Set up a Virtual Environment for Developing Global Applications

This page guides you through setting up a virtual environment for developing and debugging a global application. It is the third section of the Develop and Deploy a Global Application tutorial. In this section, you will set up a demo CockroachDB cluster, initialize the database, and set up a virtual development environment.

Before you begin

1. Complete the previous sections of the tutorial, ending with Create a Multi-Region Database Schema.

2. On your local machine:

   • Install CockroachDB.
   • Install Python 3 and Pipenv if necessary.
   • Clone the movr-flask repository. We'll reference the source code in this repository throughout the tutorial.

Set up a demo multi-region CockroachDB cluster

For debugging and development purposes, you can use the cockroach demo command. This command starts up a secure, nine-node demo cluster.

1. To set up the demo multi-region cluster, run cockroach demo, with the --nodes and --demo-locality flags. The localities specified below assume GCP region names.

   cockroach demo \
     --nodes=9 \
     --demo-locality=region=gcp-us-east1:region=gcp-us-east1:region=gcp-us-east1:\
     region=gcp-us-west1:region=gcp-us-west1:region=gcp-us-west1:\
     region=gcp-europe-west1:\
     region=gcp-europe-west1:region=gcp-europe-west1 \
     --empty
   

   Keep this terminal window open. Closing it will shut down the demo cluster.

2. In a new terminal, load the dbinit.sql script to the demo database. This file contains the movr database schema that we covered in Create a Multi-Region Database Schema.

   cockroach sql \
     --url='postgres://demo:<demo_password>@127.0.0.1:26257?sslmode=require' \
     -f dbinit.sql
   

3. Verify that the database schema loaded:

   > SHOW TABLES;
   

     table_name
   +------------+
     rides
     users
     vehicles
   (3 rows)
   

Set up a virtual development environment

For debugging, use pipenv, a tool that manages dependencies with pip and creates virtual environments with virtualenv.

1. Initialize the project's virtual environment:

   pipenv
   

   pipenv creates a Pipfile in the current directory, with the requirements needed for the app.

2. Install the packages listed in the Pipfile:

   pipenv install
   

3. Activate the virtual environment:

   pipenv shell
   

   From this shell, you can run any Python 3 application with the required dependencies that you listed in the Pipfile, and the environment variables that you listed in the .env file. You can exit the shell subprocess at any time with a simple exit command.

4. To test out the application, you can run the server file:

   python server.py
   

   To run Python commands within the virtual environment, you do not need to add 3 to the end of the command. For example, running python3 server.py instead of the above command results in an error.

5. Navigate to the application's test URL, which defaults to http://127.0.0.1:5000/.

Next steps

Now that you've set up a development environment, you can learn about developing and debugging the application.

See also

• movr-flask on GitHub
• cockroach demo