app: Add ability to retrieve logs from all systemd units of an app

Tests:

- Upto 200 lines are shown in the logs. The description and unit name of the app
is correct.

- Apps without systemd units don't have 'View Logs' menu item.

- Nextcloud container logs are shown.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>

plinth/action_utils.py

@@ -176,6 +176,27 @@ def service_reset_failed(service_name: str, check: bool = False):
     service_action(service_name, 'reset-failed', check=check)
 
 
+def service_get_logs(service_name: str) -> str:
+    """Return the last lines of journal entries for a unit."""
+    command = [
+        'journalctl', '--no-pager', '--lines=200', '--unit', service_name
+    ]
+    process = subprocess.run(command, check=False, stdout=subprocess.PIPE)
+    return process.stdout.decode()
+
+
+def service_show(service_name: str) -> dict[str, str]:
+    """Return the status of the service in dictionary format."""
+    command = ['systemctl', 'show', service_name]
+    process = subprocess.run(command, check=False, stdout=subprocess.PIPE)
+    status = {}
+    for line in process.stdout.decode().splitlines():
+        parts = line.partition('=')
+        status[parts[0]] = parts[2]
+
+    return status
+
+
 def service_action(service_name: str, action: str, check: bool = False):
     """Perform the given action on the service_name."""
     subprocess.run(['systemctl', action, service_name],

plinth/app.py

@@ -309,6 +309,28 @@ class App:
 
         return should_rerun_setup
 
+    def has_logs(self) -> bool:
+        """Return if any of the components emit logs.
+
+        This is typically true if the apps has daemons or containers.
+        """
+        from plinth import log
+        for component in self.components.values():
+            if isinstance(component, log.LogEmitter):
+                return True
+
+        return False
+
+    def get_logs(self) -> _list_type[dict[str, str]]:
+        """Return the logs in a dictionary format."""
+        from plinth import log
+        logs: list[dict[str, str]] = []
+        for component in self.components.values():
+            if isinstance(component, log.LogEmitter):
+                logs.append(component.get_logs())
+
+        return logs
+
 
 class Component:
     """Interface for an app component.

plinth/container.py

@@ -5,13 +5,13 @@ import contextlib
 
 from django.utils.translation import gettext_noop
 
-from plinth import app, privileged
+from plinth import app, log, privileged
 from plinth.daemon import diagnose_port_listening
 from plinth.diagnostic_check import (DiagnosticCheck,
                                      DiagnosticCheckParameters, Result)
 
 
-class Container(app.LeaderComponent):
+class Container(app.LeaderComponent, log.LogEmitter):
     """Component to manage a podman container."""
 
     def __init__(self, component_id: str, name: str, image_name: str,
@@ -65,6 +65,9 @@ class Container(app.LeaderComponent):
         self.devices = devices
         self.listen_ports = listen_ports or []
 
+        # For logs
+        self.unit = self.name
+
     def is_enabled(self):
         """Return if the container is enabled."""
         return privileged.container_is_enabled(self.name)

plinth/daemon.py

@@ -8,12 +8,12 @@ import subprocess
 import psutil
 from django.utils.translation import gettext_noop
 
-from plinth import action_utils, app
+from plinth import action_utils, app, log
 from plinth.diagnostic_check import (DiagnosticCheck,
                                      DiagnosticCheckParameters, Result)
 
 
-class Daemon(app.LeaderComponent):
+class Daemon(app.LeaderComponent, log.LogEmitter):
     """Component to manage a background daemon or any systemd unit."""
 
     def __init__(self, component_id: str, unit: str,
@@ -130,7 +130,7 @@ class Daemon(app.LeaderComponent):
                                self.component_id)
 
 
-class RelatedDaemon(app.FollowerComponent):
+class RelatedDaemon(app.FollowerComponent, log.LogEmitter):
     """Component to hold information about additional systemd units handled.
 
     Unlike a daemon described by the Daemon component which is enabled/disabled
@@ -202,8 +202,7 @@ def app_is_running(app_):
 
 
 def diagnose_port_listening(
-        port: int, kind: str = 'tcp',
-        listen_address: str | None = None,
+        port: int, kind: str = 'tcp', listen_address: str | None = None,
         component_id: str | None = None) -> DiagnosticCheck:
     """Run a diagnostic on whether a port is being listened on.
 

plinth/log.py

@@ -5,6 +5,7 @@ Setup logging for the application.
 
