docs(architecture): design for durable multi-instance approuter static serving - #1642
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…c serving POST /admin/rebuild mutates only the one approuter instance the CF router hits, and the push is ephemeral (a restart reverts to droplet static). With instances>1 (autoscaler) the fleet serves a mix of old/new static until the next full deploy. This design doc frames the problem, constraints (no object store; approuter binds srv-api + HANA + WS already exist), and options: A) instance-targeted fan-out (interim), B) CAP/HANA-backed versioned bundle + approuter self-sync (recommended), C) object store (needs entitlement), D) eliminate runtime push (rejected). Recommends B, phased. For review.
jung-thomas
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August 11, 2026 11:18
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Design proposal — durable multi-instance approuter static serving
Follow-up to the 2026-08-10/11 stale-static incident (root cause fixed in #1628; runtime-push guard added in #1641). This PR is a design doc only (no code) for the deeper architectural gap you asked to address.
The gap
POST /admin/rebuild(approuter/server.js:373-374) atomically swaps the localstatic/on only the one instance the CF router hits, and the push is ephemeral — acf restartre-extracts the droplet and discards it. So withinstances > 1(autoscaler), the fleet serves a mix of old/new static until the next full deploy, and autoscaled-up instances start from the (possibly stale) droplet. Key finding: "restart after rebuild" is a recovery tool, not a propagation mechanism.Options (full detail in the doc)
X-Cf-App-Instance): interim, contained; doesn't survive restart/scale-up.srv-apibinding +/ws/*; no new entitlement.Recommendation
Phased: Phase 0 done (#1628 + #1641) → Phase 1 optional fan-out → Phase 2 Option B.
Open questions for you
/ws/*WebSocket?Once you pick a direction I'll turn it into an implementation plan + PR. Draft for review.