Environments

An important part of creating a build pipeline is to define which resources are part of the build environment. In order to do that it is important to understand what is meant with the term environment as it refers to the resources in Calvinverse.

An environment is a collection of resource instances and services that work together to achieve one or more goals, i.e. in this case to provide the ability to build, test and release software.

There are several reasons to place resource instances and services inside an environment

• An environment forms a unit of separation between different services that do not need to contact each other while still allowing the resources to share an IP pool. This creates the possibility of having multiple groups of services, for instance production and a test environment.
• Resources inside an environment are referred to by a name that is unique only inside the environment. Two instances of a specific resource that live in different environments will be known, in each environment, by the same name. This means that tooling and services can be used in all environments without requiring any changes, thus enabling interchangability of services between environments, e.g. between a test and production environment.

It should be noted that there are no immediate restrictions that stop services from contacting resources in a different environment, i.e. environments are a cooperative system. In order to actually block resources and services from reaching outside the environment additional networking restrictions need to be provided by routers and firewalls.

An environment should have the following characteristics

• A way to group resources. A resource should 'know' which environment it belongs to. Note that 'knowing' the environment basically means that a resource should easily be able to contact other resources in the environment while making it difficult to contact resources outside the environment. To a resource the environment should be the only thing around.
• One or more ways to push information into an environment. An environment isn't very useful if it cannot be provided with information in some way.
• One or more ways to get information out of an environment. As with inputs an environment is not very useful if no information can leave the environment.

Calvinverse creates environments by using Consul to create environments by using the datacenter concept to define an environment. All services in a datacenter can communicate with each other either by using Consul as the DNS resolver or by using more advanced Connect feature. This means you can have multiple environments, e.g. production and test, running on the same hardware in the same physical network (or even the same VLAN). Inside the environment the instances can refer to each other based on the consul name, e.g. active.build.service.mynetwork, assuming mynetwork is your consul domain name, and calls will only got to the instance that is in that environment.

Note that if you need strict separation then you'll need to use the standard network separation methods to achieve your goal.