Leveraging the Neo4j Community Graph For Social Discovery Recently the Neo4j Developer Relations team decided to devote a few hours to work together, style, to launch a . One feature we decided was needed for launch was a trending activity feed that showed blog posts and projects that are currently trending in the community. hackathon new Neo4j community forum Fortunately, my colleague has built out the , a series of serverless functions that import data from APIs like , Twitter, Meetup, and Stackoverflow into a Neo4j instance. We use Neo4j Community Graph to keep track of what’s going on in the Neo4j community. In fact if you’ve seen Mark’s newsletter (AKA TWIN4j), a few queries to community graph surfaces each week’s content. Mark Needham Neo4j Community Graph Github This Week In Neo4j In this post I want to explain how we built out the trending activity feed feature on the Neo4j Community Forum using a GraphQL First development approach. Community Graph Data model for the Community Graph. Combining data sets and querying across them is a natural fit for a graph database like Neo4j. One of the benefits of a graph database like Neo4j is the ease with which it allows for combining datasets and querying across them. We’ve been using Neo4j to help keep track of what the Neo4j community has been working on. Neo4j Community Graph is powered by a set of serverless functions that run on AWS Lambda, periodically checking the APIs of GitHub, Twitter, StackOverflow, and Meetup for new Neo4j related updates. Any matches are imported into Neo4j. Mark has even created a so that anyone can spin up a community graph for their community! community graph CLI The Awesome Discourse API The first step was adding content from our new Discourse forum into community graph. Discourse exposes an API to enable developers to build tooling on top of Discourse. In this case Mark registered a webhook on the Discourse API so that events are sent to the serverless community graph ingest Lambda functions. So the new Discourse site becomes a new developer community data set in community graph. This allows us to capture new Discourse users and new posts, including likes and replies. We link Discourse users in the graph with their other accounts (Github, Twitter, Stackoverflow, etc) when a user fills in their Discourse profile with their user names across services. Community Trending Activity Feeds Trending activity feeds provide an overview of what is going on in the community at a glance and quickly show the posts, topics, and projects that are trending. Rather than just showing the most recent posts, we want to rank items to surface content of interest to viewers that show what is currently trending in the community. Exponential Time Decay Functions Discussion forums such as Hacker News and Reddit make use of to rank what posts float to the top and what are banished to the second page and beyond. The basis for these ranking algorithms are a function that calculates a score for each post which consists of a rating divided by the time since the post was created raised to some exponent. The rating can consist of things like upvotes, views, subjective scoring by a reviewer, or as in our case, all three. You can find , but for our purposes we’ll use a much simpler version. exponential time decay functions implementations of the functions used by Hacker News and Reddit A simple exponential time decay function for scoring posts in a discussion forum. Functions like this allow new content to appear high on the leaderboard, but quickly drop off if the community does not find it engaging. Here’s how we can query the community graph using Cypher to find our top community blog posts using an exponential decay function: const cypherQuery = ` (u: )-[: ]->(t: ) t.approved “Exclude” labels(t) *,1.0 * (duration.inSeconds(datetime(), t.createdAt)).seconds/10000 ago u, t, ( (10.0 * t.rating) + t.likeCount + t.replyCount)/(ago^2) score u, (t)[0] AS topic u, topic $first`; MATCH DiscourseUser POSTED_CONTENT DiscourseTopic WHERE AND NOT IN WITH AS WITH AS WITH COLLECT RETURN LIMIT An exponential time decay function with these parameters will surface almost every new post to the top, to give it a chance for the community to vote on it. Posts that the community votes up, or that involve active discussion stay at the top, while posts that are less captivating to the community drop off the list. GraphQL API We expose a GraphQL API on top of the Neo4j community graph instance hosted on that we can query from Discourse to populate the activity feed on the landing page. Neo4j Cloud The GraphQL Schema Defining the GraphQL schema was actually one of the first steps we took. Once we defined the schema we were able to just from the GraphQL API so and could work on the UI. Here’s the GraphQL schema for our top blog post query: return mocked data Jennifer David type {title: Stringurl: Stringauthor: DiscourseUser} CommunityBlog type {name: StringscreenName: Stringavatar: String} DiscourseUser type {topCommunityBlogsAndContent(first: Int = 10): [CommunityBlog]} Query Resolvers In a GraphQL server, resolvers are the functions that contain the logic for fetching data from our data layer. In our case each query entry point to the GraphQL API is a single Cypher query, so we can use the to execute our Cypher query and return the results, ordered by our time decay ranking score. Neo4j JavaScript driver export const resolvers = {Query: { (_, params, context) => { topCommunityBlogsAndContent: let session = context.driver.session();  
  const baseUrl = ‘[https://community.neo4j.com/’](https://community.neo4j.com/%27);

