The initial implementation of the edit monitor
Creates a class that will manager and monitor the actual edit watchdog
that run as a subprocess. As a first step, the class supports:
1) A start method that creates a pidfile and starts a subprocess with given target/args.
2) A stop method that terminates the created subprocess and removes the pidfile.
Detailed design in go/android-local-edit-monitor.
Test: atest daemon_manager_test
bug: 365617369
Change-Id: Ic6d7be67d284ade8033416235b9b0fb1e90e1b1a
diff --git a/tools/edit_monitor/Android.bp b/tools/edit_monitor/Android.bp
index 80437c0..b939633 100644
--- a/tools/edit_monitor/Android.bp
+++ b/tools/edit_monitor/Android.bp
@@ -19,3 +19,26 @@
default_applicable_licenses: ["Android-Apache-2.0"],
default_team: "trendy_team_adte",
}
+
+python_library_host {
+ name: "edit_monitor_lib",
+ pkg_path: "edit_monitor",
+ srcs: [
+ "daemon_manager.py",
+ ],
+}
+
+python_test_host {
+ name: "daemon_manager_test",
+ main: "daemon_manager_test.py",
+ pkg_path: "edit_monitor",
+ srcs: [
+ "daemon_manager_test.py",
+ ],
+ libs: [
+ "edit_monitor_lib",
+ ],
+ test_options: {
+ unit_test: true,
+ },
+}
diff --git a/tools/edit_monitor/daemon_manager.py b/tools/edit_monitor/daemon_manager.py
new file mode 100644
index 0000000..c09c321
--- /dev/null
+++ b/tools/edit_monitor/daemon_manager.py
@@ -0,0 +1,165 @@
+# Copyright 2024, The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import hashlib
+import logging
+import multiprocessing
+import os
+import pathlib
+import signal
+import subprocess
+import tempfile
+import time
+
+
+DEFAULT_PROCESS_TERMINATION_TIMEOUT_SECONDS = 1
+
+
+def default_daemon_target():
+ """Place holder for the default daemon target."""
+ print("default daemon target")
+
+
+class DaemonManager:
+ """Class to manage and monitor the daemon run as a subprocess."""
+
+ def __init__(
+ self,
+ binary_path: str,
+ daemon_target: callable = default_daemon_target,
+ daemon_args: tuple = (),
+ ):
+ self.binary_path = binary_path
+ self.daemon_target = daemon_target
+ self.daemon_args = daemon_args
+
+ self.pid = os.getpid()
+ self.daemon_process = None
+
+ pid_file_dir = pathlib.Path(tempfile.gettempdir()).joinpath("edit_monitor")
+ pid_file_dir.mkdir(parents=True, exist_ok=True)
+ self.pid_file_path = self._get_pid_file_path(pid_file_dir)
+
+ def start(self):
+ """Writes the pidfile and starts the daemon proces."""
+ try:
+ self._write_pid_to_pidfile()
+ self._start_daemon_process()
+ except Exception as e:
+ logging.exception("Failed to start daemon manager with error %s", e)
+
+ def stop(self):
+ """Stops the daemon process and removes the pidfile."""
+
+ logging.debug("in daemon manager cleanup.")
+ try:
+ if self.daemon_process and self.daemon_process.is_alive():
+ self._terminate_process(self.daemon_process.pid)
+ self._remove_pidfile()
+ except Exception as e:
+ logging.exception("Failed to stop daemon manager with error %s", e)
+
+ def _write_pid_to_pidfile(self):
+ """Creates a pidfile and writes the current pid to the file.
+
+ Raise FileExistsError if the pidfile already exists.
+ """
+ try:
+ # Use the 'x' mode to open the file for exclusive creation
+ with open(self.pid_file_path, "x") as f:
+ f.write(f"{self.pid}")
+ except FileExistsError as e:
+ # This could be caused due to race condition that a user is trying
+ # to start two edit monitors at the same time. Or because there is
+ # already an existing edit monitor running and we can not kill it
+ # for some reason.
+ logging.exception("pidfile %s already exists.", self.pid_file_path)
+ raise e
+
+ def _start_daemon_process(self):
+ """Starts a subprocess to run the daemon."""
+ p = multiprocessing.Process(
+ target=self.daemon_target, args=self.daemon_args
+ )
+ p.start()
+
+ logging.info("Start subprocess with PID %d", p.pid)
+ self.daemon_process = p
+
+ def _terminate_process(
+ self, pid: int, timeout: int = DEFAULT_PROCESS_TERMINATION_TIMEOUT_SECONDS
+ ):
+ """Terminates a process with given pid.
