Testing and Deploying your Application

Learn how to run your application locally, deploy it, and test on App Engine.

Running locally

To test your application's functionality before deploying, run your application in your local environment with the development tools that you usually use.

For example, the go run command.

Deploying your application

Deploy your application to App Engine using the gcloud app deploy command, which will correctly assemble your application's dependencies in the same way that the go tool does. This command automatically builds a container image by using the Cloud Build service and then deploys that image to the App Engine flexible environment. The container will include any local modifications that you've made to the runtime image.

To programmatically deploy your apps, use the Admin API.

Before you begin

Before you can deploy your application:

Ensuring successful deployment

If you enable updated health checks, deployments are rolled back if your application does not reach healthy status.

When you deploy your first application to the flexible environment, there might be a delay as your virtual machine (VM) and other infrastructure are set up. After the initial setup, the health checks make sure that your instance is healthy and ready to receive traffic. If your application does not reach ready status in a specified amount of time, indicated by the initial_delay_sec field in the liveness_check section of your app.yaml file, then your deployment fails and is rolled back.

Your application might need more time to become ready. For example, you might initialize your application by downloading large files or preloading caches. If you are using updated health checks, then you can increase the amount of time by modifying the app_start_timeout_sec configuration setting in the readiness_check section of in your app.yaml file.

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 GCP project you configured the gcloud tool 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 GCP project, use the --project flag.

For example, to deploy the service defined by app.yaml to a specific GCP 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.

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, you must separately deploy each service's app.yaml file. For example:

gcloud app deploy service1/app.yaml
gcloud app deploy service2/app.yaml

You can specify multiple files with a single 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.

Ignoring files

You can use a .gcloudignore file to specify files and directories not to upload to GCP 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.

Learn more about the syntax of the .gcloudignore file in the gcloud reference.

Manually building a container for deployment

To build your container images outside of Google Cloud Platform, you must first upload your images to a container image repository before you can deploy your images to App Engine with the gcloud app deploy command.

For example, if you build your container images locally with Docker, you can push those images to Google Container Registry and then specify the URL of your image in the --image-url flag of the command:

gcloud app deploy --image-url gcr.io/YOUR_PROJECT_ID/YOUR_CONTAINER_IMAGE
For more information about building your own container image, see the Extending the runtime section.

Using automated continuous deployment pipelines

You can use Cloud Build to automate deployments in continuous deployment pipelines. For more information, see Deploying artifacts, and Automating Builds using Build Triggers in the Cloud Build documentation.

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 http://YOUR_PROJECT_ID.appspot.com:

gcloud app browse

Testing on App Engine

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 and include the --no-promote flag:

    gcloud app deploy --no-promote
  2. Access your new version by navigating to the following URL:


    Now you can test your new version in the App Engine runtime environment. You can debug your application by viewing its logs in the Google Cloud Platform Console Stackdriver Logs Viewer. For more information, see Writing Application Logs.

    Requests sent to http://YOUR_PROJECT_ID.appspot.com will still be routed to the version previously configured to receive traffic.

  3. When you want to send traffic to the new version, use the GCP Console to migrate traffic:

    Manage 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:

For more information about targeting specific services and versions, see How Requests are Routed.


The following is a common error message that you might encounter when deploying apps:

PERMISSION_DENIED: Operation not allowed
The "appengine.applications.create" permission is required.
If the GCP project does not include the required App Engine application, the gcloud app deploy command can fail when it tries to run the gcloud app create command. Only accounts with Owner role have the necessary permissions to create App Engine applications.
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