dnscontrol/docs/_functions/global/FETCH.md
Tom Limoncelli 9e6d642e35
NEW FEATURE: Moving provider TYPE from dnsconfig.js to creds.json (#1500)
Fixes https://github.com/StackExchange/dnscontrol/issues/1457

* New-style creds.json implememented backwards compatible

* Update tests

* Update docs

* Assume new-style TYPE
2022-05-08 14:23:45 -04:00

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---
name: FETCH
parameters:
- url
- args
---
`FETCH` is a wrapper for the [Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API). This allows dynamically setting DNS records based on an external data source, e.g. the API of your cloud provider.
Compared to `fetch` from Fetch API, `FETCH` will call [PANIC](#PANIC) to terminate the execution of the script, and therefore DnsControl, if a network error occurs.
Otherwise the syntax of `FETCH` is the same as `fetch`.
`FETCH` is not enabled by default. Please read the warnings below.
> WARNING:
>
> 1. Relying on external sources adds a point of failure. If the external source doesn't work, your script won't either. Please make sure you are aware of the consequences.
> 2. Make sure DnsControl only uses verified configuration if you want to use `FETCH`. For example, an attacker can send Pull Requests to your config repo, and have your CI test malicious configurations and make arbitrary HTTP requests. Therefore, `FETCH` must be explicitly enabled with flag `--allow-fetch` on DnsControl invocation.
{% capture example %}
```js
var REG_NONE = NewRegistrar('none');
var DNS_BIND = NewDnsProvider('bind');
D('example.com', REG_NONE, DnsProvider(DNS_BIND), [
A('@', '1.2.3.4'),
]);
FETCH('https://example.com', {
// All three options below are optional
headers: {"X-Authentication": "barfoo"},
method: "POST",
body: "Hello World",
}).then(function(r) {
return r.text();
}).then(function(t) {
// Example of generating record based on response
D_EXTEND('example.com', [
TXT('@', t.slice(0, 100)),
]);
});
```
{% endcapture %}
{% include example.html content=example %}