diff --git a/docs/adr/0011-deployment-topology.md b/docs/adr/0011-deployment-topology.md new file mode 100644 index 0000000..6dec96f --- /dev/null +++ b/docs/adr/0011-deployment-topology.md @@ -0,0 +1,249 @@ +# ADR-0011 — Deployment topology: one binary, three blessed shapes + +- **Status:** Proposed +- **Date:** 2026-07-05 +- **Closes:** the deployment-topology ADR reserved by [ADR-0008](0008-fob-and-green-zone.md)'s + worked example ("the deployment topology itself may get its own ADR once that design closes"). +- **Origin:** [2026-07-05 deployment-topology spec](../superpowers/specs/2026-07-05-deployment-topology-design.md) + §2–§4. The TLS/edge fork was researched via a six-family survey — see the companion + [TLS/edge decision brief](../superpowers/specs/2026-07-05-tls-edge-decision-brief.md). +- **Related:** [ADR-0002](0002-north-star-and-fused-core.md) (the fused per-call vertical no + topology may split), [ADR-0005](0005-event-bus.md) (Valkey = bus + KV + presence; media never + rides the bus; the bus is never billing source-of-truth), [ADR-0006](0006-ingress-posture.md) + (two inbound protocols only; the tap is egress-only), [ADR-0007](0007-trunk-rented-transport.md) + (rented transport ⇒ public HTTPS/WSS reachability is non-negotiable), + [ADR-0008](0008-fob-and-green-zone.md) (the FOB/green-zone rule this ADR applies to + deployment), [ADR-0009](0009-spend-gate-honest-rescope.md) (ledger trait: in-memory + single-node, Valkey-backed fleets), [ADR-0010](0010-spearhead-benchmark-sim-harness.md) + (sequencing this ADR must not reorder), README pillar 6 ("one binary, one bus, one deploy"). + +## Context + +[ADR-0008](0008-fob-and-green-zone.md) made the build-vs-reuse doctrine physical in a worked +example — the all-in-one container — and reserved the topology ADR for when the design closed. +Two things have since closed it: the rented transport +([ADR-0007](0007-trunk-rented-transport.md)) is merged, so every deployment must now present a +public HTTPS/WSS edge to a CPaaS; and slice-5/seams landed the operational primitives a +deployment story needs (drain lifecycle, `/readyz`, admission cap, `MediaAddressConfig`, +`EventSink`). + +The CPaaS side imposes a hard external spec on any edge rutster ships (researched in the +[decision brief](../superpowers/specs/2026-07-05-tls-edge-decision-brief.md); restated here +because these invariants are load-bearing for every decision below): + +1. Publicly-CA-trusted cert; **no self-signed path exists** (Twilio error 31910). Auto-renewal + is availability-critical. +2. wss:// on 443, open to the whole internet: Twilio publishes no egress IPs and offers no + mTLS. Auth is application-layer only (HMAC signatures). +3. One WS per call, up to 24 h, 50 msg/s/direction at 20 ms cadence; zero tolerance for frame + buffering, connection-lifetime caps, or write-side idle timers. Neither Twilio nor Telnyx + documents WS keepalive — keepalive is entirely our job. +4. `` URLs carry **no query strings** — wss routing keys on hostname/path only. +5. `X-Twilio-Signature` is HMAC over the URL *as Twilio saw it*: the edge must forward + `X-Forwarded-Proto/Host` honestly and the FOB must reconstruct the public URL. +6. Webhook budget: sub-second for UX, 15 s hard cap — no blocking issuance in the handshake + path. +7. TLS 1.2+1.3, mainstream ECDHE, never 1.3-only; never pin Twilio certs. + +Design for Twilio; Telnyx/Vonage come for free (strictly less demanding, plus optional +source-IP allowlisting as extra hardening Twilio can't use). + +On the other side, the FOB's own physics constrain every shape: per-call state is in-process +and non-migratable (the fused vertical, [ADR-0002](0002-north-star-and-fused-core.md)), WebRTC +media is per-session UDP direct to the process, and calls run for hours. Any topology that +assumes migratable, short-lived, connectionless workloads is disqualified before it starts. + +## Decision + +**The FOB never decomposes; topology is a configuration property, not a code property.