add sample for stepfunctions using lambdas and localstack (#148)

* add sample for stepfunctions using lambdas and localstack

* ci: fix failing build

* fix nits

Author: HarshCasper

.github/workflows/makefile.yml

@@ -31,6 +31,7 @@ jobs:
     - name: Install Dependencies
       run: |
         pip install virtualenv
+        pip install --upgrade pyopenssl
         npm install -g serverless
 
     - name: Setup config

stepfunctions-lambda/Makefile

@@ -0,0 +1,69 @@
+export AWS_ACCESS_KEY_ID ?= test
+export AWS_SECRET_ACCESS_KEY ?= test
+export AWS_DEFAULT_REGION=us-east-1
+
+usage:       ## Show this help
+	@fgrep -h "##" $(MAKEFILE_LIST) | fgrep -v fgrep | sed -e 's/\\$$//' | sed -e 's/##//'
+
+install:     ## Install dependencies
+	@which awslocal || pip install awscli-local
+
+create-lambdas:         ## Create the Lambdas
+	awslocal iam create-role --role-name step-function-lambda --assume-role-policy-document file://step-trust-policy.json
+	awslocal iam attach-role-policy --role-name step-function-lambda --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaRole
+
+	cp -f lambda_adam.py lambda_function.py
+	zip package.zip lambda_function.py
+
+	awslocal lambda create-function \
+  		--function-name adam \
+  		--role arn:aws:iam::000000000000:role/lambda-demo \
+  		--runtime python3.9 --timeout 10 --memory-size 128 \
+  		--handler lambda_function.lambda_handler \
+  		--zip-file fileb://package.zip
+	
+	rm package.zip lambda_function.py
+
+	cp -f lambda_cole.py lambda_function.py
+	zip package.zip lambda_function.py
+
+	awslocal lambda create-function \
+  		--function-name cole \
+  		--role arn:aws:iam::000000000000:role/lambda-demo \
+  		--runtime python3.9 --timeout 10 --memory-size 128 \
+  		--handler lambda_function.lambda_handler \
+  		--zip-file fileb://package.zip
+
+	rm package.zip lambda_function.py
+
+	cp -f lambda_combine.py lambda_function.py
+	zip package.zip lambda_function.py
+
+	awslocal lambda create-function \
+  		--function-name combine \
+  		--role arn:aws:iam::000000000000:role/lambda-demo \
+  		--runtime python3.9 --timeout 10 --memory-size 128 \
+  		--handler lambda_function.lambda_handler \
+  		--zip-file fileb://package.zip
+
+	rm package.zip lambda_function.py
+
+start:
+	localstack start -d
+
+stop:
+	@echo
+	localstack stop
+
+ready:
+	@echo Waiting on the LocalStack container...
+	@localstack wait -t 30 && echo Localstack is ready to use! || (echo Gave up waiting on LocalStack, exiting. && exit 1)
+
+logs:
+	@localstack logs > logs.txt
+
+test-ci:
+	make start install ready create-lambdas; return_code=`echo $$?`;\
+	make logs; make stop; exit $$return_code;
+	
+.PHONY: usage install create-lambdas run stop ready logs test-ci

stepfunctions-lambda/README.md

@@ -0,0 +1,43 @@
+# Creating a Lambda function with a function URL
+
+In this example, we will demonstrate how to create an AWS Step Function with Lambda functions in LocalStack.
+
+## Prerequisites
+
+* LocalStack
+* Docker
+* `awslocal` CLI
+
+## Starting up
+
+Start LocalStack via: 
+
+```sh
+localstack start -d
+```
+
+Run the following command to create the Lambda functions:
+
+```sh
+make create-lambdas
+```
+
+## Setting up and running Step Function
+
+Create the Step Function:
+
+```sh
+awslocal stepfunctions create-state-machine --name step-demo \
+  --definition "$(cat step-definition.json)" \
+  --role-arn arn:aws:iam::000000000000:role/step-function-lambda
+```
+
+Start the execution:
+
+```sh
+awslocal stepfunctions start-execution \
+  --state-machine-arn arn:aws:states:us-east-1:000000000000:stateMachine:step-demo \
+  --input '{"adam": "LocalStack", "cole": "Stack"}'
+```
+
+This creates and invokes the flow between the three Lambda functions we created using LocalStack earlier.

stepfunctions-lambda/lambda_adam.py

@@ -0,0 +1,3 @@
+def lambda_handler(event, context):
+    print(event)
+    return event["input"]["adam"]

stepfunctions-lambda/lambda_cole.py

@@ -0,0 +1,3 @@
+def lambda_handler(event, context):
+    print(event)
+    return event["input"]["cole"]

stepfunctions-lambda/lambda_combine.py

@@ -0,0 +1,3 @@
+def lambda_handler(event, context):
+    print(event)
+    return "Together Adam and Cole say '{}'!!".format(' '.join(event["input"]))

stepfunctions-lambda/step-definition.json

@@ -0,0 +1,48 @@
+{
+    "Comment": "Parallel Demo",
+    "StartAt": "Parallel State",
+    "States": 
+    {
+      "Parallel State": {
+        "Type": "Parallel",
+        "Next": "combine",
+        "Branches": [
+          {
+            "StartAt": "adam",
+            "States": {
+              "adam": {
+                "Type": "Task",
+                "Resource": "arn:aws:states:::lambda:invoke",
+                "Parameters": {
+                  "FunctionName": "arn:aws:lambda:us-east-1:000000000000:function:adam",
+                  "Payload": {"input.$": "$"}},
+                "OutputPath": "$.Payload",
+                "End": true}}
+          },
+          {
+            "StartAt": "cole",
+            "States": {
+              "cole": {
+                "Type": "Task",
+                "Resource": "arn:aws:states:::lambda:invoke",
+                "Parameters": {
+                  "FunctionName": "arn:aws:lambda:us-east-1:000000000000:function:cole",
+                  "Payload": {"input.$": "$"}},
+                "OutputPath": "$.Payload",
+                "End": true
+              }
+            }
+          }
+        ]
+      },
+      "combine": {
+        "Type": "Task",
+        "Resource": "arn:aws:states:::lambda:invoke",
+        "Parameters": {
+          "FunctionName": "arn:aws:lambda:us-east-1:000000000000:function:combine",
+          "Payload": {"input.$": "$"}},
+        "OutputPath": "$.Payload",
+        "End": true}
+    }
+  }
+  

stepfunctions-lambda/step-trust-policy.json

@@ -0,0 +1,11 @@
+{
+    "Version": "2012-10-17",
+    "Statement": [
+      {
+        "Effect": "Allow",
+        "Principal": {"Service": ["states.amazonaws.com"]},
+        "Action": "sts:AssumeRole"
+      }
+    ]
+  }
+