Paul Ayers created CASSANDRA-20843:
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Summary: Replica filtering guardrail needs a change in the yaml
Key: CASSANDRA-20843
URL: https://issues.apache.org/jira/browse/CASSANDRA-20843
Project: Apache Cassandra
Issue Type: Bug
Reporter: Paul Ayers
In the Cassandra 5 cassandra.yaml, we have the following guardrail section:
{code:java}
# 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. (See CASSANDRA-8272 and CASSANDRA-15907 for more
details.) This
# mechanism materializes replica results by partition on-heap at the
coordinator. The more possibly
# stale results returned by the replicas, the more rows materialized during the
query.
replica_filtering_protection:
# These thresholds exist to limit the damage severely out-of-date replicas
can cause during these
# queries. They limit the number of rows from all replicas individual index
and filtering queries
# can materialize on-heap to return correct results at the desired read
consistency level.
#
# "cached_replica_rows_warn_threshold" is the per-query threshold at which
a warning will be logged.
# "cached_replica_rows_fail_threshold" is the per-query threshold at which
the query will fail.
#
# These thresholds may also be adjusted at runtime using the StorageService
mbean.
#
# If the failure threshold is breached, it is likely that either the
current page/fetch size
# is too large or one or more replicas is severely out-of-sync and in need
of repair.
cached_rows_warn_threshold: 2000
cached_rows_fail_threshold: 32000
{code}
This is confusing for some as we had a customer attempt to configure
cached_replica_rows_warn_threshold and cached_replica_rows_fail_threshold in
addition to the actual parameters. We should update the wording so the
description matches the parameters.
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