From d37dd829f021f2e3791095c1277fb5dc68cd695c Mon Sep 17 00:00:00 2001
From: Uxio Fuentefria <uxio@gnosis.pm>
Date: Fri, 28 Aug 2020 16:41:53 +0200
Subject: [PATCH] Detect duplicate notifications using Redis

---
 .../notifications/tasks.py                    | 45 +++++++++++++++++++
 .../notifications/tests/test_tasks.py         | 24 ++++++++--
 2 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/safe_transaction_service/notifications/tasks.py b/safe_transaction_service/notifications/tasks.py
index 8a52b2aed..49984a2ba 100644
--- a/safe_transaction_service/notifications/tasks.py
+++ b/safe_transaction_service/notifications/tasks.py
@@ -1,7 +1,11 @@
+import pickle
 from typing import Any, Dict, Optional, Tuple
 
+from django.conf import settings
+
 from celery import app
 from celery.utils.log import get_task_logger
+from redis import Redis
 
 from safe_transaction_service.history.models import WebHookType
 
@@ -11,6 +15,12 @@
 logger = get_task_logger(__name__)
 
 
+def get_redis() -> Redis:
+    if not hasattr(get_redis, 'redis'):
+        get_redis.redis = Redis.from_url(settings.REDIS_URL)
+    return get_redis.redis
+
+
 def filter_notification(payload: Dict[str, Any]) -> bool:
     """
     :param payload: Notification payload
@@ -34,6 +44,33 @@ def filter_notification(payload: Dict[str, Any]) -> bool:
 
     return True
 
+
+class DuplicateNotification:
+    def __init__(self, address: Optional[str], payload: Dict[str, Any]):
+        self.redis = get_redis()
+        self.address = address
+        self.payload = payload
+        self.redis_payload = self._get_redis_payload(address, payload)
+
+    def _get_redis_payload(self, address: Optional[str], payload: Dict[str, Any]):
+        new_payload = dict(payload)
+        new_payload['notification_to'] = address
+        return 'notifications:'.encode() + pickle.dumps(new_payload)
+
+    def is_duplicated(self) -> bool:
+        """
+        :return: True if payload was already notified, False otherwise
+        """
+        return bool(self.redis.get(self.redis_payload))
+
+    def set_duplicated(self) -> bool:
+        """
+        Stores notification with an expiration time of 5 minutes
+        :return:
+        """
+        return self.redis.set(self.redis_payload, 1, ex=5 * 60)
+
+
 @app.shared_task()
 def send_notification_task(address: Optional[str], payload: Dict[str, Any]) -> Tuple[int, int]:
     if not (address and payload):  # Both must be present
@@ -50,6 +87,14 @@ def send_notification_task(address: Optional[str], payload: Dict[str, Any]) -> T
     if not (tokens and filter_notification(payload)):
         return 0
 
+    # Make sure notification has not been sent before
+    duplicate_notification = DuplicateNotification(address, payload)
+    if duplicate_notification.is_duplicated():
+        logger.info('Duplicated notification about Safe=%s with payload=%s to tokens=%s', address, payload, tokens)
+        return 0
+
+    duplicate_notification.set_duplicated()
+
     logger.info('Sending notification about Safe=%s with payload=%s to tokens=%s', address, payload, tokens)
     success_count, failure_count, invalid_tokens = firebase_client.send_message(tokens, payload)
     if invalid_tokens:
diff --git a/safe_transaction_service/notifications/tests/test_tasks.py b/safe_transaction_service/notifications/tests/test_tasks.py
index 5b6addc48..300e7fa1a 100644
--- a/safe_transaction_service/notifications/tests/test_tasks.py
+++ b/safe_transaction_service/notifications/tests/test_tasks.py
@@ -1,16 +1,34 @@
 from django.test import TestCase
 
+from eth_account import Account
+
 from safe_transaction_service.history.models import (MultisigConfirmation,
-                                                     MultisigTransaction,
-                                                     WebHookType)
+                                                     MultisigTransaction)
 from safe_transaction_service.history.signals import build_webhook_payload
 
 from ...history.tests.factories import (MultisigConfirmationFactory,
                                         MultisigTransactionFactory)
-from ..tasks import filter_notification
+from ..tasks import DuplicateNotification, filter_notification
 
 
 class TestViews(TestCase):
+    def test_duplicate_notification_manager(self):
+        address = '0x1230B3d59858296A31053C1b8562Ecf89A2f888b'
+        payload = {'address': '0x1230B3d59858296A31053C1b8562Ecf89A2f888b',
+                   'type': 'INCOMING_TOKEN',
+                   'tokenAddress': '0x63704B63Ac04f3a173Dfe677C7e3D330c347CD88',
+                   'txHash': '0xd8cf5db08e4f3d43660975c8be02a079139a69c42c0ccdd157618aec9bb91b28',
+                   'value': '50000000000000'}
+        duplicate_notification = DuplicateNotification(address, payload)
+        self.assertFalse(duplicate_notification.is_duplicated())
+        self.assertFalse(duplicate_notification.is_duplicated())
+        duplicate_notification.set_duplicated()
+        self.assertTrue(duplicate_notification.is_duplicated())
+        duplicate_notification_2 = DuplicateNotification(address, {'type': 'Different_payload'})
+        self.assertFalse(duplicate_notification_2.is_duplicated())
+        duplicate_notification_3 = DuplicateNotification(Account.create().address, payload)
+        self.assertFalse(duplicate_notification_3.is_duplicated())
+
     def test_filter_notification(self):
         multisig_confirmation = MultisigConfirmationFactory()
         confirmation_notification = build_webhook_payload(MultisigConfirmation, multisig_confirmation)