Building A Graph Traversal API using Sinatra, Pacer and Neo4j

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Graph Traversal API

If you are building a graph-based web application, you will (most likely) a web API that exposes your graph to the world.

Let's see how to do that with Pacer and Sinatra...

Simple Demo

$ gem install sinatra
$ gem install trinidad

Install Sinatra and Trinidad

$ ruby sinatra_simple_demo.rb

Run the simple demo (in the root of our repo)

Make an API call

$ curl http://localhost:4567/customers/CENTC
{"phone":"(5) 555-3392",
 "companyName":"Centro comercial Moctezuma",
 "customerID":"CENTC","fax":"(5) 555-7293","type":"Customer"}

How does it work?

require 'sinatra'

# ...

@@g = Pacer.tg   # Global graph object

# ...


get '/customers/:customer_id' do
   content_type :json
   id = params[:customer_id]

   customer = @@g.v(NorthWind::Customer, customerID: id).first

   if customer
      customer.properties.to_json
   else
      status 404
   end

end

Exposing Traversals

get '/customers/:customer_id/purchases' do

   content_type :json
   id = params[:customer_id]

   products = @@g.v(NorthWind::Customer, customerID: id)
                 .products.uniq

   if products
      products.properties.to_a.to_json
   else
      status 404
   end

end

http://localhost:4567/customers/CENTC/purchases

Allows to send GET requests to

Pacer NorthWind - Demo

Building a graph traversal API using

Setup

Step 1:

gem install pacer

gem install pacer-neo4j

Step 2:

Download & install Neo4j

gem install sinatra

gem install trinidad

Step 3:

Running the demo

cd pacer-northwind

ruby run_demo.rb ~/pacer-northwind-data

The path ~/pacer-northwind-data specifies where to store the Neo4j data files.
If you do not specify a path, the demo will run with TinkerGraph, the built-in, in-memory graph we have been using all day.