Expose a runnable backend without giving the ingress layer secrets

The backend can now be inspected through a loopback-only gateway while the database-aware API remains on the internal data network. A governed synthetic demo proves readiness, pgvector retrieval, reranking, and citation output through real HTTP without invoking cloud models.

Constraint: The previously exposed Bailian key is compromised and cannot be used for live validation

Constraint: The API must be locally reachable while retaining no internet egress

Rejected: Attach the API directly to the ingress network | a real socket test proved that configuration still had egress

Rejected: Publish a port from the internal-only network | Docker Desktop did not expose the host port

Confidence: high

Scope-risk: moderate

Reversibility: clean

Directive: Keep model and database credentials out of the gateway; do not relax the fixed demo identity/profile filters

Tested: make verify; 63 pytest tests; strict mypy; Ruff; Secret scan; Compose config; three backend image builds; API/DB/gateway healthy; migration exit 0; Swagger browser check; live/ready/meta/status/search HTTP; 20/20/20 index; API egress ENETUNREACH; empty gateway mounts and business environment

Not-tested: Live Bailian calls require a newly rotated key; full generated-answer flow and React UI are not implemented

backend/app/api/v1/demo.py

@@ -0,0 +1,356 @@
+"""Read-only offline RAG demo endpoints backed by the synthetic dataset."""
+
+from __future__ import annotations
+
+import asyncio
+import hashlib
+import re
+from dataclasses import dataclass
+from typing import Annotated, Any, Literal, Protocol, cast
+
+import psycopg
+from fastapi import APIRouter, Depends, HTTPException, status
+from pgvector.psycopg import register_vector
+from pgvector.vector import Vector
+from psycopg.rows import dict_row
+from pydantic import BaseModel, Field, field_validator
+
+from app.adapters.fake import FakeEmbeddingProvider, FakeReranker
+from app.core.config import Settings, get_settings
+from app.core.demo_identity import (
+    ACCESS_SCOPE_ID,
+    DEMO_EXPECTED_CHUNKS,
+    DEMO_FAKE_EMBEDDING_MODEL,
+    DEMO_SCOPE_NAME,
+    KNOWLEDGE_BASE_ID,
+    offline_embedding_profile_hash,
+)
+from app.core.secrets import SecretFileError
+
+QUERY_MAX_LENGTH = 500
+SNIPPET_MAX_LENGTH = 600
+TITLE_MAX_LENGTH = 120
+_SPACE_PATTERN = re.compile(r"\s+")
+
+
+class DemoCounts(BaseModel):
+    """Public aggregate counts for the synthetic dataset."""
+
+    chunks: int = Field(ge=0)
+    vectors: int = Field(ge=0)
+    searchable: int = Field(ge=0)
+
+
+class DemoStatusResponse(BaseModel):
+    """Safe readiness summary without database or approval internals."""
+
+    status: Literal["ready", "empty_dataset", "incomplete_dataset"]
+    dataset: Literal["synthetic-demo"] = "synthetic-demo"
+    counts: DemoCounts
+
+
+class DemoSearchRequest(BaseModel):
+    """Bounded request accepted by the offline demo search."""
+
+    query: str = Field(min_length=1, max_length=QUERY_MAX_LENGTH)
+    top_k: int = Field(default=5, ge=1, le=10)
+
+    @field_validator("query")
+    @classmethod
+    def normalize_query(cls, value: str) -> str:
+        normalized = _SPACE_PATTERN.sub(" ", value).strip()
+        if not normalized:
+            raise ValueError("query must contain non-whitespace text")
+        return normalized
+
+
+class DemoSearchItem(BaseModel):
+    """Public synthetic result; internal identifiers and hashes are excluded."""
+
+    title: str
+    snippet: str
+    page_label: str
+    score: float = Field(ge=0.0, le=1.0)
+    citation_id: str
+
+
+class DemoSearchResponse(BaseModel):
+    """Offline retrieval response with an explicit empty-dataset state."""
+
+    status: Literal["ok", "empty_dataset"]
+    dataset: Literal["synthetic-demo"] = "synthetic-demo"
+    results: list[DemoSearchItem]
+
+
+@dataclass(frozen=True, slots=True)
+class DemoCandidate:
+    """Private retrieval projection used only while constructing safe results."""
+
+    source_key: str
+    title: str
+    text: str
+    page_start: int | None
+    page_end: int | None
+
+    @property
+    def rerank_text(self) -> str:
+        return f"{self.title}\n{self.text}"
+
+
+class DemoRepository(Protocol):
+    """Read-only persistence boundary used by the demo router."""
+
+    def counts(self) -> DemoCounts: ...
+
+    def search(self, query_vector: tuple[float, ...], *, limit: int) -> list[DemoCandidate]: ...
+
+
+class PostgresDemoRepository:
+    """Read-only PostgreSQL/pgvector projection for approved synthetic chunks."""
+
+    def __init__(self, settings: Settings) -> None:
+        self._settings = settings
+
+    def _dsn(self) -> str:
+        return (
+            self._settings.database_url()
+            .set(drivername="postgresql")
+            .render_as_string(hide_password=False)
+        )
+
+    def counts(self) -> DemoCounts:
+        profile_hash = offline_embedding_profile_hash(self._settings.embedding_dimension)
