backups: Handle common errors during borg operations

Closes: #2218.

- When borg can't acquire a lock due to it being busy, any borg operation can
fail. Show a readable message instead of a generic error.

- Also handle errors for archive already existing and archive to be deleted not
existing.

Tests:

- Functional tests for backup app work.

- Creating archive works with proper message. Providing the name of existing
archive shows proper error.

- Deleting archive works with proper message. Open two tabs by clicking on the
delete archive button. Then delete with one and try to delete the it again with
the next one. Proper error message is shown.

- While downloading an archive, delete an archive. Proper error message that
borg is busy is shown.

- Upload archive works. A proper success message is shown.

- Restore backup from archive works. A proper success message is shown.

- Restore backup from file upload works. A proper success message is shown after
upload and after restoration.

- Adding local repository works. A proper success message is shown.

- Adding remote repository works. A proper success message is shown when SSH key
is verified and repository is added.

- Removing repository works. A proper success message is shown.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/backups/errors.py

@@ -21,3 +21,15 @@ class BorgRepositoryExists(BorgError):
 
 class BorgUnencryptedRepository(BorgError):
     """Attempt to provide password on an unencrypted repository."""
+
+
+class BorgArchiveExists(BorgError):
+    """A archive with the given name already exists in the repository."""
+
+
+class BorgArchiveDoesNotExist(BorgError):
+    """Specified archive does not exist in the repository."""
+
+
+class BorgBusy(BorgError):
+    """Borg could not acquire lock being busy with another operation."""

plinth/modules/backups/privileged.py

@@ -68,6 +68,25 @@ KNOWN_ERRORS = [
         'message': None,
         'raise_as': errors.BorgRepositoryExists,
     },
+    {
+        'errors': ['Archive .* already exists'],
+        'message':
+            _('An archive with given name already exists in the repository.'),
+        'raise_as':
+            errors.BorgArchiveExists,
+    },
+    {
+        'errors': ['Archive .* not found'],
+        'message':
+            _('Archive with given name was not found in the repository.'),
+        'raise_as':
+            errors.BorgArchiveDoesNotExist,
+    },
+    {
+        'errors': ['Failed to create/acquire the lock'],
+        'message': _('Backup system is busy with another operation.'),
+        'raise_as': errors.BorgBusy,
+    },
 ]
 
 

plinth/modules/backups/views.py

@@ -3,6 +3,7 @@
 Views for the backups app.
 """
 
+import contextlib
 import logging
 import os
 import subprocess
@@ -11,7 +12,7 @@ from urllib.parse import unquote
 
 from django.contrib import messages
 from django.contrib.messages.views import SuccessMessageMixin
-from django.http import Http404, StreamingHttpResponse
+from django.http import Http404, HttpRequest, StreamingHttpResponse
 from django.shortcuts import redirect
 from django.urls import reverse, reverse_lazy
 from django.utils.decorators import method_decorator
@@ -24,7 +25,7 @@ from plinth.errors import PlinthError
 from plinth.modules import backups, storage
 from plinth.views import AppView
 
-from . import (SESSION_PATH_VARIABLE, api, forms, get_known_hosts_path,
+from . import (SESSION_PATH_VARIABLE, api, errors, forms, get_known_hosts_path,
                is_ssh_hostkey_verified, privileged)
 from .decorators import delete_tmp_backup_file
 from .repository import (BorgRepository, SshBorgRepository, get_instance,
@@ -33,6 +34,15 @@ from .repository import (BorgRepository, SshBorgRepository, get_instance,
 logger = logging.getLogger(__name__)
 
 
+@contextlib.contextmanager
+def handle_common_errors(request: HttpRequest):
+    """If any known Borg exceptions occur, show proper error messages."""
+    try:
+        yield
+    except errors.BorgError as exception:
+        messages.error(request, exception.args[0])
+
+
 @method_decorator(delete_tmp_backup_file, name='dispatch')
 class BackupsView(AppView):
     """View to show list of archives."""
@@ -101,14 +111,13 @@ class ScheduleView(SuccessMessageMixin, FormView):
         return super().form_valid(form)
 
 
-class CreateArchiveView(SuccessMessageMixin, FormView):
+class CreateArchiveView(FormView):
     """View to create a new archive."""
 
     form_class = forms.CreateArchiveForm
     prefix = 'backups'
     template_name = 'form.html'
     success_url = reverse_lazy('backups:index')
-    success_message = gettext_lazy('Archive created.')
 
     def get_context_data(self, **kwargs):
         """Return additional context for rendering the template."""
@@ -136,11 +145,14 @@ class CreateArchiveView(SuccessMessageMixin, FormView):
                 microsecond=0).isoformat()
 
         selected_apps = form.cleaned_data['selected_apps']
-        repository.create_archive(name, selected_apps)
+        with handle_common_errors(self.request):
+            repository.create_archive(name, selected_apps)
+            messages.success(self.request, _('Archive created.'))
+
         return super().form_valid(form)
 
 
-class DeleteArchiveView(SuccessMessageMixin, TemplateView):
+class DeleteArchiveView(TemplateView):
     """View to delete an archive."""
     template_name = 'backups_delete.html'
 
@@ -158,12 +170,14 @@ class DeleteArchiveView(SuccessMessageMixin, TemplateView):
     def post(self, request, uuid, name):
         """Delete the archive."""
         repository = get_instance(uuid)
-        repository.delete_archive(name)
+        with handle_common_errors(self.request):
-        messages.success(request, _('Archive deleted.'))
+            repository.delete_archive(name)
+            messages.success(request, _('Archive deleted.'))
+
         return redirect('backups:index')
 
 
-class UploadArchiveView(SuccessMessageMixin, FormView):
+class UploadArchiveView(FormView):
     form_class = forms.UploadForm
     prefix = 'backups'
     template_name = 'backups_upload.html'
@@ -196,20 +210,22 @@ class UploadArchiveView(SuccessMessageMixin, FormView):
         """Store uploaded file."""
         uploaded_file = self.request.FILES['backups-file']
         # Hold on to Django's uploaded file. It will be used by other views.
-        privileged.add_uploaded_archive(uploaded_file.name,
+        with handle_common_errors(self.request):
-                                        uploaded_file.temporary_file_path())
+            privileged.add_uploaded_archive(
-        self.request.session[SESSION_PATH_VARIABLE] = str(
+                uploaded_file.name, uploaded_file.temporary_file_path())
-            privileged.BACKUPS_UPLOAD_PATH / uploaded_file.name)
+            self.request.session[SESSION_PATH_VARIABLE] = str(
+                privileged.BACKUPS_UPLOAD_PATH / uploaded_file.name)
+            messages.success(self.request, _('Upload successful.'))
+
         return super().form_valid(form)
 
 
-class BaseRestoreView(SuccessMessageMixin, FormView):
+class BaseRestoreView(FormView):
     """View to restore files from an archive."""
     form_class = forms.RestoreForm
     prefix = 'backups'
     template_name = 'backups_restore.html'
     success_url = reverse_lazy('backups:index')
-    success_message = gettext_lazy('Restored files from backup.')
 
     def get_form_kwargs(self):
         """Pass additional keyword args for instantiating the form."""
@@ -257,7 +273,10 @@ class RestoreFromUploadView(BaseRestoreView):
         """Restore files from the archive on valid form submission."""
         path = self.request.session.get(SESSION_PATH_VARIABLE)
         selected_apps = form.cleaned_data['selected_apps']
-        backups.restore_from_upload(path, selected_apps)
+        with handle_common_errors(self.request):
+            backups.restore_from_upload(path, selected_apps)
+            messages.success(self.request, _('Restored files from backup.'))
+
         return super().form_valid(form)
 
 
@@ -275,7 +294,10 @@ class RestoreArchiveView(BaseRestoreView):
         """Restore files from the archive on valid form submission."""
         repository = get_instance(self.kwargs['uuid'])
         selected_apps = form.cleaned_data['selected_apps']
-        repository.restore_archive(self.kwargs['name'], selected_apps)
+        with handle_common_errors(self.request):
+            repository.restore_archive(self.kwargs['name'], selected_apps)
+            messages.success(self.request, _('Restored files from backup.'))
+
         return super().form_valid(form)
 
 
@@ -293,7 +315,7 @@ class DownloadArchiveView(View):
         return response
 
 
-class AddRepositoryView(SuccessMessageMixin, FormView):
+class AddRepositoryView(FormView):
     """View to create a new backup repository."""
     form_class = forms.AddRepositoryForm
     template_name = 'backups_add_repository.html'
@@ -324,14 +346,16 @@ class AddRepositoryView(SuccessMessageMixin, FormView):
             encryption_passphrase = None
 
         credentials = {'encryption_passphrase': encryption_passphrase}
-        repository = BorgRepository(path, credentials)
+        with handle_common_errors(self.request):
-        if _save_repository(self.request, repository):
+            repository = BorgRepository(path, credentials)
-            return super().form_valid(form)
+            if _save_repository(self.request, repository):
+                messages.success(self.request, _('Added new repository.'))
+                return super().form_valid(form)
 
         return redirect(reverse_lazy('backups:add-repository'))
 
 
-class AddRemoteRepositoryView(SuccessMessageMixin, FormView):
+class AddRemoteRepositoryView(FormView):
     """View to create a new remote backup repository."""
     form_class = forms.AddRemoteRepositoryForm
     template_name = 'backups_add_remote_repository.html'
@@ -356,16 +380,18 @@ class AddRemoteRepositoryView(SuccessMessageMixin, FormView):
             'ssh_password': form.cleaned_data.get('ssh_password'),
             'encryption_passphrase': encryption_passphrase
         }
-        repository = SshBorgRepository(path, credentials)
+        with handle_common_errors(self.request):
-        repository.verfied = False
+            repository = SshBorgRepository(path, credentials)
-        repository.save()
+            repository.verfied = False
-        messages.success(self.request, _('Added new remote SSH repository.'))
+            repository.save()
+            messages.success(self.request,
+                             _('Added new remote SSH repository.'))
 
         url = reverse('backups:verify-ssh-hostkey', args=[repository.uuid])
         return redirect(url)
 
 
-class VerifySshHostkeyView(SuccessMessageMixin, FormView):
+class VerifySshHostkeyView(FormView):
     """View to verify SSH Hostkey of the remote repository."""
     form_class = forms.VerifySshHostkeyForm
     template_name = 'verify_ssh_hostkey.html'
@@ -416,10 +442,11 @@ class VerifySshHostkeyView(SuccessMessageMixin, FormView):
     def form_valid(self, form):
         """Create and store the repository."""
         ssh_public_key = form.cleaned_data['ssh_public_key']
-        self._add_ssh_hostkey(ssh_public_key)
+        with handle_common_errors(self.request):
-        messages.success(self.request, _('SSH host verified.'))
+            self._add_ssh_hostkey(ssh_public_key)
-        if _save_repository(self.request, self._get_repository()):
+            messages.success(self.request, _('SSH host verified.'))
-            return redirect(reverse_lazy('backups:index'))
+            if _save_repository(self.request, self._get_repository()):
+                return redirect(reverse_lazy('backups:index'))
 
         return redirect(reverse_lazy('backups:add-remote-repository'))
 
@@ -455,7 +482,7 @@ def _save_repository(request, repository):
     return False
 
 
-class RemoveRepositoryView(SuccessMessageMixin, TemplateView):
+class RemoveRepositoryView(TemplateView):
     """View to delete a repository."""
     template_name = 'backups_repository_remove.html'
 
@@ -468,10 +495,11 @@ class RemoveRepositoryView(SuccessMessageMixin, TemplateView):
 
     def post(self, request, uuid):
         """Delete the repository on confirmation."""
-        repository = get_instance(uuid)
+        with handle_common_errors(self.request):
-        repository.remove()
+            repository = get_instance(uuid)
-        messages.success(request,
+            repository.remove()
-                         _('Repository removed. Backups were not deleted.'))
+            messages.success(
+                request, _('Repository removed. Backups were not deleted.'))
 
         return redirect('backups:index')