Looking at a client library for the Kubernetes API, I couldn't find an option to retrieve the output returned from a command execution inside the container. If we take the following python code example, can I get the actual output returned from the container start command?
# Copyright 2016 The Kubernetes Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Creates, updates, and deletes a job object.
"""
from os import path
import yaml
from kubernetes import client, config
JOB_NAME = "pi"
def create_job_object():
# Configureate Pod template container
container = client.V1Container(
name="pi",
image="perl",
command=["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"])
# Create and configurate a spec section
template = client.V1PodTemplateSpec(
metadata=client.V1ObjectMeta(labels={"app": "pi"}),
spec=client.V1PodSpec(restart_policy="Never", containers=[container]))
# Create the specification of deployment
spec = client.V1JobSpec(
template=template,
backoff_limit=4)
# Instantiate the job object
job = client.V1Job(
api_version="batch/v1",
kind="Job",
metadata=client.V1ObjectMeta(name=JOB_NAME),
spec=spec)
return job
def create_job(api_instance, job):
api_response = api_instance.create_namespaced_job(
body=job,
namespace="default")
print("Job created. status='%s'" % str(api_response.status))
def update_job(api_instance, job):
# Update container image
job.spec.template.spec.containers[0].image = "perl"
api_response = api_instance.patch_namespaced_job(
name=JOB_NAME,
namespace="default",
body=job)
print("Job updated. status='%s'" % str(api_response.status))
def delete_job(api_instance):
api_response = api_instance.delete_namespaced_job(
name=JOB_NAME,
namespace="default",
body=client.V1DeleteOptions(
propagation_policy='Foreground',
grace_period_seconds=5))
print("Job deleted. status='%s'" % str(api_response.status))
def main():
# Configs can be set in Configuration class directly or using helper
# utility. If no argument provided, the config will be loaded from
# default location.
config.load_kube_config()
batch_v1 = client.BatchV1Api()
# Create a job object with client-python API. The job we
# created is same as the `pi-job.yaml` in the /examples folder.
job = create_job_object()
create_job(batch_v1, job)
update_job(batch_v1, job)
delete_job(batch_v1)
if __name__ == '__main__':
main()
I've only attached an example code from the Python client library but I've got a specific task in which I need the actual output after the job has been completed. I need that output in the API response though, because I will need to access that programatically.
So basically:
Run job in Python
Job finishes
Get output from container inside job (output from starting command)
This code will print the log (stdout output) after the job has completed:
from kubernetes import client, config
JOB_NAMESPACE = "default"
JOB_NAME = "pi"
def main():
config.load_kube_config()
batch_v1 = client.BatchV1Api()
job_def = batch_v1.read_namespaced_job(name=JOB_NAME, namespace=JOB_NAMESPACE)
controllerUid = job_def.metadata.labels["controller-uid"]
core_v1 = client.CoreV1Api()
pod_label_selector = "controller-uid=" + controllerUid
pods_list = core_v1.list_namespaced_pod(namespace=JOB_NAMESPACE, label_selector=pod_label_selector, timeout_seconds=10)
# Notice that:
# - there are more parameters to limit size, lines, and more - see
# https://github.com/kubernetes-client/python/blob/master/kubernetes/docs/CoreV1Api.md#read_namespaced_pod_log
# - the logs of the 1st pod are returned (similar to `kubectl logs job/<job-name>`)
# - assumes 1 container in the pod
pod_name = pods_list.items[0].metadata.name
try:
# For whatever reason the response returns only the first few characters unless
# the call is for `_return_http_data_only=True, _preload_content=False`
pod_log_response = core_v1.read_namespaced_pod_log(name=pod_name, namespace=JOB_NAMESPACE, _return_http_data_only=True, _preload_content=False)
pod_log = pod_log_response.data.decode("utf-8")
print(pod_log)
except client.rest.ApiException as e:
print("Exception when calling CoreV1Api->read_namespaced_pod_log: %s\n" % e)
if __name__ == '__main__':
main()