stackery / demo-appsync-stock-trades

Demo AWS AppSync app built with Stackery

Setup

1. Add GraphQL Api
   1. Update name to Trades Api
   2. Update schema location to trades/schema.graphql
   3. Paste the following schema:

      type Mutation {
        createTrade(type: TransactionType!, symbol: String!): Trade
      }
      
      type Price {
        symbol: String!
        price: Float!
      }
      
      type Query {
        getPrice(symbol: String!): Price
        getTrade(id: ID!): [Trade]
        listTrades(limit: Int, nextToken: String): TradesConnection
      }
      
      type Subscription {
        onCreateTrade(
          id: ID,
          symbol: String,
          timestamp: AWSDateTime,
          price: Float,
          type: String
        ): Trade
          @aws_subscribe(mutations: ["createTrade"])
      }
      
      type Trade {
        id: ID!
        type: TransactionType!
        symbol: String!
        timestamp: AWSDateTime!
      }
      
      type TradesConnection {
        items: [Trade]
        nextToken: String
      }
      
      enum TransactionType {
        BUY
        SELL
      }

   4. Attach resolvers to:
      • Query getPrice
      • Query getTrade
      • Query listTrades
      • Mutation createTrade
2. Add an HTTP Proxy Endpoint
3. Connect the Query getPrice resolver to the HTTP Proxy Endpoint
4. Update the HTTP Proxy Endpoint Host to https://www.alphavantage.co
5. Add a DynamoDB Table
6. Connect the rest of the resolvers to it
7. Update the DynamoDB Table Logical ID to Trades
8. Edit Query getPrice resolver
   • Request Template:

     {
       "version": "2018-05-29",
       "method": "GET",
       "resourcePath": "/query",
       "params":{
         "query": {
           "function": "GLOBAL_QUOTE",
           "symbol": $util.toJson($ctx.args.symbol),
           "apikey": "demo"
         }
       }
     }

   • Response Template:

     #if($ctx.error)
       $util.error($ctx.error.message, $ctx.error.type)
     #end
     #if($ctx.result.statusCode == 200)
       {
         "symbol": $util.toJson($ctx.args.symbol),
         "price": $util.parseJson($ctx.result.body)["Global Quote"]["05. price"]
       }
     #else
       $utils.appendError($ctx.result.body, $ctx.result.statusCode)
     #end

9. Edit Mutation createTrade
   • Request Template:

     {
       "version" : "2017-02-28",
       "operation" : "PutItem",
       "key" : {
         ## If object "id" should come from GraphQL arguments, change to $util.dynamodb.toDynamoDBJson($ctx.args.id)
         "id": $util.dynamodb.toDynamoDBJson($util.autoId()),
       },
       "attributeValues" : {
         "type": $util.dynamodb.toDynamoDBJson($ctx.args.type),
         "symbol": $util.dynamodb.toDynamoDBJson($context.arguments.symbol),
         "timestamp": $util.dynamodb.toDynamoDBJson($util.time.nowISO8601())
       }
     }

10. Edit Query getTrade
    • Request Template:

      {
        "version": "2017-02-28",
        "operation": "GetItem",
        "key": {
          "id": $util.dynamodb.toDynamoDBJson($ctx.args.id),
        }
      }

11. Edit Query listTrades
    • Request Template:

      {
        "version": "2017-02-28",
        "operation": "Scan",
        "limit": $util.defaultIfNull($ctx.args.limit, 20),
        "nextToken": $util.toJson($util.defaultIfNullOrEmpty($ctx.args.nextToken, null)),
      }

12. Deploy!

Queries

• Get Price

  query getPrice {
    getPrice(symbol: "AMZN") {
      symbol
      price
    }
  }

• Trade Subscription (in separate window)

  subscription onCreateTrade {
    onCreateTrade {
      id
      timestamp
      type
      symbol
    }
  }

• Create Trade

  mutation createTrade {
    createTrade(type: BUY, symbol: "AMZN") {
      id
      timestamp
      type
      symbol
    }
  }

• List Trades

  query listTrades {
    listTrades {
      items {
        id
        timestamp
        type
        symbol
      }
    }
  }