Deploying QuickBooks Data Fetcher

This week I returned back to my QuickBooks project. My goal was to make my application "showcase-able", so that anyone could easily access and use it if they were interested in seeing my work.

The first step to doing this was deploying my app on the web for anyone to access. Up until then, I had been testing the application locally. After some research, I settled on using Heroku for deployment. While I likely could have used any hosting service without any issues, I decided on Heroku because it was best for simple apps such as mine. Unfortunately, it wasn't as simple as clicking "Deploy" and being done with it. Naturally, I ran into issues.

Based on my experience this week, deploying a web application on Heroku consists of:

1. Connecting your repository to Heroku, either using GitHub or Heroku CLI
2. Having Heroku "build" and deploy your application
3. Setting up a web dyno that will start a server for the application
4. Configuring environment variables, if needed

Making an account and connecting my repository with GitHub was easy enough, and while Heroku initially was unable to build my application fixing this was as simple as adding a requirements.txt file to my app. Next, I learned that without creating a web dyno the app would crash upon deployment. Finally, once my app was up and running, I ran into one final issue.

My intuit authorization client was failing to fetch data, giving the error: "Missing access token or realm ID", which are both required in order to access the API. This was confusing because this didn't happen when I ran my application locally. However, after doing some digging, I realized it was because variables don't always persist between client requests when the app is deployed on Heroku. So, while my authorization client was able to get the access token and realm ID in my callback function:

@app.route('/callback')
def callback():
    # Handle callback and exchange code for tokens
    try:
        auth_code = request.args.get('code')
        realm_id = request.args.get('realmId')

        if not auth_code or not realm_id:
            return "Error: Missing auth_code or realm ID"

        auth_client.get_bearer_token(auth_code, realm_id=realm_id)


        return render_template('authenticate.html')

it would fail to retrieve the access token and realm ID in the query function:

@app.route('/nl-query', methods=['GET', 'POST'])
def query_quickbooks():
    try:

        access_token = auth_client.access_token
        realm_id = auth_client.realm_id

        if not access_token or not realm_id:
            return "Error: Missing access token or realm ID. Please authenticate first."

Using print statements and Heroku's logs I was able to identify this as the problem. My current workaround is to store the access token and realm ID as environment variables, so they are accessible to the entire application. If I were to design this application to work at scale for better security and persistence, however, I would want to store these in a database. After fixing this issue my app was up and running like I wanted it to.

The last thing I wanted to add to my application was a "demo mode", so that anyone can test it out even if they don't have a QuickBooks account. Doing this was relatively simple. I downloaded the json formatted data from the sandbox company I had been using to test the app, and allowed the users to bypass the login portion and query from this data instead of their own. Finally, I allowed users to download the .xls files for the data they are querying from in demo mode, so they can see how accurate the query results are.

I'm happy that my project is now accessible to anyone interested in testing it. While it is relatively simple, working on it taught me a lot and I can easily come back to further develop it.