Unable to query dynamodb GSI in lambda locally

Question

So I added a lambda function category using the amplify CLI, in order to query data from the GSI(Global secondary Index) I created using the @key directive in the graphql schema. Whenever I try mocking the function locally using the amplify mock function <functionName> the callback function of the query keeps on returning null. The function can be seen below

const AWS = require("aws-sdk");
const db = new AWS.DynamoDB.DocumentClient({
  region: process.env.REGION,
  apiVersion: "2012-08-10",
});


 const params = {
  // ProjectionExpression: ["province", "gender", "updatedAt", "createdAt"],
  ExpressionAttributeValues: {
    ":provinceVal": "Sichuan",
  },
  IndexName: "RegistreesByProvince",
  KeyConditionExpression: "province = :provinceVal",
  TableName: process.env.API_PORTAL_SUBMISSIONSTABLE_NAME,
};

const calculateStatistics = async () => {
  try {
    const data = await db.query(params).promise();
    console.log(data);
  } catch (err) {
    console.log(err);
  }
};

const resolvers = {
  Query: {
    getStatistics: () => {
      return calculateStatistics();
    },
  },
};
exports.handler = async (event) => {
  // TODO implement
  const typeHandler = resolvers[event.typeName];
  if (typeHandler) {
    const resolver = typeHandler[event.fieldName];
    if (resolver) {
      var result = await resolver(event);
      return result;
    }
  }
}; // };

I then tried to capture the whole event and logged it to the console as can be seen in the calculateStatistics function, which now showed me a bit more explicit error as follows.

     { UnknownEndpoint: Inaccessible host: `dynamodb.us-east-1-fake.amazonaws.com'. This service may not be available in the `us-east-1-fake' region.
    at Request.ENOTFOUND_ERROR (/Users/apple/Documents/work/web/portal/amplify/backend/function/calcStatistics/src/node_modules/aws-sdk/lib/event_listeners.js:501:46)
    at Request.callListeners (/Users/apple/Documents/work/web/portal/amplify/backend/function/calcStatistics/src/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
    at Request.emit (/Users/apple/Documents/work/web/portal/amplify/backend/function/calcStatistics/src/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
    at Request.emit (/Users/apple/Documents/work/web/portal/amplify/backend/function/calcStatistics/src/node_modules/aws-sdk/lib/request.js:688:14)
    at ClientRequest.error (/Users/apple/Documents/work/web/portal/amplify/backend/function/calcStatistics/src/node_modules/aws-sdk/lib/event_listeners.js:339:22)
    at ClientRequest.<anonymous> (/Users/apple/Documents/work/web/portal/amplify/backend/function/calcStatistics/src/node_modules/aws-sdk/lib/http/node.js:96:19)
    at ClientRequest.emit (events.js:198:13)
    at ClientRequest.EventEmitter.emit (domain.js:448:20)
    at TLSSocket.socketErrorListener (_http_client.js:401:9)
    at TLSSocket.emit (events.js:198:13)
  message:
   'Inaccessible host: `dynamodb.us-east-1-fake.amazonaws.com\'. This service may not be available in the `us-east-1-fake\' region.',
  code: 'UnknownEndpoint',
  region: 'us-east-1-fake',
  hostname: 'dynamodb.us-east-1-fake.amazonaws.com',
  retryable: true,
  originalError:
   { Error: getaddrinfo ENOTFOUND dynamodb.us-east-1-fake.amazonaws.com dynamodb.us-east-1-fake.amazonaws.com:443
       at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:56:26)
     message:
      'getaddrinfo ENOTFOUND dynamodb.us-east-1-fake.amazonaws.com dynamodb.us-east-1-fake.amazonaws.com:443',
     errno: 'ENOTFOUND',
     code: 'NetworkingError',
     syscall: 'getaddrinfo',
     hostname: 'dynamodb.us-east-1-fake.amazonaws.com',
     host: 'dynamodb.us-east-1-fake.amazonaws.com',
     port: 443,
     region: 'us-east-1-fake',
     retryable: true,
     time: 2020-08-12T10:18:08.321Z },
  time: 2020-08-12T10:18:08.321Z }
Result:
null
Finished execution.

I then did more research and came across this thread about inaccessible-dynamodb-host-when-running-amplify-mock which I followed and tried implementing to but to no avail. Any help on this would be very much appreciated.

PS: It is worth mentioning that I was able to successfully query for this data through the Appsync console, which led me to strongly believe the problem lies in the function itself.

Answer 1

After doing more research and asking around, I finally made sense of the answer that was provided to me on github that

When running mock on a function which has access to a dynamodb table generated by API. It will populate the env with fake values. If you would like to mock your lambda function against your deployed dynamodb table you can edit the values in the sdk client so it can make the call accurately.

In summary, if you are running things locally, then you wouldn't have access to your backend variables which you might try mocking. I hope this helps someone. Thanks!