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1. Version 1.0
Guardrails - Apache Cassandra
In Cassandra lunch #107, we will discuss how Guardrails
work in Apache Cassandra
Dipan Shah
Engineer @ Anant

2. Topics
● What are guardrails?
● What is the purpose of guardrails?
● How they work?
● Guardrails options for production
● Guardrails demo
● Upcoming developments
● Q&A

3. Guardrails in Apache Cassandra
● A framework that allows operators to restrict certain functionalities in Cassandra
● Available from Apache Cassandra V 4.1
● Has been available in Datastax Enterprise from V 6.8 in some form

4. What problems does it solve?
● Operators have faced cluster stability problems due to improper usage of Cassandra
● Best practices and Anti-patterns are difficult to communicate and enforce
● Guardrails allow to restrict some of these functionalities
● Options like below have been available since earlier versions but this is different
○ Tombstone limits
○ Batch limits
○ Materialized views usage

5. How it works?
The new framework allows operators to restrict how Cassandra is used by:
● Disabling certain features
● Disallowing some specific values
● Defining soft and hard limits to certain database magnitudes

6. How it works?
Guardrail violation are validated at:
● CQL Layer
● In the background

7. CQL Guardrails Examples
● allow_filtering_enabled : false
○ Will not allow queries with “Allow filtering” if set to false
○ CQL error is reported

8. CQL Guardrails Examples
● tables_warn_threshold : 20
○ Raises a CQL client warning and logs a server-side warning message
○ CQL operation is not aborted

9. CQL Guardrails Examples
● tables_fail_threshold : 30
○ CQL operation will be aborted

10. Monitoring Guardrail events
● The triggering of a guardrail will emit a diagnostic log with guardrail event in it
● Check logs for WARN and ERROR messages related to guardrails
● Set alerts for such messages in log aggregation tools like Splunk, ELK stack, Graylog,
etc.

11. More Guardrail examples
● Secondary Indexes
○ secondary_indexes_enabled: true
○ secondary_indexes_per_table_warn_threshold: 5
○ secondary_indexes_per_table_fail_threshold: 10
● Number of fields in a UDT
○ fields_per_udt_warn_threshold: -1
○ fields_per_udt_fail_threshold: -1

12. Background Guardrails
● Some guardrails are checked in the background
● They are not associated with any specific query
● To avoid a costly read-before-write operation
● Examples:
○ Disk space usage
○ Number of items in a non-frozen collection

13. Additional Guardrails for Production
● Replication factor
○ minimum_replication_factor_warn_threshold
○ minimum_replication_factor_fail_threshold
● Read and write consistency levels
○ read_consistency_levels_warned: []
○ read_consistency_levels_disallowed: []
○ write_consistency_levels_warned: []
○ write_consistency_levels_disallowed: []

14. Additional Guardrails for Production
● IN restrictions
○ partition_keys_in_select_warn_threshold
○ partition_keys_in_select_fail_threshold
● Materialized views
○ materialized_views_per_table_warn_threshold
○ materialized_views_per_table_fail_threshold

15. Exceptions
● Guardrails are only applied to the operations of regular users
● They will neither be checked for superuser queries nor internal queries
● The configuration for guardrails is an extensible API
● Third-party alternative implementations could provide different guardrail
configurations depending on the user, or on some other factors

16. Demo

17. Upcoming developments
● New features are being developed
● Can be tracked at: https://issues.apache.org/jira/browse/CASSANDRA-
17189?jql=project%20%3D%20CASSANDRA%20AND%20text%20~%20%22guard
rail%22

18. Questions

19. Strategy: Scalable Fast Data
Architecture: Cassandra, Spark, Kafka
Engineering: Node, Python, JVM,CLR
Operations: Cloud, Container
Rescue: Downtime!! I need help.
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