project_guide.md

• working with files(reading, writing and parsing logs) -

            a sample python code for reading files {
  
                    with open("/var/log/syslog", "r") as file: # This line opens the file in read mode, with ensures the file is properly closed after use
                        for line in file:
                            print(line.strip())
                }
  
                a sample python code for writing to a file {
  
                    with open("output.log", "w") as file: # "W" mode overwrites the file if it exists, "a" mode appends new data without deleting old ones
                        file.write("Log entry: System check complete. \n")
                }
  
  
  
            A sample code to parse log files and extract errors {
  
  
                errors_logs = []
                with open("/var/log/syslog", "r") as file:
                    for line in file:
                        if "ERROR" in line:
                            errors_logs.append(line.strip())
  
                #save extracted error logs
  
                with open("error_logs.txt", "w") as output:
                    output.writelines("\n".join(error_logs))
            }
  
            - Difference between write and write lines -
                -Write is used to write a single  string to a file eg. file.write("my name is kofi")
                
                -writelines is used to write multiple lines(a list of strings to a file) eg [
                            lines = [" first line \n", "second line \n"]
                            file.writelines(lines)
                ]
  

• interacting with OS processes (subprocess, os modules) -

  • Python provides the os and subprocess modules to interact with system process

  a sample python code to list running process {

    #linux / macos
    import os
    os.system("ps aux | head -10") # list first 10 processes
  
    #windows
    import os
    os.system("tasklist")
  

  }

  • running shell commands is an integral part of python for devops and the subprocess modeule is the most effective tool more powerful than the os.system()

    • a sample code to check disk usage {

      import subprocess #capture_output captures the command output, text=True ensures output is returned as string result = subprocess.run(["df", "-h"], capture_output=True, text=True) print(result.stdout) }

    • a sample code to check CPU and Memory Usage {

      to monitor system resources. we can use the psutil library

      #pip install psutil

      import psutil

      cpu_usage = psutil.cpu_percent(interval=1) # CPU usage over 1 second mem_info = psutil.virtual_memory() # Memory details

      print(f"CPU Usage: {cpu_usage}%") print(f"Memory Usage: {mem_info.percent}%") }

ASSIGNMENT BREAK: - Write a script to log CPU & Memory usage every 5 seconds for 1 minute - save the logs to a file (sysem_monitor dot log)

    Solution {
        # first I will use the psutle library to get CPU and Memory usage 

        import psutil, time
        for r in range(12): # the script will sleep every 5 seconds so 12 times will be 1 minute (60 seconds)
            print("monitoring now")
            cpu_usage = psutil.cpu_percent(interval=1)
            mem_info = psutil.virtual_memory().percent

            with open("files/system_monitor.log", "a") as file:
                file.writelines("\n" + cpu_usage + "\n" + mem_info)
            time.sleep(5)
    }   

In the Final Project for week one, We created a live system health monitor that sent metrics to an api consumed by an django app and displayed on a dashboard