A feature in the servlet container in Undertow that relates to performance is the option to ignore flushes on a servlet output stream. Ignoring flushes can provide better performance in most cases. The current setting can be investigated using the following CLI command:

/subsystem=undertow/servlet-container=default:read-attribute(name=ignore-flush)

The default value of the ignore-flush attribute is false and can be easily changed to true using the following command in the CLI:

/subsystem=undertow/servlet-container=default:write-attribute(name=ignore-flush, value=true)

An MBean named jboss.as:subsystem=undertow,servlet-container=default is also available. The following screenshot shows you the JConsole view of the attributes of the default servlet container:

The JConsole view of the attributes of the default servlet container

The setup is also available through the Admin Console, as shown in the following screenshot:

The Admin Console view of...