Andrew created CASSANALYTICS-77:
-----------------------------------
Summary: Cassandra uses default compaction strategy in
storage_compatibility_mode which can lead to unsupported compaction strategy
during upgrades
Key: CASSANALYTICS-77
URL: https://issues.apache.org/jira/browse/CASSANALYTICS-77
Project: Apache Cassandra Analytics
Issue Type: Bug
Reporter: Andrew
Hi,
With Cassandra 5 and the cassandra-latest.yaml, UCS is selected as the default
compaction strategy. When upgrading a cluster, via a datacenter switch for
example, the compaction for system_auth, system_distributed and system_traces
gets updated to use UCS even though there's still Cassandra 4 nodes within the
cluster. This leads to a failure mode where a Cassandra 4 node cannot start up
due to an unknown compaction strategy:
{code:java}
ERROR [main] 2025-07-02 17:09:39,693 CassandraDaemon.java:898 - Exception
encountered during startup
org.apache.cassandra.exceptions.ConfigurationException: Unable to find
compaction strategy class
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy' {code}
Even with storage_compatibility_mode, the default compaction strategy is used.
To mitigate this, we can update the default compaction strategy however the
system_schema still indicates that UCS is used:
{code:java}
keyspace_name | table_name | compaction
--------------------+--------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
system_auth | cidr_groups | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'}
system_auth | cidr_permissions | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'}
system_auth | identity_to_role | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'}
system_auth | network_permissions | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'}
system_auth | resource_role_permissons_index | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'}
system_auth | role_members | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'}
system_auth | role_permissions | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'}
system_auth | roles | {'class':
'org.apache.cassandra.db.compaction.UnifiedCompactionStrategy',
'max_sstables_to_compact': '64', 'min_sstable_size': '100MiB',
'scaling_parameters': 'T4', 'sstable_growth': '0.3333333333333333',
'target_sstable_size': '1GiB'} {code}
There isn't an easy way to update the compaction strategy for these tables
either.
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