tasks/access-log-report/instruction.md

Access log report

logs/access.log is a web server access log in a combined-ish format:

<ip> - - [<timestamp>] "<METHOD> <path> HTTP/1.1" <status> <bytes> "<referer>" "<user-agent>" <duration_ms>

Some lines are damaged. The user-agent field may contain escaped double quotes (\"), so the line cannot be parsed by splitting on " -- quoted fields have to be scanned properly. bytes is - when the server did not record a size.

Write tools/report.sh in the workspace root. Running

bash tools/report.sh

from the workspace root must read logs/access.log and (re)generate the following under out/, exit 0, and print nothing that matters. It must be idempotent: deleting out/ and running it again must produce byte-identical files.

out/report.json

A JSON object with exactly these keys:

key	type	meaning
total_requests	int	number of valid lines
unique_paths	int	number of distinct normalised paths
status_counts	object	{"<status>": <count>}, keys are strings; only statuses that occur
top_paths	array	up to 3 objects {"path": str, "count": int}, highest count first, ties broken by path ascending
bytes_total	int	sum of bytes over valid lines, - counts as 0
p95_ms	int	95th percentile of duration_ms, nearest-rank method

p95_ms is the nearest-rank percentile: sort the durations ascending, take element number ceil(0.95 * n) counting from 1. With n = 36 that is the 35th smallest duration. If there are no valid lines, p95_ms is 0.

Paths are normalised by dropping everything from the first ? onwards, so /api/users?id=42 counts as /api/users.

out/malformed.txt

The 1-based line numbers of the lines that do not match the grammar above, one per line, ascending. A line is malformed if any of these hold: it is not the nine-part shape above, status is not exactly three digits, bytes is neither - nor digits, or the trailing duration_ms is missing or not digits. Malformed lines are excluded from every aggregate.

out/access.log.gz

A gzip stream whose decompressed content is byte-for-byte identical to logs/access.log.

Notes

• Only logs/access.log is input; do not edit it.
• python is on PATH (python3 is also available). Standard library only -- there is no network access.