zzdjk6 / sls-course-ts-offline

Readme

This is the work-in-progress learning project while taking this udemy course: https://www.udemy.com/course/serverless-framework/

The original repo is https://github.com/arielweinberger/course-auction-service

The goal of this repo is:

• upgrade to the latest framework version
• use TypeScript
• work in both offline and cloud
• demonstrate an organised project structure
• experiment with Cognito authentication: inline vs. authorizer
• experiment with input validation tools
• experiment with SQS
• experiment with single-table design

TODO

• Experiment on DynamoDB Stream (vs. SQS)
  • https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Streams.Lambda.Tutorial.html
• Dead letter queue for fail message deliver
• Run Lambda for scheduled tasks

Learning resources

• Amazon DynamoDB session videos from AWS re:Invent 2021
• Alex DeBrie's blog
• Working with Queries in DynamoDB

How to?

Prepare

npm install -g serverless

npm install

Run locally

# only need to run once
sls dynamodb install

# needs to run every time
sls offline cloudside

View data locally

install and use dynamodb-admin:

npm install -g dynamodb-admin

dynamodb-admin

API Access

Import postman collection: postman_collection.json and setup environment vars (e.g., root_path: http://localhost:4000/dev)

Troubleshooting

if java.net.BindException: Address already in use

# find out who is taking that port
lsof -i tcp:8000

# kill it
kill -9 xxxx

if Error: EPERM: operation not permitted, unlink ..., then rm -rf ./.build

Notes

Authentication

• Lambda Authorizer Concept
• Authorizer CDK Example
• Manual Authorizer Config
• Tutorial on FreeCodeCamp

There are several options:

1. create a separate lambda as authorizer
2. create middleware
3. create service code

In this repo, I have included example code for Option#1 and Option#3.

References:

• See createAuction for inline Cognito service call
• See getAuctions and placeBid for Cognito user pool authorizer integration

Note#1: to work with this cognito setup, we need to manually set up some users using AWS Console and CLI.

# Confirm user password
aws cognito-idp admin-set-user-password \
    --user-pool-id <cognito_user_pool_id> \
    --username <user_name> \
    --password <password> \
    --permanent
  
aws cognito-idp admin-initiate-auth \
    --user-pool-id <cognito_user_pool_id> \
    --client-id <cognito_user_client_id> \
    --auth-flow ADMIN_NO_SRP_AUTH \
    --auth-parameters USERNAME=<user_name>,PASSWORD=<password>
  

Note#2: only IdentityToken works, AccessToken is not working.

Note#3: the current example in this repo is based on API Gateway V1 (REST API).

For V2 (HTTP API), it is different -- Cognito should be configured as JWT issuer:

• https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-jwt-authorizer.html
• https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-apigatewayv2-authorizer.html
• https://www.serverless.com/framework/docs/providers/aws/events/http-api#jwt-authorizers

Input validation

Options:

1. JSON Schema
2. yup / zod / joi

Option#1:

• pros: not bound to specific language, i.e., can use same JSON schema in another language such as Java or Python
• cons: requires a very tedious coding format to do very simple stuff

Option#2:

• pros: productive, i.e., easy to read & write
• cons: library locked-in

Notification

We explore 2 options to trigger notification:

1. API Gateway -> Lambda -> SQS -> Lambda -> SES
2. DynamoDB Stream -> Lambda -> SES

Data access pattern

• Create auction
• Get auctions
  • by status, ordered by end date desc
• Get auction
  • by id
• Update auction
  • by id, update the highest bid info
• Update auctions
  • by ending date and status: close expired auction

Key divider symbol

In many examples, we see keys or attributes are using # or _ as divider, but there are some issues:

• #: if we expect the entire value to be used in url, then # needs to be encoded when sending request and decoded when receiving request, because # has special meaning in url;
• _: there might be conflicts when stored value can also have _;

So in this example, I use ::.

However, as long as we use a separate id attribute in request instead of passing PK, we can either construct PK for query or build a GSI for id.

Query key conditions

We can not use functions with Partition Key (HASH key), if we try to do so, we will receive a ValidationException: Query key condition not supported.

You must specify the partition key name and value as an equality condition -- from: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Query.html#Query.KeyConditionExpressions