sync-rancher-clusters.py

#!/usr/bin/env python3

import os
import json
from subprocess import check_output, CalledProcessError
from configparser import ConfigParser


def kubectl(command, context=None, output=True):
    context = f'--context={context}' if context else ''
    output = '-o=json' if output else ''

    command = f'kubectl {context} {command} {output}'
    result = check_output(command, shell=True)
    if output:
        result = json.loads(result.decode('utf-8'))

    return result


def main():
    config = ConfigParser()
    config.read(os.path.expanduser('~/.kube/rancher-clusters.ini'))

    existing_contexts = check_output('kubectl config get-contexts -o name', shell=True).decode('utf-8').split('\n')

    for root_cluster in config.sections():
        try:
            rancher_config = kubectl('config view --minify', context=root_cluster)
        except CalledProcessError:
            print(f'Rancher cluster {root_cluster} not found in ~/.kube/config')
            continue

        username = rancher_config['users'][0]['name']
        rancher_url_prefix = '/'.join(rancher_config['clusters'][0]['cluster']['server'].split('/')[:-1])

        clusters = kubectl('get clusters', context=root_cluster)['items']

        rancher_clusters = set()
        for cluster in clusters:
            cluster_name = root_cluster + "-" + cluster['spec']['displayName']
            cluster_id = cluster['metadata']['name']

            rancher_clusters.add(cluster_name)

            # skip root cluster as it is already defined
            if cluster_id == 'local':
                continue

            print(cluster['metadata']['name'], cluster['spec']['displayName'])

            kubectl(f'config set-cluster {cluster_name} --server {rancher_url_prefix}/{cluster_id}', output=False)
            kubectl(f'config set-context {cluster_name} --cluster {cluster_name} --user {username}', output=False)

        for cluster_name in existing_contexts:
            if cluster_name not in rancher_clusters and cluster_name != root_cluster and cluster_name.startswith(root_cluster):
                print(f'Removing missing {cluster_name}')
                check_output(f'kubectl config delete-context {cluster_name}', shell=True)
                check_output(f'kubectl config delete-cluster {cluster_name}', shell=True)


if __name__ == '__main__':
    main()