Python library for working with OpenShift.
This package provides a Python library for working with the open source OpenShift Origin project and downstream OpenShift products from Red Hat.
The library will provide the capability to work with OpenShift/Kubernetes resource objects, as well as endpoints for communicating with the OpenShift REST API.
A command line client with the name powershift is also included which provides additional functionality useful to users of the OpenShift platform. Base functionality is minimal, but can be extended by installing additional plugins.
The package requires Python 3.5 and will not work with earlier versions of Python.
If you are on MacOS X and are using OpenShift Origin 1.4 or later, or OpenShift Container Platform 3.4 or later, you will need to ensure you are using Python 3.6 from the Python Software Foundation (PSF), or use Python 3.5 or later, installed using HomeBrew. It is not possible to use Python 3.5 from the PSF, or any other Python installation, which has been compiled against the OpenSSL version which ships with MacOS X as that only supports up to TLS 1.1 and newer versions of OpenShift require at least TLS 1.2.
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.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(server=None, token=None, *, user=None, verify=None) - Create a client object for server by passing 'hostname', optionally including a port by specifying 'hostname:port', or a URL. When hostname is used, it is presumed that a secure connection should be used. If using oc proxy is being used, you will need to supply a URL and specify the protocol as http rather than https. The API access token can be supplied, as can a flag indicating whether certificate verification should be performed for a secure connection. Certificate verification is performed by default but can be disabled using the keyword argument verify. In order to issue the request and impersonate a specific user you have rights to impersonate, you can pass the keyword argument user.
If the parameters are not being supplied explicitly, they can instead be supplied using environment variables.
- OPENSHIFT_API_SERVER - The hostname, hostname:port or URL.
- 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())
When using the async client, watches are supported by passing the watch parameter to any endpoint which supports it. The result is an async context manager which in turn creates an async iterator which can be iterated over to get notifications.:
import sys import asyncio import powershift.endpoints as endpoints async def run_query(): namespace = sys.argv print('namespace=%r' % namespace) client = endpoints.AsyncClient() pods = await client.api.v1.namespaces(namespace=namespace).pods.get() for pod in pods.items: print(' OBJECT %s pod=%r' % (pod.metadata.resource_version, pod.metadata.name)) resource_version = pods.metadata.resource_version while True: try: async with client.api.v1.namespaces(namespace=namespace).pods.get(watch='', resource_version=resource_version, timeout_seconds=30) as items: async for item in items: action = item['type'] pod = item['object'] print(' %s %s pod=%r' % (action, pod.metadata.resource_version, pod.metadata.name)) resource_version = pod.metadata.resource_version except Exception: pass loop = asyncio.get_event_loop() loop.run_until_complete(run_query())
The calling conventions can be derived from the REST API documentation available at:
Specifically, by matching to the URL path for an endpoint, with the exception that /api/v1/watch and /oapi/v1/watch are not supported and instead you need to pass the watch parameter to the standard endpoint as shown above.
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.