Assign EC2 Instance to an existing VPC using CDK in C#

Question

I want to launch a EC2 instance with an existing VPC. In the Vpc parameter I have passed existing VPC Id. When I execute cdk synth for the below code, I am getting All arguments to Vpc.fromLookup() must be concrete (no Tokens) error

using Amazon.CDK;
using Amazon.CDK.AWS.EC2;
using System.Collections.Generic;
using Amazon.CDK.AWS.S3;
using Amazon.CDK.AWS.S3.Assets;
using System.IO;

namespace StandardCf
{
    public class StandardCfStack : Stack
    {
        internal StandardCfStack(Construct scope, string id, IStackProps props) : base(scope, id, props)
        {
            string[] instancetypeArray = new string[] { "t2.large","t3.large" };

            //Parameters
            //1. Key Pair Name
            var keyPairName = new CfnParameter(this, "Key Pair Name", new CfnParameterProps { Type = "String", Description = "The name of the Existing Key Pair. This key pair will be added to the set of keys authorized for this instance." });
            //2. Instance Type
            var InstanceType = new CfnParameter( this, "InstanceLauncherType", new CfnParameterProps { Type = "String", Description= "Amazon EC2 instance type for the Instance, Choose t3.large for regions US East, Africa (Cape Town), Middle East (Bahrain), Asia Pacific (Hong Kong), EU (Milan) and EU (Stockholm)", AllowedValues = instancetypeArray, Default = "t2.large"} );
            //3. Existing VPC Id
            var ExistingVPCId = new CfnParameter(this, "VpcID", new CfnParameterProps { Type = "AWS::EC2::VPC::Id", Description = "Please enter the VPC ID to choose existing VPC"});

            // VPC Creation
            var vpc = Vpc.FromLookup(this, "VPC", new VpcLookupOptions
            {
                VpcId = ExistingVPCId.ValueAsString
            });

            // Security Group Creation
            var InstanceSecurityGroup = new SecurityGroup(this, "SecurityGroup", new SecurityGroupProps
            {
                Vpc = vpc,
                 SecurityGroupName = "STANDARD-SG",
                Description = "Security Group for Standard Instance",
                AllowAllOutbound = true
            });
            // Security Group's Inbound and Outbound rules
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv4(), Port.Tcp(22), "Allows public SSH access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv4(), Port.Tcp(80), "Apache Web Server Access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv6(), Port.Tcp(80), "Apache Web Server Access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv4(), Port.Tcp(8080), "Apache Tomcat Access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv6(), Port.Tcp(8080), "Apache Tomcat Access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv4(), Port.Tcp(8161), "Apache ActiveMQ Web UI Access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv6(), Port.Tcp(8161), "Apache ActiveMQ Web UI Access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv4(), Port.Tcp(61616), "Apache ActiveMQ Broker Access");
            InstanceSecurityGroup.AddIngressRule(Peer.AnyIpv6(), Port.Tcp(61616), "Apache ActiveMQ Broker Access");

            // Configuring custom CENOTS AMI
            IDictionary<string, string> d = new Dictionary<string, string>();
           
            d.Add(new KeyValuePair<string, string>(Region,"ami-026f33d38b6410e30"));
          
            var customAWSAMI = MachineImage.GenericLinux(d);

            var path = Directory.GetCurrentDirectory();

            // Comments for user data script
            var userdata = UserData.ForLinux();
            userdata.AddCommands("yum install -y wget", "cd /tmp/", "mkdir user-data-script", "cd user-data-script/", "wget some-url-for-shell-file", "cd ../../", "sh /tmp/user-data-script/shell-script.sh");
            

            // Instance Detail Configuration
            var ec2Instance = new Instance_(this, "Instance", new InstanceProps
            {
                Vpc = vpc,
                InstanceType = new InstanceType(InstanceType.ValueAsString),
                MachineImage = customAWSAMI,
                SecurityGroup = InstanceSecurityGroup,
                
                KeyName = keyPairName.ValueAsString,
                InstanceName = "STANDARD",
                UserData = userdata
            });
        }
    }
}

How do I pass in existing VPC Id for the EC2 Instance?

Answer 1

I ran into this exact situation and found that you will need to be able to pass the string in during sythesis/deploy time using the --context (-c) option. There are ways to get the context from a scope.

So my code was something like this to get the VPC instance:

 var vpcLookupOptions = new VpcLookupOptions
 {
     VpcId = scope.Node.TryGetContext("vpcId").ToString()
 };
 var vpc = Vpc.FromLookup(this, id, vpcLookupOptions);

The command to synthesize the template would look like this:

cdk synth StandardStack -c vpcId="vpc-1234567a"

If you want to pass more than one context value use the --context option again for each key/value pair.

cdk synth -c key1="value1" -c key2="value2"

You will use the same --context values when bootstrapping and deploying as well.

This post was very useful: https://stackoverflow.com/a/64576653/3870069