Defining runtime settings

An App Engine app is configured using an app.yaml file, that contains the runtime, handlers, scaling, and other general settings including environment variables.

About app.yaml files

You can specify the runtime configuration for your Go 1.12+ app, including versions and URLs, in the app.yaml file. This file acts as a deployment descriptor of a specific service version.

You must first create the app.yaml file for the default service of your app before you can create and deploy app.yaml files for additional services.

Generally, your app.yaml file requires only the runtime element for a simple Go 1.12+ app in the standard environment, for example:

runtime: go123

App Engine provides default values for all other settings, including the F1 instance class, which determines the memory and CPU resources that are available to your app, and automatic scaling, which controls how and when new instances of your app are created.

If you need to override the default settings, create an app.yaml file and specify the settings you need. For more information, see app.yaml file reference.

You can specify a unique name for your app.yaml files, but then you must specify the file name with the deployment command as well. For example, if you name your app.yaml file service-name-app.yaml or app.standard.yaml, then you must deploy your app using either:

gcloud app deploy service-name-app.yaml
gcloud app deploy app.standard.yaml

To learn more about structuring multiple services and app.yaml files in your app, see Structuring web services.

All configuration elements

For a complete list of all the supported elements in this configuration file, see the app.yaml reference.