fix: convert DATABASE_URL to asyncpg scheme for async SQLAlchemy engine

The K8s DATABASE_URL env var uses postgresql:// which makes
create_async_engine try to load psycopg2 (sync driver). Add
_ensure_async_dsn() to convert postgresql:// and postgres:// to
postgresql+asyncpg:// at engine creation time. asyncpg is already
in dependencies.

.gitignore

@@ -62,6 +62,7 @@ test-*.mjs
 test-*.js
 test_*.mjs
 test_*.py
+!api/tests/test_*.py
 *-test-results.json
 *-results.json
 *-ui-inspection.json

api/bootnode/db/session.py

@@ -8,8 +8,25 @@ from bootnode.config import get_settings
 
 settings = get_settings()
 
+
+def _ensure_async_dsn(dsn: str) -> str:
+    """Ensure the database DSN uses the asyncpg driver.
+
+    Converts ``postgresql://`` or ``postgres://`` to
+    ``postgresql+asyncpg://`` so that SQLAlchemy's async engine
+    uses the correct driver regardless of how DATABASE_URL is set.
+    """
+    if dsn.startswith("postgresql+asyncpg://"):
+        return dsn
+    if dsn.startswith("postgresql://"):
+        return dsn.replace("postgresql://", "postgresql+asyncpg://", 1)
+    if dsn.startswith("postgres://"):
+        return dsn.replace("postgres://", "postgresql+asyncpg://", 1)
+    return dsn
+
+
 engine = create_async_engine(
-    str(settings.database_url),
+    _ensure_async_dsn(str(settings.database_url)),
     pool_size=settings.db_pool_size,
     max_overflow=settings.db_max_overflow,
     echo=settings.debug,

api/tests/test_db_session.py

@@ -0,0 +1,35 @@
+"""Tests for database session DSN handling."""
+
+from bootnode.db.session import _ensure_async_dsn
+
+
+def test_postgresql_converted():
+    """Standard postgresql:// is converted to asyncpg."""
+    dsn = "postgresql://user:pass@host:5432/db"
+    assert _ensure_async_dsn(dsn) == "postgresql+asyncpg://user:pass@host:5432/db"
+
+
+def test_postgres_converted():
+    """Short-form postgres:// is converted to asyncpg."""
+    dsn = "postgres://user:pass@host:5432/db"
+    assert _ensure_async_dsn(dsn) == "postgresql+asyncpg://user:pass@host:5432/db"
+
+
+def test_asyncpg_unchanged():
+    """Already correct DSN is returned as-is."""
+    dsn = "postgresql+asyncpg://user:pass@host:5432/db"
+    assert _ensure_async_dsn(dsn) == dsn
+
+
+def test_production_dsn():
+    """Matches the actual K8s DATABASE_URL format."""
+    dsn = "postgresql://bootnode:[email protected]:5432/bootnode"
+    expected = "postgresql+asyncpg://bootnode:[email protected]:5432/bootnode"
+    assert _ensure_async_dsn(dsn) == expected
+
+
+def test_only_first_occurrence_replaced():
+    """Only the scheme prefix is replaced, not embedded substrings."""
+    dsn = "postgresql://user:postgresql@host:5432/postgresql"
+    result = _ensure_async_dsn(dsn)
+    assert result == "postgresql+asyncpg://user:postgresql@host:5432/postgresql"