[CASSANDRA-17379] Fail starting when the same parameter exists more than once in cassandra.yaml

• Type: Improvement
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 4.1-alpha1, 4.1
• Component/s: Local/Config
• Change Category: Operability
• Complexity: Normal
• Platform: All

Source Control Link

https://github.com/apache/cassandra/commit/7ce140bd1dea311b9f98cdfbcd07dcff9fbd457c

Test and Documentation Plan

new unit test, cci run

• Assignee: Marcus Eriksson
• Reporter: Ekaterina Dimitrova

Authors

Marcus Eriksson

Reviewers

David Capwell, Ekaterina Dimitrova

• Created: 14/Feb/22 02:06
• Updated: 05/Oct/22 20:21
• Resolved: 29/Apr/22 08:40

Description

The way that SnakeYAML works, if someone has added the same parameter more than once - the last occurrence will be the one that will take precedence. 

Now after CASSANDRA-15234 we can even add the parameter with the old name and with the new name and the occurrences will replace each other. Again, whatever is last in cassandra.yaml will take precedence. Example:

If you add the following in cassandra.yaml

hinted_handoff_enabled: true
enabled_hinted_handolff: false

you will get loaded in Config - 

hinted_handoff_enabled: false

 //there is backward compatibility from the old name to load into the new one

Currently Cassandra prints in the logs what config was loaded but it is good also to detect the case mentioned and emit a warning for the user so they can verify that the value they wanted was loaded in config.

To do that you might want to look at the PropertiesChecker and the way we emit other warnings in check() in YamlConfigurationLoader. 

Issue Links

• is related to: CASSANDRA-17949 Update CCM post CASSANDRA-17379
• relates to: CASSANDRA-15234 Standardise config and JVM parameters