Merge pull request #1502 from G-Core/mariyayurlova-patch-2

Create test-cdn

documentation/cdn/cdn-resource-options/cache/test-cdn

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+---
+title: test-cdn
+displayName: Test
+published: true
+order: 55
+toc:
+pageTitle: Test
+pageDescription: Test
+---
+# Always online: provide the stale cache if the origin is unavailable
+
+The option allows serving stale cached content in case of the following errors: error (network or connectivity issues), timeout, invalid_header, updating (cache updating),http_500, http_502, http_503, http_504, http_403, http_404, http_429.
+
+HTTP response for the stale content will contain the header X-Cache: Stale. CDN will check origin availability with each user’s request. As soon as the origin becomes available, fresh files will be cached and served. If the origin is unavailable for a long time, CDN will send Stale content until origin becomes available. 
+
+Please, note that when the site is unavailable, the CDN cache may have not enough content for a correct page display. Situations, when a user will not be able to see some images, style sheets, or other static content, are possible.
+
+To manage this option go to your Resource Advanced Settings, find the **Cache** section and click **Always online**. You can enable the toggle and choose error codes for which a CDN serves stale content. 
+
+<img src="https://assets.gcore.pro/docs/cdn/cdn-resource-options/cache/always-online-provide-the-stale-cache-if-the-origin-is-unavailable/cdn-always-online-enabled.png" alt="Always Online toggle enabled" width="80%">