[GitHub] [cassandra] belliottsmith commented on a change in pull request #659: Operational Improvements & Hardening for Replica Filtering Protection

[GitBox <gi...@apache.org>]

belliottsmith commented on a change in pull request #659:
URL: https://github.com/apache/cassandra/pull/659#discussion_r449151578



##########
File path: conf/cassandra.yaml
##########
@@ -661,6 +661,23 @@ auto_snapshot: true
 tombstone_warn_threshold: 1000
 tombstone_failure_threshold: 100000
 
+# Filtering and secondary index queries at read consistency levels above ONE/LOCAL_ONE use a
+# mechanism called replica filtering protection to ensure that results from stale replicas do
+# not violate consistency. This mechanism, which operates in two phases, caches replica
+# results on-heap at the coordinator. The more stale results returned by the former, the more
+# rows cached at the latter.
+#
+# These thresholds exist to limit the damage very stale replicas can cause during these queries.
+# They essentially define the memory budget individal index and filtering queries have to meet
+# the client-desired consistency level.
+#
+# "cached_replica_rows_warn_threshold" is the threshold at which a warning will be logged.
+# "cached_replica_rows_fail_threshold" is the threshold at which the query will fail.
+#
+# These thresholds may also be adjusted at runtime using the StorageService mbean.
+cached_replica_rows_warn_threshold: 1024
+cached_replica_rows_fail_threshold: 16384

Review comment:
       Given the existing usage of materialised on the project it might be best to pick something else again :/




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