+        with psycopg.connect(
+            self._dsn(),
+            connect_timeout=2,
+            row_factory=dict_row,
+        ) as connection:
+            row = connection.execute(
+                """
+                SELECT
+                  count(*)::integer AS chunks,
+                  count(*) FILTER (WHERE chunk.embedding IS NOT NULL)::integer AS vectors,
+                  count(*) FILTER (WHERE chunk.searchable)::integer AS searchable
+                FROM rag.chunks AS chunk
+                JOIN rag.access_scopes AS scope
+                  ON scope.id = chunk.access_scope_id
+                 AND scope.knowledge_base_id = chunk.knowledge_base_id
+                JOIN rag.documents AS document
+                  ON document.id = chunk.document_id
+                 AND document.knowledge_base_id = chunk.knowledge_base_id
+                 AND document.access_scope_id = chunk.access_scope_id
+                JOIN rag.document_versions AS version
+                  ON version.id = chunk.document_version_id
+                 AND version.document_id = chunk.document_id
+                WHERE chunk.knowledge_base_id = %s
+                  AND chunk.access_scope_id = %s
+                  AND scope.name = %s
+                  AND chunk.metadata ->> 'source_type' = 'synthetic'
+                  AND chunk.index_status = 'READY'
+                  AND chunk.approval_status = 'CLOUD_APPROVED'
+                  AND chunk.deleted_at IS NULL
+                  AND chunk.embedding_model = %s
+                  AND chunk.embedding_profile_hash = %s
+                  AND document.status = 'READY'
+                  AND document.deleted_at IS NULL
+                  AND document.active_version_id = chunk.document_version_id
+                  AND version.status = 'READY'
+                  AND version.review_state = 'CLOUD_APPROVED'
+                  AND version.outbound_manifest_sha256 = chunk.outbound_manifest_sha256
+                  AND version.embedding_profile_hash = chunk.embedding_profile_hash
+                """,
+                (
+                    KNOWLEDGE_BASE_ID,
+                    ACCESS_SCOPE_ID,
+                    DEMO_SCOPE_NAME,
+                    DEMO_FAKE_EMBEDDING_MODEL,
+                    profile_hash,
+                ),
+            ).fetchone()
+        if row is None:
+            return DemoCounts(chunks=0, vectors=0, searchable=0)
+        return DemoCounts(
+            chunks=int(row["chunks"]),
+            vectors=int(row["vectors"]),
+            searchable=int(row["searchable"]),
+        )
+
+    def search(self, query_vector: tuple[float, ...], *, limit: int) -> list[DemoCandidate]:
+        if len(query_vector) != self._settings.embedding_dimension:
+            raise ValueError("query vector dimension does not match the demo index")
+
+        vector = Vector(list(query_vector))
+        profile_hash = offline_embedding_profile_hash(self._settings.embedding_dimension)
+        with psycopg.connect(
+            self._dsn(),
+            connect_timeout=2,
+            row_factory=dict_row,
+        ) as connection:
+            register_vector(connection)
+            connection.execute("SET LOCAL statement_timeout = '3000ms'")
+            connection.execute("SET LOCAL hnsw.iterative_scan = strict_order")
+            connection.execute("SET LOCAL hnsw.ef_search = 100")
+            rows = connection.execute(
+                """
+                SELECT
+                  chunk.id::text AS source_key,
+                  COALESCE(NULLIF(chunk.section_path ->> 0, ''), '合成地质资料') AS title,
+                  chunk.cloud_text AS text,
+                  chunk.page_start,
+                  chunk.page_end
+                FROM rag.chunks AS chunk
+                JOIN rag.access_scopes AS scope
+                  ON scope.id = chunk.access_scope_id
+                 AND scope.knowledge_base_id = chunk.knowledge_base_id
+                JOIN rag.documents AS document
+                  ON document.id = chunk.document_id
+                 AND document.knowledge_base_id = chunk.knowledge_base_id
+                 AND document.access_scope_id = chunk.access_scope_id
+                JOIN rag.document_versions AS version
+                  ON version.id = chunk.document_version_id
+                 AND version.document_id = chunk.document_id
+                WHERE chunk.knowledge_base_id = %s
+                  AND chunk.access_scope_id = %s
+                  AND scope.name = %s
+                  AND chunk.metadata ->> 'source_type' = 'synthetic'
+                  AND chunk.searchable IS TRUE
+                  AND chunk.embedding IS NOT NULL
+                  AND chunk.index_status = 'READY'
+                  AND chunk.approval_status = 'CLOUD_APPROVED'
+                  AND chunk.deleted_at IS NULL
+                  AND chunk.embedding_model = %s
+                  AND chunk.embedding_profile_hash = %s
