#!/usr/bin/env python3

"""
container_checker

This script is intended to be run by Monit. It will write an alerting message into
syslog if it found containers which were expected to run but were not running. At
the same time, if some containers were unexpected to run, it also writes an alerting
syslog message. Note that if print(...) statement in this script was executed, the
string in it will be appended to Monit syslog messages.

The following is an example in Monit configuration file to show how Monit will run
this script:

check program container_checker with path "/usr/bin/container_checker"
    if status != 0 for 5 times within 5 cycles then alert repeat every 1 cycles
"""

import subprocess
import sys

import swsssdk
from sonic_py_common import multi_asic


def get_command_result(command):
    """
    @summary: This function will execute the command and return the resulting output.
    @return: A string which contains the output of command.
    """
    command_stdout = ""

    try:
        proc_instance = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                                         shell=True, universal_newlines=True)
        command_stdout, command_stderr = proc_instance.communicate()
        if proc_instance.returncode != 0:
            print("Failed to execute the command '{}'. Return code: '{}'".format(
                command, proc_instance.returncode))
            sys.exit(1)
    except (OSError, ValueError) as err:
        print("Failed to execute the command '{}'. Error: '{}'".format(command, err))
        sys.exit(2)

    return command_stdout.rstrip().split("\n")


def get_expected_running_containers():
    """
    @summary: This function will get the expected running containers by following the rule:
              The 'state' field of container in 'FEATURE' table should not be 'disabled' or 'always_disabled'.
              If the device has Multi-ASIC, this function will get container list by determining the
              value of field 'has_global_scope', the number of ASICs and the value of field
              'has_per_asic_scope'.
              If the device has single ASIC, the container name was put into the list.
    @return:  A set which contains the expected running containers.
    """
    config_db = swsssdk.ConfigDBConnector()
    config_db.connect()
    feature_table = config_db.get_table("FEATURE")

    expected_running_containers = set()

    for container_name in feature_table.keys():
        if feature_table[container_name]["state"] not in ["disabled", "always_disabled"]:
            if multi_asic.is_multi_asic():
                if feature_table[container_name]["has_global_scope"] == "True":
                    expected_running_containers.add(container_name)
                if feature_table[container_name]["has_per_asic_scope"] == "True":
                    num_asics = multi_asic.get_num_asics()
                    for asic_id in range(num_asics):
                        expected_running_containers.add(container_name + str(asic_id))
            else:
                expected_running_containers.add(container_name)

    return expected_running_containers


def get_current_running_containers():
    """
    @summary: This function will get the current running container list by analyzing the
              output of command `docker ps`.
    @return:  A set which contains the current running contianers.
    """
    running_containers = set()

    command = "docker ps"
    command_stdout = get_command_result(command)
    for line in command_stdout[1:]:
        running_containers.add(line.split()[-1].strip())

    return running_containers


def main():
    """
    @summary: This function will compare the difference between the current running containers
              and the containers which were expected to run. If containers which were exepcted
              to run were not running, then an alerting message will be written into syslog.
    """
    expected_running_containers = get_expected_running_containers()
    current_running_containers = get_current_running_containers()

    not_running_containers = expected_running_containers.difference(current_running_containers)
    if not_running_containers:
        print("Expected containers not running: " + ", ".join(not_running_containers))
        sys.exit(3)

    unexpected_running_containers = current_running_containers.difference(expected_running_containers)
    if unexpected_running_containers:
        print("Unexpected running containers: " + ", ".join(unexpected_running_containers))
        sys.exit(4)


if __name__ == "__main__":
    main()