Thomas‘ Blog

Using AWS Lambda with nodejs with Javascript.

Writing own library and use them as a layer.

Combine Lambda and Layer together.

Normally in Lambda, layer is found under /opt/

const shadowLib = require('/opt/shadow-lib');

But how to analyze, if layer is not found?

Try to get a list of all Files in /opt.

But how to get a list of all files from directory /opt? In AWS. In Lambda-function.

It works with nodejs12.

Try ist Lambda

const fs = require('fs');
const path = require('path');

function getFiles(srcpath) {
    return fs.readdirSync(srcpath)
        .map(file => path.join(srcpath, file))
        .filter(path => fs.statSync(path));
}
exports.handler = async(event, context, callback) => {
const files = getFiles("/opt");
    return files;
}

Et voilá – found my tipping error very quickly!

if creating a couple of CloudFormation (cf) skripts and run them in a whole bash-script. How to get output from cf before as input for next cf?

One script runs like this:

aws cloudformation deploy --template-file myTemplate.yaml --stack-name myStackName

Or if need package before like this

aws cloudformation package --template-file template.yaml --s3-bucket my-S3-bucket --output-template-file output.yaml

aws cloudformation deploy --template-file output.yaml.yaml --stack-name myStackName

Override a parameter.

aws cloudformation deploy --template-file output.yaml.yaml --stack-name myStackName --parameter-overrides AppName='my First App' DevAccountId=23456 TestAccountId=98765

Creating bash/shell script for more than one cf is here

#!/usr/bin/env bash
AppName='my First App'
DevAccount=123456
TestAccount=98765
aws cloudformation deploy --template-file output1.yaml.yaml --stack-name myFirstStack --parameter-overrides AppName=$AppName DevAccountId=$DevAccount TestAccountId=$TestAccount
aws cloudformation deploy --template-file output2.yaml.yaml --stack-name mySecondStack --parameter-overrides AppName=$AppName DevAccountId=$DevAccount TestAccountId=$TestAccount
aws cloudformation deploy --template-file output3.yaml.yaml --stack-name myThirdStack --parameter-overrides AppName=$AppName DevAccountId=$DevAccount TestAccountId=$TestAccount

And now!

Getting output, use describe-stacks like this

aws cloudformation describe-stacks --stack-name myStackName --output text

Or with –output json or table, but you got whole stackdescription.

Reduce to output-only with this: All outputs

aws cloudformation describe-stacks --stack-name thomas-is-doph --query "Stacks[0].Outputs[].OutputValue"  --output text

or this: one specific output (Outputs[0] or Outputs[1] )

aws cloudformation describe-stacks --stack-name thomas-is-doph --query "Stacks[0].Outputs[0].OutputValue"  --output text 

You have to know the order of outputs!

But it gets better!

You can get a specific output with

aws cloudformation describe-stacks --stack-name myStackName --query "Stacks[0].Outputs[?OutputKey=='SearchTerm'].OutputValue" --output text

Now you get directly your searchTerm!

If you combine them in a script, a function would be nice

try this:

function getOutput { echo -n "function called to find $1" queryParameter="Stacks[0].Outputs[?OutputKey=='$1'].OutputValue" echo -n "Query Paramter= $queryParameter" outputVar='aws cloudformation describe-stacks --stack-name $2 --query $queryParameter - --output text' 
result=$(eval "$outputVar") 
echo "searching variable:> $result"}

In a whole script it looks like this:

#!/usr/bin/env bash

##################################################
## Getting output from CI! ##
## ##
## Needs 3 parameter ##
## $1 name of Output ##
## $2 name of Stack ##
## result name in mandatory ##
## contains result ##
## ##
## Example: ##
## getOutput KMSKey moe-cloud-stack result ##
##################################################
function getOutput {

  echo -n "function called to find $1"
  queryParameter="Stacks[0].Outputs[?OutputKey=='$1'].OutputValue"
  echo -n "Query Paramter= $queryParameter"
  outputVar='aws cloudformation describe-stacks --stack-name $2 --query $queryParameter --profile moe-ci --output text --region eu-central-1'
  result=$(eval "$outputVar")
  echo "searching variable:> $result"
}

