A templated guide to AWS serverless development with CDK

If all you're looking for is a no-frills, quick, step-by-step guide, just scroll on down to The Guide!

The Story

Or, how I learned to let go of my laptop and embrace The Cloud...

Motivation

A while ago I outlined a project that I intend to build, one that I'm rather enthusiastic about, and after spending a few hours evaluating my options I decided that an AWS solution was the right way to go: their options are configurable and solid, their pricing is very reasonable and, as an added bonus, I get to familiarize myself with tech I'll be using for my current contract!

All good.

Once I'd made the decision to use AWS, becoming generally familiar with the products on offer was easy enough and it took me very little time to flesh out a design. I was ready to get coding!

Or so I thought...

Hurdle 1

Serverless. And possibly other frameworks, I'm pretty sure I looked at a few but it seems like forever ago. Serverless shows lots of promise, and I know people who swear by it, but it's only free up to a point and I immediately ran into strange issues with my first deployment. I found the interface surprisingly unhelpful, and it looks like once you're using it you're somewhat locked in.

Pass.

Hurdle 2

Cognito. Security first. Cognito sounds like a great solution, but once I'd gotten a handle on how it works I was severely disappointed by how limiting it is, and getting everything set up takes real developer and user effort (and I suffer enough from poor interface fatigue). After playing around with user pools and looking at various code samples, I realized that I'd rather allow users to register using their email addresses / phone numbers as 2nd-factor authentication (mailgun and twilio are both straightforward options), or use oauth providers like Facebook, Google and GitHub, and I certainly want to encourage my users to use strong, memorable passwords (easily enforced with zxcvbn, and why is this still a thing?!) which Cognito doesn't allow for.

You'll need to configure Lambda authorizers either way, so I really don't think Cognito adds much value.

Hurdle 3

Lambda / DynamoDB. Okay, so writing a lambda function is really easy, and guides and examples for code that reads to and writes from DynamoDB abound. Great! Except for the part where you need to test your functions before deploying them.

My first big mistake - and so far it's proved to be the most expensive one - was not understanding at this point that "testing locally" is simply not a feasible strategy for a cloud solution.

Hurdle 4

The first code I wrote for my project was effectively a lambda environment emulator to test my lambda functions. It was far from perfect, and it did take me a couple of hours to cobble together, but it did the job and I used it to successfully test lambda functions against DynamoDB running in Docker.

Hurdle 5

Lambda Layers. Why do most guides not touch on these? Why are there so few layers guides written for Javascript? It took me a little while to get a handle on layers and build a simple script to create them from package.json files, but as far as hurdles go this was a relatively short one.

Hurdle 6

Deployment. It's nice to have code running locally, but uploading it to the cloud? Configuring API Gateway was a mixed bag of Good Interface / Bad Interface, same with the Lambda functions, and what eventually stumped me was setting up IAM to make everything play nicely together. What's the opposite of intuitive? Not counter-intuitive, in this case, as I don't feel that that word evokes nearly enough frustration.

Anyway, it became abundantly clear at that point that manual deployment of AWS configurations and components is not a viable strategy.

Hurdle 7

A coworker introduced me to two tools that could supposedly Solve All My Problems: CDK and SAM. This seemed like a worthy rabbit-hole to crawl into, but I couldn't find any examples of the two working together!

I began to build my own little framework, one that would allow me to configure my stack using CDK, synthesize the CloudFormation templates, and test locally using SAM. Piece by piece I put together this wonderful little tool, hour by hour, first handling DynamoDB, then Lambda functions, then Lambda Layers...

It was at that point that realization dawned: not only are SAM and CDK not interoperable by design, but SAM does not, in fact, provide meaningful "local" testing. Sure, you can invoke your lambda functions on your local machine, but the intention is to invoke them against your deployed cloud infrastructure. Once I got that through my head, it was revelation time: testing in the cloud is cheaper and better than testing locally.

The Guide

If you're like me, and you intend your first foray into cloud computing to be simple, yet reasonably production-ready, CDK is the easiest way forward and it's completely free (assuming you don't factor in your time figuring it out as valuable, but that's what I'm here for!).

Over the course of the past couple of weeks, I've put together the aws-cdk-js-dev-guide. It's a work in progress (next stop, lambda authenticators!), but at the time of writing this guide it's functional enough to put together a simple stack that includes Lambda Layers, DynamoDB, functions using both of those, API Gateway routes to those functions and the IAM permissions that bind them.

And that's just the tip of the CDK iceberg.

Step 1 - Tooling

It is both valuable and necessary to go through the following steps prior to creating your first CDK project:

• Create a programmatic user in IAM with admin permissions
• If you're using Visual Studio Code (recommended), configure the aws toolkit
• Set up credentials with the profile ID "default"
• Get your 12 digit account ID from My Account in the AWS console
• Follow the CDK hello world tutorial

Step 2 - Creating a new CDK project

The first step to creating a CDK project is initializing it with cdk init, and a CDK project cannot be initialized if the project directory isn't empty. If you would like to use an existing project (like aws-cdk-js-dev-guide) as a template, bear in mind that you will have to rename the stack in multiple locations and it would probably be safer and easier to create a new project from scratch and copy and paste in whatever bits you need.

