ESA provides a stale content serving feature for fault tolerance. If your origin server returns a 4xx or 5xx error or times out, ESA points of presence (POPs) serve expired static content to keep your website available. This feature applies to static resources only and does not need to be enabled for dynamic requests.
How it works
Use cases
The origin server fails or is unavailable: When the origin server is unreachable due to server downtime, network interruptions, or program errors, ESA POPs cannot fetch the latest content from the origin.
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If serving stale content is disabled: The POP forwards the request to the origin server. If the origin server is down, the request fails and the user cannot access the website.
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If serving stale content is enabled: The POP serves expired cached content when the origin server is down, keeping the website accessible.
Procedure
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In the ESA console, choose Websites. In the Website column, click the target site.
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In the navigation pane on the left, choose .
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Click Create Rule and enter a Rule Name.
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In the If requests match... section, specify the conditions for incoming requests. For more information, see Composition of rule expressions.
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In the Bypass Cache section, specify whether to bypass the cache. For more information, see Cache eligibility.
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Turn on the Serve Stale Content switch.
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Click OK.
Related documentation
Rule-related features vary in effective priority, reentrancy, and effective granularity. For details, see Properties of Rule-Related Features.