 import logging
 import logging.config
+import typing
 import warnings
 
 from . import cfg
@@ -12,6 +13,24 @@ from . import cfg
 default_level = None
 
 
+class LogEmitterProtocol(typing.Protocol):
+    unit: str
+
+
+class LogEmitter:
+    """A mixin for App components that emit logs.
+
+    Used as a simple base class for identifying components that have logs. Use
+    the self.unit property to fetch systemd journal logs of the unit.
+    """
+
+    unit: str
+
+    def get_logs(self: LogEmitterProtocol) -> dict[str, str]:
+        from plinth.privileged import service as service_privileged
+        return service_privileged.get_logs(self.unit)
+
+
 class ColoredFormatter(logging.Formatter):
     """Print parts of log message in color."""
     codes = {

plinth/privileged/__init__.py

@@ -7,15 +7,16 @@ from .container import (container_disable, container_enable,
                         container_uninstall)
 from .packages import (filter_conffile_packages, install,
                        is_package_manager_busy, remove, update)
-from .service import (disable, enable, is_enabled, is_running, mask, reload,
-                      restart, start, stop, systemd_set_default,
+from .service import (disable, enable, get_logs, is_enabled, is_running, mask,
+                      reload, restart, start, stop, systemd_set_default,
                       try_reload_or_restart, try_restart, unmask)
 
 __all__ = [
     'filter_conffile_packages', 'install', 'is_package_manager_busy', 'remove',
     'update', 'systemd_set_default', 'disable', 'enable', 'is_enabled',
     'is_running', 'mask', 'reload', 'restart', 'start', 'stop',
-    'try_reload_or_restart', 'try_restart', 'unmask', 'dropin_is_valid',
-    'dropin_link', 'dropin_unlink', 'container_disable', 'container_enable',
-    'container_is_enabled', 'container_setup', 'container_uninstall'
+    'try_reload_or_restart', 'try_restart', 'unmask', 'get_logs',
+    'dropin_is_valid', 'dropin_link', 'dropin_unlink', 'container_disable',
+    'container_enable', 'container_is_enabled', 'container_setup',
+    'container_uninstall'
 ]

plinth/privileged/service.py

@@ -104,6 +104,16 @@ def is_running(service: str) -> bool:
     return action_utils.service_is_running(service)
 
 
+@privileged
+def get_logs(service: str) -> dict[str, str]:
+    _assert_service_is_managed_by_plinth(service)
+    return {
+        'unit': service,
+        'description': action_utils.service_show(service)['Description'],
+        'logs': action_utils.service_get_logs(service)
+    }
+
+
 def _get_managed_services():
     """Get a set of all services managed by FreedomBox."""
     from plinth.container import Container

plinth/tests/test_app.py

@@ -8,12 +8,15 @@ from unittest.mock import Mock, call, patch
 
 import pytest
 
+from plinth import log
 from plinth.app import (App, Component, EnableState, FollowerComponent, Info,
                         LeaderComponent, apps_init)
 from plinth.diagnostic_check import DiagnosticCheck, Result
 
 # pylint: disable=protected-access
 
+privileged_modules_to_mock = ['plinth.privileged']
+
 
 class AppTest(App):
     """Sample App for testing."""
@@ -30,10 +33,14 @@ class AppSetupTest(App):
         self.add(info)
 
 
-class LeaderTest(FollowerComponent):
+class LeaderTest(FollowerComponent, log.LogEmitter):
     """Test class for using LeaderComponent in tests."""
     is_leader = True
 
+    @property
+    def unit(self):  # For LogEmitter
+        return self.component_id
+
     def diagnose(self) -> list[DiagnosticCheck]:
         """Return diagnostic results."""
         return [
@@ -325,6 +332,50 @@ def test_app_repair(_run_setup_on_app, app_with_components):
     assert not should_rerun_setup
 
 
+def test_app_has_logs(app_with_components):
+    """Test checking if an app has logs."""
+    app = app_with_components
+
+    # App with components that emit logs
+    assert app.has_logs()
+
+    # App with components that don't have diagnostics
+    app.remove('test-leader-1')
+    app.remove('test-leader-2')
+    assert not app.has_diagnostics()
+
+
+@patch('plinth.privileged.service._assert_service_is_managed_by_plinth')
+@patch('plinth.action_utils.service_get_logs')
+@patch('plinth.action_utils.service_show')
+def test_app_get_logs(service_show, service_get_logs, _, app_with_components,
+                      mock_privileged):
+    """Test retrieving logs from an app."""
+    service_show.side_effect = [{
+        'Description': 'Test Desc 1'
+    }, {
+        'Description': 'Test Desc 2'
+    }]
+    service_get_logs.side_effect = ['test-logs-1', 'test-logs-2']
+
+    logs = app_with_components.get_logs()
+    assert logs == [{
+        'unit': 'test-leader-1',
+        'description': 'Test Desc 1',
+        'logs': 'test-logs-1'
+    }, {
+        'unit': 'test-leader-2',
+        'description': 'Test Desc 2',
+        'logs': 'test-logs-2'
+    }]
+    assert service_show.mock_calls == [
+        call('test-leader-1'), call('test-leader-2')
+    ]
+    assert service_get_logs.mock_calls == [
+        call('test-leader-1'), call('test-leader-2')
+    ]
+
+
 def test_component_initialization():
     """Test that component is initialized properly."""
     with pytest.raises(ValueError):