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# convention 4 kubernetes: c4k-common
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[](https://clojars.org/org.domaindrivenarchitecture/c4k-common-clj) [](https://clojars.org/org.domaindrivenarchitecture/c4k-common-cljs) [](https://gitlab.com/domaindrivenarchitecture/c4k-common/-/commits/master)
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## Rationale
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There are many comparable solutions for creating c4k deployments like `helm` or `kustomize` .
`kustomize` is great to manage your k8s manifests by splitting huge files into handy parts.
`helm` is great because of its large community.
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Why do we need another one? Why do you continue the reading here?
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We combine the simplicity of `kustomize` with the ability for doing real programming as software developers would do.
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Following the principle
"Use programming language for programming"
we are clearly enjoy writing kubernetes manifests with clojure. In comparison with helms templating, things such as business logic, conventions, input validation, versions, dependencies and reuse are much easier and much more reliable to implement.
By the way, c4k means "convention for kubernetes".
### Features
c4k-common supports the following use cases:
#### Target Cli and Web Frontend
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Set up your cli as follows
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```clojure
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(defn -main [& cmd-args]
(uberjar/main-common
"c4k-forgejo" ;; name of your app
core/config? ;; schema for config validation
core/auth? ;; schema for credential validation
core/config-defaults ;; want to set default values?
core/k8s-objects ;; the function generate the k8s manifest
cmd-args ;; command line arguments given
))
```
The full example can be found here: https://repo.prod.meissa.de/meissa/c4k-forgejo/src/branch/main/src/main/clj/dda/c4k_forgejo/uberjar.clj
You can create your manifest as web-application also (using page local js without server interaction)
```html
html>
< head >
< meta charset = "utf-8" / >
< title > c4k-forgejo< / title >
< link href = "https://domaindrivenarchitecture.org/css/bootstrap.min.css" rel = "stylesheet" type = "text/css" / >
< link href = "https://domaindrivenarchitecture.org/css/fonts/fontawesome/fontawesome.css" rel = "stylesheet"
type="text/css" />
< link href = "https://domaindrivenarchitecture.org/css/custom.css" rel = "stylesheet" type = "text/css" / >
< / head >
< body >
< div id = "c4k-content" > < / div >
< script src = "js/main.js" > < / script >
< / body >
< / html >
```
[](https://domaindrivenarchitecture.org/pages/dda-provision/c4k-forgejo/)
See: https://repo.prod.meissa.de/meissa/c4k-forgejo/src/branch/main/public/index.html
and: https://repo.prod.meissa.de/meissa/c4k-forgejo/src/branch/main/src/main/cljs/dda/c4k_forgejo/browser.cljs
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#### Separate Configuration from Credentials
We think it is an good idea to have credentials separated from configuration. All our functions, cli and frontend are following this principle.
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```bash
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c4k-common config.edn auth.edn > k8s-manifest.yaml
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```
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#### Input as EDN or Yaml
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c4k-common supports all its resources, input and output as yaml and as edn.
The following command line will work also:
```bash
c4k-common config.yaml auth.yaml > k8s-manifest.yaml
```
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#### Inline k8s resources for versioning & dependencies
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We inline all resources used in our libraries & applications. You can generate k8s manifests everywhere without additional external dependencies.
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In case of
* java: Resources are included in the jar-file out of the box (see https://repo.prod.meissa.de/meissa/c4k-forgejo/src/branch/main/project.clj#L13).
* js: With a slim macro call we inline resources to the resulting js file (see https://repo.prod.meissa.de/meissa/c4k-forgejo/src/branch/main/src/main/cljc/dda/c4k_forgejo/forgejo.cljc#L72-L74)
* native: On native builds we inline resources also (see https://repo.prod.meissa.de/meissa/c4k-forgejo/src/branch/main/build.py#L126)
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#### Work on structured Data instead flat Templating
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To keep things simple, we do also templating. But we convert given k8s resources to structured data.
This allows us to have more control and do unit tests:
k8s-resource:
```yaml
apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
name: ratelimit
spec:
rateLimit:
average: AVG
burst: BRS
```
Replace values:
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```clojure
(defn-spec generate-rate-limit-middleware pred/map-or-seq?
[config rate-limit-config?]
(let [{:keys [max-rate max-concurrent-requests]} config]
(->
(yaml/load-as-edn "forgejo/middleware-ratelimit.yaml")
(cm/replace-key-value :average max-rate)
(cm/replace-key-value :burst max-concurrent-requests))))
```
Have a unit-test:
```clojure
(deftest should-generate-middleware-ratelimit
(is (= {:apiVersion "traefik.containo.us/v1alpha1",
:kind "Middleware",
:metadata {:name "ratelimit"},
:spec {:rateLimit {:average 10, :burst 5}}}
(cut/generate-rate-limit-middleware {:max-rate 10, :max-concurrent-requests 5}))))
```
#### Validate your inputs
Have you recognized the `defn-spec` marco? We use allover validation, e.g.
