POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets
PUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/BACKEND_BUCKET
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices
PUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices/BACKEND_SERVICE
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets
PUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/BACKEND_BUCKET
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices
PUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices/BACKEND_SERVICE
[[["易于理解","easyToUnderstand","thumb-up"],["解决了我的问题","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["很难理解","hardToUnderstand","thumb-down"],["信息或示例代码不正确","incorrectInformationOrSampleCode","thumb-down"],["没有我需要的信息/示例","missingTheInformationSamplesINeed","thumb-down"],["翻译问题","translationIssue","thumb-down"],["其他","otherDown","thumb-down"]],["最后更新时间 (UTC)：2025-08-14。"],[[["\u003cp\u003eCloud CDN can serve stale content, allowing continued delivery even when the origin server is unreachable or returns errors, preventing users from encountering errors.\u003c/p\u003e\n"],["\u003cp\u003eServing stale content avoids latency by delivering cached content immediately after expiration, triggering a revalidation in the background.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003ecdnPolicy.serveWhileStale\u003c/code\u003e setting determines how long Cloud CDN can serve stale content after expiration, with a default of one day (86,400 seconds), and can be configured from 0 seconds to one week (604,800 seconds).\u003c/p\u003e\n"],["\u003cp\u003eAsynchronous requests for stale content revalidation are logged separately and tagged with a \u003ccode\u003eUser-Agent\u003c/code\u003e header containing \u003ccode\u003eCloud-CDN-Google\u003c/code\u003e, appearing to the origin server like normal revalidation requests.\u003c/p\u003e\n"],["\u003cp\u003eClients can request to have content served stale by setting the \u003ccode\u003emax-stale\u003c/code\u003e cache control directive, limiting the amount of staleness they will accept.\u003c/p\u003e\n"]]],[],null,["# Serve stale content\n\nThis page provides information about serving stale, expired content with\nCloud CDN. Serving stale content lets Google's global cache continue to serve\ncontent when your origin server is unreachable or is returning errors to\nCloud CDN.\n\nThe reasons to do this are as follows:\n\n- You prefer to serve stale content to users rather than returning errors to users.\n- Serving stale content avoids latency when the cache gets a request for content that has just expired. Rather than having to wait for a synchronous revalidation to the backend, the cache serves the stale content that has just expired, while triggering a separate revalidation.\n\nTo enable this behavior, your backend can specify the `stale-while-revalidate`\ndirective in the response `Cache-Control` header. Cloud CDN will then\nserve that content from cache (if available) for the specified number of seconds\npast the cache entry expiration time. Asynchronously, Cloud CDN\nwill revalidate content with the origin.\n\nCloud CDN enables this on your behalf with the\n`cdnPolicy.serveWhileStale` setting. This setting dictates how long, after the\nresponse has expired, that Cloud CDN can continue serving a stale\nversion. If not otherwise specified in the response, this is `86400s` (1 day).\n\nCloud CDN does not support the `stale-if-error` directive. This\ndirective instructs the cache to avoid serving stale content unless synchronous\nrevalidation with the backend has failed with particular error status codes.\n\nThe default, minimum, and maximum values are as follows:\n\n- Default: 86,400 seconds (one day)\n- Minimum: 0 seconds (disables the feature)\n- Maximum: 604,800 seconds (one week)\n\nStale content is served up to the specified limit past the cache entry\nexpiration time, which is defined by the `max-age`, `s-maxage`, or `Expires`\nheaders. For more information, see [Expiration times and validation\nrequests](/cdn/docs/caching#expiration).\n\nIf a Cloud CDN edge cache does not have a cached copy of the object to\nserve stale, or the object has reached the maximum stale TTL, Cloud CDN\nsynchronously revalidates the content with the origin. If the origin returns\nan error at that time, Cloud CDN returns the origin error.\n\nLogging and User Agent\n----------------------\n\nThe asynchronous requests made by Cloud CDN appear to your origin\nserver exactly like the normal revalidation requests that occur when not serving\nstale content. The exception is that they are tagged with a `User-Agent` header\ncontaining `Cloud-CDN-Google`.\n\nAsynchronous requests are also separately logged to Cloud Logging, so a user\nrequest that is served stale generates two log entries: the first for the\ncontent actually served to the user, and the second for the revalidation request\nto the origin. Like synchronous revalidations, Cloud CDN may send a\n[conditional request](/cdn/docs/caching#response-headers-validate) in some circumstances,\nor just re-request the content unconditionally. In either case, the response\ncode logged to Cloud Logging corresponds to the original request to\nCloud CDN; for example, a `200 OK` for an unconditional request, or a\n`304 Not Modified` if the user's original response was conditional.\n\nClient `max-stale` request directive\n------------------------------------\n\nClients can request a shorter stale service time by specifying a `max-stale`\ncache-control directive. If specified, this directive controls the amount of\nstaleness the client tolerates.\n\nIf the cached content is more stale than the client's `max-stale` value,\nCloud CDN revalidates the content before serving.