Change locking boundaries for shared dict. Add a unit test.

[python_utils.git] / collect / shared_dict.py

diff --git a/collect/shared_dict.py b/collect/shared_dict.py
index 93aa452d50f9bb383d60662a3925ee51e438b644..0d8e7c2f7a36aa5ddb7c54c72aecddbf56df71c3 100644 (file)
--- a/collect/shared_dict.py
+++ b/collect/shared_dict.py
@@ -30,7 +30,7 @@ This class is based on https://github.com/luizalabs/shared-memory-dict
 import pickle
 from contextlib import contextmanager
 from functools import wraps
-from multiprocessing import shared_memory, Lock
+from multiprocessing import shared_memory, RLock
 from typing import (
     Any,
     Dict,
@@ -64,25 +64,33 @@ class PickleSerializer:
 
 class SharedDict(object):
     NULL_BYTE = b'\x00'
-    MPLOCK = Lock()
+    MPLOCK = RLock()
 
     def __init__(
         self,
         name: str,
-        size: int,
+        size_bytes: Optional[int] = None,
     ) -> None:
         super().__init__()
+        self.name = name
         self._serializer = PickleSerializer()
-        self.shared_memory = self._get_or_create_memory_block(name, size)
+        self.shared_memory = self._get_or_create_memory_block(name, size_bytes)
         self._ensure_memory_initialization()
+        self.lock = RLock()
+
+    def get_name(self):
+        return self.name
 
     def _get_or_create_memory_block(
-        self, name: str, size: int
+        self,
+        name: str,
+        size_bytes: Optional[int] = None,
     ) -> shared_memory.SharedMemory:
         try:
             return shared_memory.SharedMemory(name=name)
         except FileNotFoundError:
-            return shared_memory.SharedMemory(name=name, create=True, size=size)
+            assert size_bytes
+            return shared_memory.SharedMemory(name=name, create=True, size=size_bytes)
 
     def _ensure_memory_initialization(self):
         memory_is_empty = (
@@ -101,7 +109,6 @@ class SharedDict(object):
             return
         self.shared_memory.unlink()
 
-    @synchronized(MPLOCK)
     def clear(self) -> None:
         self._save_memory({})
 
@@ -109,12 +116,12 @@ class SharedDict(object):
         with self._modify_db() as db:
             return db.popitem()
 
-    @synchronized(MPLOCK)
     @contextmanager
     def _modify_db(self) -> Generator:
-        db = self._read_memory()
-        yield db
-        self._save_memory(db)
+        with SharedDict.MPLOCK:
+            db = self._read_memory()
+            yield db
+            self._save_memory(db)
 
     def __getitem__(self, key: str) -> Any:
         return self._read_memory()[key]
@@ -181,14 +188,16 @@ class SharedDict(object):
             return db.setdefault(key, default)
 
     def _save_memory(self, db: Dict[str, Any]) -> None:
-        data = self._serializer.dumps(db)
-        try:
-            self.shared_memory.buf[: len(data)] = data
-        except ValueError as exc:
-            raise ValueError("exceeds available storage") from exc
+        with SharedDict.MPLOCK:
+            data = self._serializer.dumps(db)
+            try:
+                self.shared_memory.buf[: len(data)] = data
+            except ValueError as exc:
+                raise ValueError("exceeds available storage") from exc
 
     def _read_memory(self) -> Dict[str, Any]:
-        return self._serializer.loads(self.shared_memory.buf.tobytes())
+        with SharedDict.MPLOCK:
+            return self._serializer.loads(self.shared_memory.buf.tobytes())
 
 
 if __name__ == '__main__':