feat: serialize official record imports

apps/api/app/importer.py

@@ -3,11 +3,12 @@ from __future__ import annotations
 import hashlib
 import re
 import time as time_module
+from contextlib import contextmanager
 from dataclasses import asdict, dataclass
 from datetime import date, datetime, time, timezone
 
 import httpx
-from sqlalchemy import select
+from sqlalchemy import select, text
 from sqlalchemy.orm import Session
 from rf4_research.official_parser import RecordsContractError, parse_official_records
 
@@ -24,6 +25,10 @@ class ImportSourceError(ValueError):
     pass
 
 
+class ImportAlreadyRunning(RuntimeError):
+    pass
+
+
 @dataclass(frozen=True, slots=True)
 class RawRecord:
     region: str
@@ -105,7 +110,42 @@ def fetch_records(
     raise AssertionError("unreachable")
 
 
+def _lock_key(url: str, region: str, category: str) -> int:
+    digest = hashlib.sha256(f"{url}|{region.upper()}|{category}".encode()).digest()
+    return int.from_bytes(digest[:8], byteorder="big", signed=True)
+
+
+@contextmanager
+def _official_import_lock(session: Session, *, url: str, region: str, category: str):
+    bind = session.get_bind()
+    if bind.dialect.name != "postgresql":
+        yield
+        return
+    connection = bind.connect()
+    key = _lock_key(url, region, category)
+    try:
+        acquired = bool(connection.scalar(text("SELECT pg_try_advisory_lock(:key)"), {"key": key}))
+    except Exception:
+        connection.close()
+        raise
+    if not acquired:
+        connection.close()
+        raise ImportAlreadyRunning("official import is already running for this source and category")
+    try:
+        yield
+    finally:
+        try:
+            connection.execute(text("SELECT pg_advisory_unlock(:key)"), {"key": key})
+        finally:
+            connection.close()
+
+
 def import_records(session: Session, *, url: str, region: str, category: str, html: str | None = None) -> OfficialRecordImport:
+    with _official_import_lock(session, url=url, region=region, category=category):
+        return _import_records_locked(session, url=url, region=region, category=category, html=html)
+
+
+def _import_records_locked(session: Session, *, url: str, region: str, category: str, html: str | None = None) -> OfficialRecordImport:
     run = OfficialRecordImport(started_at=datetime.now(timezone.utc), status=ImportStatus.running, source_url=url, rows_seen=0, rows_created=0, rows_updated=0)
     session.add(run)
     session.commit()