SvelteKit / reports
Report PDFs in SvelteKit
Post your report HTML to a render API from a +server.ts endpoint returning a Response, then return a Response built from the upstream body. No browser binary in your SvelteKit deployment.
Why reports become PDFs
A report is a snapshot of numbers at a moment in time. Its whole value is that it does not change when the underlying dashboard does. That is the difference between a document and a view of a database, and it is why analytics, operations and account teams keep asking for this.
What a report has to carry
Before any of the code below matters, the template has to produce a document that is actually a report. These are the fields that make it one, and the ones a reader or an auditor will look for first.
- the reporting period as an explicit start and end date
- the generation timestamp, distinct from the period
- the data source or filter set, so a reader can tell what was excluded
- each metric with its unit, since a bare number is not a figure
- comparison against the prior period where the report claims a trend
Turning your Svelte components, rendered server side template into a document
You already have the markup. Const { html, head } = Invoice.render(data) gives you it as a string, which is the only input the render needs. Which adapter you build with decides whether a browser binary can exist at all. adapter-node can host one; adapter-vercel, adapter-cloudflare and adapter-netlify cannot. Choosing an HTTP render keeps the adapter choice open.
The SvelteKit implementation
fetch ships with the runtime, so this adds no dependency. The render happens in a +server.ts endpoint returning a Response, and you return a Response built from the upstream body.
// src/routes/reports/[id]/pdf/+server.ts
import { error } from "@sveltejs/kit";
import { PDFPIPE_KEY } from "$env/static/private";
import ReportDocument from "$lib/documents/ReportDocument.svelte";
import { render } from "svelte/server";
export async function GET({ params, fetch }) {
const report = await getReport(params.id);
// head carries the scoped styles. Without it the document renders with
// browser defaults, because the CSS file it would link is not reachable.
const { head, body } = render(ReportDocument, { props: { report } });
const html = `<!doctype html><html><head>${head}</head><body>${body}</body></html>`;
const upstream = await fetch("https://api.pdfpipe.xyz/v1/pdf", {
method: "POST",
headers: {
Authorization: `Bearer ${PDFPIPE_KEY}`,
"Content-Type": "application/json",
},
body: JSON.stringify({
html,
options: { format: "A4", printBackground: true },
}),
});
if (!upstream.ok) error(502, "render failed");
return new Response(upstream.body, {
headers: {
"Content-Type": "application/pdf",
"Content-Disposition": `attachment; filename="report-${params.id}.pdf"`,
},
});
}The CSS that makes a report page correctly
The layout problem specific to this document is that charts and tables must not split mid-element, and a report long enough to matter will page-break somewhere awkward unless break rules are set. These rules handle it.
/* Charts and tables must not split. Sections start on a fresh
page so a heading never ends up alone at the foot of one. */
.chart, figure, table { break-inside: avoid; }
h2 { break-after: avoid; }
section { break-before: page; }
section:first-of-type { break-before: auto; }
@page { size: A4; margin: 20mm 18mm; }What goes wrong in SvelteKit
A component's render() output does not include its scoped styles unless you also emit the head string, and even then the styles reference a CSS file the renderer cannot fetch. Inline them into the markup you send.
What people try first
Most SvelteKit projects reach for puppeteer in a +server.ts route, which works locally with adapter-node and then fails on the first deploy to any edge target. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.
Where the report lives afterwards
Rendering is the short part. Reports pile up faster than any other document here because they are produced on a schedule whether or not anyone reads them. Most teams keep twelve months and expire the rest, which makes storage lifecycle a design decision rather than an afterthought.
Getting the document right
- Check the period the figures cover, because a report without an unambiguous date range is worse than no report.
- Generation is triggered by a schedule, usually month end or week end, so size the timeout for that path rather than for a health check.
- This is a batch shape: render the run through the batch endpoint rather than firing thousands of individual requests.
- Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.
Frequently asked
Do I need Chromium installed to generate reports from SvelteKit?
No. The render happens over HTTP, so your SvelteKit deployment stays the size it is now. That is the main reason to use an API rather than puppeteer in a +server.ts route, which works locally with adapter-node and then fails on the first deploy to any edge target.
How do I stop a long report using all the memory?
Return a Response built from the upstream body. A component's render() output does not include its scoped styles unless you also emit the head string, and even then the styles reference a CSS file the renderer cannot fetch. Inline them into the markup you send.
What has to be on a report?
At minimum: the reporting period as an explicit start and end date; the generation timestamp, distinct from the period; the data source or filter set, so a reader can tell what was excluded. The one to get right before anything else is the period the figures cover, because a report without an unambiguous date range is worse than no report.
Do I need to store the generated reports?
Depends on the document, and this one has a clear answer: reports pile up faster than any other document here because they are produced on a schedule whether or not anyone reads them. Most teams keep twelve months and expire the rest, which makes storage lifecycle a design decision rather than an afterthought.
Can I keep my existing report template?
Yes, if it produces HTML. Whatever renders your report view today can render the same markup for the PDF, which is why the CSS above is the only new thing you write.
Related
Other SvelteKit documents, and the same report in other stacks.
Invoice PDFs in SvelteKit
an invoice is a legal record of a demand for payment
Receipt PDFs in SvelteKit
a receipt is proof a payment happened
Certificate PDFs in SvelteKit
a certificate is meant to be shown to a third party who has no relationship with the issuing system
Report PDFs in Node.js
Using fetch, in a route handler that returns the response body directly.
Report PDFs in Python
Using httpx, in an async endpoint that returns a streaming response.
Report PDFs in PHP
Using cURL, in a controller action that echoes the body with a PDF Content-Type.
The same thing in plain Node.js
Without the framework, using fetch directly.
When the output is wrong
Blank pages, missing backgrounds, breaks in the wrong place, by symptom.
All stacks and documents
The full grid of what this covers.
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