Albatross-cljs NPM

albatross

Albatross (albatross-cljs) is a declarative deployment library and DSL.

Overview

Albatross leverages Weaver extensively to provide flexibility, concision, and code reuse. An albatross deployment is specified as a template with pre-deploy, deploy, and post-deploy steps. It is processed with the albatross.core/generate-deployment function, which returns a map. This map has a function under :run-deployment which can be run to perform the entire deployment.

Details

Templating and weaver context

The context can be specified as :weaver/context at the top level of the map (must be a map literal, but I am considering supporting afilename as well), or as metadata in a similar manner to figwheel-main (e.g. ^{:config {...}}{:deployment ...}). If both are provided, they are merged, and the metadata takes precedence. A context can also be passed explicitly to albatross.core/generate-deployment in its two arity version, in which case both metadata and :weaver/context are ignored.

The first thing that happens when generate-deployment is called is the templating of the deployment map.

Once the deployment map is templated, there are three major parts, which are top-level keys. :pre-deploy-hooks which set up for the deployment, :deployment which specifies the actual deploying, and :post-deploy-hooks which manage actions post-deployment (TODO). We will cover these in detail a bit later.

Deployment Steps

Deploy Hooks (:pre-deploy-hooks, :post-deploy-hooks)

NOTE: post-deploy-hooks are not implemented fully

Deploy hooks are effectful (usually non-deployment) steps that must be performed before or after a deployment. Examples include: generating files from templates, pulling from/pushing to Git, Setting environment variables, building an uberjar, etc.

The only supported hook type at the moment is the :weaver hook type.

:weaver

The weaver hook takes a map with :templates - a vector of templates, and :context - A context map which will be used by weaver. See weaver for more detailed documentation on specific templating.

{...
:pre-deploy-hooks [...
                   {:albatross/type :weaver
                    :context {:config {:environment "staging"
                                        :version :git/short-hash
                                        :app-name "my-service"
                                        :shortname "my-service"
                                        :external-port 30055
                                        :app-container-port 3000}}
                    :templates [{:from "k8s-edn/"
                                 :to   "target/k8s/json/"}]}
                                  
             ...]
...}

Main Deployment (:deployment)

Deployment is where the meat of the deployment happens. This is vector of maps which are each transformed into a vector of instructions (Only unix shell string commands are supported currently). Each map returns a vector of one or more instructions which are then concatenated to form a complete deployment instruction set. Deployment maps are parsed using the deployment-instructions multimethod, which can be extended as needed. Note that the deployment step is NOT effectful. Only calling the generated deployment-fn or run-deployment functions will cause the actual deployment to occur. Deployment type is specified by the :albatross/type key on the instruction map. Below are a list of deployment-instruction types supported by albatross.

:shell

This serves as an escape hatch to perform arbitrary shell instructions. Should be used responsibly, as with any escape hatch. Here's an example of a :shell configuration:

{...
:deployment [...
             {:albatross/type :shell
              :exec ["echo foo" "pwd" "echo bar"]}
             ...]
...}

The :exec key can be either a string or a vector of strings. Like the entire albatross config, it can also include weaver templating. The value of exec is either returned directly, or wrapped in a vector if necessary.

:docker

The docker deployment step represents deploying a set of docker images with a single connection to a single repository. It is composed of a URL, credentials (:user key with username and either :pass for a literal password, or a :pass-file for piping in a password from a file into stdin), and :images, a vector of images. Each image is a map with :name (the image's name), :tags (a list of desired tags), and :workspace (the directory containing the Dockerfile). The :docker step will do the following: 1. docker login using the provided credentials, connecting to the repository. 2. For each image in :images, run docker build in the specified workspace, and docker push with the specified tags 3. docker logout to close the session

Here's an example of a :docker configuration:

{...
:deployment [...
             {:albatross/type :docker
              :url "docker.mycompany.tld:PORT/"
              :user :kw-env/DOCKER_USER ;;weaver => "jenkins"
              :pass :kw-env/DOCKER_PASS ;; weaver => "password123"
              :images [{:name :config/image-name ;; weaver => "myproject"
                        :tags ["staging-latest"]
                        :workspace "./"}]} 
             ...]
...}

:kubernetes

The kubernetes deployment step represents a set of actions (performed by kubectl) associated with a single context (i.e. KUBECONFIG). The context can also be configured manually (e.g. by using environment variables or :shell steps) in which case the :kubeconfig and :use-context keys should be left blank. There is a slight difference between :kubeconfig and :use-context. They correspond to attaching a --kubeconfig flag to each kubectl command, and to running kubectl config use-context <context> before other commands respectively. They can be used together, but this is generally unnecessary and has not been tested. The kubernetes deployment step consists of a :kubeconfig and/or a :use-context, an optional, purely for logging :cluster-name, and :actions, a vector of k8s action maps. Each action in :actions is handled by the albatross.kubernetes/action-instructions which can be extended as necessary. The types are as follows:

:apply-dir, which is equivalent to running kubectl apply -f <:dir>.
:secret, this is equivalent to deleting and recreating a secret from a file or many files.

:apply-dir is intended to be used with the :weaver pre-deploy hook which generates JSON files from a source directory of EDN templates. Since apply can be used to declaratively specify a set of kubernetes objects desired and allows kubernetes to manage the transition, it is the preferred method of deployment. However, sometimes specific actions are required :secret was added due to a specific need I had. It overwrites an existing secret from a file or a set of files.

Here's an example of a :kubernetes configuration:

{...
:deployment [...
             {:albatross/type :kubernetes
              :use-context "my-context@kubernetes"
              :cluster-name "my-service"
              :actions [{:action-type :secret
                         :name "my-service-config"
                         :config-map {"app-config" "dev-config.edn"}}
                        {:action-type :apply-dir
                         :dir "target/foo/k8s/json/"}]}
             ...]
...}

Return value

weaver.core/generate-deployment in and of itself doesn't have any side-effects. It returns a map of functions that perform various tasks, as well as data about these functions. The keys are: :config :pre-deploy-hooks :pre-deploy-fn :instructions :deployment-fn :post-deploy-hooks :post-deploy-fn and :run-deployment

:config

This is the fully templated config map (i.e. post-weaver) that was used to generate this deployment.

:pre-deploy-hooks

This is a vector of maps representing the generated pre-deploy hooks. Their shape depends on the hook type, but each will have a :hook-fn and a :description.

:pre-deploy-fn

This is a function that runs all pre-deploy-hooks in order.

:instructions

This is a vector of strings (specifically bash commands) that comprise the deployment.

:deployment-fn

This is a function that executes all deployment instructions in order in a shell process

:post-deploy-hooks

TODO see :pre-deploy-hooks, similar come after a successful deployment

:post-deploy-fn

TODO see :pre-deploy-fn, similar but run after a successful deployment

:run-deployment

Runs pre-deploy-fn, then deployment-fn, then post-deploy-fn, returning the results in a vector

Development

To get an interactive development environment run:

lein fig:build

This will auto compile and send all changes to the browser without the need to reload. After the compilation process is complete, you will get a Browser Connected REPL. An easy way to try it is: