Make arbitrary processes capable of being EventHandlers (PipeIO+stdin/stdout)

lib/tfw/components/__init__.py

@@ -11,4 +11,4 @@ from .log_monitoring_event_handler import LogMonitoringEventHandler
 from .fsm_managing_event_handler import FSMManagingEventHandler
 from .snapshot_provider import SnapshotProvider
 from .pipe_io_event_handler import PipeIOEventHandlerBase, PipeIOEventHandler, PipeIOServer
-from .pipe_io_event_handler import TransformerPipeIOEventHandler
+from .pipe_io_event_handler import TransformerPipeIOEventHandler, CommandEventHandler

lib/tfw/components/pipe_io_event_handler.py

@@ -1,7 +1,11 @@
 from abc import abstractmethod
 from json import loads, dumps
-from subprocess import run, PIPE
+from subprocess import run, PIPE, Popen
 from functools import partial
+from os import getpgid, killpg
+from os.path import join
+from signal import SIGTERM
+from secrets import token_urlsafe
 
 from tfw import EventHandlerBase
 from tfw.config.logs import logging
@@ -85,3 +89,33 @@ class TransformerPipeIOEventHandler(PipeIOEventHandlerBase):
         if transformed_bytes:
             json_message = loads(transformed_bytes)
             self.server_connector.send(json_message)
+
+
+class CommandEventHandler(PipeIOEventHandler):
+    def __init__(self, key, command, permissions=DEFAULT_PERMISSIONS):
+        super().__init__(
+            key,
+            self._generate_tempfilename(),
+            self._generate_tempfilename(),
+            permissions
+        )
+
+        self._proc_stdin = open(self.pipe_io.out_pipe, 'rb')
+        self._proc_stdout = open(self.pipe_io.in_pipe, 'wb')
+        self._proc = Popen(
+            command, shell=True, executable='/bin/bash',
+            stdin=self._proc_stdin, stdout=self._proc_stdout,
+            start_new_session=True
+        )
+
+    def _generate_tempfilename(self):
+        # pylint: disable=no-self-use
+        random_filename = partial(token_urlsafe, 10)
+        return join('/tmp', f'{type(self).__name__}.{random_filename()}')
+
+    def cleanup(self):
+        process_group_id = getpgid(self._proc.pid)
+        killpg(process_group_id, SIGTERM)
+        self._proc_stdin.close()
+        self._proc_stdout.close()
+        super().cleanup()