Netty 'spring.netty-leak-detection' default property value is always applied to ResourceLeakDetector

Spring will override the Netty leak detection level set using -Dio.netty.leakDetection.level=advanced

The code below want to set leak detection if property was not null. But the property has default value as SIMPLE. This will get leak detection overridden as SIMPLE always if you set it other value like ‘advanced’ outside of Spring

public class NettyProperties {
	private LeakDetection leakDetection = LeakDetection.SIMPLE;

...
public class NettyAutoConfiguration {
	public NettyAutoConfiguration(NettyProperties properties) {
		if (properties.getLeakDetection() != null) {
			NettyProperties.LeakDetection leakDetection = properties.getLeakDetection();
			ResourceLeakDetector.setLevel(ResourceLeakDetector.Level.valueOf(leakDetection.name()));
		}
	}
}
...

changed to

if (properties.getLeakDetection() != LeakDetection.SIMPLE) {

will solve the problem as LeakDetection will be simple if not set.

Happy to raise a PR if this is

Version: current main branch

[philwebb]

We’re going to change the default value in NettyProperties to null and update the description to indicate that when not set the Netty default (which is SIMPLE) will be used.

[bclozel]

I think I’ve changed my mind. Developers can configure this with:

• a static call ResourceLeakDetector.setLevel(ResourceLeakDetector.Level.PARANOID);
• -Dio.netty.leakDetection.level=paranoid
• the Spring Boot configuration property

The configuration property should only apply if a specific value has been set, so setting the default value to null might be a good compromise. With all 3 ways involved, we’re always going to find a combination that leads to strange results. This is why we initially declined #14338.

Even with this solution, if ResourceLeakDetector.setLevel() is called within a bean, the configuration property will be overridden. This could be a breaking change if our configuration property currently shadows an existing system property - upgrading Spring Boot might change the resulting behavior.