powershift 1.3.3

Manipulating resource objects

The library always starts and ends with JSON definitions of the OpenShift/Kubernetes resource objects. The functions for loading the JSON definitions to create in memory representations of the resources are:

• powershift.resources.load(path=None) - Loads resources from JSON from a file with the specified path, or from standard input if no path specified.

• powershift.resources.loads(data) - Loads resources from JSON specified as string data.

The functions for dumping JSON definitions from the in memory representations of the resources are:

• powershift.resources.dump(obj, path=None, indent=None, sort_keys=False) - Saves resources as JSON to the specified path, or to stdout if no path supplied. The JSON can be formatted in a more readable form by supplying an indent and electing to sort_keys.

• powershift.resources.dumps(obj, indent=None, sort_keys=False) - Returns resources as JSON string data. The JSON can be formatted in a more readable form by supplying an indent and electing to sort_keys.

Example code which takes a DeploymentConfig from stdin, updating the replica count and outputting the result to stdout is:

import powershift.resources as resources

dc = resources.load()

dc.spec.replicas = 3

resources.dump(dc, indent=4, sort_keys=True)

Example code which takes a DeploymentConfig from stdin, adding some environment variables and outputting the result to stdout is:

import powershift.resources as resources

dc = resources.load()

env = dc.spec.template.spec.containers[0].env

env.append(resources.v1_EnvVar(name='VAR1', value='VALUE'))
env.append(resources.v1_EnvVar(name='VAR2', value='VALUE'))

resources.dump(dc, indent=4, sort_keys=True)

Scripts using the library could be used to make multiple changes to resource objects for a deployed application on the fly by using a command of the form:

oc get dc myapp -o json | python script.py | oc replace -f -

Note that all attribute and parameter names use snake case and not camel case.

Calling the OpenShift REST API

Requests can be made against the OpenShift REST API by first creating a client object:

• powershift.endpoints.Client(host=None, token=None, verify=None) - Create a client object for host by passing 'hostname', optionally including a port by specifying 'hostname:port'. The API access token can be supplied, as can a flag indicating whether certificate verification should be performed for the secure connection. Certificate verification is performed by default.

If the parameters are not being supplied explicitly, they can instead ben supplied using environment variables.

• OPENSHIFT_API_HOST - The hostname or hostname:port.

• OPENSHIFT_API_TOKEN - The API access token.

• OPENSHIFT_API_VERIFY - Flag indicating whether certificate verification should be performed. Set to false to disable.

If neither the parameters or environment variables are supplied, it will be assumed it is being run from inside of a container running under OpenShift. The host will default to openshift.default.svc.cluster.local and the token will be read from the file /var/run/secrets/kubernetes.io/serviceaccount/token if it exists. Certificate verification will be turned off by default in this case.

An example script which prints out the list of pods running in each project is:

import powershift.endpoints as endpoints

client = endpoints.Client()

projects = client.oapi.v1.projects.get()

for project in projects.items:
    namespace = project.metadata.name

    print('namespace=%r' % namespace)

    pods = client.api.v1.namespaces(namespace=namespace).pods.get()

    for pod in pods.items:
        print('pod=%r' % pod.metadata.name)

The client calls in this example are blocking. If you want to use the client in this manner in an asynchronous system, you will need to execute the calls in a thread and not within a main event loop callback.

The alternative if implementing any asynchronous system on top of the asyncio library and Python async/await primitives, is to use the async variant of the client:

import asyncio

import powershift.endpoints as endpoints

client = endpoints.AsyncClient()

async def run_query():
    projects = await client.oapi.v1.projects.get()

    for project in projects.items:
        namespace = project.metadata.name

        print('namespace=%r' % namespace)

        pods = await client.api.v1.namespaces(namespace=namespace).pods.get()

        for pod in pods.items:
            print('    pod=%r' % pod.metadata.name)

loop = asyncio.get_event_loop()

loop.run_until_complete(run_query())

The calling conventions can be derived from the REST API documentation available at:

• Kubernetes v1 REST API

• OpenShift Enterprise v1 REST API

Specifically, by matching to the URL path for an endpoint.

Note that all attribute and parameter names use snake case and not camel case.

The object returned is the in memory representation of resources. These are created automatically from the JSON definitions of the OpenShift/Kubernetes resource objects.

Do note though that the Kubernetes/OpenShift API definitions are inconsistent at some points and have errors. The client library overrides certain aspects of the API definition to fix up problems in the published API. For example, when referring to a namespace, you must always use namespace. The published API mixes name and namespace which can cause problems for an automatically generated API such that this package implements.