Docker provides a good basis to run composite applications in the cloud, especially if those are not cloudaware, or cloud-native. However, Docker concentrates on managing containers on one host, but SaaS providers need a container management solution for multiple hosts. Therefore, a number of tools emerged that claim to solve the problem. This paper classifies the solutions, maps them to requirements from a case study and identifies gaps and integration requirements. We conclude that the Docker ecosystem could help moving from IaaS and PaaS solutions towards a runtime environment for SaaS applications, but needs consolidation.