Add fs attachment delegate for apps

src/middlewared/middlewared/plugins/apps/fs_attachments.py

@@ -0,0 +1,53 @@
+from middlewared.common.attachment import FSAttachmentDelegate
+
+
+class AppFSAttachmentDelegate(FSAttachmentDelegate):
+    name = 'apps'
+    title = 'Apps'
+
+    async def query(self, path, enabled, options=None):
+        apps_attached = []
+        for app in await self.middleware.call('app.query'):
+            if not app['active_workloads']['volumes'] or (
+                app['state'] == 'STOPPED' if enabled else app['state'] != 'STOPPED'
+            ):
+                continue
+
+            if await self.middleware.call(
+                'filesystem.is_child', [volume['source'] for volume in app['active_workloads']['volumes']], path
+            ):
+                apps_attached.append({
+                    'id': app['name'],
+                    'name': app['name'],
+                })
+
+        return apps_attached
+
+    async def delete(self, attachments):
+        for attachment in attachments:
+            try:
+                await (await self.middleware.call('app.stop', attachment['id'])).wait(raise_error=True)
+            except Exception:
+                self.middleware.logger.error('Unable to stop %r app', attachment['id'], exc_info=True)
+
+    async def toggle(self, attachments, enabled):
+        # if enabled is true - we are going to ignore that as we don't want to scale up releases
+        # automatically when a path becomes available
+        for attachment in ([] if enabled else attachments):
+            action = 'start' if enabled else 'stop'
+            try:
+                await (await self.middleware.call(f'app.{action}', attachment['id'])).wait(raise_error=True)
+            except Exception:
+                self.middleware.logger.error('Unable to %s %r app', action, attachment['id'], exc_info=True)
+
+    async def stop(self, attachments):
+        await self.toggle(attachments, False)
+
+    async def start(self, attachments):
+        await self.toggle(attachments, True)
+
+
+async def setup(middleware):
+    middleware.create_task(
+        middleware.call('pool.dataset.register_attachment_delegate', AppFSAttachmentDelegate(middleware))
+    )