JuliaGrandury / Views-Tracking-Challenge-Siro

Views-Tracking-Challenge

Assignment

Implementing a cloud function that can update the uniqueViewCount field in the recording document given passed in parameters of viewerId and recordingId with the following requirements:

• Needs to be able to handle significant amounts of views within a day (if recording goes viral)
• Only counts unique views (one view per user on a recording)
• Must update data in such a way that a same viewer opening a same recording on different devices would only increment the uniqueViewCount once

Assumptions

• ViewerIds and RecordingIds are unique
• The trackRecordingView cloud function is called by the client every time any user opens any recording in the mobile app

Solution Design and Tradeoffs

• Added a collection of UniqueView documents in types.ts for all the unique views of all recordings
  • This allows us to handle significant amounts of writes to the UniqueView documents of recordings (given the 1MB limit of data per document)
• Used a transaction to handle read/writes to User, Recording and UniqueView documents
  • This ensures consistency between concurrent writes to a document (if a recording goes viral) as it ensures that each subsequent write sees the contents of the document before it is written
  • This ensures that if two requests for the same recording are made by the same viewer simultaneously they will not be double counted
  • However, transactions fail when the client is offline though that should not be an issue in this particular case
• Bonus from track-recording-views.ts : For the purpose of readability and maintenance, I factored out the interfaces and enum from track-recording-views.ts and placed them all in types.ts.
• Bonus from index.ts : Validated that viewerId and recordingId are strings (not null or of another type) and are non-empty.

Setting it up

• You will need to have Node.js and npm installed. If you do not, visit Download Node.js and install the latest version of npm with npm install npm@latest -g. Ensure that both are correctly installed using node -v and npm -v.
• Clone the repository with git clone https://github.com/JuliaGrandury/Views-Tracking-Challenge-Siro
• install the firebase CLI with npm install -g firebase-tools
• navigate to the functions directory and install dependencies with cd functions && npm i
• initiate and run the emulator with npm run serve (from the functions directory)

Further development outside of the scope of the project

Could account for the fact that users might briefly open the recording but not view the majority of it and therefore should not be counted as viewers in the uniqueViewCount or uniqueRecordingViewCount.