220 lines
14 KiB
Markdown
220 lines
14 KiB
Markdown
# Architecture — Dược Thư RAG Medical Chatbot
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## Overview
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A medical chatbot grounded in the Vietnamese National Drug Formulary (Dược
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thư quốc gia Việt Nam 2018), built as a microservices monorepo. Users ask
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drug-related questions through a web chat UI; answers are generated via
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retrieval-augmented generation (RAG) over the formulary content, always
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citing the source drug monograph/section, and always carrying a medical
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disclaimer.
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## Service responsibilities & communication
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| Service | Owns | Talks to |
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| **api-gateway** (NestJS) | Single public entry point; request routing, JWT validation, rate limiting | Routes to auth-service, user-service, chat-service, ai-service over internal REST |
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| **auth-service** (NestJS) | Signup/login, password hashing, JWT issuance/refresh | Postgres (users); no dependency on other services |
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| **user-service** (NestJS) | Profile data, preferences, account settings | Postgres (profiles), called by gateway |
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| **chat-service** (NestJS) | Chat session lifecycle, message history persistence | Postgres (chat_sessions, chat_messages); calls ai-service per user message, persists both turns |
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| **ai-service** (Python/FastAPI) | RAG orchestration: understand query (LLM) → route to deterministic section/drug retrieval in Qdrant → generate + verify (LLM) → return answer + citations | Qdrant (payload-filtered retrieval), AWS Bedrock (Cohere embed-v4 for query embedding where used, Qwen3 via the Converse API for understanding/generation/entailment, Cohere rerank); conversation history is an in-process dict per `RagAgent`, not yet durable — see ADR 0008 |
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| **ingestion** (Python, offline batch) | One-time/periodic job: parse PDF → monographs → chunks → embeddings → upsert to Qdrant | Qdrant (write), AWS Bedrock (`cohere.embed-v4:0`); runs as CLI/CI/k8s Job, never in the live request path |
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| **web** (Next.js) | Chat UI, auth UI, citation/disclaimer rendering, session list | Calls api-gateway only |
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**Sync vs async**: the live chat path (web → gateway → chat-service →
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ai-service → Qdrant + AWS Bedrock → back) is synchronous request/response.
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Ingestion is fully decoupled, offline, batch — it populates Qdrant ahead of
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time and is never triggered by a chat request, since parsing the 37MB PDF and
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embedding thousands of chunks takes minutes. Internal protocol is REST/JSON
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for v1; a future gRPC migration is a documented option (see ADRs), not
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needed now.
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## Data stores
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- **Vector DB: Qdrant.** Chosen over pgvector because retrieval quality here
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depends on metadata-filtered ANN search (filter by drug name / section type
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combined with vector similarity) over a highly structured corpus — Qdrant
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makes that a first-class, single query. It also scales independently from
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the transactional Postgres and has a mature Helm chart for the production
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k8s target. See `docs/adr/0001-vector-db-qdrant.md`.
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- **Relational DB: PostgreSQL.** One instance, logically separated per
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service (users/credentials, profiles, chat sessions+messages). *As built,
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only `ai-service` uses it* — for conversation turns (`rag_conversation_turn`)
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and retrieval traces (`rag_retrieval_trace`). The users/profiles/sessions
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tables belong to services that do not exist yet.
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- **Redis.** Session/refresh-token cache, rate-limit counters, and reserved
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as the future job-queue backend (BullMQ/Celery) if async admin-triggered
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re-ingestion or background jobs are added later. **Not deployed** — nothing
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in the live path reads or writes Redis, so it was left out of
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`docker-compose.prod.yml` rather than run idle.
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## RAG ingestion pipeline (PDF-specific)
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The formulary is a structured per-drug reference, not free prose — the
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pipeline exploits that structure instead of naive fixed-size chunking. This
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section reflects an actual empirical investigation of the real PDF (not
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assumptions) — see `docs/adr/0003-pdf-parsing-strategy.md` for the full
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methodology, cross-tool comparison, and validation numbers.
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1. **Extraction**: PyMuPDF (`fitz`) as primary extractor. This document has
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**no bookmark/outline** (`doc.get_toc()` returns 0 entries — confirmed,
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do not rely on it) and is a **tagged PDF with only a shallow, unusable
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structure tree** (~29 generic H1/P elements covering a fraction of 1668
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pages — also confirmed dead-end, not a data source). PyMuPDF's reading
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order was cross-validated against `pdfplumber` and `opendataloader-pdf` on
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real sample pages: pdfplumber's default text order is **unreliable** for
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this layout (scrambles paragraph order, leaks marked-content artifacts) —
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use it only for its dedicated table-extraction API, never for body text.