+
+ It first sends a SIGTERM to the process to allow it for proper
+ termination with a timeout. If the process is not terminated within
+ the timeout, kills it forcefully.
+ """
+ try:
+ os.kill(pid, signal.SIGTERM)
+ if not self._wait_for_process_terminate(pid, timeout):
+ logging.warning(
+ "Process %d not terminated within timeout, try force kill", pid
+ )
+ os.kill(pid, signal.SIGKILL)
+ except ProcessLookupError:
+ logging.info("Process with PID %d not found (already terminated)", pid)
+
+ def _wait_for_process_terminate(self, pid: int, timeout: int) -> bool:
+ start_time = time.time()
+
+ while time.time() < start_time + timeout:
+ if not self._is_process_alive(pid):
+ return True
+ time.sleep(1)
+
+ logging.error("Process %d not terminated within %d seconds.", pid, timeout)
+ return False
+
+ def _is_process_alive(self, pid: int) -> bool:
+ try:
+ output = subprocess.check_output(
+ ["ps", "-p", str(pid), "-o", "state="], text=True
+ ).strip()
+ state = output.split()[0]
+ return state != "Z" # Check if the state is not 'Z' (zombie)
+ except subprocess.CalledProcessError:
+ # Process not found (already dead).
+ return False
+ except (FileNotFoundError, OSError, ValueError) as e:
+ logging.warning(
+ "Unable to check the status for process %d with error: %s.", pid, e
+ )
+ return True
+
+ def _remove_pidfile(self):
+ try:
+ os.remove(self.pid_file_path)
+ except FileNotFoundError:
+ logging.info("pid file %s already removed.", self.pid_file_path)
+
+ def _get_pid_file_path(self, pid_file_dir: pathlib.Path) -> pathlib.Path:
+ """Generates the path to store the pidfile.
+
+ The file path should have the format of "/tmp/edit_monitor/xxxx.lock"
+ where xxxx is a hashed value based on the binary path that starts the
+ process.
+ """
+ hash_object = hashlib.sha256()
+ hash_object.update(self.binary_path.encode("utf-8"))
+ pid_file_path = pid_file_dir.joinpath(hash_object.hexdigest() + ".lock")
+ logging.info("pid_file_path: %s", pid_file_path)
+
+ return pid_file_path
diff --git a/tools/edit_monitor/daemon_manager_test.py b/tools/edit_monitor/daemon_manager_test.py
new file mode 100644
index 0000000..5be4bee
--- /dev/null
+++ b/tools/edit_monitor/daemon_manager_test.py
@@ -0,0 +1,197 @@
+# Copyright 2024, The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittests for DaemonManager."""
+
+import logging
+import multiprocessing
+import os
+import pathlib
+import signal
+import subprocess
+import sys
+import tempfile
+import time
+import unittest
+from unittest import mock
+from edit_monitor import daemon_manager
+
+TEST_BINARY_FILE = '/path/to/test_binary'
+TEST_PID_FILE_PATH = (
+ '587239c2d1050afdf54512e2d799f3b929f86b43575eb3c7b4bab105dd9bd25e.lock'
+)
+
+
+def example_daemon(output_file):
+ with open(output_file, 'w') as f:
+ f.write('running daemon target')
+
+
+def long_running_daemon():
+ while True:
+ time.sleep(1)
+
+
+class DaemonManagerTest(unittest.TestCase):
+
+ @classmethod
+ def setUpClass(cls):
+ super().setUpClass()
+ # Configure to print logging to stdout.
+ logging.basicConfig(filename=None, level=logging.DEBUG)
+ console = logging.StreamHandler(sys.stdout)
+ logging.getLogger('').addHandler(console)
+
+ def setUp(self):
+ super().setUp()
+ self.original_tempdir = tempfile.tempdir
+ self.working_dir = tempfile.TemporaryDirectory()
+ # Sets the tempdir under the working dir so any temp files created during
+ # tests will be cleaned.
+ tempfile.tempdir = self.working_dir.name
+
+ def tearDown(self):
+ # Cleans up any child processes left by the tests.
+ self._cleanup_child_processes()
+ self.working_dir.cleanup()
+ # Restores tempdir.
