Island: Fix a ZT multiple findings bug

A bug happened in zero trust findings: since multiple exploiters run at the same time, they send telemetries at the same time and those telemetries get parsed at the same time. So multiple threads fetch ZT findings at once, finds none and creates duplicate findings. With this bugfix only one thread can fetch for findings at a time. This means that one thread creates the finding and others fetch it and just add events to it

monkey/monkey_island/cc/services/zero_trust/monkey_findings/monkey_zt_finding_service.py

@@ -1,6 +1,7 @@
 from typing import List
 
 from bson import ObjectId
+from gevent.lock import BoundedSemaphore
 
 from common.common_consts import zero_trust_consts
 from monkey_island.cc.models.zero_trust.event import Event
@@ -9,6 +10,10 @@ from monkey_island.cc.models.zero_trust.monkey_finding_details import MonkeyFind
 
 
 class MonkeyZTFindingService:
+
+    # Required to synchronize db state between different threads
+    _finding_lock = BoundedSemaphore()
+
     @staticmethod
     def create_or_add_to_existing(test: str, status: str, events: List[Event]):
         """
@@ -20,6 +25,7 @@ class MonkeyZTFindingService:
         the query - this is not
         when this function should be used.
         """
+        with MonkeyZTFindingService._finding_lock:
             existing_findings = list(MonkeyFinding.objects(test=test, status=status))
             assert len(existing_findings) < 2, "More than one finding exists for {}:{}".format(
                 test, status