kubragen 0.7.2

A small example package

KubraGen: programmatic Kubernetes YAML generator

Overview

KubraGen is a Kubernetes YAML generator library that makes it possible to generate configurations using the full power of the Python programming language.

Using plugins (called Builders), it is possible to include libraries that know how to configure specific services, like Prometheus, RabbitMQ, Traefik, etc.

The jsonpatchext library (an extension of jsonpatch) is used to make it possible to check and modify the output objects in any way without accessing the returned dicts directly, including merging dicts with the deepmerge library.

See source code for examples

• Website: https://github.com/RangelReale/kubragen
• Repository: https://github.com/RangelReale/kubragen.git
• Documentation: https://kubragen.readthedocs.org/
• PyPI: https://pypi.python.org/pypi/kubragen

Example

kg = KubraGen(provider=Provider(PROVIDER_GOOGLE, PROVIDERSVC_GOOGLE_GKE), options=Options({
    'namespaces': {
        'default': 'app-default',
        'monitoring': 'app-monitoring',
    },
}))

out = OutputProject(kg)

shell_script = OutputFile_ShellScript('create_gke.sh')
out.append(shell_script)

shell_script.append('set -e')

#
# OUTPUTFILE: app-namespace.yaml
#
file = OutputFile_Kubernetes('app-namespace.yaml')

file.append(FilterJSONPatches_Apply([
    Object({
        'apiVersion': 'v1',
        'kind': 'Namespace',
        'metadata': {
            'name': 'app-default',
            'annotations': {
                'will-not-output': ValueData(value='anything', enabled=False),
            }
        },
    }, name='ns-default', source='app'), Object({
        'apiVersion': 'v1',
        'kind': 'Namespace',
        'metadata': {
            'name': 'app-monitoring',
        },
    }, name='ns-monitoring', source='app'),
], jsonpatches=[
    FilterJSONPatch(names=['ns-monitoring'], patches=[
        {'op': 'add', 'path': '/metadata/annotations', 'value': {
                'kubragen.github.io/patches': QuotedStr('true'),
        }},
    ])
]))

shell_script.append(OD_FileTemplate(f'kubectl apply -f ${{FILE_{file.fileid}}}'))

shell_script.append(f'kubectl config set-context --current --namespace=app-default')

#
# OUTPUTFILE: rabbitmq-config.yaml
#
kg_rabbit = RabbitMQBuilder(kubragen=kg, options=RabbitMQOptions({
    'namespace': OptionRoot('namespaces.monitoring'),
    'basename': 'myrabbit',
    'config': {
        'erlang_cookie': KData_Secret(secretName='app-global-secrets', secretData='erlang_cookie'),
        'enable_prometheus': True,
        'prometheus_annotation': True,
        'authorization': {
            'serviceaccount_create': True,
            'roles_create': True,
            'roles_bind': True,
        },
    },
    'kubernetes': {
        'volumes': {
            'data': {
                'persistentVolumeClaim': {
                    'claimName': 'rabbitmq-storage-claim'
                }
            }
        },
        'resources': {
            'statefulset': {
                'requests': {
                    'cpu': '150m',
                    'memory': '300Mi'
                },
                'limits': {
                    'cpu': '300m',
                    'memory': '450Mi'
                },
            },
        },
    }
})).jsonpatches([
    FilterJSONPatch(names=[RabbitMQBuilder.BUILDITEM_SERVICE], patches=[
        {'op': 'check', 'path': '/spec/ports/0/name', 'cmp': 'equals', 'value': 'http'},
        {'op': 'replace', 'path': '/spec/type', 'value': 'LoadBalancer'},
    ]),
])

kg_rabbit.ensure_build_names(kg_rabbit.BUILD_ACCESSCONTROL, kg_rabbit.BUILD_CONFIG,
                              kg_rabbit.BUILD_SERVICE)

#
# OUTPUTFILE: rabbitmq-config.yaml
#
file = OutputFile_Kubernetes('rabbitmq-config.yaml')
out.append(file)

file.append(kg_rabbit.build(kg_rabbit.BUILD_ACCESSCONTROL, kg_rabbit.BUILD_CONFIG))

shell_script.append(OD_FileTemplate(f'kubectl apply -f ${{FILE_{file.fileid}}}'))

#
# OUTPUTFILE: rabbitmq.yaml
#
file = OutputFile_Kubernetes('rabbitmq.yaml')
out.append(file)

file.append(kg_rabbit.build(kg_rabbit.BUILD_SERVICE))

shell_script.append(OD_FileTemplate(f'kubectl apply -f ${{FILE_{file.fileid}}}'))

out.output(OutputDriver_Print())
# out.output(OutputDriver_Directory('/tmp/app-gke'))

Output:

****** BEGIN FILE: 001-app-namespace.yaml ********
apiVersion: v1
kind: Namespace
metadata:
  name: app-default
  annotations: {}
---
apiVersion: v1
kind: Namespace
metadata:
  name: app-monitoring
  annotations:
    kubragen.github.io/patches: 'true'
****** END FILE: 001-app-namespace.yaml ********
****** BEGIN FILE: 002-rabbitmq-config.yaml ********
kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: myrabbit
  namespace: app-monitoring
<...more...>
****** END FILE: 002-rabbitmq-config.yaml ********
****** BEGIN FILE: 003-rabbitmq.yaml ********
apiVersion: v1
kind: Service
metadata:
  name: myrabbit-headless
  namespace: app-monitoring
spec:
<...more...>
****** END FILE: 003-rabbitmq.yaml ********
****** BEGIN FILE: create_gke.sh ********
#!/bin/bash

set -e
kubectl apply -f 001-app-namespace.yaml
kubectl config set-context --current --namespace=app-default
kubectl apply -f 002-rabbitmq-config.yaml
kubectl apply -f 003-rabbitmq.yaml

****** END FILE: create_gke.sh ********

Design Philosophy

• As the generated Kubernetes files can have critical consequences, the library is designed to fail on the minimal possibility of error, and also gives tools to users of the library to check any generated value for critical options, using the jsonpatchext library to check the data output by the builders.

• To minimize the use of dict concatenation, a special type kubragen.data.Data can be used anywhere in the object, and it has a is_enabled() method that removes the value (and its key if it is contained in a dict/list) if it returns False.

• Only YAML is supported by the library, it is not possible to generate JSON directly at the moment.

Author

Rangel Reale ([e-mail])