** The +same binary runs in every blessed shape; only `RUTSTER_*` env and what is deployed alongside it +differ. "Microservices" in rutster means *green-zone services get their own +processes/containers* — never that the per-call vertical splits +([ADR-0002](0002-north-star-and-fused-core.md)). + +### The three blessed shapes + +#### T1 — Solo (all-in-one container) — shipped artifact + +One image (`rutster-allinone`), s6-overlay as PID 1 supervising four processes: + +| Process | Role | Binding | +|---|---|---| +| `caddy` | Edge: ACME, TLS termination, WS proxy to FOB | :443/:80 public | +| `rutster` (FOB) | Engine | 127.0.0.1:8080 (behind Caddy); media UDP direct | +| `rutster-brain-realtime` | Brain | 127.0.0.1:8082 loopback tap (as today) | +| `valkey-server` | Dark on day one except `EventSink` | 127.0.0.1:6379 | + +Two volumes, both non-negotiable: `/data` (Caddy cert/ACME state — loss risks the Let's +Encrypt duplicate-cert lockout, a total-inbound-outage class of failure) and `/var/lib/valkey` +(stream/state persistence). WebRTC media UDP goes **direct to the FOB**, never through Caddy: +host networking recommended; otherwise published `RUTSTER_MEDIA_PORT_RANGE` + +`RUTSTER_MEDIA_ADVERTISED_IP` (NAT 1:1 model, no STUN — unchanged from slice-5/seams). + +Valkey ships bundled from v1 **before most consumers exist**: the operator contract (volumes, +ports, upgrade shape) is stable from day one, so the spend ledger +([ADR-0009](0009-spend-gate-honest-rescope.md)) and the fleet directory land later without +changing the deployment shape. Cost accepted: ~15 MB and one mostly-idle process. + +#### T2 — Modular (compose stack) — shipped artifact, the reference deployment + +Services: `caddy` (image `rutster-edge`), `engine` (`rutster-engine`), `brain` +(`rutster-brain`), `valkey` (upstream `valkey/valkey`). + +- **The brain shares the engine's network namespace** (`network_mode: "service:engine"`) so + the loopback-only tap posture (`resolve_tap_url` rejects non-loopback until step 6) survives + unchanged. The brain graduates to its own netns when the wss:// tap lands (step 6). +- Valkey is its own service on the compose network — network-near, satisfying + [ADR-0005](0005-event-bus.md)'s sub-ms rule. +- `stop_grace_period: 660s` paired with `RUTSTER_DRAIN_DEADLINE_SECS=600` (grace > drain). +- BYO-proxy supported: disable the `caddy` service; the engine keeps its plaintext `:8080` + mode; tuned-timeout snippets for nginx/HAProxy/Traefik ship in + [`docs/deploy/reverse-proxies.md`](../deploy/reverse-proxies.md). + +#### T3 — Fleet — ADR chapter only (paper; no code in this epoch) + +N **symmetric** nodes, each running the T1 process set *minus* valkey, plus a shared green +zone: one Valkey (presence + directory + the [ADR-0009](0009-spend-gate-honest-rescope.md) +spend ledger) and object storage (named as required, still deferred). Wildcard DNS +`*.pbx.domain`; per-node certs (see the fleet cert story below). The per-node admission cap is +the [ADR-0010](0010-spearhead-benchmark-sim-harness.md) benchmark number (replacing the +`RUTSTER_MAX_SESSIONS=64` placeholder). Scale-in is drain-then-terminate only; spot instances +are rejected for the engine tier (2026-07-04 review — a reclaimed node kills every +non-migratable call on it). + +### Edge doctrine + +#### Bundled edge: Caddy (both shipped artifacts, same build, same Caddyfile) + +Custom xcaddy build (the `rutster-edge` image): Caddy core (Apache-2.0) + a curated DNS-01 +plugin set — cloudflare, route53, porkbun, hetzner, desec (duckdns excluded: no license file). +Zero-downtime in-memory cert renewal; verified protocol-unaware WS tunneling (no frame +buffering). Config is a ~6-line Caddyfile with tuned timeouts, honest `X-Forwarded-*`, and +`stream_close_delay` above max call duration — **plus a CI e2e case for +config-reload-during-live-call, because the upstream mitigation has an open bug trail +(caddy #6420/#7222) and is not trusted untested.