Thorntail, formerly known as WildFly Swarm, is an open source (Apache License 2.0) Java application server developed by RedHat as a basis for microservice deployments.
Thorntail is a framework based on the popular WildFly Java application server to enable the creation of small, standalone microservice-based applications. Thorntail is capable of producing so-called just enough app-server to support each component of your system.
See Thorntail.io for more information.