Go 1.11 has reached end of support
and will be deprecated
on January 31, 2026. After deprecation, you won't be able to deploy Go 1.11
applications, even if your organization previously used an organization policy to
re-enable deployments of legacy runtimes. Your existing Go
1.11 applications will continue to run and receive traffic after their
deprecation date. We
recommend that you migrate to the latest supported version of Go.
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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. For apps created after
February 2020, REGION_ID.r is included in
App Engine URLs. For existing apps created before this date, the
region ID is optional in the URL.
You can use various methods to communicate between your App Engine
services or with other services, including Google Cloud services and
external applications.
The simplest approach for communicating with your App Engine service is
to send targeted HTTP requests, where the URL includes the name or ID of a
resource. For example, you can include the ID of a service or version that you
want to target, in addition to the corresponding Google Cloud project ID:
Your App Engine services can also communicate using
Pub/Sub, which provides reliable asynchronous
many-to-many messaging between processes, including App Engine. These
processes can be individual instances of your application, services, or even
external applications.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-29 UTC."],[[["\u003cp\u003eThe \u003ccode\u003eREGION_ID\u003c/code\u003e is a Google-assigned code based on the region selected during app creation, not corresponding to a specific country or province.\u003c/p\u003e\n"],["\u003cp\u003eApp Engine URLs for apps created after February 2020 include \u003ccode\u003eREGION_ID\u003c/code\u003e.r, while it's optional for older apps.\u003c/p\u003e\n"],["\u003cp\u003eYou can send targeted HTTP requests to communicate with App Engine services by including resource identifiers like service or version IDs in the URL.\u003c/p\u003e\n"],["\u003cp\u003eApp Engine services can communicate with each other and external applications using various methods, including targeted HTTP requests and Pub/Sub for asynchronous messaging.\u003c/p\u003e\n"],["\u003cp\u003eCertain URL paths are reserved and cannot be used, including those ending with \u003ccode\u003e/eventlog\u003c/code\u003e, starting with \u003ccode\u003e/_ah/\u003c/code\u003e, and some ending with \u003ccode\u003ez\u003c/code\u003e.\u003c/p\u003e\n"]]],[],null,["# Communicating Between Your Services\n\n### Region ID\n\nThe \u003cvar translate=\"no\"\u003eREGION_ID\u003c/var\u003e is an abbreviated code that Google assigns\nbased on the region you select when you create your app. The code does not\ncorrespond to a country or province, even though some region IDs may appear\nsimilar to commonly used country and province codes. For apps created after\nFebruary 2020, \u003cvar translate=\"no\"\u003eREGION_ID\u003c/var\u003e`.r` is included in\nApp Engine URLs. For existing apps created before this date, the\nregion ID is optional in the URL.\n\nLearn more\n[about region IDs](/appengine/docs/legacy/standard/go111/how-requests-are-routed#region-id). \nOK\n\nYou can use various methods to communicate between your App Engine\nservices or with other services, including Google Cloud services and\nexternal applications.\n\nThe simplest approach for communicating with your App Engine service is\nto send targeted HTTP requests, where the URL includes the name or ID of a\nresource. For example, you can include the ID of a service or version that you\nwant to target, in addition to the corresponding Google Cloud project ID: \n\n\n `https://`\u003cvar translate=\"no\"\u003eVERSION\u003c/var\u003e`-dot-`\u003cvar translate=\"no\"\u003eSERVICE\u003c/var\u003e`-dot-`\u003cvar translate=\"no\"\u003ePROJECT_ID\u003c/var\u003e`.`\u003cvar translate=\"no\"\u003e\u003ca href=\"#appengine-urls\" style=\"border-bottom: 1px dotted #999\" class=\"devsite-dialog-button\" data-modal-dialog-id=\"regional_url\" track-type=\"progressiveHelp\" track-name=\"modalHelp\" track-metadata-goal=\"regionalURL\"\u003eREGION_ID\u003c/a\u003e\u003c/var\u003e`.r.appspot.com`\n\nFor details about targeting your services, including how to define HTTPS URLs,\nsee [How Requests are\nRouted](/appengine/docs/legacy/standard/go111/how-requests-are-routed).\nTo authorize the requests between your services and other Google Cloud\nservices, see [Setting Up Authentication for Server to Server Production\nApplications](/docs/authentication/production).\nYour App Engine services can also communicate using [Pub/Sub](/pubsub/docs), which provides reliable asynchronous many-to-many messaging between processes, including App Engine. These processes can be individual instances of your application, services, or even external applications.\n\nTo share data across databases and your App Engine app or some other\nexternal application, see\n\n[Understanding Data and File\nStorage](/appengine/docs/legacy/standard/go111/storage-options).\n\n\nReserved URL paths\n------------------\n\nIt is not possible to use the following URL paths:\n\n- Paths ending with `/eventlog`\n- Paths starting with `/_ah/`\n- Some paths ending with `z`"]]
