Possible Regression with CloudWatch Timestamps in v1.34.9

[Sutto]

Confirm by changing [ ] to [x] below to ensure that it's a bug:

• I've gone though Developer Guide and API reference
• I've checked AWS Forums and StackOverflow for answers
• I've searched for previous similar issues and didn't find any solution

Describe the bug

The latest release (and I suspect #3489) is causing a regression with all code that uses the cloudwatch SDK for us. We just went from 1.34.7 to 1.34.9, and in code that posts custom metrics started receiving exceptions such as:

MalformedInput: timestamp must follow ISO8601

We aren't serializing times, instead passing aws.Time(time.Now()), and the only change was to bump our SDK version as above.

Version of AWS SDK for Go?

v1.34.9

Version of Go (go version)?

1.13.6

To Reproduce (observed behavior)

• Construct cloudwatch.MetricDatum with timestamp of aws.Time(time.Now())
• Post to cloudwatch using PutMetricData

(I unfortunately don't have a full code sample as my go is rusty, but can get one if it helps)

Expected behavior

It to continue to work as it previously did, especially since we're not explicitly constructing ISO8601 times?

Additional context

I'm assuming there is possibly a difference in the level of granularity supported for ISO8601 timestamp (hence the above PR being the possible cause?).

[niebloomj]

I believe i am experiencing the same issue. My scripts have stopped working.

[saraogivinay]

Same here

[diehlaws]

Thanks @Sutto for bringing this to our attention and thanks @niebloomj and @saraogivinay for confirming this. I'm able to reproduce the described behavior, we'll work on fixing this shortly. In the meantime as a temporary workaround you can reformat time.Now as shown below to continue using this version of the SDK.

t, _ := time.Parse(time.RFC3339, time.Now().Format(time.RFC3339))

input := &cloudwatch.PutMetricDataInput{
  MetricData: []*cloudwatch.MetricDatum{
    {
      MetricName: aws.String("go-3498"),
      Timestamp:  aws.Time(t),
      Value:      aws.Float64(0.50),
      Unit:       aws.String("Count"),
    },
  },
  Namespace: aws.String("go-3498"),
}

[jasdel]

You can also simplify this with Time.Truncate, and avoid the Parse and Format.

input := &cloudwatch.PutMetricDataInput{
  MetricData: []*cloudwatch.MetricDatum{
    {
      MetricName: aws.String("go-3498"),
      Timestamp:  aws.Time(t.Truncate(time.Second)),
      Value:      aws.Float64(0.50),
      Unit:       aws.String("Count"),
    },
  },
  Namespace: aws.String("go-3498"),
}