** + +#### In-process TLS: staged — the ratified end-state, not adopted wholesale now + +[ADR-0008](0008-fob-and-green-zone.md) claims the trust-domain edge as security-constitutive +FOB territory, and str0m already terminates DTLS-SRTP in-process on the same aws-lc-rs +provider — "keep TLS out of the FOB" is not the objection. The objection is economics: owning +an ACME renewal state machine forever, in a 45-day-cert world. + +- **Phase 1 (this epoch):** `axum-server` + rustls with operator-supplied certs + (`RUTSTER_TLS_CERT`/`RUTSTER_TLS_KEY`), hot-reload without dropping live WS. + Plaintext-behind-Caddy stays the artifact default. +- **Phase 2 (in-binary ACME) triggers, named:** (a) Let's Encrypt dns-persist-01 confirmed GA + (closes the wildcard/CGNAT issuance gap; instant-acme already parses it); (b) a field + incident where Caddy reload/`stream_close_delay` drops live calls; (c) fleet or + VPS-forwarder topology making encrypted-to-the-binary a selling point; (d) maintenance + fatigue with the curated xcaddy plugin build. Until a trigger fires, Phase 2 is deliberately + not built — no turnkey ACME crate fits the tree today (rustls-acme conflicts with the + deny.toml rcgen/x509-parser posture). + +#### Fleet cert story + +Per-node public TLS names are CPaaS-imposed (invariant 4 + node-addressed placement). Two +blessed patterns: + +1. **Wildcard `*.pbx.domain` via DNS-01** with central issuance/distribution. +2. **Per-node distinct certs** (`node-N.domain`) where the wildcard private key must not live + on every node — one compromised node otherwise burns the whole namespace. + +Traps, stated so nobody re-discovers them in production: N nodes independently requesting the +*identical* wildcard hit the Let's Encrypt duplicate-cert limit (5/week) — distinct names or +central distribution only. **Caddy on-demand TLS is rejected for node names**: the first +handshake to a fresh name blocks seconds on issuance, colliding with the sub-second webhook +budget (invariant 6), and its rate-limit knobs are deprecated. Node names known at provision +time get pre-issued certs. + +### Fleet placement paradigm (the trunk webhook handler and session API grow *toward* this; no fleet code in this epoch) + +**Node-addressed URLs + Valkey presence; no router tier.** (Decision 2026-07-05 over the two +rejected alternatives below.) + +- Nodes heartbeat capacity into Valkey (TTL'd presence keys — the + [ADR-0005](0005-event-bus.md) presence layer). +- Placement happens **at answer time** by whichever node the request lands on (`api.domain`, + DNS round-robin): read fleet capacity → pick owner → return TwiML whose Stream URL is + `wss://node-K.pbx.domain/...`. The media WS dials the owning node directly — zero extra + hops, consistent with connection-follows-ownership. Twilio's answer-time Stream URL is + purpose-shaped for this: invariant 4 permits hostname routing. +- WebRTC: the create-session response carries the owner's node-addressed base URL + advertised + media IP (UDP is already direct). +- Misdirected control ops (e.g. a DELETE hitting a non-owner) consult the Valkey directory and + **307-redirect** to the owner. +- **Degraded mode (Valkey dark): the answering node self-places if it has capacity**; presence + heals via TTL on recovery. Fail-safe degradation, consistent with + [ADR-0009](0009-spend-gate-honest-rescope.md)'s posture. +- Single-node is the degenerate case of the same code: a one-entry directory. + +**Rejected: a routing tier that proxies everything.** It would put every 20 ms media frame +through an extra userspace hop and re-create exactly the SPOF the symmetric design avoids — +and it buys nothing, because the CPaaS already lets the answer-time URL do the routing. + +**Rejected: a distinguished control node.** It breaks node symmetry (two artifacts, two +failure stories, a promotion protocol) to solve a problem the presence directory already +solves; placement needs fleet state either way, and Valkey is already the fleet-state home +([ADR-0005](0005-event-bus.md)). + +### Rejected shapes + +- **Decomposing the FOB into services** — rejected **permanently**, not deferred. + Media/reflex/tap/spend stay one process, one trust domain + ([ADR-0002](0002-north-star-and-fused-core.md)). +- **Serverless.** Lambdas are categorically unfit for the engine: non-migratable multi-hour + calls, per-session UDP sockets, in-process media state. Webhook-on-Lambda buys nothing + because placement needs fleet state anyway. +- **Tunnels in production.