Refactor database access through managed connections

tests/test_db.py

@@ -0,0 +1,111 @@
+from __future__ import annotations
+
+import threading
+import time
+from pathlib import Path
+
+import pytest
+from peewee import InterfaceError
+
+from repub.db import get_database_connection
+from repub.model import AppSetting, database, initialize_database
+
+
+def test_queries_require_managed_database_context(tmp_path: Path) -> None:
+    initialize_database(tmp_path / "managed-context.db")
+
+    with pytest.raises(
+        RuntimeError, match="database.reader\\(\\)|database.writer\\(\\)"
+    ):
+        AppSetting.select().count()
+
+
+def test_writer_and_reader_contexts_allow_persisted_queries(tmp_path: Path) -> None:
+    initialize_database(tmp_path / "reader-writer.db")
+
+    with database.writer():
+        AppSetting.create(key="feed_url", value='"https://mirror.example"')
+
+    with database.reader():
+        setting = AppSetting.get(AppSetting.key == "feed_url")
+
+    assert setting.value == '"https://mirror.example"'
+
+
+def test_managed_connections_disable_peewee_autoconnect(tmp_path: Path) -> None:
+    initialize_database(tmp_path / "autoconnect-disabled.db")
+
+    connection = get_database_connection()
+
+    assert connection is not None
+    assert connection.writer_db.autoconnect is False
+    assert all(reader_db.autoconnect is False for reader_db in connection.reader_dbs)
+
+    reader_db = connection.reader_dbs[0]
+    reader_db.close()
+
+    with pytest.raises(InterfaceError, match="database connection not opened"):
+        reader_db.execute_sql("SELECT 1")
+
+
+def test_database_connection_initializes_four_readers_and_one_writer(
+    tmp_path: Path,
+) -> None:
+    initialize_database(tmp_path / "pool-shape.db")
+
+    connection = get_database_connection()
+
+    assert connection is not None
+    assert connection.pool_size == 4
+    assert len(connection.reader_dbs) == 4
+    assert connection._reader_pool.qsize() == 4
+    assert connection.writer_db is not None
+
+
+def test_reader_lease_is_returned_to_the_pool_after_use(tmp_path: Path) -> None:
+    initialize_database(tmp_path / "reader-lease.db")
+
+    connection = get_database_connection()
+
+    assert connection is not None
+    initial_size = connection._reader_pool.qsize()
+
+    with database.reader():
+        assert connection._reader_pool.qsize() == initial_size - 1
+
+    assert connection._reader_pool.qsize() == initial_size
+
+
+def test_writer_contexts_serialize_through_the_single_writer(tmp_path: Path) -> None:
+    initialize_database(tmp_path / "single-writer.db")
+
+    events: list[str] = []
+    entered_first_writer = threading.Event()
+    allow_first_writer_to_exit = threading.Event()
+
+    def first_writer() -> None:
+        with database.writer():
+            events.append("first-entered")
+            entered_first_writer.set()
+            allow_first_writer_to_exit.wait(timeout=1)
+            events.append("first-exiting")
+
+    def second_writer() -> None:
+        entered_first_writer.wait(timeout=1)
+        with database.writer():
+            events.append("second-entered")
+
+    first_thread = threading.Thread(target=first_writer)
+    second_thread = threading.Thread(target=second_writer)
+    first_thread.start()
+    second_thread.start()
+
+    assert entered_first_writer.wait(timeout=1) is True
+    time.sleep(0.05)
+    assert events == ["first-entered"]
+
+    allow_first_writer_to_exit.set()
+    first_thread.join(timeout=1)
+    second_thread.join(timeout=1)
+
+    assert events == ["first-entered", "first-exiting", "second-entered"]