Error sending mail with Mailgun API within a docker

Question

I'm using Mailgun API to send emails.

It's working in the local environment but when I create an image and run it with Docker I receive an error regarding the fetch.

I've checked and the env variables are correct.

The back-end code in node.js for sending the email:

const API_KEY = process.env.MAILGUN_API_KEY;
const DOMAIN = process.env.MAILGUN_DOMAIN_NAME;

const formData = require('form-data');
const Mailgun = require('mailgun.js');

const mailgun = new Mailgun(formData);
const client = mailgun.client({ username: 'api', key: API_KEY });



const sendEmail = async (to, subject, text) => {
    try {
        const messageData = {
            from: `Noreply <noreply@${DOMAIN}>`,
            to: to,
            subject: subject,
            text: text
        };
        const res = await client.messages.create(DOMAIN, messageData)
    } catch (error) {
        console.error(error);
        return error;
    }

    }
sendEmail("[email protected]", "aa", "aa");

The error received in the docker container:

docker-firebase-1  | (node:1) ExperimentalWarning: The Fetch API is an experimental feature. This feature could change at any time
docker-firebase-1  | (Use `node --trace-warnings ...` to show where the warning was created)
    TypeError: fetch failed
    docker-firebase-1  |     at Object.processResponse (node:internal/deps/undici/undici:5570:34)     
    docker-firebase-1  |     at node:internal/deps/undici/undici:5896:42
    docker-firebase-1  |     at node:internal/process/task_queues:140:7
    docker-firebase-1  |     at AsyncResource.runInAsyncScope (node:async_hooks:202:9)
    docker-firebase-1  |     at AsyncResource.runMicrotask (node:internal/process/task_queues:137:8) {
    docker-firebase-1  |   cause: TypeError: object2 is not iterable
    docker-firebase-1  |       at action (node:internal/deps/undici/undici:1651:39)
    docker-firebase-1  |       at action.next (<anonymous>)
    docker-firebase-1  |       at Object.pull (node:internal/deps/undici/undici:1699:52)
    docker-firebase-1  |       at ensureIsPromise (node:internal/webstreams/util:172:19)
    docker-firebase-1  |       at readableStreamDefaultControllerCallPullIfNeeded (node:internal/webstreams/readablestream:1884:5)
    docker-firebase-1  |       at node:internal/webstreams/readablestream:1974:7
    docker-firebase-1  | }

Answer 1

After some testing, I found the source of the problem was in the image's version of node I've been using in the Dockerfile.

I've been using the image node: alpine which does not support the fetch API the mailgun.js is using (because it is a slimmer version of node).

I've switched up to node:16.14.2-buster and it's now working.