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Deploy Imposter to AWS Lambda using the CLI

This section describes how to deploy Imposter as an AWS Lambda function using Imposter CLI.

Other ways to deploy to Lambda

You can also deploy Imposter as a Lambda function using the AWS Console, infrastructure as code tools (e.g. Terraform) or a framework such as Serverless.

Overview

The key steps are:

  • use the Imposter CLI to configure AWS Lambda as the remote deployment target
  • use the Imposter CLI to deploy your configuration (bundled with the Imposter engine) as a Lambda function to the desired AWS region
  • access the Lambda function via a Lambda Function URL

Prerequisites

  • You must have an AWS account and permission to deploy Lambda functions, fetch an IAM role (and optionally create a role if not using an existing role).
  • You must install the Imposter CLI.

Deployment steps

For the purposes of this guide, we will assume your working directory contains an Imposter configuration file.

$ ls -l
mock-config.yaml   response.txt

Note See the Configuration section for more information.

Step 1: Prepare your workspace

To begin, create a workspace in this directory:

$ imposter workspace new example

created workspace 'example'

A workspace holds configuration, such as details of the remote deployment.

You can always check the active workspace by running the imposter workspace show command:

$ imposter workspace show

active workspace: example

You can commit your workspace directory to your source control system (by default, stored under the .imposter subdirectory).

Step 2: Configure the remote

A workspace has a 'remote', where Imposter will be deployed. Set the remote type to AWS Lambda:

$ imposter remote set-type awslambda

set remote type to 'awslambda' for remote: example

Once you have the remote type, you can further configure the remote using the imposter remote config command.

For example:

$ imposter remote config region=eu-west-1

Available configuration options are:

Property Meaning Default
anonAccess Whether to permit anonymous access to the Lambda function URL (true or false) false
architecture The lambda architecture, which can be x86_64 or arm64 x86_64
engineVersion The version of the Imposter engine to use, such as 3.2.1 latest unless set by CLI config file
functionName The name of the AWS Lambda function, which must adhere to the AWS function naming rules imposter-<dir name> e.g. imposter-example if config dir name was example
iamRoleName The name of a custom IAM Role for the Lambda's execution role. If it doesn't exist, it will be created with this name. ImposterLambdaExecutionRole
memory The amount of memory, in megabytes, for the function, such as 768 768
region The AWS Region in which to deploy the function, such as eu-west-1 us-east-1

Step 3: Deploy to Lambda

Now the remote is configured, deploy the Lambda function:

$ imposter remote deploy

Note The deploy command uses the standard AWS mechanisms for locating credentials. For example, you may have set environment variables, or use the ~/.aws/ directory, or an instance role if running within EC2.

If you receive a credential error, check that:

  • you have active AWS credentials, e.g. run aws iam get-user
  • you have the permissions described in the Prerequisites section

Deployment may take a minute or so, depending on your connection speed, but it should look similar to:

deploying workspace 'example' to awslambda remote
bundling 2 files from workspace
created function: example with arn: arn:aws:lambda:us-east-1:123456789:function:example
deployed workspace 'example'

Base URL: https://url-to-invoke-lambda-function
Status: https://url-to-invoke-lambda-function/system/status

Step 4: Test your Lambda

If all has gone well, you should be able to reach your Lambda function using the status URL:

$ curl https://url-to-invoke-lambda-function/system/status

{ "status": "ok" }

Note If you receive the following error:

{"Message":"Forbidden"}

...then you may need to enable anonymous access to the Lambda function URL.

To enable anonymous access, run:

$ imposter remote config anonAccess=true

...then redeploy with imposter remote deploy

You should be able to call your mock endpoints, such as:

$ curl https://url-to-invoke-lambda-function/

Hello world!

If you need to change a configuration option, such as memory, use the imposter remote config command and then run imposter remote deploy again.

Note If you change the function name of your Lambda after deployment, future deployments will use the new name. This means that the old function with the previous name will still exist. Depending on your use case this may or may not be what you want to happen.

What's next