This is a serverless application to mimic the basic functionality of the popular twitter app. The application lets you sign up as a user to post images with comment as a user tweet, like tweets, retweet, add comment to tweet and delete a tweet.
This application will allow creating/removing/updating/fetching Tweet items. Each Tweet item can have an attachment image and a comment. Each user only has access to Tweet items that he/she has created. Each user can Like, Comment on Tweet items. Users can also retweet a posted tweet.
The application should store Tweet items, and each Tweet item contains the following fields:
tweetId(string) - a unique id for a tweet itemcreatedAt(string) - date and time when an item was createdlike(int) - number indicating the likes of a tweet ( zero by default)comment(string)? - comment added to tweet in tweet creationcommentList(Array) - list of comments on already posted tweetuserId(string) - the user id for posting the tweettweethandler(string) - the user for posting the tweet. (e.g. @name )attachmentUrl(string) (optional) - a URL pointing to a thumbnail image attached to a Tweet item
To implement this project, you need to implement the following functions and configure them in the serverless.yml file:
-
Auth- this function should implement a aws cognito authorizer for API Gateway that should be added to all other functions. -
GetTweets- should return all Tweets for a current user. A user id can be extracted from a JWT token that is sent by the frontend
It should return data that looks like this:
{
"items": [
{
"tweetId": "123",
"createdAt": "2019-07-27T20:01:45.424Z",
"like": 3,
"comment": "Not good",
"commentList": [
{"comment":"This is great",
"tweethandler": "@ken",
"createdAt": "2019-05-27T20:01:45.424Z"
}
],
"userId": 34555,
"tweethandler": "@somebody",
"attachmentUrl": "http://example.com/image.png"
},
{
"tweetId": "453",
"createdAt": "2019-05-27T20:01:45.424Z",
"like": 0,
"comment": "it is cool",
"commentList": [
{"comment":"This is great",
"tweethandler": "@ken",
"createdAt": "2019-05-27T20:01:45.424Z"
}
],
"userId": 5564,
"tweethandler": "@nobody",
"attachmentUrl": "http://example.com/image.png"
},
]
}CreateTweet- should create a new Tweet for a current user. A shape of data send by a client application to this function can be found in theCreateTweetRequest.tsfile
It receives a new Tweet item to be created in JSON format that looks like this:
{
"createdAt": "2019-05-27T20:01:45.424Z",
"like": 0,
"comment": "new tweet",
"commentList": [],
"userId": 5564,
"tweethandler": "@nobody",
"attachmentUrl": "http://example.com/image.png"
}It should return a new Tweet item that looks like this:
{
"item": {
"createdAt": "2019-05-27T20:01:45.424Z",
"like": 0,
"comment": "new tweet",
"commentList": [],
"userId": 5564,
"tweethandler": "@nobody",
"attachmentUrl": "http://example.com/image.png"
}
}UpdateTweet- should update a Tweet item created by a current user. A shape of data send by a client application to this function can be found in theUpdateTwetRequest.tsfile
It receives an object that contains one field that can be updated in a Tweet item:
{
"createdAt": "2019-05-27T20:01:45.424Z",
"like": 7,
"comment": "new tweet",
"commentList": [],
"userId": 5564,
"tweethandler": "@nobody",
"attachmentUrl": "http://example.com/image.png"
}The id of an item that should be updated is passed as a URL parameter.
It should return an empty body.
DeleteTweet- should delete a Tweet item created by a current user. If tweets from other users is deleted, it should not delete the tweet of the followed user but remove it from the tweets feed of the current user. Expects an id of a Tweet item to remove.
It should return an empty body.
AddComments- should add comments to a post. followed users can add their comments to a post.
It receives a new Tweet comments to be added in JSON format that looks like this:
{
"comment":"This is great",
"tweethandler": "@ken",
"createdAt": "2019-05-27T20:01:45.424Z"
}
it should return tweet item with added comments that looks like thus
{
"createdAt": "2019-05-27T20:01:45.424Z",
"like": 0,
"comment": "nice picture",
"commentList": [
{
"comment":"This is great",
"tweethandler": @ken,
"createdAt": "2019-05-27T20:01:45.424Z"
},
{
"comment":"This is fat",
"tweethandler": @Okra,
"createdAt": "2019-05-27T20:01:45.424Z"
}
],
"userId": 5564,
"tweethandler": "@nobody",
"attachmentUrl": "http://example.com/image.png"
}
Retweet- should copy the tweet data of the chosen tweet and repost the tweet.
