[DBMON-5536] collect index stats on replica set secondaries (DataDog#20819)

* collect index stats on replica set secondaries

* add changelog

Author: lu-zhengda

mongo/changelog.d/20819.added

@@ -0,0 +1 @@
+Collect index stats metric `mongodb.collection.indexes.accesses.opsps` on replica set secondary nodes. 

mongo/datadog_checks/mongo/collectors/index_stats.py

@@ -5,6 +5,7 @@
 from pymongo.errors import OperationFailure
 
 from datadog_checks.mongo.collectors.base import MongoCollector, collection_interval_checker
+from datadog_checks.mongo.common import ReplicaSetDeployment
 from datadog_checks.mongo.metrics import INDEX_METRICS
 
 
@@ -20,7 +21,16 @@ def __init__(self, check, db_name, tags, coll_names=None):
         self._collector_key = (self.__class__.__name__, db_name)  # db_name is part of collector key
 
     def compatible_with(self, deployment):
-        # Can only be run once per cluster.
+        if isinstance(deployment, ReplicaSetDeployment):
+            # Collecting index stats on both primary and secondary nodes for replica set
+            if deployment.is_arbiter:
+                self.log.debug("IndexStatsCollector can not be run on arbiter nodes.")
+                return False
+            if deployment.use_shards:
+                self.log.debug("IndexStatsCollector can not be run on shards on sharded clusters.")
+                return False
+            return True
+        # Collecting index stats for standalone or mongos on sharding deployments
         return deployment.is_principal()
 
     def _get_collections(self, api):

mongo/tests/test_integration.py

@@ -782,6 +782,7 @@ def test_integration_replicaset_secondary(
         'dbstats-local',
         'fsynclock',
         'hostinfo',
+        'indexes-stats',
     ]
     if collect_custom_queries:
         metrics_categories.append('custom-queries')