The growth of infrastructure and applications has been enabled in part by an increasing trend towards automation everywhere. Configuration as code (such as Chef or Puppet with Packer) has enabled automated machine configuration. Infrastructure as code (such as Terraform) has enabled automatic infrastructure creation. And schedulers (such as Nomad and Kubernetes) have enabled automatic application deployment. Sentinel enables guardrails to be put in place on automation while allowing the codification and automatic enforcement of business requirements in critical areas of your infrastructure.
Meanwhile, businesses have business requirements and sometimes legal requirements which must be expressed in policies. Traditionally, these policies are enforced by humans. But in a highly automated world, the automation is only as fast as its slowest component. In many cases, this is the human verification step.
As an example: before infrastructure as code and autoscaling, if an order came through for 5,000 new machines, a human would likely respond to the ticket verifying that the user really intended to order 5,000 new machines. Today, automation can almost always freely order 5,000 new compute instances without any hesitation, which can result in unintended expense or system instability.
Sentinel introduces policy as code and a powerful framework built-in to HashiCorp tooling to allow automation guardrails, business requirements, legal compliance, and more to be actively enforced by the running systems in realtime.
With Sentinel, you can require an override to create certain numbers of infrastructure resources. You can disallow unsafe deployment configurations with Nomad. You can enforce certain key/value formats in Consul. You can restrict secret access by time in Vault. And more.