snapdok

Guides · Ruby · Net::HTTP

Verify a fillable PDF render without opening the file in Ruby with Net::HTTP

When form-PDF generation is part of a pipeline — nightly exports, CI checks, a queue worker — "did it actually come out fillable?" needs a machine answer, not a human opening Acrobat. snapdok puts the verification data in the response headers, so your code can assert on the render it just received.

Below is a complete, runnable Ruby program using Net::HTTP, no third-party dependency needed. It reads your API key from the SNAPDOK_KEY environment variable — free keys take about thirty seconds and need no card.

require "json"
require "net/http"
require "uri"

uri = URI("https://snapdok.io/v1/render")

res = Net::HTTP.start(uri.host, uri.port, use_ssl: true, read_timeout: 90) do |http|
  req = Net::HTTP::Post.new(uri)
  req["Authorization"] = "Bearer #{ENV.fetch("SNAPDOK_KEY")}"
  req["Content-Type"] = "application/json"
  req.body = JSON.generate({
    url: "https://your-app.com/intake-form",
    format: "pdf",
    pdf_forms: true,
    pdf_form_only: true,
})
  http.request(req)
end

raise "snapdok error #{res.code}: #{res.body}" unless res.is_a?(Net::HTTPSuccess)

File.binwrite("checked.pdf", res.body)
puts "#{res["X-Form-Fields"]}  # assert on this in CI"

Three headers carry the contract. X-Form-Fields is the number of AcroForm fields placed — assert it equals the number of controls your form has, and you have a regression test that catches a broken deploy of your own form page, too. X-Form-Skipped counts controls that could not convert (file pickers, hidden inputs, iframe forms); a sudden rise means someone changed the form. X-Form-Extracted tells you whether pdf_form_only actually pruned the page or fell back to the full page — fallback is legitimate output, but your layout expectations may differ.

Two operational notes for pipelines: failed renders are never metered, and a repeat of an identical request inside 24 hours returns X-Cache: HIT and is also not charged — so a retrying job that occasionally double-fires does not eat quota. Rate limits surface as HTTP 429 with a Retry-After header; honour it instead of hammering.

Notes for Net::HTTP

Stdlib only — no gems. The traps Net::HTTP is famous for, all handled in the sample: TLS is not automatic (set use_ssl: true or you will POST in the clear to port 80 and get a redirect); the default read_timeout of 60 s is close enough to real render times that raising it is wise; and the response body is a binary-ready String, but write it with File.binwrite — plain File.write on Windows would mangle line-ending bytes in the PDF. Check is_a?(Net::HTTPSuccess): Net::HTTP never raises on HTTP error statuses.

Response headers worth reading

HeaderMeaning
X-Form-FieldsFields placed — the number to assert on.
X-Form-SkippedUnconvertible controls; watch for regressions.
X-Form-ExtractedPrune result when pdf_form_only was requested.
Retry-AfterPresent on 429 — seconds to back off.

Full parameter reference: the docs. Hard numbers on caps and timeouts: limits.

Related guides

Same task, other stacks

More with Ruby + Net::HTTP

In the wild