Running a scheduled function on Val Town to import Atom feeds into Datasette Cloud#

Configuring secrets in environment variables#

Because this Val needs to be able to call the Datasette Cloud API with an API token, I needed to figure out Val Town secrets. These are pretty straight-forward: you can set multiple environment variables for your account on this page:

https://www.val.town/settings/environment-variables

Those variables are then made available to your Vals through Deno.env.get("VARIABLE_NAME").

Scheduling a Val#

The Val Town logged in homepage looks like this:

Clicking “Scheduled function” creates a new private Val with a random name that looks like this:

The cog next to “Runs every 1hr” can be used to set a different interval.

Writing the code#

After some experimentation I landed on this as the content of my Val:

1
export default async function(interval: Interval) {
2
  const { default: Parser } = await import("npm:rss-parser");
3
  let parser = new Parser();
4
  let feed = await parser.parseURL("https://simonwillison.net/atom/everything/");
5
  const token = Deno.env.get("DATASETTE_CLOUD_SIMON_FEED_WRITE");
6
  const url = "https://simon.datasette.cloud/data/feed/-/insert";
7
  const body = {
8
    "rows": feed.items,
9
    "replace": true,
10
  };
11
  const response = await fetch(url, {
12
    method: "POST",
13
    headers: {
14
      "Content-Type": "application/json",
15
      "Authorization": `Bearer ${token}`,
16
    },
17
    body: JSON.stringify(body),
18
  });
19
  if (response.ok) {
20
    const responseData = await response.json();
21
    console.log("Response data:", responseData);
22
  } else {
23
    console.error("Request failed:", response.statusText);
24
  }
25
}

• Any NPM module can be imported directly into a Val using await import("npm:name-of-package")
• I used rss-parser to parse the feed - it was the first option I tried and provided exactly what I wanted
• As mentioned earlier, Deno.env.get() provides access to configured environment variables
• Deno’s fetch() function is modeled on the browser standard
• console.log() and console.error() log to a dedicated log for that Val, visible beneath it

The blue “Run” button can be clicked any time to try out the Val. Once I got it working I left it running, and it’s been executing once an hour ever since.