Step 3 - Stack Definition

There are many viable approaches to setting up stages, mine is to replicate my entire stack for development, testing and production. If my stack wasn't entirely serverless - if it included EC2 or Fargate instances, for example - then this approach might not be feasible from a cost point of view.

Stack definitions are located in the /lib folder, and this is where the stacks and all their component relationships are configured. Here you define your stacks programmatically, creating components and connecting them.



I find that the /lib folder is a good place to put your region configurations.



Once you have completed this, the code to synthesize the stack(s) is located in the /bin folder. If you intend, like I do, to deploy multiple replications of your stack, this is the place to configure that.



See the AWS CDK API documentation for reference.

Step 4 - Lambda Layers

I've got much more to learn about layers at the time of writing, but my present needs are simple: the ability to make npm packages available to my lambda functions. CDK's Code.fromAsset method requires the original folder (as opposed to an archive file, which is apparently an option), and that folder needs to have the following internal structure:

.
.nodejs
.nodejs/package.json
.nodejs/node_modules/*

You can manually create this folder anywhere in your project, maintain the package.json file and remember to run npm install and npm prune every time you update it... or you can just copy in the build-layers script, maintain a package.json file in the layers/src/my-layer-name directory and run the script as part of your build process.

Step 5 - Lambda Functions

There are a number of ways to construct lambda functions, I prefer to write mine as promises. There are two important things to note when putting together your lambda functions:

1. Error handling: if you don't handle your errors, lambda will handle them for you... and not gracefully. If you do want to implement your lambda functions as promises, as I have, try to use "resolve" to return your errors.

2. Response format: your response object MUST be in the following structure:

This example lambda demonstrates using a promise to return both success and failure responses:

Step 6 - Deployment

There are three steps to deploying and redeploying your stacks:

1. Build your project
   If you're using Typescript, run
   > tsc
   If you're using layers, run the build-layers script (or perform the manual steps)
   
2. Synthesize your project
   > cdk synth
   
3. Deploy your stacks
   > cdk deploy stack-name
   Note: you can deploy multiple stacks simultaneously using wildcards

At the end of deployment, you will be presented with your endpoints. Unless your lambda has its own routing configured - see the sample dynamodb API examples that follow - simply make your HTTP requests to those URLs as is.

Sample dynamodb API call examples:
• List objects
  GET https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/objects
• Get specific object
  GET https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/objects/b4e01973-053c-459d-9bc1-48eeaa37486e
• Create a new object
  POST https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/objects
• Update an existing object
  POST https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/objects/b4e01973-053c-459d-9bc1-48eeaa37486e

Step 7 - Debugging

Error reports from the API Gateway tend to hide useful details. If a function is not behaving correctly or is failing, go to your CloudWatch dashboard and find the log group for the function.

Step 8 - Profit!!!

I hope you've gotten good use of this guide! If you have any comments, questions or criticism, please leave them in the comments section or create issues at https://github.com/therightstuff/aws-cdk-js-dev-guide.

@mysql/xdevapi joy!

after hitting a wall last night with the existing node.js mysql packages, which for some reason have been years behind integrating with mysql 8's authentication, i discovered @mysql/xdevapi. the documentation's a bit heavy and not really comprehensive, but now that i've figured out how to use it, i'm very pleased with how it operates! unfortunately, i'm going to have to roll my own migrations management, but that's a small price to pay for being able to interface with the latest mysql databases in an intelligent way.

in the interests of reducing friction for other adopters, i've rolled some sample queries into my database creation script. enjoy!

UPDATE: i've subsequently learned that table joins have not been implemented, so to perform those you'd have to use the session.sql method and use it in the same way (the same promise chaining) as the CRUD methods. seems like a serious oversight, but whatever.

simple-free-encryption-tool frontend now handles files

If your browser supports it, simple-free-encryption-tool can now encrypt and decrypt any local files you wish!

Handling emails with node.js and Mailparser

After sorting out mail forwarding and piping emails with postfix, I then needed to understand how to handle emails being POSTed to an API endpoint.

To parse an email with node.js, I recommend using Mailparser's simpleParser. I'm using express with bodyParser configured as follows:

app.use(bodyParser.json({
 limit : config.bodyLimit
}));

In your handler:

const express = require('express');
const router = express.Router();
const simpleParser = require('mailparser').simpleParser;

or

import { Router } from 'express';
import { simpleParser } from 'mailparser';

and then

api.post('/', (req, res) => {
    simpleParser(req)
        .then(parsed => {
            res.json(parsed);
        })
        .catch(err => {
            res.json(500, err);
        });
});

Mailparser is excellent, and documented, but the documentation assumes that we're familiar with the email format. Fortunately, oblac's example email exists for those of us who aren't!

To test, send the example email to the endpoint via curl:

curl --data-binary "@./example.eml" http://your-domain-name/api/email

or Postman (attach file to "binary").

And we're good to go!

