How to setup a Spring Boot application with embedded tomcat session clustering?

Question

I want to setup a Spring Boot application with embedded tomcat session clustering.

Since embedded tomcat does not have a server.xml file, I\'ve created

Answer 1

In Spring Boot 2.0.x, you need to use a WebServerFactoryCustomizer to configure the clustering.

@Component
public class WebServerCustomizer implements WebServerFactoryCustomizer<TomcatServletWebServerFactory> {
    @Override
    public void customize( final TomcatServletWebServerFactory factory ) {
        factory.addContextCustomizers( new TomcatClusterContextCustomizer() );
    }
}

public class TomcatClusterContextCustomizer implements TomcatContextCustomizer {
    @Override
    public void customize( final Context context ) {
        // Call method defined in the question text above, but pass Engine 
        // instead of Tomcat
        configureCluster( (Engine)context.getParent().getParent() );
    }
}

Answer 2

The key was to make the context distributable, and setting manager.

When I modified the code of the question as follows, the session clustering worked.

@Configuration
public class TomcatConfig
{
    @Bean
    public EmbeddedServletContainerFactory servletContainerFactory()
    {
        TomcatEmbeddedServletContainerFactory factory = new TomcatEmbeddedServletContainerFactory()
        {
            ...
        };

        factory.addContextCustomizers(new TomcatContextCustomizer()
        {
            @Override
            public void customize(Context context)
            {
                context.setManager(new DeltaManager());
                context.setDistributable(true);
            }
        });

        return factory;
    }

    ...
} 

For Spring Boot 1.2.4, context.setManager() is not needed. But for Spring Boot to 1.3.0, if context.setManager() is not called, clustering fails and the following log is shown.

2015-11-18 19:59:42.882  WARN 9764 --- [ost-startStop-1] o.a.catalina.ha.tcp.SimpleTcpCluster     : Manager [org.apache.catalina.session.StandardManager[]] does not implement ClusterManager, addition to cluster has been aborted.

I am somewhat worried about this version dependency. So I opened an issue for this.