+                  AND document.status = 'READY'
+                  AND document.deleted_at IS NULL
+                  AND document.active_version_id = chunk.document_version_id
+                  AND version.status = 'READY'
+                  AND version.review_state = 'CLOUD_APPROVED'
+                  AND version.outbound_manifest_sha256 = chunk.outbound_manifest_sha256
+                  AND version.embedding_profile_hash = chunk.embedding_profile_hash
+                ORDER BY chunk.embedding <=> %s
+                LIMIT %s
+                """,
+                (
+                    KNOWLEDGE_BASE_ID,
+                    ACCESS_SCOPE_ID,
+                    DEMO_SCOPE_NAME,
+                    DEMO_FAKE_EMBEDDING_MODEL,
+                    profile_hash,
+                    vector,
+                    limit,
+                ),
+            ).fetchall()
+
+        return [
+            DemoCandidate(
+                source_key=cast(str, row["source_key"]),
+                title=cast(str, row["title"]),
+                text=cast(str, row["text"]),
+                page_start=cast(int | None, row["page_start"]),
+                page_end=cast(int | None, row["page_end"]),
+            )
+            for row in rows
+        ]
+
+
+def get_demo_repository(
+    settings: Annotated[Settings, Depends(get_settings)],
+) -> DemoRepository:
+    """Build the default repository without loading any model credential."""
+
+    return PostgresDemoRepository(settings)
+
+
+def _bounded_text(value: str, max_length: int) -> str:
+    normalized = _SPACE_PATTERN.sub(" ", value).strip()
+    if len(normalized) <= max_length:
+        return normalized
+    return f"{normalized[: max_length - 1]}…"
+
+
+def make_citation_id(source_key: str) -> str:
+    """Derive a stable opaque citation without returning an internal UUID."""
+
+    digest = hashlib.sha256(f"{DEMO_SCOPE_NAME}:{source_key}".encode()).hexdigest()
+    return f"demo-{digest[:16]}"
+
+
+def make_page_label(page_start: int | None, page_end: int | None) -> str:
+    if page_start is None or page_end is None:
+        return "页码未知"
+    if page_start == page_end:
+        return f"第 {page_start} 页"
+    return f"第 {page_start}-{page_end} 页"
+
+
+def _safe_result(candidate: DemoCandidate, score: float) -> DemoSearchItem:
+    return DemoSearchItem(
+        title=f"合成资料｜{_bounded_text(candidate.title, TITLE_MAX_LENGTH)}",
+        snippet=_bounded_text(candidate.text, SNIPPET_MAX_LENGTH),
+        page_label=make_page_label(candidate.page_start, candidate.page_end),
+        score=round(max(0.0, min(1.0, score)), 6),
+        citation_id=make_citation_id(candidate.source_key),
+    )
+
+
+def _database_unavailable(exc: BaseException) -> HTTPException:
+    return HTTPException(
+        status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+        detail="database unavailable",
+    )
+
+
+router = APIRouter(prefix="/api/v1/demo", tags=["offline-demo"])
+
+
+@router.get("/status", response_model=DemoStatusResponse)
+def demo_status(repository: Annotated[DemoRepository, Depends(get_demo_repository)]) -> Any:
+    try:
+        counts = repository.counts()
+    except (OSError, SecretFileError, psycopg.Error) as exc:
+        raise _database_unavailable(exc) from exc
+    state: Literal["ready", "empty_dataset", "incomplete_dataset"]
+    if counts.chunks == 0:
+        state = "empty_dataset"
+    elif (
+        counts.chunks == DEMO_EXPECTED_CHUNKS
+        and counts.vectors == DEMO_EXPECTED_CHUNKS
+        and counts.searchable == DEMO_EXPECTED_CHUNKS
+    ):
+        state = "ready"
+    else:
+        state = "incomplete_dataset"
+    return DemoStatusResponse(status=state, counts=counts)
+
+
+@router.post("/search", response_model=DemoSearchResponse)
+async def demo_search(
+    request: DemoSearchRequest,
+    repository: Annotated[DemoRepository, Depends(get_demo_repository)],
+    settings: Annotated[Settings, Depends(get_settings)],
+) -> Any:
+    embedder = FakeEmbeddingProvider(settings.embedding_dimension)
+    reranker = FakeReranker()
+    query_result = await embedder.embed_query(request.query)
+    candidate_limit = min(max(request.top_k * 3, 10), 20)
+    try:
+        candidates = await asyncio.to_thread(
+            repository.search,
+            query_result.vectors[0],
+            limit=candidate_limit,
+        )
+    except (OSError, SecretFileError, psycopg.Error) as exc:
+        raise _database_unavailable(exc) from exc
+
+    if not candidates:
+        return DemoSearchResponse(status="empty_dataset", results=[])
+
+    reranked = await reranker.rerank(
+        request.query,
+        [candidate.rerank_text for candidate in candidates],
+        top_n=min(request.top_k, len(candidates)),
+    )
+    results = [
+        _safe_result(candidates[item.index], item.relevance_score) for item in reranked.items
+    ]
+    return DemoSearchResponse(status="ok", results=results)