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Raw per-page extraction is persisted to `ingestion/data/interim/` so
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re-segmentation doesn't require re-running the expensive extraction step.
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2. **Segmentation**: drug-entry boundaries are detected via **bold-font
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spans** (PyMuPDF span `font` containing `"Bold"`), not font-size alone —
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font size for title/heading spans varies between monographs (confirmed:
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10.0pt and 9.5pt both occur for genuine drug-title headings), so bold is
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the reliable signal, all-caps + short length narrows it to monograph
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titles specifically. Section headings inside a monograph are also bold
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spans, cross-checked against a canonical taxonomy (`chi_dinh`,
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`chong_chi_dinh`, `lieu_dung`, `tac_dung_phu`, `tuong_tac_thuoc`, plus
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real observed extras like `ten_thuong_mai` "Tên thương mại" not in the
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book's own documented 19-field list — treat the taxonomy as open/
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extensible, not a fixed enum). Multi-line wrapped titles/headings (long
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Vietnamese names/vaccine names) must be merged across consecutive
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bold+all-caps lines before matching — this was the single largest source
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of missed detections in validation. Output: `{drug_id, drug_name,
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source_page_range, sections: {...}}` per drug, persisted to
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`ingestion/data/processed/monographs.jsonl` and validated both
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automatically (see ADR 0003) and via manual spot-check in
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`ingestion/notebooks/`.
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3. **Chunking** (monograph range only, pp. 99-1496 — see
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`docs/adr/0004-chunking-strategy.md` for the full measured rationale):
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each `(drug_id, section_key)` pair is the chunk unit; a section stays one
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chunk if it's under an **800-token ceiling** (chars/4 estimate — a
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validated line, not a guess: whole-corpus measurement across 682
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monographs shows ~16 of 18 section types clear it comfortably at their
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p90). Two sections routinely exceed it — `dược lý và cơ chế tác dụng`
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(35.7% of monographs that have it) and `liều lượng và cách dùng`
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(29.6%) — sub-chunking is the **routine** path for those two, not a rare
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edge case. Oversized sections are split with a **sentence-boundary-aware
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sliding window** (~600-700 tokens/sub-chunk, ~1 sentence/50-80 token
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overlap), never a blind character/line window — PDF line-wrap points
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are not safe cut points, and a mid-sentence split risks separating an
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adult/child dosing instruction (a measured, common pattern — outlier
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catalog item 17) into two chunks. Every chunk carries `chunk_id`,
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`drug_id`, `drug_name`, `section_key`, `section_display_name`,
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`atc_codes`, `source_page_range`, `part_index`/`part_count` as Qdrant
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payload — this is what makes citations possible. **Known open gaps**
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(see ADR 0004): sub-compound tagging inside class-level/multi-ATC
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monographs (25.5% of the corpus) is not yet solved; `source_page_range`
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is monograph-level, not sub-chunk-exact; chunking for general chapters/
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appendices is a separate, not-yet-designed task; a confirmed
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header/footer-boilerplate leak into section text (98.4% of monographs
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affected) must be fixed upstream before this design runs against real
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data.
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4. **Embedding + load**: AWS Bedrock `cohere.embed-v4:0` in batches
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(cached by `(model_id, input_kind, text_sha256)` so a reload needs no
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repeat cloud calls), upserted into Qdrant collection `duocthu_v1`
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(15,100 points, live) keyed by `uuid5(chunk_id)` for idempotent re-runs; a
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`<collection>__manifest` sidecar records the corpus sha/model/dimensions
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and `ai-service` refuses to start against a mismatched one (F-05).
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5. **Batch job, not synchronous**: runs as a CLI command locally, and as a
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Kubernetes `Job`/`CronJob` in production — never inside the ai-service
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request path.
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## Safety / guardrails
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- **System prompt** instructs the model to answer only from retrieved
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context, never state a dosage/contraindication/interaction not present in
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it, always append a disclaimer, and say "not found in the formulary"
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rather than guess when retrieval is irrelevant.
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- **Deterministic routing, not a similarity-confidence gate.** The live
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path resolves drug + section by exact payload filter (`section_key`
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routing moved contraindication hit@1 from 0.05 to 1.00 — similarity
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ranking alone was not reliable enough to gate on). A quarantined table/
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formula in the retrieved evidence, or missing page provenance, forces
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`VERIFY_PDF`/abstain deterministically — never an LLM-reported confidence
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score. Dense vector similarity search exists (`QdrantRetriever.search()`)
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but is reachable only in the legacy no-generator-configured mode, not the
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live agent path. See ADR 0008.
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- **Citations from metadata, not LLM prose**: the `citations` list is built
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directly from retrieved-chunk metadata, independent of what the LLM says,
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so the frontend can always show verifiable sources.
