Added a basic notification system. Long processes will call the notification API, and the notification events are registered. For now, notifications are pushed to the client by polling (client polls every second for new events). A basic status message is now displayed when the sync process starts and ends.

app/YtManagerApp/management/jobs/synchronize.py

@@ -10,6 +10,8 @@ from YtManagerApp.management.downloader import fetch_thumbnail, downloader_proce
 from YtManagerApp.models import *
 from YtManagerApp.utils import youtube
 
+from YtManagerApp.management import notification_manager
+
 log = logging.getLogger('sync')
 __lock = Lock()
 
@@ -104,6 +106,7 @@ def synchronize():
 
     try:
         log.info("Running scheduled synchronization... ")
+        notification_manager.notify_status_update(f'Synchronization started for all subscriptions.')
 
         # Sync subscribed playlists/channels
         log.info("Sync - checking videos")
@@ -119,6 +122,7 @@ def synchronize():
         __fetch_thumbnails()
 
         log.info("Synchronization finished.")
+        notification_manager.notify_status_update(f'Synchronization finished for all subscriptions.')
 
     finally:
         __lock.release()
@@ -128,6 +132,8 @@ def synchronize_subscription(subscription: Subscription):
     __lock.acquire()
     try:
         log.info("Running synchronization for single subscription %d [%s]", subscription.id, subscription.name)
+        notification_manager.notify_status_update(f'Synchronization started for subscription <strong>{subscription.name}</strong>.')
+
         yt_api = youtube.YoutubeAPI.build_public()
 
         log.info("Sync - checking videos")
@@ -141,6 +147,7 @@ def synchronize_subscription(subscription: Subscription):
         __fetch_thumbnails()
 
         log.info("Synchronization finished for subscription %d [%s].", subscription.id, subscription.name)
+        notification_manager.notify_status_update(f'Synchronization finished for subscription <strong>{subscription.name}</strong>.')
 
     finally:
         __lock.release()

app/YtManagerApp/management/notification_manager.py

@@ -0,0 +1,93 @@
+from django.contrib.auth.models import User
+from typing import Dict, Deque, Any, Optional
+from collections import deque
+from datetime import datetime, timedelta
+from YtManagerApp.utils.algorithms import bisect_left
+from threading import Lock
+
+# Clients will request updates at most every few seconds, so a retention period of 60 seconds should be more than
+# enough. I gave it 15 minutes so that if for some reason the connection fails (internet drops) and then comes back a
+# few minutes later, the client will still get the updates
+__RETENTION_PERIOD = 15 * 60
+__NOTIFICATIONS: Deque[Dict] = deque()
+__NEXT_ID = 0
+__LOCK = Lock()
+
+
+# Messages enum
+class Messages:
+    STATUS_UPDATE = 'st-up'
+    STATUS_OPERATION_PROGRESS = 'st-op-prog'
+    STATUS_OPERATION_END = 'st-op-end'
+
+
+def __add_notification(message, user: User=None, **kwargs):
+    global __NEXT_ID
+
+    __LOCK.acquire()
+
+    try:
+        # add notification
+        notification = {
+            'time': datetime.now(),
+            'msg': message,
+            'id': __NEXT_ID,
+            'uid': user and user.id,
+        }
+        notification.update(kwargs)
+        __NOTIFICATIONS.append(notification)
+        __NEXT_ID += 1
+
+        # trim old notifications
+        oldest = __NOTIFICATIONS[0]
+        while len(__NOTIFICATIONS) > 0 and oldest['time'] + timedelta(seconds=__RETENTION_PERIOD) < datetime.now():
+            __NOTIFICATIONS.popleft()
+            oldest = __NOTIFICATIONS[0]
+
+    finally:
+        __LOCK.release()
+
+
+def get_notifications(user: User, last_received_id: Optional[int]):
+
+    __LOCK.acquire()
+
+    try:
+        first_index = 0
+        if last_received_id is not None:
+            first_index = bisect_left(__NOTIFICATIONS,
+                                 {'id': last_received_id},
+                                 key=lambda item: item['id'])
+
+        for i in range(first_index, len(__NOTIFICATIONS)):
+            item = __NOTIFICATIONS[i]
+            if item['uid'] is None or item['uid'] == user.id:
+                yield item
+
+    finally:
+        __LOCK.release()
+
+
+def get_current_notification_id():
+    return __NEXT_ID
+
+
+def notify_status_update(status_message: str, user: User=None):
+    __add_notification(Messages.STATUS_UPDATE,
+                       user=user,
+                       status=status_message)
+
+
+def notify_status_operation_progress(op_id: Any, status_message: str, progress_percent: float, user: User=None):
+    __add_notification(Messages.STATUS_OPERATION_PROGRESS,
+                       user=user,
+                       operation=op_id,
+                       status=status_message,
+                       progress=progress_percent)
+
+
+def notify_status_operation_ended(op_id: Any, status_message: str, user: User=None):
+    __add_notification(Messages.STATUS_OPERATION_END,
+                       user=user,
+                       operation=op_id,
+                       status=status_message)