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scrabble-game/gateway/README.md
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Ilia Denisov 408da3f201
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Stage 6: gateway edge (Connect/FlatBuffers over h2c, platform/email/guest auth, sessions, rate-limit, admin passthrough, live push bridge)
New public ingress and the first network edge. Framework + a vertical slice of
operations end-to-end; remaining ops reuse the same transcode pattern in Stage 7.

Contracts (new module scrabble/pkg):
- push.proto (backend->gateway gRPC server-stream) + scrabble.fbs (FlatBuffers
  edge payloads), committed generated Go; buf/flatc Makefiles (dev-time codegen).

Backend:
- REST handlers on the /api/v1 groups: internal session endpoints
  (telegram/guest/email login -> mint, resolve, revoke) and the user slice
  (profile, submit_play, state, lobby enqueue/poll, chat).
- internal/notify in-process Publisher hub + internal/pushgrpc gRPC server
  (BACKEND_GRPC_ADDR) streaming your_turn/opponent_moved/chat/nudge/match_found;
  emission in game.commit, social, matchmaker.
- migration 00005 accounts.is_guest; guests are durable rows excluded from stats;
  ProvisionGuest; email-as-login (RequestLoginCode/LoginWithCode).

Gateway (new module scrabble/gateway):
- Connect Gateway service over h2c (Execute + Subscribe), FlatBuffers<->JSON
  transcode registry, Telegram initData HMAC validator (seam), session cache,
  token-bucket rate limiter (3 classes), push fan-out hub, backend REST + push
  gRPC client, admin Basic-Auth reverse proxy.

go.work: use ./pkg, ./gateway + replace scrabble/pkg. CI: gateway/**, pkg/**
path filters; unit build/vet/test span all three modules. Docs (PLAN,
ARCHITECTURE, FUNCTIONAL+ru, TESTING, READMEs) updated; gateway/pkg unit tests +
guest/email-login integration tests.
2026-06-02 22:38:24 +02:00

4.1 KiB

gateway

The Scrabble platform's only public ingress (module scrabble/gateway). It terminates the client's Connect-RPC + FlatBuffers traffic over HTTP/2 cleartext (h2c), authenticates the originating credential, mints/resolves a thin opaque session, rate-limits, injects X-User-ID when forwarding to the backend over REST/JSON, and bridges the backend's gRPC push stream to each client's in-app live channel. It also fronts the backend admin API behind HTTP Basic-Auth. See ../docs/ARCHITECTURE.md §2, §3, §10, §12.

Package layout

cmd/gateway/            # main: config -> backend client -> session cache ->
                        #   push hub -> Connect h2c server (+ admin) -> serve
proto/edge/v1/          # Connect envelope contract (committed generated Go)
internal/config/        # GATEWAY_* env config
internal/backendclient/ # typed REST client (+ X-User-ID) and push gRPC client
internal/session/       # in-memory session cache (LRU/TTL, backend fallback)
internal/ratelimit/     # token-bucket limiter (golang.org/x/time/rate)
internal/auth/          # Telegram initData HMAC validator (seam + fixtures)
internal/push/          # live-event fan-out hub (per-user client streams)
internal/transcode/     # FlatBuffers<->REST bridge + message_type registry
internal/connectsrv/    # the Connect Gateway service over h2c
internal/admin/         # Basic-Auth reverse proxy to the backend admin API

The FlatBuffers payloads and the backend push proto are the shared wire contracts in ../pkg.

Transport contract

A single Gateway Connect service: Execute(message_type, payload, request_id) for unary operations and Subscribe for the live stream. The payload bytes are FlatBuffers tables (scrabble/pkg/fbs); the gateway transcodes them to and from the backend's JSON. The session token rides in Authorization: Bearer; auth.* operations are unauthenticated and return the minted token. A unary domain outcome rides back in ExecuteResponse.result_code (HTTP 200); only edge failures become Connect error codes.

The Stage 6 message-type slice: auth.telegram, auth.guest, auth.email.request, auth.email.login, profile.get, game.submit_play, game.state, lobby.enqueue, lobby.poll, chat.post; live events your_turn, opponent_moved, chat_message, nudge, match_found. Further operations follow the same transcode pattern (added in Stage 7).

Configuration

Variable Default Notes
GATEWAY_HTTP_ADDR :8081 public Connect/h2c listener
GATEWAY_ADMIN_ADDR :8082 admin proxy listener (enabled only with creds)
GATEWAY_LOG_LEVEL info zap level
GATEWAY_BACKEND_HTTP_URL http://localhost:8080 backend REST base URL
GATEWAY_BACKEND_GRPC_ADDR localhost:9090 backend push gRPC address
GATEWAY_BACKEND_TIMEOUT 5s per backend REST call
GATEWAY_ADMIN_USER / GATEWAY_ADMIN_PASSWORD unset enable + guard the admin proxy
GATEWAY_TELEGRAM_BOT_TOKEN unset enable the Telegram auth path
GATEWAY_SESSION_TTL 10m cached session lifetime
GATEWAY_SESSION_CACHE_MAX 50000 cached session cap
GATEWAY_PUSH_HEARTBEAT_INTERVAL 15s live-stream keep-alive

Rate-limit defaults (built-in): public 30/min·IP (burst 10), authenticated 120/min·user (burst 40), admin 60/min·IP (burst 20), email-code 5/10 min·IP.

Run

GATEWAY_BACKEND_HTTP_URL=http://localhost:8080 \
GATEWAY_BACKEND_GRPC_ADDR=localhost:9090 \
go run ./gateway/cmd/gateway   # Connect edge on :8081

Generated code

The Connect envelope Go is committed under proto/edge/v1. Regenerate after editing the .proto (dev-time, like backend/cmd/jetgen):

make -C gateway tools   # go install protoc-gen-go + protoc-gen-connect-go
make -C gateway gen     # buf generate (local plugins)

The FlatBuffers payloads are generated in ../pkg (make -C pkg fbs).

Tests

go test -count=1 ./gateway/...

All gateway tests are hermetic: no real network, a fake backend (httptest) and credential fixtures. There is no integration (Docker) suite — the gateway holds no database.