代码在本地工作但不在 AWS 上工作 Lambda

Question

I have written a small piece of code in NodeJS to update a MongoDB collection. The code works fine when I run it on my local machine. But once deployed to AWS it doesn't

exports.handler = async (event) => {
  console.log("I am here");

  const { MongoClient } = require("mongodb");
  const uri =
    "xxxxxxx";
  const client = new MongoClient(uri);

  async function run() {
    console.log("Inside the function");
    try {
      const database = client.db("mydb");
      const movies = database.collection("TACountryMapping");
      // create a filter for a movie to update
      var filter = { Key: "Value" };
      // this option instructs the method to create a document if no documents match the filter
      const options = { upsert: true };
      // create a document that sets the plot of the movie
      const updateDoc = {
        $set: { Key: "updatedValue", address: "Canyon 123" },
      };
      const result = await movies.updateOne(filter, updateDoc, options);

      console.log(result);
      console.log(
        `${result.matchedCount} document(s) matched the filter, updated ${result.modifiedCount} document(s)`
      );
    } finally {
      await client.close();
    }
  }

  run().catch(console.dir);
  return 0;
};

//exports.handler();

The result object just doesn't seem to be getting created in lambda.

Following are the logs when running the code from my local machine:

I am here
Inside the function
{
  acknowledged: true,
  modifiedCount: 1,
  upsertedId: null,
  upsertedCount: 0,
  matchedCount: 1
}
1 document(s) matched the filter, updated 1 document(s)

And when run from Lambda, the following are the logs:

START RequestId: 3cdc0764-7238-4218-bdf2-954556f10c77 Version: $LATEST
2022-12-04T03:18:56.383Z 3cdc0764-7238-4218-bdf2-954556f10c77 INFO  I am here
2022-12-04T03:18:56.505Z 3cdc0764-7238-4218-bdf2-954556f10c77 INFO  Inside the function
END RequestId: 3cdc0764-7238-4218-bdf2-954556f10c77
REPORT RequestId: 3cdc0764-7238-4218-bdf2-954556f10c77  Duration: 478.33 ms Billed Duration: 479 ms Memory Size: 128 MB Max Memory Used: 78 MB  

I have tried to remove the await from await movies.updateOne(filter, updateDoc, options); , but that just skips the code entirely and doesn't work

Answer 1

I think it's because you are awaiting for the movies.updateOne statement but not awaiting for the entire run() function to complete before ending the execution of the lambda.

When a Lambda function doesn't wait for the event loop to be empty and a container is re-used, the event loop will be "paused" until the next invocation occurs.

Try refactoring your code to what is shown below. Note the use of await run() statement that will make sure the entire code has completed execution before ending execution.

exports.handler = async (event) => {
  console.log("I am here");

  const { MongoClient } = require("mongodb");
  const uri ="xxxxxxx";
  const client = new MongoClient(uri);

  await run();
  return 0;
};

async function run() {
  console.log("Inside the function");
  try {
    const database = client.db("mydb");
    const movies = database.collection("TACountryMapping");
    // create a filter for a movie to update
    var filter = { Key: "Value" };
    // this option instructs the method to create a document if no documents match the filter
    const options = { upsert: true };
    // create a document that sets the plot of the movie
    const updateDoc = {
      $set: { Key: "updatedValue", address: "Canyon 123" },
    };
    const result = await movies.updateOne(filter, updateDoc, options);

    console.log(result);
    console.log(
      `${result.matchedCount} document(s) matched the filter, updated ${result.modifiedCount} document(s)`
    );
  }
  catch(e){
    console.error(e);
  }
  finally {
    await client.close();
  }
}

PS: I'm assuming your connection to the database is working fine here and no connection errors were noticed in AWS Cloudwatch .