Keeping Watch

Reliability is a crucial aspect of a computer system, especially for servers. Because continuous active monitoring isn't feasible, implementing mechanisms to alert the system administrator in case of a malfunction can be very useful. This article explores how to develop a simple tool that monitors the status of a process and sends a Telegram message in the event of a crash.

Prerequisites

To follow the development of this project, you'll need an integrated development environment enabled for Python programming and some basic knowledge of the Python language. On Ubuntu, it is possible to download VS Code from the App Center by simply finding the VS Code page in the App Center and clicking the Install button. If you prefer to proceed with the installation via the command line, the VS Code documentation provides all the necessary details for completing the procedure on various distributions [1]. I recommend installing the Pylance, Python, and Python Debugger extensions to make development easier. Simply click on the extensions button (on the left side), select the extension, and proceed with the installation.

In addition, you will need a Telegram account and the Telegram messaging application [2] installed on a smartphone or PC. For Ubuntu users, the application is available on the Snapstore. From the command line, you can install it with apt using the command

sudo apt install telegram-desktop

See the box entitled "Why Telegram?" for more on why I chose it for this task.

Setting up a Telegram Bot

The first step is to create a Telegram bot, which you can control using a Python script to send notifications. After launching Telegram, access the search function by clicking on the appropriate icon at the top of the main screen. Search for the string BotFather and select the corresponding entry. Then type the following commands:

/start
/new bot

BotFather will guide you through the process of creating a new bot, prompting you to choose a name and a username for your bot. You will receive a token that you can use to interact with the bot via a script. At this point, I need to retrieve the user ID of the person to whom I will send the messages. I can use the Get Chat ID bot for this purpose. Just click on the User button and select the desired contact from the list. Make a note of the token and the user ID, which you will need to specify as parameters when running the script from the console.

Developing the Script

The monitoring script will check whether a process is running at user-defined intervals. If the application is running, the script prints a log string on the screen; otherwise, a warning message is sent to a specified user on Telegram.

The first step is to handle the application arguments, which include the token provided by Telegram, the user ID, the name of the process to monitor, and the time interval expressed in minutes (Listing 1).

01 import requests
02 import time
03 from datetime import datetime
04 import psutil
05 import argparse
06
07 try:
08   parser=argparse.ArgumentParser()
09   parser.add_argument("token", help="Token assigned by Telegram when creating your Bot", type=str)
10   parser.add_argument("user_id",help="User ID on Telegram", type=str)
11   parser.add_argument("process_name",help="Name of the process to check for",type=str)
12   parser.add_argument("interval",help="Minutes of interval between checks",type=int)
13   args=parser.parse_args()

The essential part of the script consists of a loop that repeats as long as the process under examination is running (Listing 2). The boolean variable found is set to False at the beginning of the iteration. Then the script retrieves the list of active processes. If the process specified by the args.process_name parameter is present in this list, the script prints an informative note to the screen with the current date and time. It then sets the variable found to True. At the end of each iteration, if the process is not active, the script outputs an alert string then sends the same message to the user specified by the args_user_id parameter using the Telegram REST API. The application is then closed. The main function is enclosed in a try-except block, and in case of an error, an informative message is displayed (Figure 1).

01 while True:
02     found=False
03     for process in psutil.process_iter():
04       if(process.name()==args.process_name):
05         print(args.process_name +" up and running at " +str(datetime.now()))
06         found=True
07
08     if(found==False):
09       message = "Process " +args.process_name + " is currently down"
10       print(message)
11       url = f"https://api.telegram.org/bot{args.token}/sendMessage?chat_id={args.user_id}&text={message}"
12       requests.get(url).json()
13       quit()
14
15     time.sleep(args.interval * 60)
16
17 except Exception as e:
18   print(f"Error {type(e)}")

Figure 1: The script sends the user a message if the process is down.

Practical Example

Launch the script from the terminal with the following syntax:

python crashinspector.py token:user_id process_name interval

where token is the token provided by BotFather, user_ID is the Telegram user ID provided by the Get Chat ID bot, process_name is the name of the process you are monitoring, and interval is the time interval for performing the checks (in minutes). For example, run the following command to check the status of the filezilla process every 30 minutes:

python crashinspector.py 7237372881:AAEA-ZPF9WMRX5aNSa0PoJDCiUePoNqu0Uk 17130319 filezilla 30

Assuming that filezilla is terminated after about two and a half hours, the output will be similar to Listing 3.

filezilla up and running at 2024-07-21 16:49:13.559405
filezilla up and running at 2024-07-21 17:19:13.616971
filezilla up and running at 2024-07-21 17:49:13.621785
filezilla up and running at 2024-07-21 18:19:13.624988
filezilla up and running at 2024-07-21 18:49:13.628092
Process filezilla is currently down

Conclusion

When launched from the console, the script described in this article obtains the list of running processes and checks for an instance of the process. If an instance of the process is active, a string indicating the date and time of the check is printed. The cycle continues in the same manner for the specified time interval. If the process is not running during an iteration of the cycle, the application prints a warning on the console and sends an alert message via Telegram.