AWS CloudWatch returns InvalidNextToken - amazon-web-services

Question

I am trying to get some CloudWatch metrics using .NET SDK. The code that is seen below returns some data points but after returning about 20 data points it raises an Exception of InvalidNextToken.
private static void Main(string[] args)
{
Console.Clear();
var creds = new StoredProfileAWSCredentials();
var c = new AmazonCloudWatchClient(creds, RegionEndpoint.EUCentral1);
Task<GetMetricDataResponse> t = null;
string nextToken = null;
do
{
var req = new GetMetricDataRequest
{
EndTimeUtc = DateTime.UtcNow,
MaxDatapoints = 10,
StartTimeUtc = DateTime.UtcNow.AddHours(-1),
ScanBy = new ScanBy("TimestampDescending"),
NextToken = nextToken,
MetricDataQueries = new List<MetricDataQuery>
{
new MetricDataQuery
{
Id = "a" + Guid.NewGuid().ToString().Replace("-", ""),
MetricStat = new MetricStat
{
Stat = "Maximum",
Metric = new Metric
{
MetricName = "CPUUtilization",
Dimensions = new List<Dimension>
{
new Dimension
{
Name = "InstanceId",
Value = "i-04f27d16c91c70119"
}
},
Namespace = "AWS/EC2"
},
Period = 60,
Unit = StandardUnit.Percent
}
}
}
};
t = c.GetMetricDataAsync(req);
t.Wait();
var usage = t.Result;
if (usage.MetricDataResults.Any())
foreach (var r in usage.MetricDataResults)
foreach (var rValue in r.Values)
Console.WriteLine(Math.Round(rValue * 100));
nextToken = t.Result.NextToken;
} while (!string.IsNullOrEmpty(nextToken));
Console.ReadKey();
}
The exact Exception message is:
InvalidNextTokenException: The service returned an error with Error
Code InvalidNextToken and HTTP Body:
Sender
InvalidNextToken 795050a1-3bcd-4a44-9794-5becd0c4f5cf

Answer 1

For nextToken to work, you need to send the exact same request, with only the token changing between calls.
You have id, StartTimeUtc and EndTimeUtc changing between requests.
Initializing them before the loop should fix your problem.
Try something like this:
private static void Main(string[] args)
{
Console.Clear();
var creds = new StoredProfileAWSCredentials();
var c = new AmazonCloudWatchClient(creds, RegionEndpoint.EUCentral1);
Task<GetMetricDataResponse> t = null;
string nextToken = null;
var endTime = DateTime.UtcNow;
var startTime = endTime.AddHours(-1);
var id = "a" + Guid.NewGuid().ToString().Replace("-", "");
do
{
var req = new GetMetricDataRequest
{
EndTimeUtc = endTime,
MaxDatapoints = 10,
StartTimeUtc = startTime,
ScanBy = new ScanBy("TimestampDescending"),
NextToken = nextToken,
MetricDataQueries = new List<MetricDataQuery>
{
new MetricDataQuery
{
Id = id,
MetricStat = new MetricStat
{
Stat = "Maximum",
Metric = new Metric
{
MetricName = "CPUUtilization",
Dimensions = new List<Dimension>
{
new Dimension
{
Name = "InstanceId",
Value = "i-04f27d16c91c70119"
}
},
Namespace = "AWS/EC2"
},
Period = 60,
Unit = StandardUnit.Percent
}
}
}
};
t = c.GetMetricDataAsync(req);
t.Wait();
var usage = t.Result;
if (usage.MetricDataResults.Any())
foreach (var r in usage.MetricDataResults)
foreach (var rValue in r.Values)
Console.WriteLine(Math.Round(rValue * 100));
nextToken = t.Result.NextToken;
} while (!string.IsNullOrEmpty(nextToken));
Console.ReadKey();
}