It receives a the coppied Tweet data to be added in JSON format that looks like this:
{
"comment":"This is great",
"tweethandler": "@ken",
"attachmentUrl": "http://example.com/image.png"
}
it should return tweet item with copied tweet info that looks like this
{
"createdAt": "2019-05-27T20:01:45.424Z",
"like": 0,
"comment":"This is great",
"commentList":[],
"userId": 5564,
"tweethandler": "retweeted by @nobody",
"attachmentUrl": "http://example.com/image.png"
}
GenerateUploadUrl- returns a pre-signed URL that can be used to upload an attachment file for a Tweet item and a url to fetch from s3.
It should return a JSON object that looks like this:
{
"uploadUrl": "https://s3-bucket-name.s3.eu-west-2.amazonaws.com/image.png",
"imageUrl": "https://s3-bucket-name.s3.eu-west-2.amazonaws.com/ffh4544334icvmir5y5t3lkrdlvdlgfh54r3fm"
}All functions are already connected to appropriate events from API Gateway.
An id of a user can be extracted from a JWT token passed by a client.
You also need to add any necessary resources to the resources section of the serverless.yml file such as DynamoDB table and S3 bucket.
The client\MiniTwiter folder contains a web application that can use the API that should be developed in the project.
To implement authentication in your application, you would have to create an Auth0 application and copy "domain" and "client id" to the config.ts file in the client/MiniTwitter folder. We recommend using asymmetrically encrypted JWT tokens.
Also, Provide a URL that can be used to download a certificate that can be used to verify JWT token signature. this should be done in the backend\src\lambda\auth\auth0Authorizer.ts
Fears of cloud vendor lock-in stem from a number of places. First, it's the loss of control over the data and infrastructure that power business' applications. Not having complete control over aspects like security, uptime, and overall infrastructure management can be a scary thing.
The serverless project was built inside a business model with datalayers to enable easy shift to other cloud providers in the future.
The starter code comes with a configured Winston logger that creates JSON formatted log statements. You can use it to write log messages like this:
import { createLogger } from '../../utils/logger'
const logger = createLogger('auth')
// You can provide additional information with every log statement
// This information can then be used to search for log statements in a log storage system
logger.info('User was authorized', {
// Additional information stored with a log statement
key: 'value'
})To store Tweet items, you might want to use a DynamoDB table with local secondary index(es). A create a local secondary index you need to create a DynamoDB resource like this:
TodosTable:
Type: AWS::DynamoDB::Table
Properties:
AttributeDefinitions:
- AttributeName: partitionKey
AttributeType: S
- AttributeName: sortKey
AttributeType: S
- AttributeName: indexKey
AttributeType: S
KeySchema:
- AttributeName: partitionKey
KeyType: HASH
- AttributeName: sortKey
KeyType: RANGE
BillingMode: PAY_PER_REQUEST
TableName: ${self:provider.environment.TODOS_TABLE}
LocalSecondaryIndexes:
- IndexName: ${self:provider.environment.INDEX_NAME}
KeySchema:
- AttributeName: partitionKey
KeyType: HASH
- AttributeName: indexKey
KeyType: RANGE
Projection:
ProjectionType: ALL # What attributes will be copied to an index
To query an index you need to use the query() method like:
await this.dynamoDBClient
.query({
TableName: 'table-name',
IndexName: 'index-name',
KeyConditionExpression: 'paritionKey = :paritionKey',
ExpressionAttributeValues: {
':paritionKey': partitionKeyValue
}
})
.promise()To add an item to a list use, the update() method looks like:
await this.dynamoDBClient
.update({
TableName: 'table-name',
Key:{
"keyOne": valOne,
"KeyTwo": valTwo
},
UpdateExpression: 'set someList = list_append(someList, :vals)',
ExpressionAttributeValues: {
':vals': newList
}
})
.promise()To deploy an application run the following commands:
cd backend
npm install
sls deploy -v
To run a client application first edit the client/MiniTweet/src/config.ts file to set correct parameters. And then run the following commands:
cd client/MiniTweet
npm install
ionic serve --port 3000
This should start a development server with the Ionic application that will interact with the serverless Tweeter application.
An alternative way to test your API, you can use the Postman collection that contains sample requests. You can find a Postman collection in this project. To import this collection, do the following.