Learn how to run your application locally, deploy it, and test on App Engine. ## Before deploying your application Before you can deploy your application: * The [Owner](/appengine/docs/legacy/standard/java/access-control#owner) of the Google Cloud project must [enable App Engine](/appengine/docs/legacy/standard/java/console/#create). * You must ensure that your user account includes the [required privileges](/appengine/docs/legacy/standard/java/access-control#basic_roles). ## Deploying your application Deploy your application to App Engine using the [`gcloud app deploy`](/sdk/gcloud/reference/app/deploy) command. During deployment, the [Cloud Build](/build/docs/) service builds a container image of your application to run in the App Engine standard environment. The builds are created in the app's region. Learn more in [Manage build images](#manage_build_images). To programmatically deploy your apps, use the [Admin API](/appengine/docs/admin-api/deploying-overview). ### Deploying a service You deploy your application to App Engine by deploying versions of your application's services and each of their configuration files. To deploy a version of your application's service, run the following command from the directory where the `app.yaml` file of your service is located: 
gcloud app deploy
Specifying no files with the command deploys only the `app.yaml` file in your current directory. By default, the `deploy` command generates a unique ID for the version that you deploy, deploys the version to the Google Cloud project you configured the gcloud CLI to use, and routes all traffic to the new version. You can change the default behavior of the command by targeting specific files or including additional parameters: * To deploy the other configuration files of your service, you must target and deploy each file separately. For example: 
gcloud app deploy *cron.yaml* gcloud app deploy *dispatch.yaml* gcloud app
deploy *index.yaml*
* To specify a custom version ID, use the `--version` flag. * To prevent traffic from being automatically routed to the new version, use the `--no-promote` flag. * To deploy to a specific Google Cloud project, use the `--project` flag. For example, to deploy the service defined by the `app.yaml` file to a specific Google Cloud project, assign it a custom version ID, and prevent traffic from being routed to the new version: 
gcloud app deploy --project *PROJECT_ID* --version *VERSION_ID* --no-promote
For more information about this command, see the `gcloud app deploy` [reference](/sdk/gcloud/reference/app/deploy). Note: You can [set properties](/sdk/gcloud/reference/config/set) for the gcloud CLI and create and manage [SDK configurations](/sdk/docs/configurations) so you don't need to specify flags such as `--project` every time you deploy. ### Deploying multiple services You use the same deployment command for deploying or updating the multiple services that make up your application. To deploy multiple services, separately deploy each service's `app.yaml` file. You can specify multiple files with a single `gcloud app deploy` command: 
gcloud app deploy *service1/app.yaml service2/app.yaml*
#### Requirements for deploying multiple services * You must initially deploy a version of your application to the `default` service before you can create and deploy subsequent services. * The ID of each of your services must be specified in their corresponding `app.yaml` configuration files. To specify the service ID, include the `service` element definition in each configuration file. By default, excluding this element definition from your configuration file deploys the version to the `default` service. ### Viewing build logs Cloud Build streams build and deploy logs that are viewable in the [Cloud Build history section of the Google Cloud console](https://console.cloud.google.com/cloud-build/builds). To view builds in the app's region, use the **Region** drop-down menu at the top of the page to choose the region you would like to filter by. ### Ignoring files You can use a `.gcloudignore` file to specify files and directories that will not be uploaded to App Engine when you deploy your services. This is useful for ignoring build artifacts and other files that do not need to be uploaded with your deployment. Note: You cannot specify the `skip_files` field in your `app.yaml` file if you have a `.gcloudignore` file. ### Manage build images Here are the steps that occur each time you deploy a new version: 1. App Engine creates a container image using the [Cloud Build](/build/docs/) service. 1. Cloud Build builds the container image in the app's region, and runs in the standard environment. 1. App Engine stores built container images in [{{ar_name}}](https://console.cloud.google.com/artifacts/). You can download these images to keep or run elsewhere. After deployment is complete, App Engine no longer needs the container images. The container images aren't automatically deleted. To avoid reaching your storage quota, you can safely delete any images you don't need. However, if you might need the images in the future or want to keep a copy of the images, you need to export a copy prior to deletion. For more information about managing images in {{ar_name}}, see [Manage images](/artifact-registry/docs/docker/manage-images). ### Viewing your application After you deploy your application to App Engine, you can run the following command to launch your browser and view it at https://PROJECT_ID.REGION_ID.r.appspot.com: 
gcloud app browse
## Testing on App Engine before shifting traffic Before configuring a new version to receive traffic, you can test it on App Engine. For example, to test a new version of your `default` service: 1. Deploy your new version, but prevent traffic from being automatically routed to the new version: 
gcloud app deploy --no-promote
