/e2e/logging_test.go.
Good enough for know, we can merge and follow up.

[jmhbnz]

/cherrypick release-3.5

[k8s-infra-cherrypick-robot]

@jmhbnz: new pull request created: #18288

In response to this:

/cherrypick release-3.5

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