Setting Up Deployment

Nedryland provides a set of convenience functionality for creating deployments. Note that deployment is not actually done inside the derivation, instead it generates a deploy script that can be run outside of a nix context. This is because things like credentials and network access make deployment inherently impure.

An example might look like

base.mkComponent {
  ...
  deployment = {
    terraform = base.deployment.mkTerraformDeployment {
      terraformPackage = package;
      inherit preDeployPhase postDeployPhase deployShellInputs;
    };
  };
}

Building a deployment script from this declaration can be done in two ways.

1. The attribute <componentName>.deployment.terraform.
2. The attribute <componentName>.deploy which is a combined target containing all deployments (which in this example is only one).

A deploy can now be performed by running the script in bin/deploy in the resulting derivation (usually accessed by the result symlink). Most deployments also comes with a deployment shell that is typically used to interact with the deployed environment. To enter this shell run bin/shell in the resulting derivation.

Setting up project deployment targets

mkProject accepts extra targets and deploy is conventionally used for project deployment targets and can be accessed through deploy.<attribute>.

All values in this set should be deployment derivations, or combinations of them which can be created with the convenience function mkCombinedDeployment available in base.

nedryland.mkProject {
  ...
  deploy = { mkCombinedDeployment }: {
    group = {
      comp1 = component1.deploy;
      comp2 = component2.deploy;
    }
    combined = mkCombinedDeployment "combined" {
      comp3 = component3.deploy;
      comp4 = component4.deploy;
    }
  }
}

• deploy.group.comp1 will create a deploy script for component1.
• deploy.group will create two separate deploy script for component1 and component2.
• deploy.combined will create one deploy script for component3 and component4.
• deploy.combined.comp3 will not work.

Creating new deployment types

To aid in creating the deploy script and shell Nedryland provides the function base.deployment.mkDeployment. This function takes one mandatory argument.

deployPhase: This is the actual deploy script. This can either be the inline deploy script or call an external utility. The environment is similar to the shell one, but it is recreated outside of nix

Furthermore it accepts these optional arguments.

preDeployPhase: Script code to execute before the deploy phase and when opening the shell. A typical usecase is to aquire credentials and set up connection details. postDeployPhase: Script code to execute after the deploy phase. Used to cleaning up resources aquired during preDeployPhase. inputs: A list of derivations that will be added to path for the deployment script. These are typically dependencies you only need to do the deployment of the artifact that aren't necessarily dependencies of the artifact itself. shellInputs: A list of derivations that will be added to path for the shell. deployShell: Is true by default, set it to false if you do not want to have a deploy shell generated in your output.

Deployment will also pick up preDeploy, postDeploy and preDeployShell hooks.