[sonic-py-common] Add task_base.py (#5049)

Add new task_base.py module from sonic-daemon-base into sonic-py-common package

src/sonic-py-common/sonic_py_common/task_base.py

@@ -0,0 +1,50 @@
+import multiprocessing
+import os
+import signal
+import threading
+
+
+#
+# ProcessTaskBase =====================================================================
+#
+class ProcessTaskBase(object):  # TODO: put this class to swss-platform-common
+    def __init__(self):
+        self.task_process = None
+        self.task_stopping_event = multiprocessing.Event()
+
+    def task_worker(self):
+        pass
+
+    def task_run(self):
+        if self.task_stopping_event.is_set():
+            return
+
+        self.task_process = multiprocessing.Process(target=self.task_worker)
+        self.task_process.start()
+
+    def task_stop(self):
+        self.task_stopping_event.set()
+        os.kill(self.task_process.pid, signal.SIGKILL)
+
+
+#
+# ThreadTaskBase =====================================================================
+#
+class ThreadTaskBase(object):  # TODO: put this class to swss-platform-common;
+    def __init__(self):
+        self.task_thread = None
+        self.task_stopping_event = threading.Event()
+
+    def task_worker(self):
+        pass
+
+    def task_run(self):
+        if self.task_stopping_event.is_set():
+            return
+
+        self.task_thread = threading.Thread(target=self.task_worker)
+        self.task_thread.start()
+
+    def task_stop(self):
+        self.task_stopping_event.set()
+        self.task_thread.join()