agent-census

What's hitting your site, classified by how it behaves -- not just what it claims to be.

Most of the traffic to a typical site isn't people; it's software, and a fair bit of it lies about what it is. agent-census reads your access log and sorts the clients by what they actually do -- whether they pull a page's sub-resources like a browser, walk the site like a crawler, poll a feed on a schedule, or go looking for known-vulnerable paths. Anything claiming to be a known crawler is checked against DNS and published address ranges, so a Googlebot arriving from some random datacentre gets called what it is. What you end up with is your traffic broken down by what each client is for. The User-Agent still counts -- it's just treated as a claim to weigh against behaviour and origin, not a fact to take on trust.

Here's a sample report generated from a real access log.

Install

pipx is recommended:

pipx install agent-census

Use: Analysis

The simplest case is analyzing one or more Apache logs in the default combined format:

agent-census analyze access.log* > census.html

Several rotated logs are pooled into one analysis. You can pass them in any order (a shell glob is fine): each file is peeked and the set is sorted into chronological order before analysis, so a client spanning rotations is treated as one and timing metrics see requests in time order. Plain and .gz files mix freely.

The presets common, combined, and vhost_combined are available via --log-format-preset.

For a custom log format, pass the LogFormat/CustomLog directive string verbatim from your Apache config. Tab separators (\t), quoted fields with spaces, %{...}x SSL variables, and %{...}e environment variables are all handled:

agent-census analyze access.log \
    --log-format '%h %l %u %t "%r" %>s %b "%{Referer}i" "%{User-Agent}i" %D'

See "What to log" below for the most important information to gather.

Cloudflare Logpush logs (newline-delimited JSON) are also supported, as another preset:

agent-census analyze cloudflare-logs.json --log-format-preset cloudflare

Options

Use agent-census analyze -h for the full list of analysis options.

robots.txt compliance: Use --robots-file to supply a local file, hostname, or URL:

agent-census analyze access.log --robots-file ./robots.txt

Output format: Output is a self-contained HTML page by default; redirect it with -o, or pass --md for Markdown:

agent-census analyze access.log -o census.html
agent-census analyze access.log --md

Browsable per-client detail: when an HTML report is written to a file (-o), each client is clickable — a click opens its full trace and classification rationale in-page, no separate inspect run needed. The per-client files are written to a directory named after the report (census.html → census.inspect/), which the report links to. This is on by default; --no-inspect-data skips it (and its per-client trace capture):

agent-census analyze access.log -o census.html
# writes census.html and its sibling census.inspect/ directory
agent-census analyze access.log -o census.html --no-inspect-data
# just census.html, no per-client data

The report and its <name>.inspect/ directory travel together — serve or move them as a pair. Because the directory is named after the report:

• Re-running the same report (e.g. a cron job to census.html) overwrites census.inspect/, pruning files for clients that no longer appear — so disk use tracks the latest run, not the sum of all runs.
• Keeping history needs nothing special: write to a dated name (census-2024-06-01.html) and each run gets its own …inspect/ directory, leaving earlier ones untouched.
• Several reports in one folder don't collide — each has its own directory.

Serve the report over HTTP (the in-page view fetches the data files); a report opened as a local file, or one built with --no-inspect-data, still copies a client's id on click, as before.

Host header filtering: --vhost SUBSTRING analyses only the lines served for a matching host:

agent-census analyze access.log --log-format-preset vhost_combined \
    --vhost mnot.net --vhost www.mnot.net

Time window: --since limits the analysis to recent traffic (e.g. 1w, 36h, 90m; units s/m/h/d/w). A log file that falls entirely outside the window is skipped without being read — and the count of skipped files is reported so it's never a silent omission. The window is anchored at the current time by default; for archived logs whose newest entry is itself in the past, add --from-latest to anchor it at the newest timestamp in the logs instead.

agent-census analyze access.log* --since 1w
agent-census analyze archive/access.log.*.gz --since 1w --from-latest

Client identity: Use --identity to change how requests are associated with clients. The default, ip_ua, groups by (IP, User-Agent). Behind a CDN, use forwarded (the left-most X-Forwarded-For); for IP-rotating bots in one range, ip_ua_subnet.

agent-census analyze access.log --identity forwarded

AS lookups: If your logs don't record the AS number, point --mm-asn-db at a MaxMind ASN database to recover it from each client's IP. The database is consulted first (it can be fresher than the log) and is remembered between runs:

agent-census analyze access.log --mm-asn-db ./GeoLite2-ASN.mmdb

Country flags: point --mm-country-db at a MaxMind country (or city) database to show a small flag next to the highest-traffic non-human clients we haven't tied to a specific operator — an unknown scraper or an impersonator, where the origin country adds signal (a verified, IP/rDNS-identified crawler gets none). For a client spanning many IPs the flag is its traffic-majority country; a client with no country above 70% of its traffic shows a neutral 🌐 instead. In HTML the flag carries the country name as a tooltip and each address gets its own flag on expansion. Also remembered between runs:

agent-census analyze access.log --mm-country-db ./GeoLite2-Country.mmdb

A directory of databases: if you keep your .mmdb files in one place (e.g. a geoipupdate target), point --mm-db-dir at it and both databases are picked up automatically — by each file's metadata, so it doesn't matter what they're named or which vendor they're from. An explicit --mm-asn-db / --mm-country-db still wins for that one role.

agent-census analyze access.log --mm-db-dir /usr/share/GeoIP

Remembered settings

Some options are sticky, so you needn't retype them. --log-format / --log-format-preset, --identity, and --robots-file / --robots-url are saved to ~/.config/agent-census/config.json and reused when a later run omits them; the MaxMind database paths (--mm-asn-db / --mm-country-db / --mm-db-dir) are remembered the same way, as noted with their own options above. Passing one updates the saved value. Use --config PATH to read and write a different settings file (handy for a checked-in, per-project config).

Per-site settings. If you analyse more than one site, --site NAME keeps their settings apart. Each site remembers its own log files, --vhost filter, log format, identity, and robots source, so after seeding a site you can analyse it by name alone:

# seed the site: its settings, log files, and vhost filter are saved under "blog"
agent-census analyze /var/log/access.log* --site blog \
    --vhost blog.example --robots-file /srv/blog/robots.txt

# later runs need only the name
agent-census analyze --site blog

A site's settings override the global defaults; anything passed on the command line overrides the site (and is remembered under it). Resolution is command line → site → defaults.

What goes per-site vs. global follows what a setting describes:

• Per-site — settings that describe the site's data: which log files are it, which --vhost lines are it, how they're formatted, and its robots policy.
• Global — settings that describe this machine or account: the Cloudflare API token and the MaxMind database paths. These are the same whatever site you look at, so they always live in the defaults.

The preference-style keys (log format, identity, robots source) can also be set without --site to give a global baseline that any site inherits until it sets its own. The "which data" keys (log files, --vhost) only ever attach to a site — a global default there would silently filter unrelated runs.

Use: Inspecting a client

To see why a client was classified the way it was, use inspect. It shows every signal that fired (including the runners-up), the measured features, the robots.txt finding, and the request trace:

agent-census inspect access.log --kind vuln_scanner
agent-census inspect access.log --client 203.0.113.66
agent-census inspect access.log --kind scraper --network aws

--network matches a substring of the origin-network name and composes with --kind, so the two together select a single cell of the cross-tab.

inspect emits Markdown. For the same detail browsable from the report itself, write the HTML report to a file (-o) and click a client (see --inspect-data above).

Most analyze options apply; see agent-census inspect -h for a full list of options.

What to log

The Apache combined format already carries everything the core analysis needs. The common preset drops the User-Agent and the Referer, so prefer combined, or a custom format that includes them.

Required (all present in combined):

• Client address (%h) -- the identity everything else groups on, and the basis for the network, datacentre, and crawler-verification checks.
• Timestamp (%t) -- timing regularity, peak request rate, the reported time range, ordering and --since windowing across multiple files, and (with --quiescent-hours) freeing memory mid-run.
• Request line ("%r") -- the method and path; the most load-bearing field, behind vulnerability probing, feed detection, path coverage, and crawl shape.
• Status code (%>s) -- the status mix, 404 storms, 304 Not Modified (the has-cache tag), and robots.txt compliance.
• User-Agent ("%{User-Agent}i") -- browser, bot, and declared-crawler recognition.

Strongly Recommended. The first two are already in combined; the rest aren't in any preset, so add them to a custom LogFormat (quoted) -- they're worth it:

• Referer ("%{Referer}i", in combined) -- referer-following, which separates crawlers from scrapers and flags fabricated referers.
• Bytes sent (%b or %B, in combined) -- the bandwidth figures in the report.
• AS organisation and number ("%{MM_ASORG}e" and "%{MM_ASN}e", MaxMind mod_maxminddb) -- name datacentre clients by their hosting organisation, and recognise datacentres and ASN-listed crawlers by AS number. Much of Networks and hosting leans on these; log both (the number drives recognition, the org names it). Can't log them? --mm-asn-db recovers the AS from a MaxMind database instead (see Options).
• Content-Type ("%{Content-Type}o") -- the response media type, which sharpens feed-reader detection (an RSS/Atom type, not just a feed-shaped URL).
• X-Forwarded-For ("%{X-Forwarded-For}i") -- if you're behind a CDN or proxy, for --identity forwarded.