```clojure
(def rate-limit-config? (s/keys :req-un [::max-rate
::max-concurrent-requests]))
(defn-spec generate-rate-limit-middleware pred/map-or-seq?
[config rate-limit-config?]
...)
```
#### Ingress
In most cases we use 'generate-ingress-and-cert' which generates an ingres in combination with letsencrypt cert for a named service.
```clojure
(deftest should-generate-ingress-and-cert
(is (= [{:apiVersion "cert-manager.io/v1",
...}
{:apiVersion "networking.k8s.io/v1",
:kind "Ingress",
...
:spec
{:tls [{:hosts ["test.jit.si"], :secretName "web"}],
:rules
[{:host "test.jit.si",
:http {:paths [{:path "/",
:pathType "Prefix",
:backend
{:service {:name "web",
:port {:number 80}}}}]}}]}}]
(cut/generate-ingress-and-cert {:fqdns ["test.jit.si"]
:service-name "web"
:service-port 80}))))
```
#### Postgres Database
If your application needs a database, we often use postgres:
```clojure
(deftest should-generate-deployment
(is (= [{:image "postgres:16"
:name "postgresql"
:env
[{:name "POSTGRES_USER" ...}
{:name "POSTGRES_PASSWORD" ...}
{:name "POSTGRES_DB" ...}]
:volumeMounts [{:name "postgre-data-volume" ...}]}]
(get-in (cut/generate-deployment
{:postgres-image "postgres:16"})
[:spec :template :spec :containers]))))
```
We optimized our db installation to run between 2Gb anf 16Gb Ram usage.
#### Monitoring with Grafana Cloud
With minimal config of
```clojure
(def conf
{:k3s-cluster-name "your-cluster-name"
:k3s-cluster-stage :prod
:grafana-cloud-url "your-url"})
(def auth
{:grafana-cloud-user "user"
:grafana-cloud-password "password"})
(monitoring/generate conf auth)
```
You can attach your application to grafana cloud.
## Refactoring & Module Overview
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| Module | Version | [common load-as-edn][edn1] | [groups for webview][bgrp1] | [use common ingress][ing1] | [use common monitoring][mon1] | [validate examples][val1] | [ci with pyb][cipyb] | [inline-macro to load resources][macro] |[native build][native] |
| ------------- |---------| :------------------------: | :-------------------------: | :------------------------: | :---------------------------: | :-----------------------: |:--------------------:| :-------------------------------------: |:---------------------:|
| c4k-keycloak | 0.2 | x | x | x | x | x | | | |
| c4k-taiga | 0.1 | | | | | | | | |
| c4k-nextcloud | 4.0 | x | x | x | x | x | | | |
| c4k-jitsi | 1.6 | x | x | x | x | x | x | x | |
| c4k-forgejo | 3.0 | x | x | x | x | x | x | x | x |
| c4k-shynet | 1.0 | | | | | | | | |
| c4k-website | 1.1 | x | x | x | x | x | | | |
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[edn1]: https://gitlab.com/domaindrivenarchitecture/c4k-website/-/merge_requests/1
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[ing1]: https://repo.prod.meissa.de/meissa/c4k-jitsi/commit/214aa41c28662fbf7a49998e17404e7ac9216430
[bgrp1]: https://repo.prod.meissa.de/meissa/c4k-jitsi/commit/7ea442adaef727d5b48b242fd0baaaf51902d06e
[mon1]: https://repo.prod.meissa.de/meissa/c4k-jitsi/commit/19e580188ea56ea26ff3a0bfb08ca428b881ad9a
[val1]: https://repo.prod.meissa.de/meissa/c4k-jitsi/commit/5f08a108072569473463fb8f19150a12e564e54f
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[repo1]: https://repo.prod.meissa.de/meissa/c4k-forgejo/commit/e9ee6136f3347d5fccefa6b5b4a02d30c4dc42e1
[cipyb]: https://gitlab.com/domaindrivenarchitecture/c4k-jitsi/-/merge_requests/1
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[macro]: https://repo.prod.meissa.de/meissa/c4k-jitsi/commit/61d05ceedb6dcbc6bb96b96fe6f03598e2878195
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[native]: https://repo.prod.meissa.de/meissa/c4k-forgejo/pulls/4/files
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## Development & mirrors
Development happens at: https://repo.prod.meissa.de/meissa/c4k-common
Mirrors are:
* https://gitlab.com/domaindrivenarchitecture/c4k-common (issues and PR)
* https://github.com/DomainDrivenArchitecture/c4k-common
For more details about our repository model see: https://repo.prod.meissa.de/meissa/federate-your-repos
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## License
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Copyright © 2022, 2023, 2024 meissa GmbH
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Licensed under the [Apache License, Version 2.0 ](LICENSE ) (the "License")
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Pls. find licenses of our subcomponents [here ](doc/SUBCOMPONENT_LICENSE )
