tail.py

#
# Script to print logs from container in PODs.
#
# Usage:
#       python tail.py <namespace> <prefix for pods' name> [-n LINES] [-f]
#
# Example:
#       python tail.py kube-system kube-dns -f
#
#       It will be streaming logs from all containers from PODs which name ~ "^kube-dns.*"
#

import argparse
import asyncio

from kubernetes_asyncio import client, config
from kubernetes_asyncio.client.api_client import ApiClient, Configuration


def parse_args():
    parser = argparse.ArgumentParser(description="Tail for pods")
    parser.add_argument("namespace", help="k8s namespace")
    parser.add_argument("pod", help="pod name or prefix")
    parser.add_argument(
        "-f",
        "--follow",
        action="store_true",
        help="output appended data as the file grows",
    )
    parser.add_argument("-n", "--lines", default=10, help="show the last LINES lines")
    return parser.parse_args()


async def print_pod_log(v1_api, pod, namespace, container, lines, follow):
    if not follow:
        resp = await v1_api.read_namespaced_pod_log(
            pod, namespace, container=container, tail_lines=lines
        )
        print(resp)
    else:
        resp = await v1_api.read_namespaced_pod_log(
            pod,
            namespace,
            container=container,
            tail_lines=lines,
            follow=True,
            _preload_content=False,
        )
        while True:
            line = await resp.content.readline()
            if not line:
                break
            print(line.decode("utf-8"), end="")


async def main():
    args = parse_args()

    client_configuration = Configuration()
    loader = await config.load_kube_config(client_configuration=client_configuration)
    api = ApiClient(configuration=client_configuration)
    v1_api = client.CoreV1Api(api)
    ret = await v1_api.list_namespaced_pod(args.namespace)
    cmd = []
    for pod in ret.items:
        if pod.metadata.name.startswith(args.pod):
            for container in pod.spec.containers:
                cmd.append(
                    print_pod_log(
                        v1_api,
                        pod.metadata.name,
                        args.namespace,
                        container.name,
                        args.lines,
                        args.follow,
                    )
                )

    if cmd == []:
        print("No matching PODs !")
        await api.close()
        return

    if args.follow:
        # autorefresh gcp token
        cmd.append(
            config.refresh_token(
                loader=loader, client_configuration=client_configuration
            )
        )

    await asyncio.wait(cmd)
    await api.close()


if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())
    loop.close()