Using the local development server

The Google Cloud CLI includes a local development server ( You can use the local development server to simulate running your App Engine application in production as well as use it to access App Engine bundled services.

The simulated environment enforces some sandbox restrictions, such as restricted system functions and PHP 5 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 using Google APIs HTTP endpoints.

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 both Python interpreters on your machine:

    Both Python interpreters are required even if your app is written in another runtime or language version.

  2. Verify that you have installed the gcloud component that includes the App Engine extension for Python 2 (app-engine-python):

    gcloud components list

    If the app-engine-python component is not installed, run the following command:

    gcloud components install app-engine-python
  3. Set the CLOUDSDK_DEVAPPSERVER_PYTHON environment variable in your shell to the path of your Python 2 interpreter.

  4. Locate the installation path of Google Cloud SDK by running the following command:

    gcloud info

    The command returns the root directory where you installed Google Cloud SDK, for example:

    Installation Root: [/Users/myname/google-cloud-sdk]

  5. Locate the tool under the /bin/ folder where you installed Google Cloud CLI, for example:

  6. Note the path to the for later.

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 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 command.

    Windows / macOS

    Specify the directory path to your app, for example:

      python3 [CLOUD_SDK_ROOT]/bin/ [PATH_TO_YOUR_APP]

    Alternatively, you can specify the configuration file of a specific service, for example:

      python3 [CLOUD_SDK_ROOT]/bin/ app.yaml

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

      python3 [CLOUD_SDK_ROOT]/bin/ --port=9999 [PATH_TO_YOUR_APP]

    Linux / cust. php-cgi

    If you're on Linux or if you want to use a custom version of php-cgi, you need to specify the directory path to the php-cgi:

    1. Build your own version of App Engine PHP Extension on your local machine.

    2. Start the local development server with both the --php_executable_path and --php_gae_extension_path options:

       python3 CLOUD_SDK_ROOT/bin/ --php_executable_path=[PATH_TO_PHP_CGI] --php_gae_extension_path=[PATH_TO_APPENGINE_EXTENSION] app.yaml

      where --php_executable_path is the location of the PHP interpreter you are using, and where --php_gae_extension_path is the location of the file that you built in the previous step.

    To learn more about the command options, see Local Development Server Options.

  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 AppIdentityService::getApplicationId function. To get the hostname of the running app, use the AppIdentityService::getDefaultVersionHostname function.

Detecting 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 SERVER_SOFTWARE environment variable:

if (strpos(getenv('SERVER_SOFTWARE'), 'Development') === 0){
  echo 'Local development server';
} else {
  echo 'Production';

Store data

App Engine for PHP supports reading and writing to Cloud Storage via PHP's streams API. You can read and write to Cloud Storage by specifying a Cloud Storage URI (gs://) when using any PHP function that supports PHP Streams implementation such as fopen, fwrite or file_get_contents.

The local development server emulates this functionality by reading and writing to temporary local files that are preserved between requests.

Browse the local Datastore

If your app has written data to your local Datastore using the local development server, you can browse it in the local development console.

To browse local Datastore:

  1. Start the development server.

  2. Access the Datastore Viewer in the local development console. (The URL is http://localhost:8000/datastore.)

  3. View your local Datastore contents.

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 createLoginURL and createLogoutURL functions return URLs for /_ah/login and /_ah/logout on the local server.

Use Mail

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.

Using SMTP

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

python3 [CLOUD_SDK_ROOT]/bin/ --smtp_port=25 \
    --smtp_user=ajohnson --smtp_password=k1tt3ns [PATH_TO_YOUR_APP]

where you set the --smtp_host, --smtp_port, --smtp_user and --smtp_password options with your own values.

Using Sendmail

To enable mail support with Sendmail, invoke as follows:

python3 [CLOUD_SDK_ROOT]/bin/ --enable_sendmail=yes [PATH_TO_YOUR_APP]

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

Use URL Fetch

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.

Debug locally with XDebug

If you have a debugger that is compatible with the XDebug debugger, and you have the xdebug module installed, you can use XDebug with the local development server.

To enable XDebug on the Development Server on Linux or macOS:

  1. Export the XDEBUG_CONFIG environment variable with an idekey for your IDE to connect to

    export XDEBUG_CONFIG="idekey=netbeans-xdebug remote_host=localhost"
  2. Invoke the Development Server with --php_remote_debugging=yes