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The advantages of configuration management tools
Config Battle
The hype surrounding Docker has raised the awareness of many administrators regarding a category of programs that were almost unknown before now: fleet and configuration managers. Several representatives of this species are vying for the attention of users: Etcd [1], Consul [2], and ZooKeeper [3] are just a few.
What are these configuration managers actually about? What are their preferred fields of application, and why should administrators employ this innovation? In this article, I explain the ideas behind the tools and then let three candidates do battle.
Was Everything Better in the Past?
Administrators often reminisce about how managing IT environments used to be easier: Each host had a defined role that did not change over the course of the server's life. When people started looking into clusters, it was usually a matter of small, high-availability setups, such as Pacemaker and DRBD synchronizing data between hosts. However, administrators were fighting a problem that still exists today: The configuration of services needs to be identical on two hosts so that if one system fails the other can take over without any problems; therefore, it is essential to synchronize configuration files in some way. Home-made solutions based on Rsync were often used in these cases, and although they might not have been pretty, they served the purpose.
In recent years, however, IT setups have continued to grow and, especially, to become more dynamic. The self-made solutions that administrators used to keep the configuration files at the same level between hosts became more and more complex. Keeping the state of services consistent across multiple hosts also proved to be more and more difficult. Moreover, with scale-out setups, it is
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