FreeVote: anonymous Q&A app

I can't believe something like this doesn't exist already! It's far from a polished product, but it's already pretty functional. Feel free to send me feedback, it'll help me prioritize the long list of improvements I've already come up with. This was inspired by my coworkers, every retrospective we all write down answers to sensitive questions "anonymously" on folded papers that one team member gathers and reviews... this way we can do it truly anonymously and all see the results.

FreeVote

C# / OPENSSH RSA ENCRYPTION MADE EVEN EASIER

A long time ago, I posted about importing and exporting Javascript-compatible RSA certificates to and from C#. Last night I realized that I needed a simple and reliable way to shared encrypted code with non-technical folk and decided to put everything I've learned into a comprehensive package called simple-free-encryption-tool that runs on a node.js backend, in your browser, and doesn't even need to be cloned for quick abuse.

This makes strong RSA key generation and encryption and AES encryption simple to implement, and practical to use for client-server communications. It also allows me to give someone an encryption package on a stick (just copy the dist folder) that they can open on any machine.

Online JSON / CSV Converter

I needed a good JSON / CSV converter and couldn't find one, so I made one: Online JSON / CSV Converter

C# / OpenSSH RSA Encryption made easy

[EDIT: please see C# / OPENSSH RSA ENCRYPTION MADE EVEN EASIER]

The struggle to uncover the secrets of importing from and export to OpenSSH keys with Microsoft's .NET RSACryptoServiceProvider is real. It's possible but not practical to do this without BouncyCastle, which may or may not be well-documented (navigating their website is far from a joyful experience), but after trawling the web and playing around I've created the following gists that should be of assistance to anyone who needs to do this in a straightforward manner.
And if you want to share RSA keys between JavaScript and .NET platforms, well, you're going to need to do this.
Import and export RSA Keys between C# and PEM format using BouncyCastle
And just because the actual encryption and decryption are always annoying:
Simple RSA Encryption to and Decryption from Base64 encoded strings in C#

connecting node.js to the azure table storage emulator

Once again, solid software is rendered useless by a lack of documentation. I've just wasted way too much time connecting my node app to an emulated table, so I'm going to spell it out for you so that you don't have to do the same.

1. The npm azure-storage package instructions are found here, the emulator software is found here and the storage explorer is found here.
   
2. Once the emulator has been installed, you'll need to start it. The init operation worked fine for me (I'm running SQL Server 2012 Express anyway), but the start operation failed and it took a while to realize that ports 10000 - 10002 (or is that 3?) need to be available; the software blocking could be anywhere from backup software or bittorrent to malware.
   Good to know.
   There doesn't appear to be any way to customize the ports used.
   
3. To verify that your emulator is running correctly, connect using the storage explorer.
   1. Select "Use a storage account name and key"
   2. Set the account name and authentication key (see point 6 below)
   3. Set the storage endpoints domain to "Other" with a value of 127.0.0.1
   4. Select "Use HTTP"
      
4. The emulator runs on http NOT https, which shouldn't affect you once you've got your connection configured correctly. For some people the authentication requires setting your system time to UTC / GMT, for others it's setting the environment variable NODE_TLS_REJECT_UNAUTHORIZED to 0; the latter can be done in node.js with

   process.env.NODE_TLS_REJECT_UNAUTHORIZED = 0;
   
   

5. There are two ways to instantiate a table service object. Assuming

   var azure = require('azure-storage');

   1. var tableSvc = azure.createTableService(account, key, '127.0.0.1:10002');

      or

   2. process.env.AZURE_STORAGE_ACCOUNT = account;
      
      process.env.AZURE_STORAGE_ACCESS_KEY = key;
      
      process.env.AZURE_STORAGE_CONNECTION_STRING = connectionString;
      
      var tableSvc = azure.createTableService();

6. The account name, authentication key and connection string are public, invariable and for emulation purposes only:
   Account name: devstoreaccount1
   
   Authentication Key:
   Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq/K1SZFPTOtr/KBHBeksoGMGw==
   
   Connection String: UseDevelopmentStorage=true

Passing data from C# to Node.js via Edge.js

Edge.js is a phenomenal tool, but its documentation is a hit and miss.  Sending data to C# from Node.js is straightforward, and the JSON object is translated to a dynamic object automatically:

public async Task<dynamic> Invoke(dynamic input) {
   // echo input message
   await doSomething(input.message);
}

Returning data is not trivial, however, because any kind of complex object I tried to return caused unreported exceptions.

Until now!

It turns out that Edge .js returns associative arrays if and only if they're correctly JSON formatted. I don't recall seeing this documented anywhere, but it makes perfect sense (20/20 hindsight). So in order to return an associative array to Node.js, make sure to use a Dictionary object where the first element type is a string; if you want to send a list of usernames with their IDs, for example, you would either use

Dictionary<string, string>

with the ID cast to string for transmission or

Dictionary<string, int>

with the ID / username columns switched from their normal positions.

Of course, one could go about creating more intricate objects using the dynamic type, but that's beyond the scope of this post.

Web Worker callback design pattern

I couldn't find a way to post messages to a callback and define a handler for each individual message, and the following is what I've come up with. If you have suggestions or a better solution, let me know!

UPDATE: my goodness, looking back at my original post I wonder if I wasn't having a stroke. I've rewritten it and used gist to make it readable: