Use the local development server after runtimes reach end of support

You can't use the latest version of dev_appserver.py to locally run your applications for runtimes that reached end of support. To continue using an archived version of dev_appserver.py, follow the instructions in this guide.

You can use the local development server to simulate running your App Engine application in production, as well as using it to access App Engine legacy bundled services. The simulated environment enforces some sandbox restrictions, such as restricted system functions and runtime language module imports, but not others, like request timeouts or quotas.

The local development server also simulates the services provided by the libraries in the SDK for App Engine, including Datastore, Memcache, and Task Queues, by performing their tasks locally. When your application is running in the development server, you can still make remote API calls to the production infrastructure by using the Google API HTTP endpoints.

Before you begin

To download an archived version of devapp_server.py, follow these steps:

  1. From the archive, download the zipped folder that contains the dev_appserver.py server for runtimes that have reached the end of support.

  2. Extract the directory's contents to your local file system, such as to your /home directory. You can find dev_appserver.py in the google_appengine/ directory.

Set up the local development server

To run the local development server tool, you must set up the following:

  1. Verify that you have installed a Python 2 interpreter of version 2.7.12 or later.

  2. Set the DEVAPPSERVER_PYTHON environment variable in your shell to the path of your Python 2 interpreter.

  3. Locate the dev_appserver.py tool under the /google_appengine/ folder where you extract the downloaded archive, for example:

    DEVAPPSERVER_ROOT/google_appengine/dev_appserver.py
    

Run the local development server

After setting up the local development server and creating the app.yaml configuration file for your app, you can use the dev_appserver.py command to run your app locally.

To start the local development server:

  1. In the directory that contains your app.yaml configuration file, run the dev_appserver.py command.

    Specify the directory path to your app, for example:

       python2 DEVAPPSERVER_ROOT/google_appengine/dev_appserver.py --runtime_python_path=/usr/bin/python2 [PATH_TO_YOUR_APP]
    

    You can also set the argument to a comma-separated list of [RUNTIME_ID]=[PYTHON_INTERPRETER_PATH] pairs. For example:

       python2 DEVAPPSERVER_ROOT/google_appengine/dev_appserver.py --runtime_python_path="python27=/usr/bin/python2.7" [PATH_TO_YOUR_APP]
    

    To change the port, include the --port option:

       python2 DEVAPPSERVER_ROOT/google_appengine/dev_appserver.py  --runtime_python_path=/usr/bin/python2 --port=9999 [PATH_TO_YOUR_APP]
    

    Replace DEVAPPSERVER_ROOT with the path to the folder where you extract the archived version of devapp_server.py.

  2. The local development server is now running and listening for requests. You can visit http://localhost:8080/ in your web browser to see the app in action.

    If you specified a custom port with the --port option, remember to open your browser to that port.

To stop the local server from the command line, press the following:

  • macOS or Linux: Control+C
  • Windows: Control+Break

Specify application IDs

To access your App ID in the local server, for example to spoof an email address, use the get_application_id() function.

To get the hostname of the running app, use the get_default_version_hostname() function.

Detect application runtime environment

To determine whether your code is running in production or in the local development server, you can check the value of the GAE_ENV environment variable:

if os.getenv('GAE_ENV', '').startswith('standard'):
  # Production in the standard environment
else:
  # Local development server

Use the Mail service

The local development server can send email for calls to the App Engine mail service using either an SMTP server or a local installation of Sendmail.

To enable mail support with an SMTP server, invoke dev_appserver.py as follows:

    python2 DEVAPPSERVER_ROOT/google_appengine/dev_appserver.py --smtp_host=smtp.example.com --smtp_port=25 \
  --smtp_user=ajohnson --smtp_password=k1tt3ns PATH_TO_YOUR_APP

Replace:

  • DEVAPPSERVER_ROOT with the path to the folder where you extract the archived version of devapp_server.py.
  • --smtp_host, --smtp_port, --smtp_user and --smtp_password options with your own configuration values.
  • PATH_TO_YOUR_APP with the path to your application.

To enable mail support with Sendmail, invoke dev_appserver.py as follows:

  python2 DEVAPPSERVER_ROOT/google_appengine/dev_appserver.py --enable_sendmail=yes PATH_TO_YOUR_APP

Replace:

  • DEVAPPSERVER_ROOT with the path to the folder where you extract the archived version of devapp_server.py.
  • PATH_TO_YOUR_APP with the path to your application.

The local server uses the sendmail command to send email messages with your installation's default configuration.

Use the URL Fetch service

When your application uses the URL fetch API to make an HTTP request, the local development server makes the request directly from your computer. The URL Fetch behavior on the local server may differ from production App Engine if you use a proxy server for accessing websites.

Use the Users service

App Engine provides a Users service to simplify authentication and authorization for your application. The local development server simulates the behavior of Google Accounts with its own sign-in and sign-out pages.

While running under the local development server, the functions return URLs for /_ah/login and /_ah/logout on the local server.

Command-line arguments

For the local development server command options, see Local development server options.