AWS-Lambda I get an error message “ MissingRequiredParameter: Missing required key 'Data' in params” but have no 'Data' parameter called

Question

I am trying to use AWS-Lambda to post data throught AWS-api gateway onto a client-side web-page but I am stuck on the above error message. When run the function run the database is displayed but then gets stuck on the error message. The three sets of code pasted bellow is what I'm using. If you can help let me know also if you need more info let me know

database.js[
let AWS = require("aws-sdk");

//Create new DocumentClient
let docClient = new AWS.DynamoDB.DocumentClient();

//Returns all of the connection IDs
module.exports.getConnectionIds = async() => {
    let params = {
        TableName: "WebSocketClients"
    };
    return docClient.scan(params).promise();
};


module.exports.getCNYData = async() => {
    let params = {
        TableName: "Currency",
        Limit: 100,
        ScanIndexForward: true,
        IndexName: "Currency_Name-Date-index",
        KeyConditionExpression: "Currency_Name = :Currency",

        ExpressionAttributeValues: {
            ":Currency": "CNY",
        }

    };
    return docClient.query(params).promise();
};

module.exports.getGBXData = async() => {
    let params = {
        TableName: "Currency",
        Limit: 100,
        ScanIndexForward: false,
        IndexName: "Currency_Name-Date-index",
        KeyConditionExpression: "Currency_Name = :Currency",
        ExpressionAttributeValues: {
            ":Currency": "GBX",
        }
    };
    return docClient.query(params).promise();
};

module.exports.getSARData = async() => {
    let params = {
        TableName: "Currency",
        Limit: 100,
        ScanIndexForward: false,
        IndexName: "Currency_Name-Date-index",
        KeyConditionExpression: "Currency_Name = :Currency",
        ExpressionAttributeValues: {
            ":Currency": "SAR",
        }
    };
    return docClient.query(params).promise();
};

module.exports.getUSDData = async() => {
    let params = {
        TableName: "Currency",
        Limit: 100,
        ScanIndexForward: false,
        IndexName: "Currency_Name-Date-index",
        KeyConditionExpression: "Currency_Name = :Currency",
        ExpressionAttributeValues: {
            ":Currency": "USD",
        }
    };
    return docClient.query(params).promise();
};

module.exports.getPositiveSentimentData = async() => {
    let params = {
        TableName: "Sentiment",
        Limit: 100,
        ScanIndexForward: false,
        IndexName: "Sentiment-Id-index",
        KeyConditionExpression: "Sentiment = :sentiment",
        ExpressionAttributeValues: {
            ":sentiment": "POSITIVE",
        }
    };
    return docClient.query(params).promise();
};

module.exports.getNegativeSentimentData = async() => {
    let params = {
        TableName: "Sentiment",
        Limit: 100,
        ScanIndexForward: false,
        IndexName: "Sentiment-Id-index",
        KeyConditionExpression: "Sentiment = :sentiment",
        ExpressionAttributeValues: {
                    ":sentiment": "NEGATIVE",
        }
    };
    return docClient.query(params).promise();
};

module.exports.getData = async() => {
    let pSentiment = await module.exports.getPositiveSentimentData();
    let nSentiment = await module.exports.getNegativeSentimentData();
    let SAR = await module.exports.getSARData();
    let CNY = await module.exports.getCNYData();
    let USD = await module.exports.getUSDData();
    let GBX = await module.exports.getGBXData();
    let data = {
        positive: pSentiment,
        negative: nSentiment,
        CNY: CNY,
        GBX: GBX,
        SAR: SAR,
        USD: USD,
    };
    return data;
};

//Deletes the specified connection ID
module.exports.deleteConnectionId = async(connectionId) => {
    console.log("Deleting connection Id: " + connectionId);

    let params = {
        TableName: "WebSocketClients",
        Key: {
            ConnectionId: connectionId
        }
    };
    return docClient.delete(params).promise();
};
]

websocket.js[
let AWS = require("aws-sdk");

// Add ApiGatewayManagementApi to the AWS namespace
require('aws-sdk/clients/apigatewaymanagementapi');

//Import functions for database
let db = require('database');

module.exports.getSendMessagePromises = async(message, domainName, stage) => {
    //Get connection IDs of clients 
    let clientIdArray = (await db.getConnectionIds()).Items;
    console.log("\nClient IDs:\n" + JSON.stringify(clientIdArray));

