What is Salt?
We’re not just talking about NaCl.
Distributed Remote Execution
Salt is a distributed remote execution system used to execute commands and query data. It was developed in order to bring the best solutions found in the world of remote execution together and make them better, faster and more malleable. Salt accomplishes this via its ability to handle larger loads of information, and not just dozens, but hundreds or even thousands of individual servers, handle them quickly and through a simple and manageable interface.
Versatility between massive scale deployments and smaller systems may seem daunting, but Salt is very simple to set up and maintain, regardless of the size of the project. The architecture of Salt is designed to work with any number of servers, from a handful of local network systems to international deployments across disparate datacenters. The topology is a simple server/client model with the needed functionality built into a single set of daemons. While the default configuration will work with little to no modification, Salt can be fine tuned to meet specific needs.
The core function of Salt is to enable remote commands to be called in parallel rather than in serial, to use a secure and encrypted protocol, the smallest and fastest network payloads possible, and with a simple programmer interface. Salt also introduces more granular controls to the realm of remote execution, allowing for commands to be executed in parallel and for systems to be targeted based on more than just hostname, but by system properties.
Building on Proven Technology
Salt takes advantage of a number of technologies and techniques. The networking layer is built with the excellent ZeroMQ networking library, so Salt itself contains a viable, and transparent, AMQ broker inside the daemon. Salt uses public keys for authentication with the master daemon, then uses faster AES encryption for payload communication, this means that authentication and encryption are also built into Salt. Salt takes advantage of communication via Python pickles, enabling fast and light network traffic.
Python Client Interface
In order to allow for simple expansion, Salt execution routines can be written as plain Python modules and the data collected from Salt executions can be sent back to the master server, or to any arbitrary program. Salt can be called from a simple Python API, or from the command line, so that Salt can be used to execute one-off commands as well as operate as an integral part of a larger application.
Fast, Flexible, Scalable, Secure
The result is a system that can execute commands across groups of varying size, from very few to very many servers at considerably high speed. A system that is very fast, easy to set up and amazingly malleable, able to suit the needs of any number of servers working within the same system. Salt’s unique architecture brings together the best of the remote execution world, amplifies its capabilities and expands its range, resulting in this system that is as versatile as it is practical, able to suit any network. Our source code is pretty (pep8, pylint, pychecker), well documented, and since we use a battle-tested branching model (gitflow), we are able to deliver stable software while keeping a fast pace. Last but not least, security is an intrinsic part of salt and something not just influencing how source code is written and how tests are done, but also something that defines the overall architecture and has heavy influence on the core design of salt.
Salt is developed under the Apache 2.0 licence, and can be used for open and proprietary projects. Please submit your expansions back to the Salt project so that we can all benefit together as Salt grows. So, please feel free to sprinkle some of this around your systems and let the deliciousness come forth.