No way to execute dry-run EC2 operations (e.g. StartInstances)

[sstragier-prosperops]

Describe the bug

There doesn't appear to be a way to execute dry-run EC2 operations (e.g. StartInstances) since DryRun isn't a parameter of the StartInstancesRequest and the DryRun method in AmazonEC2Client (which isn't exposed on the interface, #3594) doesn't work because it appears to be looking for the old non-async request methods which are no longer public.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

I should be able to run EC2 operations that support a DryRun flag (e.g. StartInstances, StopInstances)

Current Behavior

I am not able to run EC2 operations with the DryRun flag to check access to these operations

Reproduction Steps

var ec2Client = new AmazonEC2Client();
var response = ec2Client.DryRun(new StartInstances { InstanceIds = new() { "i-xxxxxxx" } });
// response.Error = "Unrecognized request"

Possible Solution

No response

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

AWSSDK.EC2 3.7.405.7

Targeted .NET Platform

.NET 6

Operating System and version

Windows 10

[ashishdhingra]

@sstragier-prosperops Good afternoon. Thanks for opening the issue. The reason why IAmazonEC2 interface does not have access to the DryRun() method defined in AmazonEC2Client is because:

• IAmazonEC2 (taking netstandard target as an example) interface is auto-generated from ec2 service model (notice that it's in Generated folder).
• AmazonEC2Client.DryRun() is more kind of custom extension method (notice it as defined under Custom folder).

Your analysis appears to be correct. The logic here is checking that return type ends with Response. But the return type for public methods starts with Task< and ends with Response> (e.g. Task<StartInstancesResponse> for StartInstancesAsync()) for projects targeting netstandard (BCL targets have define public interface for the methods where return type ends with Response and should work fine).

To fix this issue, code here could have check based on conditional compilation symbols for different targets (we might also need to revisit other logic as well).

The SetDryRunParameterCallback is just setting the request parameter DryRun to true. The manual workaround would be to explicitly set DryRun property for the API operations you would like to invoke via AmazonEC2Client. (this is not applicable since request model doesn't expose boolean DryRun property due to it being excluded as part of ec2.customizations.json)

This issue needs review with team.

Thanks,
Ashish

[sstragier-prosperops]

Thanks for the follow up. Yes, I've been able to workaround by using the request's BeforeRequestHandler to add the DryRun property to the request (similar to the code in AmazonEC2Client). However, it would be nice to have this functionality baked into the SDK.

public static void SetDryRun(this AmazonWebServiceRequest request)
{
    request.AddBeforeRequestHandler(SetDryRunParameterCallback);

    void SetDryRunParameterCallback(object sender, RequestEventArgs args)
    {
        var a = args as WebServiceRequestEventArgs ?? throw new InvalidOperationException("Expected WebServiceRequestEventArgs");
        a.ParameterCollection["DryRun"] = new StringParameterValue("true");

        // After the callback has been invoked, remove it
        request.RemoveBeforeRequestHandler(SetDryRunParameterCallback);
    }
}