1. Access your new version by navigating to the following URL: https://VERSION-dot-PROJECT_ID.REGION_ID.r.appspot.com Note: You can find the version ID in the [Google Cloud console](https://console.cloud.google.com/appengine/versions) or specify one when you deploy with the `--version flag`. The gcloud CLI also outputs the version ID when you deploy. Now you can test your new version in the App Engine runtime environment. You can debug your application by viewing its logs. For more information, see [Writing Application Logs](/appengine/docs/legacy/standard/java/writing-application-logs). App Engine routes requests sent to https://PROJECT_ID.REGION_ID.r.appspot.com to the version previously configured to receive traffic. 1. When you want to send traffic to the new version, use the Google Cloud console to migrate traffic: [Manage versions](https://console.cloud.google.com/appengine/versions) Select the version you just deployed and click **Migrate traffic**. You can use the same process to test new versions of other services by replacing `default` in the URL with your service's name: https://VERSION-dot-SERVICE-dot-PROJECT_ID.REGION_ID.r.appspot.com For more information about targeting specific services and versions, see [How Requests are Routed](/appengine/docs/legacy/standard/java/how-requests-are-routed). ## Using the local development server You can use `dev_appserver` to run your apps locally to simulate your application running in production App Engine. This development server partially simulates the environment in which your application runs, allowing you to test apps written for any of the standard environment runtimes. Since Go 1.11 has reached the [end of support](/appengine/docs/standard/lifecycle/runtime-lifecycle#end_of_support), you can no longer use the latest version of `dev_appserver.py` to locally run your applications. To continue using `dev_appserver.py`, follow the instructions in [Using the local development server](/appengine/docs/legacy/standard/java/tools/using-local-server#before_you_begin). ### Running the local development server After you create the [`app.yaml`](/appengine/docs/legacy/standard/java/config/appref) configuration file for your app, you can start the local development server with the `dev_appserver.py` command to run your app locally. 1. To obtain access credentials for your user account, run: ```shell gcloud auth login ``` 1. Allow your local application to temporarily use your user credentials for API access: ```shell gcloud auth application-default login ``` 1. To start the local development server: In the directory that contains your `app.yaml` configuration file, run the `dev_appserver.py` command and specify your project ID and path to your `app.yaml` file: 
python2 *DEVAPPSERVER_ROOT*/google_appengine/dev_appserver.py/dev_appserver.py --application=*PROJECT_ID* app.yaml
To change the port, include the `--port` option: 
python2 *DEVAPPSERVER_ROOT*/google_appengine/dev_appserver.py/dev_appserver.py --application=*PROJECT_ID* app.yaml --port=9999
Replace *DEVAPPSERVER_ROOT* with the path to the folder where you extract the archived version of `devapp_server.py`. For more information about downloading and using the archived version of `dev_appserver.py`, see [Using the local development server](/appengine/docs/legacy/standard/java/tools/using-local-server#before_you_begin). To learn more about the `dev_appserver.py` command options, see [Local development server options](/appengine/docs/legacy/standard/java/tools/local-devserver-command). 1. As the local development server starts, it sets up a development environment that pre-installs the dependencies found in your `requirements.txt` file. 1. The local development server is now running and listening for requests. Visit [http://localhost:8080/](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. 1. To stop the local server from the command line, press Control-C on your keyboard. ### Detecting application runtime environment To determine whether your code is running in production or in the local development server, you can check the `GAE_ENV` environment variable: 
if os.getenv('GAE_ENV', '').startswith('standard'):
# Production in the standard environment else: # Local execution.
### Using the local development server with Google Cloud services You can integrate `dev_appserver` with other Google Cloud components. #### Cloud client libraries Many {{client_lib_name}} depend on the presence of the `GOOGLE_CLOUD_PROJECT` environment variable, which should be your Google Cloud project ID. You can find its value by running the `gcloud config list project` command or looking at your project page in the Google Cloud console. To ensure that this environment variable is set correctly during local development, initialize `dev_appserver` using the --application=*PROJECT_ID* parameter as shown in the previous example. #### Cloud emulators You can test your application with emulators for [Cloud Datastore](/datastore/docs/tools/datastore-emulator), [Cloud Bigtable](/bigtable/docs/emulator) and [Cloud Pub/Sub](/pubsub/docs/emulator). ### Auto-reloading `requirements.txt` and `app.yaml` changes The local development server automatically installs dependencies found in your `requirements.txt` file. `dev_appserver` also allows you to test functionality that is configured via `app.yaml`. For example, you can test your app's ability to [serve static files](/appengine/docs/legacy/standard/java/serving-static-files). When `dev_appserver` is running, any changes to `requirements.txt` and `app.yaml` automatically restarts your app to reflect these changes. This may result in a temporary delay as dependencies are downloaded and installed. ### Instance management and routing in the development server #### Discovering instance addresses The local development server creates all manual scaling instances at startup. Instances for automatic and basic scaling services are managed dynamically. The server assigns a port to each service, and clients can depend on the server to load-balance and select an instance automatically. The port assignments for addressing each service appear in the server's log message stream. Here are the ports for an app that defines three services: 
INFO Starting module "default" running at: http://localhost:8084
INFO Starting module "service1" running at: http://localhost:8082 INFO Starting
module "service2" running at: http://localhost:8083
When you use a service's address, for example `http://localhost:8082/`, the server creates or selects an instance of the service and sends the request to that instance. The server assigns unique ports to each instance of a service. You can use the admin server to discover these ports. There is a unique port for the admin server, which appears in the message log: 
INFO Starting admin server at: http://localhost:8000
This address takes you to the admin server console. Click on **Instances** to see the dynamic state of your app's instances A separate entry appears for each manual and basic instance. The instance numbers are links with unique port addresses for each instance. Click on the link to send a request directly to that instance. #### Dispatch files If your app includes a `dispatch.yaml` file, the log messages stream includes a dispatcher port: 
INFO Starting dispatcher running at: http://localhost:8080
Requests to this port are routed according to the rules in the dispatch file. The server does **not** support `dispatch.yaml` file rules that include hostnames, for example, `url: "customer1.myapp.com/*"`). Rules with relative path patterns (`url: "*/fun"`, **do** work, so you can use URLs like `http://localhost/fun/mobile` to reach instances. The server reports an error in the log stream if you try to start an application with a `dispatch.yaml` file that contains host-based rules.