Malformed Lambda proxy response with AWS Lambda and API Gateway NodeJs

Question

I'm using API Gateway and AWS Lambda to exchange with another AWS Lambda function.

I'm supposed to send a response after an initial request to insert data, whether it's a success or a failure. I'm using a specific route with API Gateway.

Here's the structure :

Now I keep getting 502 Malformed Lambda proxy response and this is in my API Test logs :

Tue Sep 22 06:56:10 UTC 2020 : Endpoint response headers: {Date=Tue, 22 Sep 2020 06:56:10 GMT, Content-Type=application/json, Content-Length=4, Connection=keep-alive, x-amzn-RequestId=xxxxxxxx, x-amzn-Remapped-Content-Length=0, X-Amz-Executed-Version=$LATEST, X-Amzn-Trace-Id=xxxxxxx}
Tue Sep 22 06:56:10 UTC 2020 : Endpoint response body before transformations: null
Tue Sep 22 06:56:10 UTC 2020 : Execution failed due to configuration error: Malformed Lambda proxy response
Tue Sep 22 06:56:10 UTC 2020 : Method completed with status: 502

The problem is that I am returning a real response. As I said before, I'm using API Gateway with lambda-api a package that handles API Gateway routing like Express and this is what I'm doing :

api.post('/database-manager/create-request', async (lambdaRequest, lambdaResponse, callback) => {
    await provideConnectionInfo()
    let connection = mysql.createConnection({
            host: mySQLHost,
            user: mySQLUser,
            password: mySQLPassword,
            database: mySQLDatabase
        }
    )
    requestNb = lambdaRequest.headers["request-id"]
    pipelineId = lambdaRequest.headers["pipeline-id"]

    connection.connect(function (err) {
            if (err) throw err
            let query = "INSERT INTO ec2_request(request_id, pipeline_id) VALUES (?,?)"
            connection.query(query,[requestNb,pipelineId], function (err, result) {
                    if (err) {
                        connection.end()
                        console.log("insertion did not work : " + err)
                        let response = {
                            "statusCode": 404,
                            "headers": {},
                            "isBase64Encoded": false,
                            "body": JSON.stringify({message: "Record not inserted"})
                        }
                         return response
                        )

                    } else {
                        connection.end()
                        console.log("1 record inserted")
                        let response = {
                            "statusCode": 200,
                            "headers": {},
                            "isBase64Encoded": false,
                            "body": JSON.stringify({message: "tired of this bs"})
                        }
                        return response

                    }
                }
            )
        }
    )

})

And the worst part is my logs that don't show anything wrong :

1600758637213   START RequestId: f804577b-c0a2-4d11-8822-52363fa41c7d Version: $LATEST
1600758639189   2020-09-22T07:10:39.188Z    f804577b-c0a2-4d11-8822-52363fa41c7d    INFO    1 record inserted
1600758639348   END RequestId: f804577b-c0a2-4d11-8822-52363fa41c7d
1600758639348   REPORT RequestId: f804577b-c0a2-4d11-8822-52363fa41c7d  Duration: 2134.45 ms    Billed Duration: 2200 ms    Memory Size: 128 MB Max Memory Used: 94 MB  Init Duration: 555.23 ms

If someone sees where I might've made a mistake, I'll buy them a donut.

Wondering it's the status that's wrong...

Thanks a lot in advance,

Fares

Assael Azran · Accepted Answer · 2020-09-22 08:27:57Z

You are using callback function inside async without waiting.

Here are a couple of options

Remove async from api.post('/database-manager/create-request', async (lambdaRequest, lambdaResponse, callback) => {.

Keep async and wrap query function as Promise and use await

api.post('/database-manager/create-request', async (lambdaRequest, lambdaResponse, callback) => {
 await provideConnectionInfo()
 let connection = mysql.createConnection({
         host: mySQLHost,
         user: mySQLUser,
         password: mySQLPassword,
         database: mySQLDatabase
     }
 )
 requestNb = lambdaRequest.headers["request-id"]
 pipelineId = lambdaRequest.headers["pipeline-id"]


 const res = await new Promise(function(resolve, reject) {
     connection.connect();
     let query = "INSERT INTO ec2_request(request_id, pipeline_id) VALUES (?,?)"

     connection.query(query,[requestNb,pipelineId], function (err, result) {
         if (err) {
             connection.end()
             console.log("insertion did not work : " + err)
             let response = {
                 "statusCode": 404,
                 "headers": {},
                 "isBase64Encoded": false,
                 "body": JSON.stringify({message: "Record not inserted"})
             }
             reject(response)

         } else {
             connection.end()
             console.log("1 record inserted")
             let response = {
                 "statusCode": 200,
                 "headers": {},
                 "isBase64Encoded": false,
                 "body": JSON.stringify({message: "tired of this bs"})
             }
             resolve(response)

         }
     })
 });

 return res;   
})

Note: Code has not been tested.

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