Known Issues in the App Engine Flexible Environment

Region ID

The REGION_ID is an abbreviated code that Google assigns based on the region you select when you create your app. The code does not correspond to a country or province, even though some region IDs may appear similar to commonly used country and province codes. Including REGION_ID.r in App Engine URLs is optional for existing apps and will soon be required for all new apps.

To ensure a smooth transition, we are slowly updating App Engine to use region IDs. If we haven't updated your Google Cloud project yet, you won't see a region ID for your app. Since the ID is optional for existing apps, you don't need to update URLs or make other changes once the region ID is available for your existing apps.

Learn more about region IDs.

For a full list of known issues or to report a new issue, see the issue tracker.

  • After you deploy your application with gcloud app deploy, you might need to wait 1-2 minutes before your application starts serving at Until then, you might see HTTP 503 errors.

  • You cannot use the App Engine flexible environment if the organization policy on your project restricts access to external IPs, for example:

    • The effective policy for constraints/compute.vmExternalIpAccess is set to DENY_ALL.
    • The effective policy for constraints/compute.vmExternalIpAccess is set to allow only specific VM instances.

    These constraints are not automatically detected, and deployments might time out and fail. You can check the organization policy for your project by running the command gcloud beta resource-manager org-policies describe compute.vmExternalIpAccess --project=my-project --effective.

  • After you deploy a new version of an existing service in the App Engine flexible environment with gcloud app deploy, the "Count/sec" metric shown in the "Summary" graph of the App Engine dashboard may decrease significantly. The metric will gradually return to the expected request count over the next 5-10 minutes.

    This does not mean that your application is serving fewer requests. When you deploy a new version of your application, there is a delay between the time the new version is ready to serve requests and the time that the metrics for new instances become available.

    To ensure that this metric is unaffected by a new version deployment:

    1. Deploy your new version with gcloud app deploy --no-promote.
    2. Wait 15 minutes after the deployment completes.
    3. Migrate traffic to the new version.

    If you deploy with --no-promote but allocate any amount of traffic to the new version before the 15 minute window after the deployment completes, this metric may be impacted.