Merge pull request #553 from dkavanagh/dak-add-step-functions

Add step functions

README.md

@@ -48,6 +48,7 @@ Table of Contents
 | [Fargate](#fargate) | [📗](#fargate-basics) | [📘](#fargate-tips) | [📙](#fargate-gotchas-and-limitations) |
 | [Lambda](#lambda) | [📗](#lambda-basics) | [📘](#lambda-tips) | [📙](#lambda-gotchas-and-limitations) |
 | [API Gateway](#api-gateway) | [📗](#api-gateway-basics) | [📘](#api-gateway-tips) | [📙](#api-gateway-gotchas-and-limitations) |
+| [Step Functions](#step-functions) | [📗](#step-function-basics) | [📘](#step-function-tips) | [📙](#step-function-gotchas-and-limitations) |
 | [Route 53](#route-53) | [📗](#route-53-basics) | [📘](#route-53-tips) |  |
 | [CloudFormation](#cloudformation) | [📗](#cloudformation-basics) | [📘](#cloudformation-tips) | [📙](#cloudformation-gotchas-and-limitations) |
 | [VPCs, Network Security, and Security Groups](#vpcs-network-security-and-security-groups) | [📗](#vpc-basics) | [📘](#vpc-and-network-security-tips) | [📙](#vpc-and-network-security-gotchas-and-limitations) |
@@ -1493,6 +1494,29 @@ API Gateway
 
 🚧 [*Please help expand this incomplete section.*](CONTRIBUTING.md)
 
+Step Functions
+------
+
+### Step Functions Basics
+-	📒 [Homepage](https://aws.amazon.com/step-functions/) ∙ [Developer guide](http://docs.aws.amazon.com/step-functions/latest/dg/welcome.html) ∙ [FAQ](https://aws.amazon.com/step-functions/faqs/) ∙ [Pricing](https://aws.amazon.com/step-functions/pricing/)
+-	**Step Functions** is AWS’ way to create state machines that manage a serverless workflow.
+
+### Step Functions Tips
+-   A variety of structures are supported including branching, parallel operations and waits
+-   [Tasks](https://docs.aws.amazon.com/step-functions/latest/dg/concepts-tasks.html) represent the real work nodes and are frequently Lambda functions, but can be [Activities](https://docs.aws.amazon.com/step-functions/latest/dg/concepts-activities.html) which are externally driven tasks implemented any way you like.
+-   State machines have [data](https://docs.aws.amazon.com/step-functions/latest/dg/concepts-state-machine-data.html) that "flows" through the steps and can be modified and added to as the state machine executes.
+-   It's best if your tasks are idempotent, in part because you may want to re-run the state machine with the same input data during debugging
+-   The AWS Console facilitates your examining the execution state at various steps.
+    -   The console lets you do this with a few steps:
+        -   select the "input" tab from the failed execution
+        -   copy the input data (JSON)
+        -   select the state machine name in the breadcrumbs
+        -   start a new execution, pasting the input data you copied previously
+
+### Step Functions Gotchas and Limitations
+-   Step Functions are free tier eligible up to an initial 4000 transitions per month. Thereafter, the charge is $0.025 per 1000 state transitions.
+-   You can have many, simulatanous, executions, but be aware of lambda throttling limits. This has been per-account, pre-region, but recently became settable per-lambda.
+
 Route 53
 --------