    //Create API Gateway management class.
    const apigwManagementApi = new AWS.ApiGatewayManagementApi({
        apiVersion: '2018-11-29',
        endpoint: domainName + '/' + stage
    });

    //Try to send message to connected clients
    let msgPromiseArray = clientIdArray.map(async item => {
        try {

            console.log("Sending message '" + message + "' to: " + item.ConnectionId);



            //Create parameters for API Gateway

            let apiMsg = {

                ConnectionId: item.ConnectionId,

                Data: JSON.stringify(await db.getData)

            };



            //Wait for API Gateway to execute and log result

            await apigwManagementApi.postToConnection(apiMsg).promise();

            console.log("Message '" + message + "' sent to: " + item.ConnectionId);

        }

        catch (err) {

            console.log("Failed to send message to: " + item.ConnectionId);



            //Delete connection ID from database

            if (err.statusCode == 410) {

                try {

                    await db.deleteConnectionId(item.ConnectionId);

                }

                catch (err) {

                    console.log("ERROR deleting connectionId: " + JSON.stringify(err));

                    throw err;

                }

            }

            else {

                console.log("UNKNOWN ERROR: " + JSON.stringify(err));

                throw err;

            }

        }

    });
    return msgPromiseArray;
};

]


index.js[
//Import external library with websocket functions
let ws = require("websocket");
let db = require("database");

//Hard coded domain name and stage - use when pushing messages from server to client
let domainName = "*********";
let stage = "dev";

exports.handler = async (event) => {
    try {
        //Get Message from event
        const msg = JSON.stringify(await db.getData(), function(key, value){
            if (typeof value === "bigint") {
                return value.toString();
            } else {
                return value;
            }
        });


        //Allocate domain name and stage dynamically
        //domainName = event.requestContext.domainName;
        //stage = event.requestContext.stage;
        console.log("Domain: " + domainName + " stage: " + stage);

        //Get promises message to connected clients
        let sendMsgPromises = await ws.getSendMessagePromises(msg, domainName, stage); 

        //Execute promises
        await Promise.all(sendMsgPromises);
    }
    catch(err){
        return { statusCode: 500, body: "Error: " + (err)};
    }

    //Success
    return { statusCode: 200, body: "Data sent successfully." };
};
]

Edit: For the two Dynamodb tables: Name:Currency Primary Partition Key: Date(String), Primary Sort Key: Currency_Name(String), Field: Price(BigInt), Index: Currency_Name-Date-index.

Second table: Name: Sentiment Primary Partition Key: Id(Number), Primary Sort Key: Text(String), Field: Sentiment(string), Index: Sentiment-Id-index.

Error Message:

Response:
{
  "statusCode": 500,
  "body": "Error: MissingRequiredParameter: Missing required key 'Data' in params"
}

Request ID:
"e2fee9cd-4af1-489e-8aac-98e16139dd4d"

