An App Engine app is configured using anapp.yamlfile, that contains the runtime, handlers, scaling, and other general settingsincluding environment variables.

Aboutapp.yaml files

You must first create theapp.yaml file for thedefault service of your appbefore you can create and deployapp.yaml files for additional services.

Generally, yourapp.yaml file requires only theruntime element for a simpleRuby app in the standard environment, forexample:

runtime:ruby34

App Engine provides default values for all other settings, includingtheF1 instance class, whichdetermines the memory and CPU resources that are available to your app, andautomatic scaling,which controls how and when new instances of your app are created.

If you need to override the default settings, create anapp.yaml file andspecify the settings you need. For more information, seeapp.yaml file reference.

You can specify a unique name for yourapp.yaml files, but then you mustspecify the file name with thedeploymentcommandas well. For example, if you name yourapp.yaml fileservice-name-app.yamlorapp.standard.yaml, then you must deploy your app using either:

gcloudappdeployservice-name-app.yamlgcloudappdeployapp.standard.yaml

All configuration elements

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