Redesign Cloudflare cache purging

[richardlau]

I believe most of the server issues we're currently having with nodejs.org stem from our rather crude "purge everything" strategy. This is currently done by ansible/www-standalone/resources/scripts/cdn-purge.sh.j2 (which runs every five minutes) if a purge has been locally queued.

Purges are queued by calling ansible/www-standalone/resources/scripts/queue-cdn-purge.sh. This is done every time:

• the website is rebuilt

  build/ansible/www-standalone/resources/scripts/build-site.sh

  Line 61 in 3221213

  /home/nodejs/queue-cdn-purge.sh $site build-site

  . This also includes when the website index HTML page is detected as being older than index.json which triggers a website rebuild (I believe this is so the website picks up the most recent current and LTS releases for the download buttons/pages)

  build/ansible/www-standalone/resources/scripts/check-build-site.sh

  Line 16 in 3221213

  [ $indexjson -nt $indexhtml ] && $buildsite $site

• a release is promoted (during shasum creation)

  build/ansible/www-standalone/tools/promote/resha_release.sh

  Line 28 in 3221213

  /home/nodejs/queue-cdn-purge.sh $site resha_release

• a build (e.g. nightly/V8 canary/release) is promoted

  build/ansible/www-standalone/tools/promote/_promote.sh

  Line 61 in 3221213

  /home/nodejs/queue-cdn-purge.sh $site promote

  . Note that nightly/V8 canary builds get promoted every 30 mins which may mean an iojs+release build can have multiple promotions depending on when the sub-builds complete and upload their assets to staging.

To give an idea of frequency, these are the cdn-purges from today (including the Node.js 20.4.0 release):

2023-07-05T06:35:01+00:00, nodejs, promote
2023-07-05T07:35:01+00:00, nodejs, promote
2023-07-05T11:05:01+00:00, nodejs, promote
2023-07-05T12:35:01+00:00, nodejs, promote
2023-07-05T13:35:02+00:00, nodejs, promote
2023-07-05T14:00:01+00:00, nodejs, promote resha_release
2023-07-05T14:55:01+00:00, nodejs, build-site
2023-07-05T16:30:01+00:00, nodejs, build-site

The first two "promote"s are from the nightly build, the next three from the V8 canary, and the last "promote" (and "resha_release") from the manual promotion of 20.4.0. The subsequent "build-sites" are from merging nodejs/nodejs.org#5473 and nodejs/nodejs.org#5474 respectively.

Purging everything is rather heavy handed, but our current options in Cloudflare are to either purge everything (as we are doing) or purge a list of static URLs (there are further options only available for enterprise accounts which we do not have access to). Switching to a more selective cache purge requires us to determine what URLs to purge for all of the above scenarios that we are currently purging everything.

[richardlau]

I guess an interesting question would be, what would happen if we didn't purge the Cloudflare cache at all? One assumes that that may lead to getting stale pages/content (may even vary depending on what CF server you end up connecting to). Would new builds/releases not show up as 404 not founds are cached?

We could temporarily comment out

build/ansible/www-standalone/resources/scripts/cdn-purge.sh.j2

Lines 43 to 49 in 917f85f

	# purge full cache
	curl -X DELETE \
	"https://api.cloudflare.com/client/v4/zones/${zone_id}/purge_cache" \
	-H "X-Auth-Email: ${api_email}" \
	-H "X-Auth-Key: ${api_key}" \
	-H "Content-Type: application/json" \
	--data '{"purge_everything":true}'

or the cron job that runs that script on the 5 min timer

build/ansible/www-standalone/tasks/site-setup.yaml

Line 103 in 3221213

- "*/5 * * * * root /home/nodejs/cdn-purge.sh"

.

[richardlau]

Now that we have a CF enterprise account, we have more purging options available to us, but that still requires engineering work to determine what (if anything) needs to be purged and pass that information between queue-cdn-purge.sh and cdn-purge.sh (or design something else completely) and make the relevant CF API call.

[nschonni]

The only thing I can think of that might need a low expiry would be the index.tab/json.

I can't think of anything that really would need to be purged unless the cache got poisoned.

[targos]

Also directory indexes

[nschonni]

Was looking for something else, and found a little previous discussion over in #2375 and #2396 too

[targos]

And for the website, all the generated html pages. JS and CSS chunks should be fine since they have content hashes in their file names.

[targos]

There are also all "latest" symlinks like https://nodejs.org/docs/latest, https://nodejs.org/dist/latest/, https://nodejs.org/dist/latest-v20.x/, etc.

[targos]

Note that we now have access to enterprise features such as:

• Purge by URL prefix
• Purge by cache-tags

[richardlau]

I think cache-tags may make sense for the website, but for releases/nightlies/v8-canary we'd probably need to do either URL prefix (most likely because of docs) or by URL.