[Linux] [AWS Lambda] Cron format setting manual

background

Regarding the Cron format that enables scheduled execution when performing things such as website crawling and server life and death monitoring database backup on a regular basis, setting methods and setting examples on Linux and setting methods on AWS Lambda Here is a summary of setting examples.

I would like to take this opportunity to thank you for solving the problem by borrowing the wisdom of our predecessors, and I am very sorry to say that I will summarize it here as my own memo.

environment

• AWS EC2 (Amazon Linux 2)
• AWS Lambda --Python 3.7.9 * Default on Amazon Linux 2 as of 12/10/2020
• Django 3.1.3 --PostgreSQL 11.5 * Same as above --Nginx 1.12 * Same as above
• Gunicorn
• PuTTY 0.74

1. Setting method / setting example in Linux

1-1. Format

<Minutes> <Time> <Day> <Moon> <曜Day> <command>

1-2. Parameters

--All parameters are required. --The time zone is UTC (Coordinated Universal Time) only and cannot be changed. <font color = # 0000FF> ** To specify as JST (Japan Standard Time), it is necessary to set "-9 hours" to UTC (minus 9 hours). ** --Specifying less than minutes (in seconds) is not supported.

1-3. Wildcard

--Specifying less than minutes (in seconds) is not supported. --When you actually specify it, you do not need to write "" in the wildcard.

1-4. Setting example

crontab

#8 am daily(UTC)To'backup.py'To run
 0 8 * * * source ~/venv_<Project name>/bin/activate; cd ~/venv_<Project name>/<Project name>; python manage.py backup > ~/cron.log 2>&1

#11:45 pm daily(UTC)Reload Nginx to
 45 23 * * * sudo systemctl reload nginx.service

#17:30 on the first day of every month(UTC)Let's Renew Encrypt SSL certificate
 30 17 1 * * /home/<Superuser>/certbot/certbot-auto renew -q --renew-hook "/usr/bin/sysytemctl reload nginx.service"
#Or
 30 17 1 * * /home/<Superuser>/certbot/certbot-auto renew -q --renew-hook "/usr/bin/sysytemctl reload nginx.service"

#Monday-Friday(UTC)Pings a static IP every 5 minutes
 0/5 * * MON-FRI * ping ＜Elastic IP＞
#Or
 0/5 * * 2-6 * ping ＜Elastic IP＞

2. Setting method / setting example in AWS Lambda

2-1. Format

cron <Minutes> <Time> <Day> <Moon> <曜Day> <Year>

2-2. Parameters

--All parameters are required. --The time zone is UTC (Coordinated Universal Time) only and cannot be changed. <font color = # 0000FF> ** To specify as JST (Japan Standard Time), it is necessary to set "-9 hours" to UTC (minus 9 hours). ** --Specifying less than minutes (in seconds) is not supported. --When you actually specify it, you do not need to write "" in the wildcard.

2-3. Wildcard

--Specifying less than minutes (in seconds) is not supported. --When you actually specify it, you do not need to write "" in the wildcard. --The value for either day or week must be a "?" (Question mark).

2-4. Setting example

#8 am daily(UTC)To run
cron(0 8 * * ? *)

#12:45 pm daily(UTC)To run
cron(45 12 * * ? *)

#Monday-Friday 5:30 pm(UTC)To run
cron(30 17 ? * MON-FRI *)
#Or
cron(30 17 ? * 2-6 *)

#Monday-Friday(UTC)Runs every 5 minutes
cron(0/5 * ? * MON-FRI *)
#Or
cron(0/5 * ? * 2-6 *)

(reference)

AWS official website (Lambda): Scheduled expression using Rate or Cron (https://docs.aws.amazon.com/ja_jp/lambda/latest/dg/services-cloudwatchevents-expressions.html) Rule schedule formula (English)

(Editor's note)

It's easy to forget the time difference between JST and UTC (▲ 9 hours). Even though I want to move it at night at the end of the month, it moves in the daytime at the beginning of the month and an alert is raised! I decided to always look at this manual when setting so that there is no such thing.