|
| 1 | +#!/usr/local/bin/python3 |
| 2 | + |
| 3 | +from crontab import CronTab |
| 4 | +import argparse |
| 5 | +import logging |
| 6 | +import time |
| 7 | +import subprocess |
| 8 | +import sys |
| 9 | +import signal |
| 10 | +import os |
| 11 | + |
| 12 | + |
| 13 | +def _parse_crontab(crontab_file: str) -> list: |
| 14 | + """The method includes a functionality to parse the crontab file, and it returns a list of CronTab jobs |
| 15 | +
|
| 16 | + Keyword arguments: |
| 17 | + crontab_file -> Specify the inserted crontab file |
| 18 | + """ |
| 19 | + |
| 20 | + logger = logging.getLogger("parser") |
| 21 | + |
| 22 | + logger.info(f"Reading crontab from {crontab_file}") |
| 23 | + |
| 24 | + if not os.path.isfile(crontab_file): |
| 25 | + logger.error(f"Crontab {crontab_file} does not exist. Exiting!") |
| 26 | + sys.exit(1) |
| 27 | + |
| 28 | + with open(crontab_file, "r") as crontab: |
| 29 | + lines: list = crontab.readlines() |
| 30 | + |
| 31 | + logger.info(f"{len(lines)} lines read from crontab {crontab_file}") |
| 32 | + |
| 33 | + jobs: list = list() |
| 34 | + |
| 35 | + for i, line in enumerate(lines): |
| 36 | + line: str = line.strip() |
| 37 | + |
| 38 | + if not line: |
| 39 | + continue |
| 40 | + |
| 41 | + if line.startswith("#"): |
| 42 | + continue |
| 43 | + |
| 44 | + logger.info(f"Parsing line {line}") |
| 45 | + |
| 46 | + expression: list = line.split(" ", 5) |
| 47 | + cron_expression: str = " ".join(expression[0:5]) |
| 48 | + |
| 49 | + logger.info(f"Cron expression is {cron_expression}") |
| 50 | + |
| 51 | + try: |
| 52 | + cron_entry = CronTab(cron_expression) |
| 53 | + except ValueError as e: |
| 54 | + logger.critical( |
| 55 | + f"Unable to parse crontab. Line {i + 1}: Illegal cron expression {cron_expression}. Error message: {e}" |
| 56 | + ) |
| 57 | + sys.exit(1) |
| 58 | + |
| 59 | + command: str = expression[5] |
| 60 | + |
| 61 | + logger.info(f"Command is {command}") |
| 62 | + |
| 63 | + jobs.append([cron_entry, command]) |
| 64 | + |
| 65 | + if len(jobs) == 0: |
| 66 | + logger.error( |
| 67 | + "Specified crontab does not contain any scheduled execution. Exiting!" |
| 68 | + ) |
| 69 | + sys.exit(1) |
| 70 | + |
| 71 | + return jobs |
| 72 | + |
| 73 | + |
| 74 | +def _get_next_executions(jobs: list): |
| 75 | + """The method includes a functionality to extract the execution time and job itself from the submitted job list |
| 76 | +
|
| 77 | + Keyword arguments: |
| 78 | + jobs -> Specify the inserted list of jobs |
| 79 | + """ |
| 80 | + |
| 81 | + logger = logging.getLogger("next-exec") |
| 82 | + |
| 83 | + scheduled_executions: tuple = tuple( |
| 84 | + (x[1], int(x[0].next(default_utc=True)) + 1) for x in jobs |
| 85 | + ) |
| 86 | + |
| 87 | + logger.debug(f"Next executions of scheduled are {scheduled_executions}") |
| 88 | + |
| 89 | + next_exec_time: int = int(min(scheduled_executions, key=lambda x: x[1])[1]) |
| 90 | + |
| 91 | + logger.debug(f"Next execution is in {next_exec_time} second(s)") |
| 92 | + |
| 93 | + next_commands: list = [x[0] for x in scheduled_executions if x[1] == next_exec_time] |
| 94 | + |
| 95 | + logger.debug( |
| 96 | + f"Next commands to be executed in {next_exec_time} are {next_commands}" |
| 97 | + ) |
| 98 | + |
| 99 | + return next_exec_time, next_commands |
| 100 | + |
| 101 | + |
| 102 | +def _loop(jobs: list, test_mode: bool = False): |
| 103 | + """The method includes a functionality to loop over all jobs inside the crontab file and execute them |
| 104 | +
|
| 105 | + Keyword arguments: |
| 106 | + jobs -> Specify the inserted jobs as list |
| 107 | + test_mode -> Specify if you want to use the test mode or not (default False) |
| 108 | + """ |
| 109 | + |
| 110 | + logger = logging.getLogger("loop") |
| 111 | + |
| 112 | + logger.info("Entering main loop") |
| 113 | + |
| 114 | + if test_mode is False: |
