Kubernetes templating engine based on Jinja2
Project description
k8t
Pronounced katie [ˈkeɪti]
Simple cluster and environment specific aware templating for kubernetes manifests.
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Installation
run this
$ pip install --user --upgrade k8t
note: k8t is not Python 2 compatible
Completion
Run the following and store the file in your distribution/OS specific spot
bash:
$ _K8T_COMPLETE=source k8t > k8t-completion.sh
zsh:
$ _K8T_COMPLETE=source_zsh k8t > k8t-completion.sh
Concepts
By combining those concepts you can quickly add completely new environments to your deployment pipeline just by modifying specializing values and sharing the rest.
Check out our examples here.
Clusters and Environments
k8t comes with a builtin framework for clusters and environments (e.g. production, staging). This came from the need to be able to deploy the same application over multiple clusters and in different environments with completely different setups and values. This idea is helped by the fact that k8t deep-merges values and configs, allowing easy variation through different stages of your application deployment.
Both clusters and environments are intentionally working the same way and can be used to add another degree of freedom when combined. Environments however are also available globally, meaning clusters can share environment specific configuration while specifying differences in those environments.
Templating
Templating is supported via Jinja. k8t also comes with some additional helper functions and a validation function with verbose output to quickly verify the written templates.
Template helper functions
random_password(N: int)
- generate a random string of length Nenvvar(key: str, [default])
- get a value from any environment variable with optional defaultb64encode(value: str)
- encodes a value in base64 (usually required for secrets)b64decode(value: str)
- decodes a value from base64hash(value: str, [method: str])
- hashes a given value (default usingsha256
)get_secret(key: str)
- provides a secret value from a given provider (see here)bool(value: Any)
- casts value to boolean ("true", "on", "yes", "1", 1 are considered asTrue
)
Usage
Scaffolding
Create a new project folder with a cluster directory and an empty defaults file
$ k8t new project .
Create a new cluster
$ k8t new cluster MyCluster
Create a new environment
$ k8t new environment staging
Generate a new deployment template for cluster MyCluster (for a list of available templates see the k8t new template --help
)
$ k8t new template deployment -c MyCluster -e staging
Config management
To ease file access a little bit k8t can open config and value files in your $EDITOR
or fallback to a sensible
default.
$ k8t edit values --environment staging
$ k8t edit config --cluster MyCluster
Validate templates
While validation is done before generating, templates can be validated for environment files easily.
$ k8t validate
To validate for clusters/environments the usual options can be used
$ k8t validate -c MyCluster -e production
Generate manifests
The --cluster flag will load variables from a directory. By default the file default.yaml in that directory will be loaded, however an environment can be specified with --environment.
$ k8t gen -c MyCluster -e staging
Additionally k8t will attempt to load a file defaults.yaml in the root directory. This way a set of default variables can be specified and selectively overriden via cluster and environment.
Additional values can be given via flag --value-file in the form of a file or --value KEY VALUE, both can be supplied multiple times.
Variables will be merged via deep merging. Default merge strategy is left-to-right.
Overriding templates
Templates can be overriden on a cluster/environment level.
If a file application.yaml
exists in the root templates folder, simply add a file with the same name to the
cluster/environment template folder.
Managing secrets
Secrets can be interpolated with the helper function get_secret
. It requires a key as first argument and providers
are configurable by environment/cluster.
foobar: "{{ get_secret('/my-key') }}"
Providers
SSM
Setup secrets on SSM
secrets:
provider: ssm
region: "eu-central-1"
prefix: "/foobar"
Keep in mind that SSM parameter names can be formed as a path and they can only consist of sub-paths divided by slash symbol; each sub-path can be formed as a mix of letters, numbers and the following 3 symbols:
.-_
Be careful to follow this format when setting up the provider
prefix
andget_secret(key)
.
Random
Random secrets can be generated easily by using the random provider. This provider uses a global dictionary to store results for the time of the run in python so keys should always produce the same result.
secrets:
provider: random
TODO
- testing needs to be expanded
- the ability to add additional template directories via the CLI
- validation functions for template values (e.g. memory/cpu values)
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