\n\nThe client cannot request a `max-stale` value greater than the value\nconfigured with the `serve-while-stale` configuration option and the\n`stale-while-revalidate` cache-control directive from the origin.\n\nBefore you begin\n----------------\n\n- Read about [cache modes and static content](/cdn/docs/caching#cache-modes).\n\n- Ensure that Cloud CDN is enabled; for instructions, see\n [Using Cloud CDN](/cdn/docs/using-cdn).\n\n- If necessary, update to the latest version of the Google Cloud CLI:\n\n ```\n gcloud components update\n ```\n | **Note:** Make sure that you're using gcloud CLI version `322.0.0` or later.\n\nServe stale content while revalidating\n--------------------------------------\n\n### Console\n\n1. In the Google Cloud console, go to the **Load balancing** page.\n\n [Go to Load balancing](https://console.cloud.google.com/networking/loadbalancing/list)\n2. Click the name of your external Application Load Balancer.\n3. Click edit**Edit**.\n4. For **Backend configuration** , select a backend, and then click edit**Edit**.\n5. Make sure that **Enable Cloud CDN** is selected.\n6. At the bottom of the window, click **Advanced configurations**.\n7. For **Additional CDN options** , select one of the following options for **Serve while stale** :\n - 1 minute\n - 5 minutes\n - 10 minutes\n - 30 minutes\n - 1 day (recommended)\n - 7 days\n8. Click **Update**.\n9. Click **Update** again.\n\n### gcloud\n\nFor backend buckets, use the [`gcloud compute backend-buckets\ncreate` command](/sdk/gcloud/reference/compute/backend-buckets/create) or\nthe [`gcloud compute backend-buckets\nupdate` command](/sdk/gcloud/reference/compute/backend-buckets/update)\nwith the `--serve-while-stale` flag.\n\nFor backend services, use the [`gcloud compute backend-services\ncreate` command](/sdk/gcloud/reference/compute/backend-services/create) or\nthe [`gcloud compute backend-services\nupdate` command](/sdk/gcloud/reference/compute/backend-services/update) command\nwith the `--serve-while-stale` flag. \n\n```\ngcloud compute backend-buckets (create | update) BACKEND_BUCKET_NAME\n --serve-while-stale=SECONDS\n``` \n\n```\ngcloud compute backend-services (create | update) BACKEND_SERVICE_NAME\n --serve-while-stale=SECONDS\n```\n\nFor example: \n\n```\ngcloud compute backend-services update my-backend-service\n --serve-while-stale=180s\n```\n\n### API\n\nFor backend buckets, use the\n[`Method: backendBuckets.insert`](/compute/docs/reference/rest/v1/backendBuckets/insert) or\n[`Method: backendBuckets.update`](/compute/docs/reference/rest/v1/backendBuckets/update)\nAPI call.\n\nFor backend services, use the\n[`Method: backendServices.insert`](/compute/docs/reference/rest/v1/backendServices/insert) or\n[`Method: backendServices.update`](/compute/docs/reference/rest/v1/backendServices/update)\nAPI call.\n\nUse one of the following API calls: \n\n```\nPOST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets\nPUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/BACKEND_BUCKET\nPOST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices\nPUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices/BACKEND_SERVICE\n```\n\nAdd the following snippet to the JSON request body: \n\n```\n\"cdnPolicy\": {\n \"serveWhileStale\": SECONDS\n}\n```\n\nDisable serving stale content\n-----------------------------\n\n### Console\n\n1. In the Google Cloud console, go to the **Load balancing** page.\n\n [Go to Load balancing](https://console.cloud.google.com/networking/loadbalancing/list)\n2. Click the name of your external Application Load Balancer.\n3. Click edit**Edit**.\n4. For **Backend configuration** , select a backend, and then click edit**Edit**.\n5. Make sure that **Enable Cloud CDN** isn't selected.\n6. At the bottom of the window, click **Advanced configurations**.\n7. For **Additional CDN options** \\\u003e **Serve while stale** , select **Disable serve while stale**.\n8. Click **Update**.\n9. Click **Update** again.\n\n### gcloud\n\nFor backend buckets, use the [`gcloud compute backend-buckets\ncreate`](/sdk/gcloud/reference/compute/backend-buckets/create) or\n[`gcloud compute backend-buckets\nupdate`](/sdk/gcloud/reference/compute/backend-buckets/update) command\nwith the `--serve-while-stale` flag value set to `0`.\n\nFor backend services, use the [`gcloud compute backend-services\ncreate` command](/sdk/gcloud/reference/compute/backend-services/create) or\nthe [`gcloud compute backend-services\nupdate` command](/sdk/gcloud/reference/compute/backend-services/update) command\nwith the `--serve-while-stale` flag value set to `0`. \n\n```\ngcloud compute backend-services (create | update) (BACKEND_SERVICE_NAME | BACKEND_BUCKET_NAME)\n --serve-while-stale=0\n```\n\n### API\n\nFor backend buckets, use the\n[`Method: backendBuckets.insert`](/compute/docs/reference/rest/v1/backendBuckets/insert) or\n[`Method: backendBuckets.update`](/compute/docs/reference/rest/v1/backendBuckets/update)\nAPI call.\n\nFor backend services, use the\n[`Method: backendServices.insert`](/compute/docs/reference/rest/v1/backendServices/insert) or\n[`Method: backendServices.update`](/compute/docs/reference/rest/v1/backendServices/update)\nAPI call.\n\nUse one of the following API calls: \n\n```\nPOST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets\nPUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/BACKEND_BUCKET\nPOST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices\nPUT https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendServices/BACKEND_SERVICE\n```\n\nAdd the following snippet to the JSON request body: \n\n```\n\"cdnPolicy\": {\n \"serveWhileStale\": 0\n}\n```"]]