| 115 | + while True: |
| 116 | + sleep_time, commands = _get_next_executions(jobs) |
| 117 | + |
| 118 | + logger.debug(f"Sleeping for {sleep_time} second(s)") |
| 119 | + |
| 120 | + if sleep_time <= 1: |
| 121 | + logger.debug("Sleep time <= 1 second, ignoring.") |
| 122 | + time.sleep(1) |
| 123 | + continue |
| 124 | + |
| 125 | + time.sleep(sleep_time) |
| 126 | + |
| 127 | + for command in commands: |
| 128 | + _execute_command(command) |
| 129 | + else: |
| 130 | + sleep_time, commands = _get_next_executions(jobs) |
| 131 | + |
| 132 | + logger.debug(f"Sleeping for {sleep_time} second(s)") |
| 133 | + |
| 134 | + if sleep_time <= 1: |
| 135 | + logger.debug("Sleep time <= 1 second, ignoring.") |
| 136 | + time.sleep(1) |
| 137 | + |
| 138 | + time.sleep(sleep_time) |
| 139 | + |
| 140 | + for command in commands: |
| 141 | + _execute_command(command) |
| 142 | + |
| 143 | + |
| 144 | +def _execute_command(command: str): |
| 145 | + """The method includes a functionality to execute a crontab command |
| 146 | +
|
| 147 | + Keyword arguments: |
| 148 | + command -> Specify the inserted command for the execution |
| 149 | + """ |
| 150 | + |
| 151 | + logger = logging.getLogger("exec") |
| 152 | + |
| 153 | + logger.info(f"Executing command {command}") |
| 154 | + |
| 155 | + result = subprocess.run( |
| 156 | + command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True |
| 157 | + ) |
| 158 | + |
| 159 | + logger.info(f"Standard output: {result.stdout}") |
| 160 | + logger.info(f"Standard error: {result.stderr}") |
| 161 | + |
| 162 | + |
| 163 | +def _signal_handler(): |
| 164 | + """The method includes a functionality for the signal handler to exit a process""" |
| 165 | + |
| 166 | + logger = logging.getLogger("signal") |
| 167 | + logger.info("Exiting") |
| 168 | + sys.exit(0) |
| 169 | + |
| 170 | + |
| 171 | +def main(): |
| 172 | + """The method includes a functionality to control and execute crontab entries |
| 173 | +
|
| 174 | + Arguments: |
| 175 | + -c -> Specify the inserted crontab file |
| 176 | + -L -> Specify the inserted log file |
| 177 | + -C -> Specify the if the output should be forwarded to the console |
| 178 | + -l -> Specify the log level |
| 179 | + """ |
| 180 | + signal.signal(signal.SIGINT, _signal_handler) |
| 181 | + signal.signal(signal.SIGTERM, _signal_handler) |
| 182 | + |
| 183 | + parser = argparse.ArgumentParser(description="cron") |
| 184 | + parser.add_argument("-c", "--crontab", required=True, type=str) |
| 185 | + logging_target = parser.add_mutually_exclusive_group(required=True) |
| 186 | + logging_target.add_argument("-L", "--logfile", type=str) |
| 187 | + logging_target.add_argument("-C", "--console", action="store_true") |
| 188 | + parser.add_argument( |
| 189 | + "-l", |
| 190 | + "--loglevel", |
| 191 | + choices=["DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"], |
| 192 | + default="INFO", |
| 193 | + type=str, |
| 194 | + ) |
| 195 | + |
| 196 | + args = parser.parse_args() |
| 197 | + |
| 198 | + log_level = getattr(logging, args.loglevel.upper(), logging.INFO) |
| 199 | + |
| 200 | + if args.console: |
| 201 | + logging.basicConfig( |
| 202 | + filemode="w", |
| 203 | + level=log_level, |
| 204 | + format="%(asctime)s %(name)-12s %(levelname)-8s %(message)s", |
| 205 | + ) |
| 206 | + else: |
| 207 | + logging.basicConfig( |
| 208 | + filename=args.logfile, |
| 209 | + filemode="a+", |
| 210 | + level=log_level, |
| 211 | + format="%(asctime)s %(name)-12s %(levelname)-8s %(message)s", |
| 212 | + ) |
| 213 | + |
| 214 | + logger = logging.getLogger("main") |
| 215 | + |
| 216 | + logger.info("Starting cron") |
| 217 | + |
| 218 | + jobs: list = _parse_crontab(args.crontab) |
| 219 | + |
| 220 | + _loop(jobs) |
| 221 | + |
| 222 | + |
| 223 | +if __name__ == "__main__": |
| 224 | + main() |
0 commit comments