rcotter / graphql-federated-dotnet-rest

GraphQL Federation example using .Net HotChocolate and peer RESTful services

graphql-federated-dotnet-rest

GraphQL Federation example using .Net HotChocolate and peer RESTful services

Microservices bring a lot of benefits but also new complexity for clients. Information that the old monolith served up custom formatted for usage scenarios is now disassociated, requiring multiple network calls and manually stitching them together. Each client must re-acquire the domain stitching knowledge.

GraphQL Federation presents a gateway solution to stitching subgraphs, each maintained and published by their own respective domain service, into a single cohesive graph.

Info

• How Netflix Scales Its API with GraphQL Federation @ InfoQ 2021
• GraphQL, gRPC or REST? Resolving the API Developer's Dilemma

Running

Companies Service

1. Run CompaniesService.
2. Go to http://localhost:4001/api/companies to see RESTfully served JSON.
3. Go to http://localhost:4001/graphql/ and run queries in the Operations tab:
   1. Try getting all companies:

      {
        companies {
          id
          name              
        }
      }

   2. Get a single company (adding in address and aliasing street):

      {
        companyById(id: 1) {
          id
          name 
          address {
            st: street
            number
          }             
        }
      } 

Products Service

1. Run ProductsService
2. Go to http://localhost:4002/api/products to see RESTfully served JSON.
3. Go to http://localhost:4002/graphql/ and run queries in the Operations tab:
   1. Get all products:

      {
        products {
          id
          name        
          companyId      
        }
      }

   2. Get a single company:

      {
        productById(id: 1) {
          id
          name 
          companyId             
        }
      } 

Stitch Them Together

Notice that products have references to companies. If our app needs to work with a company's products, two REST or two GraphQL calls are required and then some painful merging of the two responses.

Happily we can use GraphQL Federation and its stitching. As a client we can get what we want without any knowledge of the multiple underlying services. Our gateway brings it all together using our capabilities and references that domain services publish. The gateway code does not maintain its own knowledge of how to stitch domain responses together.

1. Run GraphqlGateway
2. Go to http://localhost:4000/graphql/ and run queries in the Operations tab:
   1. Get all companies with their products

      {
        companies {
          id
          name
          address {
            street
            number
          }
          products {
            id
            name
          }
        }
      }

   2. Get a single company with its products

      {
        companyById(id: 1) {
          id
          name
          address {
            street
            number
          }
          products {
            id
            name
          }
        }
      }

Implementation

GraphQL was setup as per HotChocolate.

This is not the Production ready implementation. HotChocolate demonstrates using a Redis DB as the schema store that domain services publish to for consumption by the gateway.