#!/usr/bin/python3

import argparse
import sys
import syslog

import psutil
import swsssdk


def check_process_existence(container_name, process_cmdline):
    """
    @summary: Check whether the process in the specified container is running or not and
              an alerting message will written into syslog if it failed to run.
    """
    config_db = swsssdk.ConfigDBConnector()
    config_db.connect()
    feature_table = config_db.get_table("FEATURE")

    if container_name in feature_table:
        # We look into the 'FEATURE' table to verify whether the container is disabled or not.
        # If the container is diabled, we exit.
        if ("state" in feature_table[container_name]
                and feature_table[container_name]["state"] == "disabled"):
            sys.exit(0)
        else:
            # We leveraged the psutil library to help us check whether the process is running or not.
            # If the process entity is found in process tree and it is also in the 'running' or 'sleeping'
            # state, then it will be marked as 'running'.
            is_running = False
            for process in psutil.process_iter(["cmdline", "status"]):
                try:
                    if ((' '.join(process.cmdline())).startswith(process_cmdline) and process.status() in ["running", "sleeping"]):
                        is_running = True
                        break
                except psutil.NoSuchProcess:
                    pass

            if not is_running:
                # If this script is run by Monit, then the following output will be appended to
                # Monit's syslog message.
                print("'{}' is not running.".format(process_cmdline))
                sys.exit(1)
    else:
        syslog.syslog(syslog.LOG_ERR, "container '{}' is not included in SONiC image or the given container name is invalid!"
                      .format(container_name))


def main():
    parser = argparse.ArgumentParser(description="Check whether the process in the specified \
             container is running and an alerting message will be written into syslog if it \
             failed to run.", usage="/usr/bin/process_checker <container_name> <process_cmdline>")
    parser.add_argument("container_name", help="container name")
    parser.add_argument("process_cmdline", nargs=argparse.REMAINDER, help="process command line")
    args = parser.parse_args()

    check_process_existence(args.container_name, ' '.join(args.process_cmdline))


if __name__ == '__main__':
    main()