Category Archives: node.js

this.query is not a function – error when using promisify with mysql

Hi everyone,

I ran into the following error while attempting to promisify my node.js mysql transactions:

TypeError: this.query is not a function
    at rollback (/var/task/node_modules/mysql/lib/Connection.js:179:15)
    at rollback (internal/util.js:230:26)

This took a while to track down but it turns out that I needed to bind the connection after promisifying the function. Instead of:


Add bind to the end of it:


Thanks to the following stackoverflow post for the insight:


Upload an Image to S3 Using Post and a Presigned Url

Hi everyone,

Today I’ve been converting my “PUT” upload to S3 to a “POST”. The main motivator for this was to restrict the file size of uploads using a signed policy. Unfortunately this was a pretty tedious process and the error responses from S3 were very vague. Thankfully it’s working now and here’s what I needed to do!

Here’s an excerpt from my nodejs lambda function that generates the presigned url:

/* Creates a pre-signed upload url and then stores a reference in a table */
exports.createUploadUrl = async params => {

    var { databaseHandler, bucketHandler } = params;

    // Create id for upload
    var uploadId = uuidv4();

    // Retrieve pre-signed url
    var bucketDataPromise = createPresignedPostPromise({
        Bucket: process.env.BUCKET_UPLOADS,
        Expires: 60 * 60,
        Conditions: [            
            ["content-length-range", 0, 300000], // 300kb
            [ "eq", "$key", uploadId],
            [ "eq", "$Content-Type", 'image/jpeg' ],

    // var ddbData = await ddbDataPromise;
    var bucketData = await bucketDataPromise;

    // Wait for database handler to complete operation and then return
    return Helpers.generateResponse({
        data: {
            uploadData: bucketData,
            additionalFields: {
                key: uploadId,
                "Content-Type": 'image/jpeg',
        statusCode: 200

You can then retrieve the upload details using a request like the following (Python):

resp = requests.put("", data=open(path, 'rb'))

This will return a response similar to the following:

    "messages": [],
    "data": {
        "uploadUrl": {
            "url": "YOUR UPLOAD URL",
            "fields": {
                "bucket": "YOUR BUCKET",
                "X-Amz-Algorithm": "AWS4-HMAC-SHA256",
                "X-Amz-Credential": "XXX",
                "X-Amz-Date": "20190107T125044Z",
                "X-Amz-Security-Token": "SECURITY_TOKEN",
                "Policy": "YOUR BASE64 ENCODED POLICY",
                "X-Amz-Signature": "SIGNATURE"
        "uploadId": "UPLOAD_ID"

And once you have those details you can use them to upload the image:

# Attempt to retrieve upload url etc
json = resp.json()
data = json["data"]
uploadUrl = data["uploadData"]["url"]
uploadFields = data["uploadData"]["fields"]

    print("Uploading image...",end='')
    headers = {'Content-Type': 'multipart/form-data' }
    files = { 'file': open(path, 'rb')}
    resp =, data=uploadFields, files=files)

    # Only show content if there's an error
    if resp.status_code == 200:

except Exception as e:
    print("\r\nFailed to upload image.")
    print("Upload data:")

Hopefully that’s been able to help you out, but feel free to let me know in the comments below if you need more info!

Thanks to these links for the info:

4: /codebuild/output/tmp/ pip: not found – Node.js and CodeStar

Hi everyone,

I ran into the following CodeBuild error after upgrading my build environment from the default nodejs8.10 to nodejs10.14:

4: /codebuild/output/tmp/ pip: not found

This one was a little confusing, but thankfully fairly easy to fix. In your buildspec.yml file update the pip steps to reference pip3 instead of pip:

// Original
      # Install dependencies needed for running tests
      - npm install

      # Upgrade AWS CLI to the latest version
      - pip install --upgrade awscli
// Modified
      # Install dependencies needed for running tests
      - npm install

      # Upgrade AWS CLI to the latest version
      - pip3 install --upgrade awscli

Parsing DynamoDB Items – AWS Lambda with Node.js

Hi everyone,

A quick post on how to parse DynamoDB items into something more readable when using lambda with Node.js:



    CatBreedId: { S: '17acbc81-2b4a-462b-be87-bcc49580b1ae'},
    Name: { S: 'Cat #1'}



    "CatBreedId": "17acbc81-2b4a-462b-be87-bcc49580b1ae",
    "Name": "Cat #1"

Official doco is here:

Thanks to the following stackoverflow post for the info: