Amazon.CDK.AWS.CloudWatch: MathExpression throws Newtonsoft.Json.JsonSerializationException:

[haassto]

Describe the bug

I'm not able to create a MathExpression, instead 'cdk diff' throws an exception.

My code looks something like this:

        Queue[] queues;

        var props = new MathExpressionProps {
            Expression = "SUM(METRICS())",
            UsingMetrics = new Dictionary<string, IMetric>
            {
                {"1", queues[0].MetricApproximateNumberOfMessagesVisible()},
                {"2", queues[1].MetricApproximateNumberOfMessagesVisible()},
            }
        };
        var combinedMetrics = new MathExpression(props);

I'm not able to find some problem in my code. I also used a different expression, but the result is the same (analog to Docu [1])

[1] https://docs.aws.amazon.com/cdk/api/v2/dotnet/api/Amazon.CDK.AWS.CloudWatch.MathExpression.html#Amazon_CDK_AWS_CloudWatch_MathExpression_Expression

Expected Behavior

No exception

Current Behavior

This is the exception I get

Unhandled exception. Newtonsoft.Json.JsonSerializationException: Error converting value "Error" to type 'Amazon.JSII.JsonModel.Api.Response.ErrorResponseName'. Path 'name'. ---> System.ArgumentException: Requested value 'Error' was not found. at Newtonsoft.Json.Utilities.EnumUtils.ParseEnum(Type enumType, NamingStrategy namingStrategy, String value, Boolean disallowNumber) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType) --- End of inner exception stack trace --- at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMemb er, Object existingValue) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.ResolvePropertyAndCreatorValues(JsonObjectContract contract, JsonProperty containerProperty, JsonReader reader, Type objectType) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObjectUsingCreatorWithParameters(JsonReader reader, JsonObjectContract contract, JsonProperty containerProperty, ObjectConstructor1 creator, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Obj
ect existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMemb
er, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
at Newtonsoft.Json.Linq.JToken.ToObject(Type objectType, JsonSerializer jsonSerializer)
at Newtonsoft.Json.Linq.JToken.ToObject(Type objectType)
at Newtonsoft.Json.Linq.JToken.ToObjectT
at Amazon.JSII.Runtime.Services.Client.TryDeserialize[TResponse](String responseJson)
at Amazon.JSII.Runtime.Services.Client.ReceiveResponseTResponse
at Amazon.JSII.Runtime.Services.Client.Send[TRequest,TResponse](TRequest requestObject)
at Amazon.JSII.Runtime.Services.Client.Create(CreateRequest request)
at Amazon.JSII.Runtime.Services.Client.Create(String fullyQualifiedName, Object[] arguments, Override[] overrides, String[] interfaces)
at Amazon.JSII.Runtime.Deputy.DeputyBase..ctor(DeputyProps props)
at Amazon.CDK.AWS.CloudWatch.MathExpression..ctor(IMathExpressionProps props)
`

Reproduction Steps

        Queue[] queues;

        var props = new MathExpressionProps {
            Expression = "SUM(METRICS())",
            UsingMetrics = new Dictionary<string, IMetric>
            {
                {"1", queues[0].MetricApproximateNumberOfMessagesVisible()},
                {"2", queues[1].MetricApproximateNumberOfMessagesVisible()},
            }
        };
        var combinedMetrics = new MathExpression(props);

Possible Solution

No response

Additional Information/Context

I changed to Version 2.50 and 2.41 with the same result.

CDK CLI Version

2.46.0

Framework Version

No response

Node.js Version

v18.12.0

OS

Windows 10/Linux (both)

Language

.NET

Language Version

dotnet 6

Other information

No response

[peterwoodworth]

Thanks for reporting this issue, I was able to reproduce the same issue in .NET on the latest version of CDK. Here's my full stack code:

using Amazon.CDK;
using Constructs;
using Amazon.CDK.AWS.CloudWatch;
using Amazon.CDK.AWS.SQS;

namespace Dotnet
{
    public class DotnetStack : Stack
    {
        internal DotnetStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
        {
            var queue1 = new Queue(this, "Queue1");
            var queue2 = new Queue(this, "Queue2");
            var sprops = new MathExpressionProps {
                Expression = "SUM(METRICS())",
                UsingMetrics = new System.Collections.Generic.Dictionary<string, IMetric>
                {
                    {"1", queue1.MetricApproximateNumberOfMessagesVisible()},
                    {"2", queue2.MetricApproximateNumberOfMessagesVisible()},
                }
            };
            var combinedMetrics = new MathExpression(sprops);
            }
    }
}

I was not able to reproduce the same issue in TypeScript, which indicates to me that this is a JSII issue when translating between .NET and JavaScript. So, I'm going to move this issue to the JSII repo. Let's see what they say 🙂

[kaizencc]

I am able to reproduce this in CDK v2.46.0. The error message is very opaque. However in later versions (at least in CDK v2.78.0+) we produce a different error that is more illuminating:

Unhandled exception. System.Exception: Invalid variable names in expression: 1,2. Must start with lowercase letter and only contain alphanumerics.

The problem here is that you can't name your variables 1 and 2. They must start with a-z. I can confirm that after updating to get your variables in line with the requirements the code deploys successfully.

Hope this helps, and sorry about the opaque error message!

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