log_analyzer.cs in C#

Regex, LINQ and a little math turn a raw log into answers.

// log_analyzer: parse request lines, bucket by status, find the slow tail
using System.Text.RegularExpressions;

var log = """
GET /api/users 200 45ms
POST /api/login 401 12ms
GET /api/users 200 38ms
GET /static/app.js 200 5ms
POST /api/orders 500 220ms
GET /api/users 304 9ms
""";

var pattern = new Regex(@"(\w+) (\S+) (\d{3}) (\d+)ms");
var requests = log.Split('\n')
    .Select(line => pattern.Match(line))
    .Where(m => m.Success)
    .Select(m => (Path: m.Groups[2].Value,
                  Code: int.Parse(m.Groups[3].Value),
                  Ms: int.Parse(m.Groups[4].Value)))
    .ToList();

foreach (var group in requests.GroupBy(r => r.Code / 100))
{
    Console.WriteLine($"{group.Key}xx: {group.Count()}");
}

var sorted = requests.Select(r => r.Ms).OrderBy(ms => ms).ToList();
var median = sorted[sorted.Count / 2];
Console.WriteLine($"median {median}ms, slowest {sorted[^1]}ms");

var errors = requests.Where(r => r.Code >= 500).Select(r => r.Path);
Console.WriteLine($"5xx on: {string.Join(",", errors)}");

How it works

1. One pattern parses verb, path, status and duration per line.
2. GroupBy(r => r.Code / 100) buckets into 2xx/4xx/5xx.
3. Sorting durations yields the median and the slowest request.

Keywords and builtins used here

• foreach
• group
• in
• int
• new
• static
• using
• var

The run, in numbers

Lines

32

Characters to type

971

Tokens

260

Three-star pace

85 tpm

At the three-star pace of 85 tokens a minute, this run takes about 184 seconds.

Type this snippet

Step 1 of 2 in Encore, step 16 of 17 in The .NET library.

← Previous Next →