fix(deploy): recover maintenance page on tab refocus & bfcache restore#167
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The maintenance page only re-checked /api/healthz via a 5s setInterval and a 20s <meta refresh>. Both are timers, which browsers throttle or suspend in backgrounded tabs and asleep devices. A tab parked on the page during a deploy window could stay stranded on "Brewing a new version" indefinitely after origin recovered. Also poll healthz on visibilitychange (tab refocused) and pageshow (back/forward cache restore) so the live app returns the instant the user looks at the tab, not whenever a throttled timer happens to fire.
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Why
Prod-incident report: user stranded on the "Brewing a new version" maintenance page while the origin was fully healthy (verified
/and/api/healthz→ 200 end-to-end through CF→tunnel→nginx→sa-web;cf-cache-status: DYNAMIC, no stale edge copy, no service worker). The page was a stale tab, not a live outage.Root cause
docker/maintenance.htmlonly re-checked/api/healthzvia a 5ssetIntervaland a 20s<meta refresh>. Both are timers — browsers throttle/suspend timers in backgrounded tabs and asleep devices (mobile Safari especially). A tab parked on the page during a deploy window can sit on "Brewing…" indefinitely after origin recovers, because the auto-reload timer never fires.Fix
Also poll healthz on:
visibilitychange(tab brought back to foreground)pageshow(restored from back/forward cache)So the live app returns the instant the user looks at the tab, instead of waiting on a throttled timer. Dependency-free, no behavior change to the happy path;
<meta refresh>remains the no-JS fallback.Test
Static HTML page; no automated test harness for it. Manual: load page, background the tab, bring it back → fires an immediate healthz check.