Question 195041 in Javascript Question posted in
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Javascript – AWS Lambda Node JS Promise Rejection

I’m having an issue with one of my AWS Lambda Node JS functions when I call the function from axios in my Next JS frontend. The first time the function is called, it is successful and returns correctly but when I call it again, it returns ‘Error: Runtime exited with error: exit status 128’ and ‘ERROR Unhandled Promise Rejection Runtime.UnhandledPromiseRejection’. When I call it again after a failed attempt, it runs successfully and returns correctly. Is there an issue with my code (below)? I’ve got context.callbackWaitsForEmptyEventLoop set to false but I can’t see why the function fails with rapid fire calls. Thanks in advance

const MongoClient = require("mongodb").MongoClient;
const ObjectId = require("mongodb").ObjectId;

const MONGODB_URI = process.env.MONGODB_URI;

let cachedDb = null;

async function connectToDatabase() {
  if (cachedDb) {
    return cachedDb;
  }

  const client = await MongoClient.connect(MONGODB_URI);

  const db = await client.db(process.env.MONGODB_NAME);

  cachedDb = db;
  return db;
}

exports.handler = async (event, context) => {
  console.log(event.queryStringParameters);
  console.log(event.body);
  let docType = event.queryStringParameters.docType;
  let docId = event.queryStringParameters.docId;
  const bodyData = JSON.parse(event.body);
  let fundId = event.queryStringParameters.fundId;

  context.callbackWaitsForEmptyEventLoop = false;

  const db = await connectToDatabase();

  try {
  const data = await db.collection(docType).findOneAndUpdate({_id : ObjectId(docId), "profile_subscription_documents.fund_id" : fundId},{
    $push: {"profile_subscription_documents.$[psd].profile_fund_subscription_documents": {...bodyData} }
  },
  {
    arrayFilters: [
      {
        "psd.fund_id": fundId
      }]
  },
  {
    returnDocument: "after"
  });
  
  console.log("Here", data);

  const response = {
    statusCode: 200,
        headers: {
            "Access-Control-Allow-Headers" : "*",
            "Access-Control-Allow-Origin": "http://localhost:3000/",
            "Access-Control-Allow-Methods": "*"
        },
    body: JSON.stringify(data),
  };

  return response;
  } catch (error) {
    console.error(error);
  }
  
};
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2

Answers


  1. Chosen as BEST ANSWER
    0

    Found the problem to this: the console.log("Here", data); line was returning undefined which I'm guessing meant the function wasn't completing properly. By trial and error I figured that it was the returnDocument: "after" which was causing the issue so I removed that part and now the 'ERROR Unhandled Promise Rejection Runtime.UnhandledPromiseRejection' error has gone and everything is working smoothly!


  2. 0

    The first thing that comes to mind is that the connections to the db are not being closed.

    I would add a finally statement closing the db connection like:

      ...
  return response;
  } catch (error) {
    console.error(error);
  } finally {
    db.close();
  }
  ...

    I got this suggestion from the MongoDB package docs: https://www.npmjs.com/package/mongodb

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