execute commands within Kubernetes pod in python

Question

I am trying to run a series of commands to create and add the same type of user to multiple mongodbs. Currently I make a connection to the pod I want: connect = os.system("kubectl exec -n epic-dev zerodtmongo-0 -it -- /bin/sh"

but my python script ends there and the new shell for that pod opens within the python terminal.

I would like to continue the python script to execute this block of code within multiple pods I have stored in a list.

    # Create roles to create roles 'listDatabase' & 'readChangeStream'
mongo -u admin -p admin localhost:27017/admin <<-EOF
  db.runCommand(
  {
    createRole: "listDatabases", 
    privileges: [
      { 
        resource: {cluster : true}, 
        actions: ["listDatabases"]
      }
    ],
    roles: []
  }
);

  db.runCommand(
  {
    createRole: "readChangeStream",
    privileges: [
      { 
        resource: { db: "", collection: ""}, 
        actions: [ "find", "changeStream" ] 
      }
    ],
    roles: []
   });
EOF


# Create a debezium user
mongo -u admin -p admin localhost:27017/admin <<-EOF
  db.createUser(
  {
    user: 'foo',
    pwd: 'bar',
    roles: [
      { role: "read", db: "admin" }
    ]
  });
EOF

Something like:

for pods in list:
    connect(pod)
    add user
    close connection

Adiii · Accepted Answer · 2022-08-02 16:49:48Z

4

you should use the python Kubernetes client to leverage the maximum benefit.

kubernetes-client-python

Here is the working example that expects the Kube config already set up.

helm install my-release bitnami/mongodb


from click import command
from kubernetes import client, config
from kubernetes.stream import stream

def pod_exec(name, namespace, command, api_instance):
    exec_command = ["/bin/sh", "-c", command]

    resp = stream(api_instance.connect_get_namespaced_pod_exec,
                  name,
                  namespace,
                  command=exec_command,
                  stderr=True, stdin=False,
                  stdout=True, tty=False,
                  _preload_content=False)

    while resp.is_open():
        resp.update(timeout=1)
        if resp.peek_stdout():
            print(f"STDOUT: \n{resp.read_stdout()}")
        if resp.peek_stderr():
            print(f"STDERR: \n{resp.read_stderr()}")

    resp.close()

    if resp.returncode != 0:
        raise Exception("Script failed")

command = """mongo -u root -p $MONGODB_ROOT_PASSWORD localhost:27017/admin <<-EOF
  db.runCommand(
  {
    createRole: "listDatabases", 
    privileges: [
      { 
        resource: {cluster : true}, 
        actions: ["listDatabases"]
      }
    ],
    roles: []
  }
);

  db.runCommand(
  {
    createRole: "readChangeStream",
    privileges: [
      { 
        resource: { db: "", collection: ""}, 
        actions: [ "find", "changeStream" ] 
      }
    ],
    roles: []
   });
EOF"""
print (command)
pod = "my-release-mongodb-7bcd6b847-qzjxz"
config.load_kube_config()

v1 = client.CoreV1Api()

pod_exec(pod, "mongodb", command, v1)

python3 k8_create_db.py

answered Aug 2, 2022 at 16:49

Adiii

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7 Comments

ctheising98 Over a year ago

what is helm install my-release bitnami/mongodb used for?

Adiii Over a year ago

For mongodb, you don't need this as your already have one

Adiii Over a year ago

Specify the pod name and name space in the execs command

ctheising98 Over a year ago

I am running into a 403 error kubernetes.client.exceptions.ApiException: (0) Reason: Handshake status 403 Forbidden. This has to do with connect_get_namespaced_pod_exec no?

Adiii Over a year ago

As i mentioned it expect you already configure the kubeconfig file

|

Harsh Manvar · Accepted Answer · 2022-08-02 16:51:36Z

Using official K8s client,

Ref : https://github.com/kubernetes-client/python/blob/master/examples/pod_exec.py

import time

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 stream


def exec_commands(api_instance):
    name = 'busybox-test'
    resp = None
    try:
        resp = api_instance.read_namespaced_pod(name=name,
                                                namespace='default')
    except ApiException as e:
        if e.status != 404:
            print("Unknown error: %s" % e)
            exit(1)

    exec_command = ['/bin/sh']
    resp = stream(api_instance.connect_get_namespaced_pod_exec,
                  name,
                  'default',
                  command=exec_command,
                  stderr=True, stdin=True,
                  stdout=True, tty=False,
                  _preload_content=False)
    commands = [
        "echo This message goes to stdout",
        "echo \"This message goes to stderr\" >&2",
    ]

    while resp.is_open():
        resp.update(timeout=1)
        if resp.peek_stdout():
            print("STDOUT: %s" % resp.read_stdout())
        if resp.peek_stderr():
            print("STDERR: %s" % resp.read_stderr())
        if commands:
            c = commands.pop(0)
            print("Running command... %s\n" % c)
            resp.write_stdin(c + "\n")
        else:
            break

    resp.write_stdin("date\n")
    sdate = resp.readline_stdout(timeout=3)
    print("Server date command returns: %s" % sdate)
    resp.write_stdin("whoami\n")
    user = resp.readline_stdout(timeout=3)
    print("Server user is: %s" % user)
    resp.close()


def main():
    config.load_kube_config()
    try:
        c = Configuration().get_default_copy()
    except AttributeError:
        c = Configuration()
        c.assert_hostname = False
    Configuration.set_default(c)
    core_v1 = core_v1_api.CoreV1Api()

    exec_commands(core_v1)


if __name__ == '__main__':
    main()

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