Skip to content

[Cache] Adds information about smart edge revalidation #19486

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jan 30, 2025
Merged

[Cache] Adds information about smart edge revalidation #19486

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ed389d3
Adds information about smart edge revalidation
angelampcosta Jan 28, 2025
b9142d5
Apply suggestions from code review
angelampcosta Jan 28, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 8 additions & 2 deletions src/content/docs/cache/concepts/revalidation.mdx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,11 @@ pcx_content_type: concept

import { GlossaryTooltip } from "~/components"

Revalidation is a caching mechanism that involves checking the [freshness](/cache/concepts/retention-vs-freshness/) of cached data before serving it to a client or user. If a cached object is no longer [fresh](/cache/concepts/retention-vs-freshness/#freshness-ttl) and Cloudflare receives a request for it, a request is made to the origin to revalidate the object in the Cloudflare cache.
Revalidation is a caching mechanism that checks the [freshness](/cache/concepts/retention-vs-freshness/#freshness-ttl) of cached data before serving it to users. If a cached object is no longer fresh and Cloudflare receives a request for it, the system makes a request to the origin to revalidate the object in the Cloudflare cache. By using headers like `If-Modified-Since` and `ETag`, Cloudflare validates content without fully re-fetching it. When these headers are missing, Smart Edge Revalidation generates a `Last-Modified` header, ensuring efficient updates and delivery of fresh content while reducing origin traffic.

## Example scenarios
## Revalidation towards origin

For stale (expired TTL) content, Cloudflare will send a revalidation request to the origin. If the stale content is still valid Cloudflare will set a new TTL. If the content is expired, then the origin will provide new fresh content to replace the old.

Consider the following example scenarios.

Expand All @@ -19,3 +21,7 @@ One-thousand (1,000) requests arrive simultaneously at Cloudflare's network, and
### Example 2

One-thousand (1,000) requests arrive simultaneously at a single Cloudflare data center, and the requested asset is not in Cloudflare's cache (a cache miss). These requests will use a <GlossaryTooltip term="cache lock">cache lock</GlossaryTooltip> to communicate with your origin. This means that only the first request will go to origin to fetch the asset. The remaining 999 requests wait for the first request to fetch the data, after which the response is [streamed](https://blog.cloudflare.com/introducing-concurrent-streaming-acceleration/) to all the waiting requests. The cache lock ensures that Cloudflare only sends the origin one request at a time for a given asset from a location in Cloudflare's network, preventing the origin from getting too much traffic.

## Smart revalidation towards users

When both [`Last-Modified`](https://datatracker.ietf.org/doc/html/rfc7232?cf_history_state=%7B%22guid%22%3A%22C255D9FF78CD46CDA4F76812EA68C350%22%2C%22historyId%22%3A15%2C%22targetId%22%3A%226C8153BAEF7BC0C5A331E28F8BCF1ABA%22%7D#section-2.2) and [`Etag`](https://datatracker.ietf.org/doc/html/rfc7232?cf_history_state=%7B%22guid%22%3A%22C255D9FF78CD46CDA4F76812EA68C350%22%2C%22historyId%22%3A13%2C%22targetId%22%3A%226C8153BAEF7BC0C5A331E28F8BCF1ABA%22%7D#section-2.3) headers are absent from the origin server response, Smart Edge Revalidation will use the time the object was cached on Cloudflare's global network as the `Last-Modified` header value. When a browser sends a revalidation request to Cloudflare using `If-Modified-Since` or `If-None-Match`, our global network can answer those revalidation questions using the `Last-Modified` header generated from Smart Edge Revalidation. In this way, our global network can ensure efficient revalidation even if the headers are not sent from the origin.
Loading