  // cypherQuery is defined above  
  return session.run(cypherQuery, params)  
  .then( result => {  
    const resData = result.records.map(record => {  
      const user = record.get(“u”).properties,  
           topic = record.get(“topic”).properties;

      return {  
        title: topic.title,  
        url: baseUrl + “t/” + topic.slug,  
        author: {  
          name: user.name,  
          screenName: user.screenName,  
          avatar: getAvatarUrl(user.avatarTemplate)  
        }  
      }  
    })  
    return resData;

  })  
  .catch(error => {  
    console.log(error);  
  })  
  .finally( ()=> {  
    session.close();  
  })  
} }}; Apollo Server We use in a Node.js app to allow us to build a GraphQL API from a GraphQL schema (type definitions) and resolvers. We inject a Neo4j driver instance into the context so that it is available in the resolver functions. Apollo Server import { typeDefs, resolvers } from “./graphql-schema”;import { ApolloServer, makeExecutableSchema } from “apollo-server”;import { v1 as neo4j } from “neo4j-driver”;import dotenv from “dotenv”; dotenv.config(); const schema = makeExecutableSchema({ , }); typeDefs resolvers const driver = neo4j.driver(process.env.NEO4J_URI || “bolt://localhost:7687”,neo4j.auth.basic(process.env.NEO4J_USER || “neo4j”,process.env.NEO4J_PASSWORD || “neo4j”)); const server = new ApolloServer({context: { driver },schema: schema}); server.listen(process.env.GRAPHQL_LISTEN_PORT, ‘0.0.0.0’).then(({ url }) => {console.log(`GraphQL API ready at ${url}`);}); One of the benefits of using Apollo Server is that we automatically get GraphQL Playground, a tool for exploring GraphQL APIs. GraphQL Playground allows us to explore the schema, including entry points and types, and to execute GraphQL requests against the API. makes it easy to explore GraphQL APIs. GraphQL Playground Try it here. The Neo4j Community Forum Landing Page The GraphQL first development approach was a fun and productive way for us to quickly build out a feature that allowed us to put it into production after a few hours of collaborative work. When it’s all said and done, here’s how the landing page looks: Not bad for a few hours hacking on a rainy day ☔ Check it out . here I skipped over how we populate the “This Week in Neo4j”, “Popular Community Projects”, and “New Certified Developers” sections, but it all comes from Neo4j Community Graph! You can find the GraphQL API code to see how those bits work. here neo4j-graphql-js and GRANDstack If you’re interested in exposing a GraphQL API on top of a graph database like Neo4j (we think GraphQL and graph databases are an obvious match for each other) be sure to check out the library and for building full stack applications. neo4j-graphql-js GRANDstack Be sure to join the Neo4j community forum on Discourse You can find the code for the GraphQL API . here Further Reading . A GraphQL API for the GraphQL Community Graph on top of Neo4j. GraphQL Community Graph And finally, here are a few more resources about Community Graph: — includes code for spinning up your own community graph Community Graph Github org GraphQL APIs for Developer Communities Five Common GraphQL Problems and How Neo4j-GraphQL Aims to Solve Them — GraphQL, React, Apollo, Neo4j Database full stack development GRANDstack.io

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