Fix #86: add wn.config.allow_multithreading

When set to `True`, the `check_same_thread` parameter to
`sqlite3.connect()` is set to `False`

CHANGELOG.md

@@ -5,7 +5,7 @@
 ### Added
 
 * `wn.Lexicon.specifier()`
-
+* `wn.config.allow_multithreading` ([#86])
 
 ### Removed
 
@@ -192,6 +192,7 @@ abandoned, but this is an entirely new codebase.
 [#79]: https://github.com/goodmami/wn/issues/79
 [#81]: https://github.com/goodmami/wn/issues/81
 [#83]: https://github.com/goodmami/wn/issues/83
+[#86]: https://github.com/goodmami/wn/issues/86
 [#90]: https://github.com/goodmami/wn/issues/90
 [#92]: https://github.com/goodmami/wn/issues/92
 [#93]: https://github.com/goodmami/wn/issues/93

docs/api/wn.rst

@@ -177,6 +177,13 @@ directly. Configuration should occur through the single
 
    .. autoattribute:: data_directory
    .. autoattribute:: database_path
+   .. attribute:: allow_multithreading
+
+      If set to :python:`True`, the database connection may be shared
+      across threads. In this case, it is the user's responsibility to
+      ensure that multiple threads don't try to write to the database
+      at the same time. The default is :python:`False`.
+
    .. autoattribute:: downloads_directory
    .. automethod:: add_project
    .. automethod:: add_project_version

tests/db_test.py

@@ -1,5 +1,6 @@
 
 import sqlite3
+import threading
 
 import pytest
 
@@ -11,3 +12,34 @@ def test_schema_compatibility():
     conn = sqlite3.connect(str(wn.config.database_path))
     schema_hash = wn._db.schema_hash(conn)
     assert schema_hash in wn._db.COMPATIBLE_SCHEMA_HASHES
+
+
+@pytest.mark.usefixtures('mini_db')
+def test_db_multithreading():
+    """
+    See https://github.com/goodmami/wn/issues/86
+    Thanks: @fushinari
+    """
+
+    class WNThread:
+        w = None
+
+        def __init__(self):
+            w_thread = threading.Thread(target=self.set_w)
+            w_thread.start()
+            w_thread.join()
+            self.w.synsets()
+
+        def set_w(self):
+            if self.w is None:
+                self.w = wn.Wordnet()
+
+    # close the connections by resetting the pool
+    wn._db.pool = {}
+    with pytest.raises(sqlite3.ProgrammingError):
+        WNThread()
+    wn._db.pool = {}
+    wn.config.allow_multithreading = True
+    WNThread()  # no error
+    wn.config.allow_multithreading = False
+    wn._db.pool = {}

wn/_config.py

@@ -23,6 +23,7 @@ def __init__(self):
         self._data_directory = DEFAULT_DATA_DIRECTORY
         self._projects = {}
         self._dbpath = self._data_directory / DATABASE_FILENAME
+        self.allow_multithreading = False
 
     @property
     def data_directory(self) -> Path:

wn/_db.py

@@ -72,7 +72,11 @@ def connect() -> sqlite3.Connection:
     dbpath = wn.config.database_path
     if dbpath not in pool:
         initialized = dbpath.is_file()
-        conn = sqlite3.connect(str(dbpath), detect_types=sqlite3.PARSE_DECLTYPES)
+        conn = sqlite3.connect(
+            str(dbpath),
+            detect_types=sqlite3.PARSE_DECLTYPES,
+            check_same_thread=not wn.config.allow_multithreading,
+        )
         # foreign key support needs to be enabled for each connection
         conn.execute('PRAGMA foreign_keys = ON')
         if DEBUG: