...

• Guardrail: Interface defining a guardrail that guards against a particular usage/condition.
• DefaultGuardrail: Abstract class implementing Guardrail. It implements the default behaviour when the guardrail is triggered consisting on throwing warnings or errors.
• GuardrailsFactory: Interface defining a factory for building instances of Guardrail.
• DefaultGuardrailsFactory: Class implementing GuardrailsFactory, it builds instances of DefaultGuardrail.
• CustomGuardrailsFactory: Abstract class instantiating a custom GuardrailsFactory, so users can provide their own implementations of guardrails through a system property named cassandra.custom_guardrails_factory_class.
• GuardrailsConfig: Configuration settings for Guardrails, which are populated from cassandra.yaml . This contains a main setting enabled, controlling if Guardrails are globally active or not, and individual settings to control each Guardrail.
• cassandra.yaml: allows configuring individual Guardrails at startup, being globally disabled by default.
• Guardrails: Entry point for guardrails, storing all the defined guardrail instances and additional helper methods. These Guardrail instances are built at startup with the provided GuardrailsFactory and GuardrailsConfig.

...

# guardrails
  # enabled: false
  # column_value_size_failure_threshold_in_kb: -1
  # columns_per_table_failure_threshold: -1
  # secondary_index_per_table_failure_threshold: -1
  # materialized_view_per_table_failure_threshold: -1
  # tables_warn_threshold: -1
  # tables_failure_threshold: -1
  # table_properties_disallowed: 
  # write_consistency_levels_disallowed:
  # partition_size_warn_threshold_in_mb: -1
  # partition_keys_in_select_failure_threshold: -1
  # disk_usage_percentage_warn_threshold: -1
  # disk_usage_percentage_failure_threshold: -1
  # in_select_cartesian_product_failure_threshold: -1
  # user_timestamps_enabled: true
  # read_before_write_list_operations_enabled: true
  # fields_per_udt_failure_threshold: -1
  # collection_size_warn_threshold_in_kb: -1
  # items_per_collection_warn_threshold: -1

It will also be possible to dynamically configure guardrails at runtime through JMX and possibly virtual tables.

Migrating existing cassandra.yaml warn/fail thresholds

...

Guardrails allow C* operators to impose system-wide restrictions that are configured through yaml and JMX/virtual tables. Capability restrictions are focused on imposing restrictions on particular users and offer a new CQL API to do so. Both concepts are not mutually exclusive and are complementary.

...