AppName='my First App'
DevAccount=123456
TestAccount=98765
aws cloudformation deploy --template-file output1.yaml.yaml --stack-name myFirstStack --parameter-overrides AppName=$AppName DevAccountId=$DevAccount TestAccountId=$TestAccount

getOutput important myFirstStack result
first=$result

getOutput moreImportant myFirstStack result
second=$result

aws cloudformation deploy --template-file output2.yaml.yaml --stack-name mySecondStack --parameter-overrides AppName=$AppName moreImportant=$second important=$first

very nice, isnt it?

My third app is ready!

You can find the story behind that here: Story

What I have done:

New in this app:

• Using AWS Polly for sound.
• Using AWS-SDK locally.
• Using native Audio from html 5 for playing sound.

I took the “Day2-App” with the same AWS API Gateways and Lambdas and poured in some new features on the client App.

Spending time

While working with Polly I spent much time to find a solution for playing a sound file on the client with the ionic-framework. As the solution should have worked on both Android and iOS, I tried new Plugins (like the native-media or the native-audio-plugin), upgrading and downgrading existing ones but nothing worked out at all.
It could have been so easy as ionic and Cordova support the use of HTML5. As I decided to try that out with a few lines…

let myAudio = new Audio (file);

myAudio.play();

Thats all, thats easy, that was not expected!

Second challenge was to convert javascript example into typescript.

Using the example in JavaScript would have cost me an hour. But as I’m more a fan of typescript, so… converting code was the next step. Took like half a day in the end but was worth the work!

What I learned?

• Keep it simple (stupid) KISS Pattern.
• Dont ask the framework, what it can do for you, ask yourself if its neccessary. First learn basics, then learn frameworks.
• Convert javascript into typescript is possible.

Video

Whole Story

Story

Roadmap

My first app is complete!

You can find the story behind that here: Story

What I have done:

• AWS Rekognition Service for finding text in the image supplied by the client
• AWS APIGateway as endpoint for the app
• AWS Lambda to combine APIGateway and Rekognition Service
• CloudFormation for automatic deployings
• Ionic Framework for the client app on iOS and Android
  
• Swagger to generate an Angular Client

What I learned?

• AWS is awesome! Because it is very easy to use and to combine AWS services.
• My lambda function is obsolete, because of using Rekognition Service directly from APIGateway (next app, day-two or app-three)
• Swagger is awesome too! Generate it from APIGateway, then using it to generate a technical client or server (maybe next times). This time I just focused on the domainmodel.
• With ionic, Android Version works easier then iOS version. That’s a pity.

Video

http://blog.thomasmichael.de/wp-content/uploads/2019/03/40-days-40-apps-day-one.mp4

Die Nutzung von enums in TypeScript ist ein wenig sperrig, aber nicht unmöglich!
Enum in einer TS-Datei definieren:

export enum MeinEnum{
A=1,
B=2,
C=4,
D=8,
D=16,
}

Einbinden in TS:

import {MeinEnum} from 'HierLiegtMeinEnum';


Nutzung in TS:

MeinEnum[MeinEnum.A];


liefert den Wert A als String zurück.

MeinEnum[MeinEnum.A].toLowerCase();


um den String vereinheitlicht zu nutzen, für Stringvergleiche.

Für die Nutzung in HTML benötigt TS noch ein Property auf das Enum:

private meinEnumInTS = MeinEnum;


und dann in HTML:


hatEinesDieserEnumWerte(meinEnumInTS.A, meinEnumInTS.D)


welches in TS zugreift auf:


hatEinesDieserEnumWerte(...e : MeinEnum): boolean{
// some Code
}


Nebenbei die Args – Notation für eine variable Anzahl gleicher Parameter!