** Cloudflare Tunnel and ngrok see plaintext audio at the vendor + edge (an unconsented subprocessor — DPA/BAA/PCI failure), document mid-call WS kills, and + cloudflared has an open Twilio handshake bug (cloudflared #1465). ngrok is the blessed + 5-minute demo path (the only tunnel with a proven Media Streams record); Tailscale Funnel is + the privacy-clean single-user demo (TLS terminates on-node), unsizable beyond that. **No + tunnel carries inbound UDP → homelab behind CGNAT is PSTN-only, period.** The production + graduation path is a cheap VPS + WireGuard as a dumb TCP forwarder with TLS terminating at + home, or running the engine on the VPS — see + [`docs/deploy/homelab.md`](../deploy/homelab.md). +- **NLB TLS listeners — never.** Fixed 350 s idle timeout that silently drops flows, and no + HTTP context, so `X-Forwarded-*` headers for signature validation (invariant 5) don't exist. + The ALB path is documented as a docs-only appendix + ([`docs/deploy/aws.md`](../deploy/aws.md)), never a shipped artifact. +- **k8s manifests/Helm.** Compose-first (README pillar 6). k8s notes live in docs only (drain + vs `terminationGracePeriodSeconds`); manifests are a later rung if demand appears. + +### Deferred, named (so the boundary is deliberate) + +- **T3 fleet implementation** (presence heartbeats, directory redirects, placement code). +- **The zero-egress / air-gap profile** (SBC layer-2 ingress per + [ADR-0007](0007-trunk-rented-transport.md) layer 2 + a self-hosted brain): a defined + profile, no code this epoch. T1 is about one-command simplicity, not isolation. +- **In-binary ACME (rustls Phase 2)** — behind the four named triggers above. +- **Durable CDR pipeline**: `ValkeyEventSink` is evidence preservation on a capped stream — + explicitly NOT the billing ledger ([ADR-0005](0005-event-bus.md) source-of-truth rule). + CDR → object storage stays deferred. +- **Multi-tenancy** (needs its own ADR before schemas ossify); wss:// tap + brain fleet + + resume tokens (step 6); media-thread sharding graduation; arm64 images. + +## Consequences + +- **Positive:** one binary and one mental model across all three shapes — an operator's + knowledge transfers from `docker run` to a fleet; the CPaaS invariants are satisfied by a + decade-hardened ACME loop (Caddy) rather than a DIY renewal state machine; the fleet + paradigm needs zero new infrastructure beyond what [ADR-0005](0005-event-bus.md) already + bundles; the rejected shapes are written down, so nobody burns a week discovering that + Lambda or NLB-TLS can't work. +- **Negative:** the curated xcaddy DNS-plugin set is a permanent maintenance surface until + dns-persist-01 GA; Caddy config-reload behavior vs live calls is mitigated + (`stream_close_delay` + CI e2e) but has an open upstream bug trail; homelab WebRTC behind + CGNAT is unsolved **by design** — only the VPS graduation fixes it, and the docs must say so + loudly or operators will read "homelab supported" as including browser calls. +- **Mitigation:** the Phase-2 triggers convert both negatives into a planned exit; the + `docs/deploy/` tree ships with a copy-paste-to-first-call acceptance bar so the honest + limits are in the operator's face, not in a footnote. + +## References + +- [2026-07-05 deployment-topology spec](../superpowers/specs/2026-07-05-deployment-topology-design.md) — §2–§4 are this ADR's source +- [TLS/edge decision brief](../superpowers/specs/2026-07-05-tls-edge-decision-brief.md) — six-family survey + the CPaaS ground truth (external citations live there) +- [ADR-0002](0002-north-star-and-fused-core.md) · [ADR-0005](0005-event-bus.md) · [ADR-0006](0006-ingress-posture.md) · [ADR-0007](0007-trunk-rented-transport.md) · [ADR-0008](0008-fob-and-green-zone.md) · [ADR-0009](0009-spend-gate-honest-rescope.md) · [ADR-0010](0010-spearhead-benchmark-sim-harness.md) +- The `docs/deploy/` tree: [topologies](../deploy/topologies.md) · [quickstart-docker](../deploy/quickstart-docker.md) · [homelab](../deploy/homelab.md) · [aws](../deploy/aws.md) · [reverse-proxies](../deploy/reverse-proxies.md) · [certificates](../deploy/certificates.md)