+ tempfile.tempdir = self.original_tempdir
+ super().tearDown()
+
+ def test_start_success(self):
+ damone_output_file = tempfile.NamedTemporaryFile(
+ dir=self.working_dir.name, delete=False
+ )
+ dm = daemon_manager.DaemonManager(
+ TEST_BINARY_FILE,
+ daemon_target=example_daemon,
+ daemon_args=(damone_output_file.name,),
+ )
+ dm.start()
+ dm.daemon_process.join()
+
+ # Verifies the expected pid file is created.
+ expected_pid_file_path = pathlib.Path(self.working_dir.name).joinpath(
+ 'edit_monitor', TEST_PID_FILE_PATH
+ )
+ self.assertEqual(dm.pid_file_path, expected_pid_file_path)
+ self.assertTrue(expected_pid_file_path.exists())
+
+ # Verifies the daemon process is executed successfully.
+ with open(damone_output_file.name, 'r') as f:
+ contents = f.read()
+ self.assertEqual(contents, 'running daemon target')
+
+ def test_start_failed_to_write_pidfile(self):
+ pid_file_path_dir = pathlib.Path(self.working_dir.name).joinpath(
+ 'edit_monitor'
+ )
+ pid_file_path_dir.mkdir(parents=True, exist_ok=True)
+ # Makes the directory read-only so write pidfile will fail.
+ os.chmod(pid_file_path_dir, 0o555)
+
+ dm = daemon_manager.DaemonManager(TEST_BINARY_FILE)
+ dm.start()
+
+ # Verifies no daemon process is started.
+ self.assertIsNone(dm.daemon_process)
+
+ def test_start_failed_to_start_daemon_process(self):
+ dm = daemon_manager.DaemonManager(
+ TEST_BINARY_FILE, daemon_target='wrong_target', daemon_args=(1)
+ )
+ dm.start()
+
+ # Verifies no daemon process is started.
+ self.assertIsNone(dm.daemon_process)
+
+ def test_stop_success(self):
+ dm = daemon_manager.DaemonManager(
+ TEST_BINARY_FILE, daemon_target=long_running_daemon
+ )
+ dm.start()
+ dm.stop()
+
+ self.assert_no_subprocess_running()
+ self.assertFalse(dm.pid_file_path.exists())
+
+ @mock.patch('os.kill')
+ def test_stop_failed_to_kill_daemon_process(self, mock_kill):
+ mock_kill.side_effect = OSError('Unknown OSError')
+ dm = daemon_manager.DaemonManager(
+ TEST_BINARY_FILE, daemon_target=long_running_daemon
+ )
+ dm.start()
+ dm.stop()
+
+ self.assertTrue(dm.daemon_process.is_alive())
+ self.assertTrue(dm.pid_file_path.exists())
+
+ @mock.patch('os.remove')
+ def test_stop_failed_to_remove_pidfile(self, mock_remove):
+ mock_remove.side_effect = OSError('Unknown OSError')
+
+ dm = daemon_manager.DaemonManager(
+ TEST_BINARY_FILE, daemon_target=long_running_daemon
+ )
+ dm.start()
+ dm.stop()
+
+ self.assert_no_subprocess_running()
+ self.assertTrue(dm.pid_file_path.exists())
+
+ def assert_no_subprocess_running(self):
+ child_pids = self._get_child_processes(os.getpid())
+ for child_pid in child_pids:
+ self.assertFalse(
+ self._is_process_alive(child_pid), f'process {child_pid} still alive'
+ )
+
+ def _get_child_processes(self, parent_pid):
+ try:
+ output = subprocess.check_output(
+ ['ps', '-o', 'pid,ppid', '--no-headers'], text=True
+ )
+
+ child_processes = []
+ for line in output.splitlines():
+ pid, ppid = line.split()
+ if int(ppid) == parent_pid:
+ child_processes.append(int(pid))
+ return child_processes
+ except subprocess.CalledProcessError as e:
+ self.fail(f'failed to get child process, error: {e}')
+
+ def _is_process_alive(self, pid):
+ try:
+ output = subprocess.check_output(
+ ['ps', '-p', str(pid), '-o', 'state='], text=True
+ ).strip()
+ state = output.split()[0]
+ return state != 'Z' # Check if the state is not 'Z' (zombie)
+ except subprocess.CalledProcessError:
+ return False
+
+ def _cleanup_child_processes(self):
+ child_pids = self._get_child_processes(os.getpid())
+ for child_pid in child_pids:
+ try:
+ os.kill(child_pid, signal.SIGKILL)
+ except ProcessLookupError:
+ # process already terminated
+ pass
+
+
+if __name__ == '__main__':
+ unittest.main()