recommendation

Open source recommendation system based on time-series data and statistical analysis. Written in TypeScript and Node.js using Redis for storage. The recommendation system uses the Jaccard index to calculate the intersection between two sets. One set is represented by the maximum possible sum of tag score and the other set is the score sum of user events per tag. The higher the Jaccard index, the higher the recommendation. It uses numbers to represent sets to increase performance.

Features

• Use tag score and Jaccard index
• Content-based filtering
• Event-driven powered engine
• Naive exploration of new tags
• Suitable for product and content recommendation
• Fine-tuning of tag weights
• Minimalist and lightweight
• Written in TypeScript and Node.js

Overview video

How it works

How the data is stored:

• Actors are stored in Redis as simple String keys with create date timestamps as value.
• Items are Set type with tags as members. The item may have multiple tags.
• Events are String type with actorId:id:tag:timestamp:ttl and an expire attribute set to ensure freshness of recommendations.

How the data is accessed:

• Get the actor with events
  • Check if the actor exists with EXISTS actor:${id}
  • Get all user events with SCAN ${loop cursor} MATCH actor:${id}
• Delete a single actor
  • Scan for each related to actor key SCAN ${loop cursor} MATCH actor:${id}*
  • For each key delete with DEL ${key}
• Add a single actor
  • Scan for each related to actor key SCAN ${loop cursor} MATCH actor:${id}*
  • For each key delete with DEL ${key}
  • Add new actor with SET actor:${id} ${Date.now().toString()}
• Add a single event
  • Check if actor exists if flag is set using EXISTS actor:${id}
  • Add event with SET actor:${id}:${tag}:${date}:${ttl} ${score}
  • If TTL has been provided, set expiration for event with EXPIRE actor:${id}:${tag}:${date}:${ttl} ${ttl}
• Get all items with tags
  • Get all items with SCAN ${loop cursor} MATCH item:*
  • For each item get all tags with SMEMBERS ${itemKey}
• Get a single item with tags
  • Get all tags of item with SMEMBERS item:${id}
• Delete single item
  • Call with DEL item:${id}
• Add a single item
  • Check if item already exists EXISTS item:${id}
  • If so, then remove DEL item:${id}
  • And add item with tags SADD item:${id} ${tags}

How to run it locally?

# clone repository with the source code
git clone

# install dependencies
yarn

# build the application from ts to js
yarn build

# start the application
yarn start

# alternatively use ts-node in the developer mode
yarn dev

Deployment

To make deploys work, you need to create free account on Redis Cloud

Google Cloud Run

Tests

To run tests use the following command:

yarn test

You should see the following output:

 PASS  src/__tests__/recommendations.spec.ts
  Recommendations
    √ should item 1 has score 1 and be the first (7 ms)
    √ should item 2 has score 1 and be the first (1 ms)
    √ should return two recommendation with the same score of 1 (1 ms)
    √ should return two recommendation with the same score of 0.5
    √ should return three recommendation with 1, 1 and 0.5 score

 PASS  src/__tests__/envs.spec.ts
  Envs
    √ should return one recommendation (2 ms)
    √ should return two recommendations
    √ should return recommendation with 0.125 score (1 ms)
    √ should return recommendation with 0.0625 score
    √ should clamp results to 0

Environment variables

# redis host
REDIS_HOST="localhost"

# redis port
REDIS_PORT="6379"

# redis password
REDIS_PASSWORD="mysecretpassword"

# write additional logs to stdout
VERBOSE="true"

# do not check if an actor exists when adding an event
DO_NOT_CHECK_ACTOR_EXISTENCE="true"

# maximum size of a candidate pool of items to calculate recommendation positions
ITEMS_LIMIT="100000"

# maximum number of events to use for recommendation calculation
EVENTS_LIMIT="100000"

# maximum number of recommendations to return
RECOMMENDATIONS_LIMIT=100

# wait to finish event insertion before http response
WAIT_FOR_EVENT_INSERTION="false"

# chance of recommending irrelevant item, used for exploration of new tags
# to minimize the recommendation bubble effect
EXPLORATION_NOISE="0.1"

# max sum of events score set per tag
# e.g. 1 (view event) + 2 (like event) + 5 (lead event) = 8 
JACCARD_MAX_TAG_SCORE="8"

# clamp the recommendation results between 0 and 1
JACCARD_CLAMP_RESULT_RECOMMENDATIONS="true"

API

Set (add or replace) actor

POST /api/actors
{
    "externalId": "string"
}

Get specific actor by actorId

GET /api/actors/:actorId

Get recommendation for actor

GET /api/actors/:actorId/recommendation

Delete specific actor

DELETE /api/actors/:actorId

Add new event to an actor

POST /api/actors/:actorId/events
{
    "tag": "tag1",
    "score": 3,
    "ttl": 60
}

Set (add or replace) item

POST /api/items
{
    "externalId": "string",
    "tags": ["tag1", "tag2", "..."]
}

Get specific item by itemId

GET /api/items/:itemId

Delete specific item

DELETE /api/items/:itemId

More Information about Redis Stack

Here some resources to help you quickly get started using Redis Stack. If you still have questions, feel free to ask them in the Redis Discord or on Twitter.

Getting Started

1. Sign up for a free Redis Cloud account using this link and use the Redis Stack database in the cloud.
2. Based on the language/framework you want to use, you will find the following client libraries:
   • Redis OM .NET (C#)
     • Watch this getting started video
     • Follow this getting started guide
   • Redis OM Node (JS)
     • Watch this getting started video
     • Follow this getting started guide
   • Redis OM Python
     • Watch this getting started video
     • Follow this getting started guide
   • Redis OM Spring (Java)
     • Watch this getting started video
     • Follow this getting started guide

The above videos and guides should be enough to get you started in your desired language/framework. From there you can expand and develop your app. Use the resources below to help guide you further:

1. Developer Hub - The main developer page for Redis, where you can find information on building using Redis with sample projects, guides, and tutorials.
2. Redis Stack getting started page - Lists all the Redis Stack features. From there you can find relevant docs and tutorials for all the capabilities of Redis Stack.
3. Redis Rediscover - Provides use-cases for Redis as well as real-world examples and educational material
4. RedisInsight - Desktop GUI tool - Use this to connect to Redis to visually see the data. It also has a CLI inside it that lets you send Redis CLI commands. It also has a profiler so you can see commands that are run on your Redis instance in real-time
5. Youtube Videos
   • Official Redis Youtube channel
   • Redis Stack videos - Help you get started modeling data, using Redis OM, and exploring Redis Stack
   • Redis Stack Real-Time Stock App from Ahmad Bazzi
   • Build a Fullstack Next.js app with Fireship.io
   • Microservices with Redis Course by Scalable Scripts on freeCodeCamp

License

MIT