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# Copyright 2020 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.
"""
Shows the functionality of portforward streaming using an nginx container.
"""
import select
import socket
import time
import six.moves.urllib.request as urllib_request
from kubernetes import config
from kubernetes.client import Configuration
from kubernetes.client.api import core_v1_api
from kubernetes.client.rest import ApiException
from kubernetes.stream import portforward
##############################################################################
# Kubernetes pod port forwarding works by directly providing a socket which
# the python application uses to send and receive data on. This is in contrast
# to the go client, which opens a local port that the go application then has
# to open to get a socket to transmit data.
#
# This simplifies the python application, there is not a local port to worry
# about if that port number is available. Nor does the python application have
# to then deal with opening this local port. The socket used to transmit data
# is immediately provided to the python application.
#
# Below also is an example of monkey patching the socket.create_connection
# function so that DNS names of the following formats will access kubernetes
# ports:
#
# <pod-name>.<namespace>.kubernetes
# <pod-name>.pod.<namespace>.kubernetes
# <service-name>.svc.<namespace>.kubernetes
# <service-name>.service.<namespace>.kubernetes
#
# These DNS name can be used to interact with pod ports using python libraries,
# such as urllib.request and http.client. For example:
#
# response = urllib.request.urlopen(
# 'https://metrics-server.service.kube-system.kubernetes/'
# )
#
##############################################################################
def portforward_commands(api_instance):
name = 'portforward-example'
resp = None
try:
resp = api_instance.read_namespaced_pod(name=name,
namespace='default')
except ApiException as e:
if e.status != 404:
print(f"Unknown error: {e}")
exit(1)
if not resp:
print(f"Pod {name} does not exist. Creating it...")
pod_manifest = {
'apiVersion': 'v1',
'kind': 'Pod',
'metadata': {
'name': name
},
'spec': {
'containers': [{
'image': 'nginx',
'name': 'nginx',
}]
}
}
api_instance.create_namespaced_pod(body=pod_manifest,
namespace='default')
while True:
resp = api_instance.read_namespaced_pod(name=name,
namespace='default')
if resp.status.phase != 'Pending':
break
time.sleep(1)
print("Done.")
pf = portforward(
api_instance.connect_get_namespaced_pod_portforward,
name, 'default',
ports='80',
)
http = pf.socket(80)
http.setblocking(True)
http.sendall(b'GET / HTTP/1.1\r\n')
http.sendall(b'Host: 127.0.0.1\r\n')
http.sendall(b'Connection: close\r\n')
http.sendall(b'Accept: */*\r\n')
http.sendall(b'\r\n')
response = b''
while True:
select.select([http], [], [])
data = http.recv(1024)
if not data:
break
response += data
http.close()
print(response.decode('utf-8'))
error = pf.error(80)
if error is None:
print("No port forward errors on port 80.")
else:
print(f"Port 80 has the following error: {error}")
# Monkey patch socket.create_connection which is used by http.client and
# urllib.request. The same can be done with urllib3.util.connection.create_connection
# if the "requests" package is used.
socket_create_connection = socket.create_connection
def kubernetes_create_connection(address, *args, **kwargs):
dns_name = address[0]
if isinstance(dns_name, bytes):
dns_name = dns_name.decode()
dns_name = dns_name.split(".")
if dns_name[-1] != 'kubernetes':
return socket_create_connection(address, *args, **kwargs)
if len(dns_name) not in (3, 4):
raise RuntimeError("Unexpected kubernetes DNS name.")
namespace = dns_name[-2]
name = dns_name[0]
port = address[1]
if len(dns_name) == 4:
if dns_name[1] in ('svc', 'service'):
service = api_instance.read_namespaced_service(name, namespace)
for service_port in service.spec.ports:
if service_port.port == port:
port = service_port.target_port
break
else:
raise RuntimeError(
f"Unable to find service port: {port}")
label_selector = []
for key, value in service.spec.selector.items():
label_selector.append(f"{key}={value}")
pods = api_instance.list_namespaced_pod(
namespace, label_selector=",".join(label_selector)
)
if not pods.items:
raise RuntimeError("Unable to find service pods.")
name = pods.items[0].metadata.name
if isinstance(port, str):
for container in pods.items[0].spec.containers:
for container_port in container.ports:
if container_port.name == port:
port = container_port.container_port
break
else:
continue
break
else:
raise RuntimeError(
f"Unable to find service port name: {port}")
elif dns_name[1] != 'pod':
raise RuntimeError(
f"Unsupported resource type: {dns_name[1]}")
pf = portforward(api_instance.connect_get_namespaced_pod_portforward,
name, namespace, ports=str(port))
return pf.socket(port)
socket.create_connection = kubernetes_create_connection
# Access the nginx http server using the
# "<pod-name>.pod.<namespace>.kubernetes" dns name.
response = urllib_request.urlopen(
f'http://{name}.pod.default.kubernetes')
html = response.read().decode('utf-8')
response.close()
print(f'Status Code: {response.code}')
print(html)
def main():
config.load_kube_config()
c = Configuration.get_default_copy()
c.assert_hostname = False
Configuration.set_default(c)
core_v1 = core_v1_api.CoreV1Api()
portforward_commands(core_v1)
if __name__ == '__main__':
main()
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