[mongo] Continue coll/index stats collection if user is not authorize…

…d to perform aggregation (DataDog#18044)

* Continue collection of coll stats if user is not authorized to perform collStats aggregation

* add changelog

* fix lint

* continue on index stats collection if user is not authorized

* update changelog

mongo/changelog.d/18044.fixed

@@ -0,0 +1 @@
+Fix coll or index stats metrics failure when the agent user is not authorized to perform $collStats or $indexStats aggregation on a collection. This fix prevents check to fail when an OperationFailure is raised to run $collStats or $indexStats on system collections such as system.replset on local database.

mongo/datadog_checks/mongo/collectors/coll_stats.py

@@ -2,6 +2,7 @@
 # All rights reserved
 # Licensed under a 3-clause BSD style license (see LICENSE)
 
+from pymongo.errors import OperationFailure
 from six import iteritems
 
 from datadog_checks.base import AgentCheck
@@ -32,7 +33,14 @@ def collect(self, api):
         coll_names = self._get_collections(api)
         for coll_name in coll_names:
             # Grab the stats from the collection
-            for coll_stats in api.coll_stats(self.db_name, coll_name):
+            try:
+                collection_stats = api.coll_stats(self.db_name, coll_name)
+            except OperationFailure as e:
+                # Atlas restricts $collStats on system collections
+                self.log.warning("Could not collect stats for collection %s: %s", coll_name, e)
+                continue
+
+            for coll_stats in collection_stats:
                 # Submit the metrics
                 storage_stats = coll_stats.get('storageStats', {})
                 latency_stats = coll_stats.get('latencyStats', {})

mongo/datadog_checks/mongo/collectors/index_stats.py

@@ -2,6 +2,8 @@
 # All rights reserved
 # Licensed under a 3-clause BSD style license (see LICENSE)
 
+from pymongo.errors import OperationFailure
+
 from datadog_checks.mongo.collectors.base import MongoCollector
 
 
@@ -34,6 +36,9 @@ def collect(self, api):
                     ]
                     val = int(stats.get('accesses', {}).get('ops', 0))
                     self.gauge('mongodb.collection.indexes.accesses.ops', val, idx_tags)
+            except OperationFailure as e:
+                # Atlas restricts $indexStats on system collections
+                self.log.warning("Could not collect index stats for collection %s: %s", coll_name, e)
             except Exception as e:
                 self.log.error("Could not fetch indexes stats for collection %s: %s", coll_name, e)
                 raise e