Quickstart: Build a Python app using Azure Cosmos DB's API for MongoDB

In this quickstart, you use an Azure Cosmos DB for Mongo DB API account or the Azure Cosmos DB Emulator to run a Python Flask To-Do web app cloned from GitHub. Azure Cosmos DB is a multi-model database service that lets you quickly create and query document, table, key-value, and graph databases with global distribution and horizontal scale capabilities.

Prerequisites

Clone the sample application

Now let's clone a Flask-MongoDB app from GitHub, set the connection string, and run it. You see how easy it is to work with data programmatically.

  1. Open a command prompt, create a new folder named git-samples, then close the command prompt.

    md "C:\git-samples"
    
  2. Open a git terminal window, such as git bash, and use the cd command to change to the new folder to install the sample app.

    cd "C:\git-samples"
    
  3. Run the following command to clone the sample repository. This command creates a copy of the sample app on your computer.

    git clone https://github.com/Azure-Samples/CosmosDB-Flask-Mongo-Sample.git
    
  4. Run the following command to install the python modules.

    pip install -r .\requirements.txt
    
  5. Open the folder in Visual Studio Code.

Review the code

This step is optional. If you're interested in learning how the database resources are created in the code, you can review the following snippets. Otherwise, you can skip ahead to Run the web app.

The following snippets are all taken from the app.py file and uses the connection string for the local Azure Cosmos DB Emulator. The password needs to be split up as seen below to accommodate for the forward slashes that cannot be parsed otherwise.

  • Initialize the MongoDB client, retrieve the database, and authenticate.

    client = MongoClient("mongodb://127.0.0.1:10250/?ssl=true") #host uri
    db = client.test    #Select the database
    db.authenticate(name="localhost",password='C2y6yDjf5' + r'/R' + '+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw' + r'/Jw==')
    
  • Retrieve the collection or create it if it does not already exist.

    todos = db.todo #Select the collection
    
  • Create the app

    app = Flask(__name__)
    title = "TODO with Flask"
    heading = "ToDo Reminder"
    

Run the web app

  1. Make sure the Azure Cosmos DB Emulator is running.

  2. Open a terminal window and cd to the directory that the app is saved in.

  3. Then set the environment variable for the Flask app with set FLASK_APP=app.py, $env:FLASK_APP = app.py for PowerShell editors, or export FLASK_APP=app.py if you are using a Mac.

  4. Run the app with flask run and browse to http://127.0.0.1:5000/.

  5. Add and remove tasks and see them added and changed in the collection.

Create a database account

If you want to test the code against a live Azure Cosmos DB account, go to the Azure portal to create an account.

  1. In a new browser window, sign in to the Azure portal.

  2. In the left menu, select Create a resource.

    Create a resource in the Azure portal

  3. On the New page, select Databases > Azure Cosmos DB.

    The Azure portal Databases pane

  4. On the Create Azure Cosmos DB Account page, enter the settings for the new Azure Cosmos DB account.

    Setting Value Description
    Subscription Your subscription Select the Azure subscription that you want to use for this Azure Cosmos DB account.
    Resource Group Create new

    Then enter the same name as Account Name
    Select Create new. Then enter a new resource group name for your account. For simplicity, use the same name as your Azure Cosmos DB account name.
    Account Name Enter a unique name Enter a unique name to identify your Azure Cosmos DB account. Your account URI will be mongo.cosmos.azure.com appended to your unique account name.

    The account name can use only lowercase letters, numbers, and hyphens (-), and must be between 3 and 31 characters long.
    API Azure Cosmos DB for Mongo DB API The API determines the type of account to create. Azure Cosmos DB provides five APIs: Core (SQL) for document databases, Gremlin for graph databases, Azure Cosmos DB for Mongo DB API for document databases, Azure Table, and Cassandra. Currently, you must create a separate account for each API.

    Select Azure Cosmos DB for Mongo DB API because in this quickstart you are creating a collection that works with MongoDB.

    Learn more about Azure Cosmos DB for MongoDB API.
    Location Select the region closest to your users Select a geographic location to host your Azure Cosmos DB account. Use the location that's closest to your users to give them the fastest access to the data.

    Select Review+Create. You can skip the Network and Tags section.

    The new account page for Azure Cosmos DB

  5. The account creation takes a few minutes. Wait for the portal to display the Congratulations! Your Azure Cosmos DB for Mongo DB API account is ready page.

    The Azure portal Notifications pane

Update your connection string

To test the code against the live Azure Cosmos DB account, get your connection string information. Then copy it into the app.

  1. In your Azure Cosmos DB account in the Azure portal, in the left navigation select Connection String, and then select Read-write Keys. You'll use the copy buttons on the right side of the screen to copy the username, connection string, and password.

  2. Open the app.py file in the root directory.

  3. Copy your username value from the portal (using the copy button) and make it the value of the name in your app.py file.

  4. Then copy your connection string value from the portal and make it the value of the MongoClient in your app.py file.

  5. Finally copy your password value from the portal and make it the value of the password in your app.py file.

You've now updated your app with all the info it needs to communicate with Azure Cosmos DB. You can run it the same way as before.

Deploy to Azure

To deploy this app, you can create a new web app in Azure and enable continuous deployment with a fork of this GitHub repo. Follow this tutorial to set up continuous deployment with GitHub in Azure.

When deploying to Azure, you should remove your application keys and make sure the section below is not commented out:

    client = MongoClient(os.getenv("MONGOURL"))
    db = client.test    #Select the database
    db.authenticate(name=os.getenv("MONGO_USERNAME"),password=os.getenv("MONGO_PASSWORD"))

You then need to add your MONGOURL, MONGO_PASSWORD, and MONGO_USERNAME to the application settings. You can follow this tutorial to learn more about Application Settings in Azure Web Apps.

If you don't want to create a fork of this repo, you can also select the Deploy to Azure button below. You should then go into Azure and set up the application settings with your Azure Cosmos DB account info.

Click to Deploy to Azure

Note

If you plan to store your code in GitHub or other source control options, please be sure to remove your connection strings from the code. They can be set with application settings for the web app instead.

Review SLAs in the Azure portal

The Azure portal monitors your Cosmos DB account throughput, storage, availability, latency, and consistency. Charts for metrics associated with an Azure Cosmos DB Service Level Agreement (SLA) show the SLA value compared to actual performance. This suite of metrics makes monitoring your SLAs transparent.

To review metrics and SLAs:

  1. Select Metrics in your Cosmos DB account's navigation menu.

  2. Select a tab such as Latency, and select a timeframe on the right. Compare the Actual and SLA lines on the charts.

    Azure Cosmos DB metrics suite

  3. Review the metrics on the other tabs.

Clean up resources

When you're done with your app and Azure Cosmos DB account, you can delete the Azure resources you created so you don't incur more charges. To delete the resources:

  1. In the Azure portal Search bar, search for and select Resource groups.

  2. From the list, select the resource group you created for this quickstart.

    Select the resource group to delete

  3. On the resource group Overview page, select Delete resource group.

    Delete the resource group

  4. In the next window, enter the name of the resource group to delete, and then select Delete.

Next steps

In this quickstart, you learned how to create an Azure Cosmos DB for Mongo DB API account, and use the Azure Cosmos DB Emulator to run a Python Flask To-Do web app cloned from GitHub. You can now import additional data to your Azure Cosmos DB account.