AWS Lambda Dynamo update does not update the item

Question

There is a DynamoDB table called Portal. From a Lambda function written in node I want to update the status and ts fields of an item (by calling a signalJobStart function) and wait for the async update function to finish with a promise before continuing. On some reason no update is happening, however no errors are raised during the operation. There is no error in the logs, and I can see the "FINISHED" log message in the logs.

Why there is no change made on the item in the table? Why I cannot see neither the error nor the success message in the logs?

(I also tried without the promise, with the same outcome. The table item does not get updated - even asynchronously.)

Here is the code from the Lambda:

const AWS = require('aws-sdk');
const docClient = new AWS.DynamoDB.DocumentClient({region: 'eu-west-1'});

module.exports = {
signalJobStart: function(accountId, jobId) {
    console.log("Signaling job start for account %s and job %s", accountId, jobId);

    let table = "Portal";

    let params = {
        TableName: table,
        Key:{
            "accountid": accountId,
            "entity": jobId
        },
        UpdateExpression: "SET status = :s, ts = :t",
        ExpressionAttributeValues:{
            ":s": "running",
            ":t": Date.now()
        },
        ReturnValues:"UPDATED_NEW"
    };

    let updatePromise = docClient.update(params, function(err, data) {
        if (err) {
            console.error("Unable to update item. Error JSON:", JSON.stringify(err, null, 2));
        } else {
            console.log("UpdateItem succeeded:", JSON.stringify(data, null, 2));
        }
    }).promise();

    updatePromise.then(function(data) {
      console.log('Success');
    }).catch(function(err) {
      console.log(err);
    });

    console.log("FINISHED");
}};

Answer 1

What helped in my case:

1. Do in async/await way:

   exports.handler = async (event) => {
   ...
   let _result = "";
   try {
      _result = await docClient.update(_updateParams).promise();
   } catch(ex){
      _result = ex;
   }
   ..
   

2. Make sure the field I was writing to is not a reserved word like in the following case ("data" is reserved word):

   {
   ..
   UpdateExpression: "set data = :newdata",
   ExpressionAttributeValues: {
   ":newdata": "blah"
   },
   ..
   

   To check this: rename column to, say, "data2" - it worked no problem.

3. Make sure you have permissions in "Execution Role" in IAM Console.

Answer 2

In your query status is reserve keywords and prohibited in dynamodb. So use ExpressionAttributeNames in Your query.

Also use new Promise for handle promise

Please check below its help you:

module.exports = {
  signalJobStart: function (accountId, jobId) {
    return new Promise(function (resolve, reject) {
      console.log("Signaling job start for account %s and job %s", accountId, jobId);

      let table = "Portal";

      let params = {
        TableName: table,
        Key: {
          "accountid": accountId,
          "entity": jobId
        },
        UpdateExpression: "SET #status = :s, ts = :t",
        ExpressionAttributeNames: {
          '#status': 'status'
        },
        ExpressionAttributeValues: {
          ":s": "running",
          ":t": Date.now()
        },
        ReturnValues: "UPDATED_NEW"
      };

      docClient.update(params, function (err, data) {
        if (err) {
          console.error("Unable to update item. Error JSON:", JSON.stringify(err, null, 2));
          reject(err)
        } else {
          console.log("UpdateItem succeeded:", JSON.stringify(data, null, 2));
          resolve({ message: 'sucsss', data: data })
        }
      })
    });
  }
};

Note: Please also confirm accountid and entity are both Key in you DB.

Answer 3

I think you could

docClient.update(params).promise()

and then continue to use the .then(...) statements flow to make it work. Personally, I think the error handler syntax (for update) might not yield you a promise.

Let me know if that does not works.