Scenario

An application log file needs to be analyzed to count occurrences of different log levels. You need to parse the log file and generate a summary of log level counts.

Task

Write a Python script at /home/interview/count_logs.py that reads /var/log/app.log, counts occurrences of each log level (DEBUG, INFO, WARN, ERROR) in a case-insensitive manner, and saves the counts as JSON to /home/interview/log_counts.json.

Example

Expected output format in /home/interview/log_counts.json:

{
  "DEBUG": 15,
  "INFO": 42,
  "WARN": 8,
  "ERROR": 3
}

Step 1: Examine the log file format

head /var/log/app.log

Review the log format to understand where the log level appears in each line.

Step 2: Create the Python script

nano /home/interview/count_logs.py

Write a script that parses the log file and counts each log level:

import json
import re

# Initialize counters
log_counts = {
    "DEBUG": 0,
    "INFO": 0,
    "WARN": 0,
    "ERROR": 0
}

# Read and parse log file
with open('/var/log/app.log', 'r') as f:
    for line in f:
        # Extract log level from line (case-insensitive)
        line_upper = line.upper()
        for level in log_counts.keys():
            if level in line_upper:
                log_counts[level] += 1
                break

# Save counts as JSON
with open('/home/interview/log_counts.json', 'w') as f:
    json.dump(log_counts, f, indent=2)

print("Log level counts:")
for level, count in log_counts.items():
    print(f"  {level}: {count}")

Step 3: Run the script

python3 /home/interview/count_logs.py

Step 4: Verify the output

cat /home/interview/log_counts.json

Should show a JSON object with counts for each log level.