Stock News Twitter Service

Daily tweets containing stock news articles. Built with Node.js and AWS.

How to Use the Service

Subscribe to a stock by tweeting @stocknewsbot subscribe $TICKER

Unsubscribe from a stock by tweeting @stocknewsbot unsubscribe $TICKER

Architecture

The application is composed of the following microservices:

1. Subscription Service
2. Queue Loader Service
3. Tweet Service
4. Error Handling Service

Diagram

Service Overview

Subscription Service

The subscription service begins by retreiving tweets containing the keyword @stocknewsbot via the Twitter API. We parse each retrieved tweet to check if the tweet is a subscription request. A tweet is a subscription request if the first word following @stocknewsbot is either subscribe or unsubscribe.

If the tweet is a valid subscription request, we perform the subscribe/unsubscribe action for the given ticker. If we encounter an error, we place the tweet in the Error Handling Queue for additional processing.

User subscriptions are stored in DynamoDB the following format:

item = {
        username: string,
        subscriptions: [string]
	   }

Subscriptions are processed by appending the $TICKER to the the item.subscriptions array. Unsubscriptions are processed by removing the $TICKER from the item.subscriptions array.

Queue Loader Service

The queue loader scans the DynamoDB table to retreive all current users and their stock subscriptions.

Each row in the resulting scan represents a task that must be completed. The service adds these tasks to an SQS queue in the following format: @username_$TICKER.

Tweet Service

The tweet service polls from the loaded SQS Queue and processes the message. The message is parsed to retrieve the username and stock ticker of the current task.

The stock ticker is used as a query string parameter in an API request to the CloudIEX Financial API. We retreive the news article for that stock from the response.

Finally, we compose and send a tweet containing the news article to the username via the Twitter API.

Error Handling Service

Tweets that fail to be processed as a subscribe or unsubscribe action are processed for error handling.

This service polls off the Error Handling queue and runs an Edit Distance DP algorithm on the failed action. The action is the first word directly after @stocknewsbot in the tweet.

If the Edit Distance between the failed action and subscribe or unsubscribe is less than 4, we reply back to the user asking if they meant subscribe or unsubscribe.

Case 1

Error Tweet: @stocknewsbot sscribe $TSLA

Failed action -> 'sscribe' 

Edit Distance between 'sscribe' and 'subscribe' is less than 4.
-> So reply to the tweet asking if they meant to 'subscribe'. 

Case 2

Error Tweet: @stocknewsbot Hello World!

Failed action -> 'Hello' 

Edit Distance between 'sscribe' and 'subscribe' is greater than 4.
-> So do not reply to the tweet.