workload-discovery-on-aws VS middy

Workload Discovery on AWS has recently released a new version - would that work for you?

It's interpreted line-by-line so that each line represents one state of the diagram. There are commands to delete nodes: when I delete a node I just remove it from its parent but leave it in the top-level state. That has the neat effect that if I re-add it, I get the node with all its descendents and connections restored in one step, which I can use to pre-diagram things I talk about often.

After calculating the drawing state by applying all the commands from the start to the current selection, the next step is to limit this to the visible pieces. I make a copy of the drawing state, starting from the currently zoomed node and following all children. Then I add all connections, if all the 'to' ends of the connections are visible.

Next, I do layout. Starting with the visible tree, annotate all nodes with positions of the box (if any), the icon, and the label. The diagrams I'm drawing are similar to those produced by AWS Perspective: https://aws.amazon.com/solutions/implementations/aws-perspec... , so if a node has no children I draw it as a large icon with a label below, if it has children, it is a box with a small icon to the top left, a centred label at the top. Each node can choose one of a small number of layouts that I can do automatically with just a list of children: 'ring' (a circle of nodes), 'row', 'column', or 'snake' (the default: alternate rtl-ltr rows to evenly fill the space; this will be a grid if that fits or could end up like 4-3-4-3 if it doesn't). In ring & snake, boxes are always 4:3; in row and column they are stretched to fit.

Next, I do animation. I keep around the previous layed-out state, and use window.requestAnimationFrame to calculate the position of boxes between the start and end state. A box that is in both start and end states is moved, if it is only in start or end I fade it in or out as need be. This lets me animate between _any_ two states of the drawing, so I can talk about one bit of the diagram, then jump back and forth by clicking in the command window, and it smoothly animates between them. I found animating for just 0.5s worked best for interactivity; it's nice to see a slower move but it feels laggy when typing.

I calculate arrow positions after calculating the final position of boxes and icons. I chose to use circular arcs, because you will never get an awkward situation where an arc lies directly along the edge of a box; straight things are always boxes, curvy things are always arrows. SVG wants two endpoints and a centre to draw these. So, I start with an arc between the centres of the two boxes, choose a radius twice as long as the distance between these points; then I calculate the intersection of the arc with the boxes, and use those two intersection points as the start/end of the arc. (this isn't that difficult, the formula for the arc is in the svg spec, and it's checking 4 straight lines, choose the intersection point closest to the other box). Like the boxes, the arrows fade in and out if they are not needed in one of the start or end states.

All of this then just replaces the content of the svg. It's surprisingly smooth.

One last detail is icons. I'm using the icons from mingrammer (https://github.com/mingrammer/diagrams/tree/master/resources), which gives me about 1600(!). Finding an icon _while you type_ is awkward and initially I had to drop to the shell to find the file I was going to refer to. I tried giving the drawing tool a mode that would let me visually pick the icon, but 1600 is too many. So I changed it to use a fuzzy search to find an appropriate icon: it looks for the icon where the sequence of characters appear in the shortest substring of the icon path: eg for 'ec2' it constructs the regex `.(e.?c.*?2)`, scoring the matching substring 'ec2' better than 'elastic2', and the shorter containing string 'aws/compute/ec2' better than eg 'aws/compute/ec2-rounded'. (I have a further round of preferences so that the top level aws iconset is preferred to eg the ibm one, which has terrible icons). This gives you an icon for almost anything you type, and encourages a more playful approach to picking the icon than the exact-match approach.

There's a bit more to it, I also accept some markdown which fades from the diagram to slides with bullet points, then back to the diagram if the current command is a diagramming command. But the description above is most of it. I could probably have done this better with eg d3 to do the drawing but I am not a front end developer at all and the whole thing was more of a hack over a couple of weekends. I should clean it up a bit, but it works.

I serve up pre-prepared pages with this js attached from github pages, I can walk through eg the flow of data clicking the down arrow to change the selection which causes it to animate to the next state which has the next arrow... and so on.

AWS has a solution called AWS Perspective that will do exactly this. The solution itself is free and open source, you only pay for the resources it creates. You can also export the diagrams to draw.io if you want to edit them manually. Also, it will show you how much your solution(s) and each of its components is costing you.

Check out - https://aws.amazon.com/solutions/implementations/aws-perspective/

In many cases, you will have to write the same authorization code in multiple functions. For example, you might want to check that the user is in the requested organization. You can share this code in a middleware. If you are using AWS Lambda, you can rely on middy.

Adding the is-test flag to our object metadata gave us our way of passing some kind of test context into our workload. The next step was to make the Lambda Function capable of discovering the context and then using that to control how it behaves under test. For this we used Middy.

I also decided to use the middy library to add CORS management to our lambda function. This will allow us to call our lambda function from our frontend, without having to worry about CORS.

Is there any equivalent to Node based https://middy.js.org/ for Golang?

And if your requirements were to change at a later date, it’s straightforward to swap out SSM Parameter Store with Secrets Manager there and then. Especially if you’re accessing the relevant service through a middleware layer such as Middy for javascript Lambda functions.

This function uses the Middy middleware engine to handle unhandled errors and add CORS headers in the response.

I mean I'm literally building an AWS lambda function that outputs HTML when it's called via API Gateway. So someone hits https://mydomain.com/mycoolpage, then the MyCoolPage AWS Lambda function is executed and outputs whatever.

If you're interested, I use https://middy.js.org/ as a middleware engine for my AWS lambda functions which I find helpful.

I use the open sourced serverless framework for doing deploys https://www.serverless.com/

middy for lambda-side middleware

That is it from the CDK side. Now let us create the handler and retrieve that secret. I like to use middy which describes itself as "stylish Node.js middleware engine for AWS Lambda". It offers some helpful middlewares like ssm which will help us retrieve and cache values from SSM Parameter Store. (Middy provides various other official middlewares including one for Secrets Manager.) I prefer a middleware for this because it keeps the code for retrieving the secret out of your handler which should deal with actual business logic.