Have services declare their dependencies on other services, both within a single node set, and across entire deployment. Make sure that dependencies of all services are mutually compatible before deployment starts.

Discussion:

Following point were raised during discussion of this epic, which need to be considered before resolution.

In no particular order.

• Undeclared and unchecked dependencies will add to confusion on part of customer
• Many configurations, that is sequences of services, are invalid
• Implementing checking algorithm would be reasonably simple
• Maintenance of service-on-service dependency relationships would be time consuming
• Without proper care the dependency tree may include all services, degrading deployment performance
• Multiple checks for dependencies will inevitably lead to performance degradation
• Incorrect, that is too aggressive dependency declaration would lead to failed deployments for no good reason
• Documenting dependencies will suffer from some of the same issues, but with much engineering time required