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- **Disclaimer enforced at multiple layers**: system prompt + a
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non-LLM-generated static string always appended to the API response + a
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persistent, non-dismissible UI banner.
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- **Scoped refusal**: out-of-scope questions (e.g. general symptom
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diagnosis) get a scoped refusal directing to a professional, not an
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ungrounded general-knowledge answer.
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## Build roadmap
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1. **Ingestion pipeline + populated, queryable vector DB.** Done when a CLI
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run populates Qdrant and a test script retrieves the correct
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drug/section chunk for a sample query — no API, no LLM call yet.
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2. **ai-service (FastAPI) wrapping RAG + AWS Bedrock.** Done when a `curl` to
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`/v1/rag/query` returns a grounded answer with a traceable citation and an
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always-present disclaimer. **Done** — live since 2026-08-05, see ADR 0008.
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3. **auth/user/chat services + api-gateway.** Done when register → login →
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chat message flows end-to-end through the gateway only, persisted in
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Postgres. **Not started** — all four directories still hold only a
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`README.md` and a `package.json`. Phases 4-6 were done around this gap,
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so the live system has no gateway and no auth (see below).
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4. **Next.js frontend chat UI.** Done when a browser user can log in, ask a
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question, and see a grounded answer with citation + disclaimer banner.
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**Done except the login half** — chat, citations, evidence panel and the
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disclaimer banner are live; there is no login because Phase 3 does not
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exist. The browser calls `apps/web`'s own route handlers, which proxy
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directly to `ai-service`.
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5. **Containerize + docker-compose local.** Done when `docker compose up`
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from a clean checkout brings up the full stack and the Phase 4 flow works.
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**Done** — 2026-08-10. `infra/docker/docker-compose.prod.yml` is what
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production actually runs.
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6. **Kubernetes/Helm + Terraform + CI + ArgoCD (GitOps) deployment.** Done
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when CI builds/tests/pushes an image and bumps the target environment's
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Helm values file, the team's ArgoCD instance (see `infra/argocd/`,
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`docs/adr/0002-argocd-gitops.md`) picks up the change and syncs the
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cluster, and the Phase 4 flow works against the k8s-hosted stack. CI
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never runs `kubectl`/`helm` directly against a cluster. Cloud provider
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choice (AWS/GCP/Azure) only affects the Terraform module implementations,
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not this repo's structure.
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**Still the destination — not started, not dropped.** Production was
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shipped ahead of it on an interim single-box setup (see "Deployment as
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actually built" below), which is a stopgap, not a replacement: ADR 0002
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remains *Accepted*. Nothing here exists yet — `infra/k8s/`,
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`infra/helm/medical-chatbot/templates/` and `infra/terraform/` are empty
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scaffolds (`.gitkeep` only), the chart is version `0.0.0`, and every ArgoCD
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`Application` manifest still carries unresolved `TODO`s for project, repo
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URL and destination cluster.
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This phase also includes a **repository move to the team's self-hosted
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Gitea** on the company domain, which is where the GitOps repo is intended
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to live; the project stays on private GitHub until that move is made
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deliberately. Hard boundary meanwhile: the team's existing
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`git.vinmec.tech/ai-team/gitops` repository is **reference-only — never
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push this project into it**.
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## Deployment as actually built (2026-08-10)
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Production is **not** the Phase 6 design. It is a single AWS EC2 `t3.large`
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running `infra/docker/docker-compose.prod.yml` — postgres, qdrant,
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ai-service, web, and Caddy terminating TLS for `realvuxbaro.me` via
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automatic Let's Encrypt. Bedrock is reached through an IAM instance role, so
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no long-lived AWS key exists on the box or in any env file.
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CI/CD is `.github/workflows/deploy.yml`: a push to `master` SSHes in, resets
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the checkout, rebuilds only `ai-service`/`web`, runs migrations and
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health-checks both. It does not touch postgres/qdrant/caddy, so the 15,100
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Qdrant points survive deploys (they live in a named volume).
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This is an **interim setup, not a decision against Phase 6.** It exists
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because a working public demo was needed sooner than the Kubernetes path
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could deliver one. The expensive prerequisite for that path — containerising
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both apps — is exactly what this work produced, so the Dockerfiles and
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compose services port over when the Gitea + team-ArgoCD migration is
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actually done. Phase 6 and ADR 0002 both stand as written.
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See `docs/adr/` for architecture decision records. `docs/runbooks/` is still
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**empty** — the operational knowledge that would live there (restoring a
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Qdrant snapshot onto a fresh box, what a failed deploy looks like, why
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`uvicorn --reload` must not be used on Windows here) currently only exists
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in `docs/progress-log.md`.
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