Function Logs:
019-10-23"},{"Currency_Name":"USD","Price":"48.50","Date":"2019-10-22"},{"Currency_Name":"USD","Price":"47.32","Date":"2019-10-21"},{"Currency_Name":"USD","Price":"47.48","Date":"2019-10-18"},{"Currency_Name":"USD","Price":"48.69","Date":"2019-10-17"},{"Currency_Name":"USD","Price":"48.25","Date":"2019-10-16"},{"Currency_Name":"USD","Price":"47.00","Date":"2019-10-15"},{"Currency_Name":"USD","Price":"46.49","Date":"2019-10-14"},{"Currency_Name":"USD","Price":"46.10","Date":"2019-10-11"},{"Currency_Name":"USD","Price":"43.81","Date":"2019-10-10"},{"Currency_Name":"USD","Price":"43.65","Date":"2019-10-09"},{"Currency_Name":"USD","Price":"44.10","Date":"2019-10-08"},{"Currency_Name":"USD","Price":"45.66","Date":"2019-10-07"},{"Currency_Name":"USD","Price":"44.91","Date":"2019-10-04"},{"Currency_Name":"USD","Price":"42.70","Date":"2019-10-03"},{"Currency_Name":"USD","Price":"43.50","Date":"2019-10-02"},{"Currency_Name":"USD","Price":"45.50","Date":"2019-10-01"},{"Currency_Name":"USD","Price":"44.62","Date":"2019-09-30"},{"Currency_Name":"USD","Price":"45.67","Date":"2019-09-27"},{"Currency_Name":"USD","Price":"46.22","Date":"2019-09-26"},{"Currency_Name":"USD","Price":"44.42","Date":"2019-09-25"},{"Currency_Name":"USD","Price":"47.33","Date":"2019-09-24"},{"Currency_Name":"USD","Price":"45.83","Date":"2019-09-23"},{"Currency_Name":"USD","Price":"47.89","Date":"2019-09-20"},{"Currency_Name":"USD","Price":"48.23","Date":"2019-09-19"},{"Currency_Name":"USD","Price":"48.04","Date":"2019-09-18"},{"Currency_Name":"USD","Price":"47.77","Date":"2019-09-17"},{"Currency_Name":"USD","Price":"47.53","Date":"2019-09-16"},{"Currency_Name":"USD","Price":"49.21","Date":"2019-09-13"},{"Currency_Name":"USD","Price":"49.50","Date":"2019-09-12"},{"Currency_Name":"USD","Price":"47.74","Date":"2019-09-11"},{"Currency_Name":"USD","Price":"46.75","Date":"2019-09-10"},{"Currency_Name":"USD","Price":"47.19","Date":"2019-09-09"},{"Currency_Name":"USD","Price":"46.65","Date":"2019-09-06"},{"Currency_Name":"USD","Price":"45.39","Date":"2019-09-05"},{"Currency_Name":"USD","Price":"42.48","Date":"2019-09-04"},{"Currency_Name":"USD","Price":"41.79","Date":"2019-09-03"},{"Currency_Name":"USD","Price":"42.87","Date":"2019-08-30"},{"Currency_Name":"USD","Price":"41.63","Date":"2019-08-29"},{"Currency_Name":"USD","Price":"39.61","Date":"2019-08-28"},{"Currency_Name":"USD","Price":"40.72","Date":"2019-08-27"},{"Currency_Name":"USD","Price":"40.47","Date":"2019-08-26"},{"Currency_Name":"USD","Price":"42.07","Date":"2019-08-23"},{"Currency_Name":"USD","Price":"43.45","Date":"2019-08-22"},{"Currency_Name":"USD","Price":"43.25","Date":"2019-08-21"},{"Currency_Name":"USD","Price":"42.95","Date":"2019-08-20"},{"Currency_Name":"USD","Price":"43.53","Date":"2019-08-19"},{"Currency_Name":"USD","Price":"40.19","Date":"2019-08-16"},{"Currency_Name":"USD","Price":"39.77","Date":"2019-08-15"},{"Currency_Name":"USD","Price":"40.90","Date":"2019-08-14"},{"Currency_Name":"USD","Price":"39.55","Date":"2019-08-13"},{"Currency_Name":"USD","Price":"39.85","Date":"2019-08-12"},{"Currency_Name":"USD","Price":"41.25","Date":"2019-08-09"}],"Count":100,"ScannedCount":100,"LastEvaluatedKey":{"Currency_Name":"USD","Date":"2019-08-09"}}}' to: KYSQycomoAMCJdA=
2020-04-03T14:09:16.092Z    e2fee9cd-4af1-489e-8aac-98e16139dd4d    INFO    Sending message '{"positive":{"Items":[{"Sentiment":"POSITIVE","Id":"1238393433607131100n","Text":"\"Nice, didn’t get boated 🤗 *********""}],"Count":1,"ScannedCount":1},"negative":{"Items":[{"Sentiment":"NEGATIVE","Id":"1238395098741825500n","Text":"\"RT @keira_churchill: GBP plummets against the Euro because coronavirus. GBP plummets against the USD because coronavirus. GBP plummets agai…\""},{"Sentiment":"NEGATIVE","Id":"1238392914813816800n","Text":"\"@keira_churchill GBP was already weakened by Brexit uncertainty/risks. Add CoronavEND RequestId: e2fee9cd-4af1-489e-8aac-98e16139dd4d

Answer 1

postToConnection requires Data attribute. In your case it will be undefined since JSON.stringify will return undefined when you try to stringify a function. This happens because you forgot the parenthesis when calling getData function.

Replace:

let apiMsg = {
  ConnectionId: item.ConnectionId,
  Data: JSON.stringify(await db.getData) // This results in undefined.
};

With:

let apiMsg = {
  ConnectionId: item.ConnectionId,
  Data: JSON.stringify(await db.getData()) // This works like you are expecting.
};