Server online-status check with reporting to telegram

in a docker container - working automated via a cronjob

This simple script uses cURL to check if a web application is running on a server. If the service is not running, it utilizes the telegram bot API for sending a message to inform the operator of the server.

before you start

• have docker installed (works on wsl2 / docker for desktop on windows as well)
• checkout this repo
• read the readme and edit the serverUp.sh accordingly

how to setup and test the telegram part

1. Register the bot

Go to the BotFather bot-account and create a bot by writing /newbot. Then, copy the token.

2. Find your chat-id

Send a message to you newly created bot (you can find the link to your bot in the success message sent by BotFather).

Visit https://api.telegram.org/bot{token}/getUpdates to get your chat id: result => 0 => message => chat => id
Please note that the token must be directly behind bot in the URL. If your token starts with AAAA the URL looks like /botAAAA and so on.

3. Configure the script

Fill in the four variables server, port (SSL is on 443 by default), botToken and chatId. . Wheras the serverList is comma seperated list.

4. Make the script executable

Execute chmod +x serverUp.sh to make the script executable.

5. Test the script

To test the script, enter an unused port and execute it via ./serverUp.sh. Don't forget to change the port number after testing.

6. cron in a docker container with docker-cron

A simple docker container that runs a cron invoking a shell script.

how to build docker container and run it

Copy the repository and build from the Dockerimage:

On Linux run: $ sudo docker build --rm -t docker-cron .

Run the docker container in the background (docker returns the id of the container):

$ sudo docker run --restart=always -t -i -d docker-cron
b149b5e7306dba492558c7024809f13cfbb616cccd0f4020db61bf715f4db836

To check if it is running properly, connect to the container using the id and view the logfile. (You may have to wait a few minutes)

$ sudo docker exec -i -t b149b5e7306dba492558c7024809f13cfbb616cccd0f4020db61bf715f4db836 /bin/bash
root@b149b5e7306d:/# cat /var/log/serverUp.log
INFO: google.com:443 up! Mon, 15. November 2021, 10:20:01
INFO: yahoo.com:443 up! Mon, 15. November 2021, 10:20:01
INFO: Mon, 15. November 2021, 10:20:01: executed script

The cron job is running. Now let's modify the interval and the actual job executed!

##Crontab for termux on Android:

pkg install cronie termux-services

restart termux

sv-enable crond
crontab -e

it will open default text editor , write your job in it and save it,

For example :

`*/5 * * * * /path/to/your/script/script.sh`

Every time you start/restart Termux, you need to start the cron service by running the command:

 sv up crond

Check for running crond pidof crond

how to modify

To change the interval the cron job is runned, just simply edit the crontab file. In default, the job is runned every 5 minutes. You don't need a user because it runs with your local Termux user. (To find your user type whoami) To find your working directoy where the script should be stored somwhere type pwd

*/5 * * * * /path/to/the/script/serverUp.sh

To change the actual job performed just change the content of the serverUp.sh file. In default, the script writes the date into a file located in ${pwd}/serverUp.log To check the working directory type pwd

echo "$(date): executed script" >> ${pwd}/serverUp.log 2>&1

That's it!

Special thanks to RundesBalli and Chris Heyer

RundesBalli - Server online-status check and reporting to telegram
Chris Heyer - docker-cron