Railway•3w ago

Private networking in SvelteKit app

I've deployed a SvelteKit application on Railway using a Dockerfile. Within that project I have a separate service for cron jobs, also deployed with a Dockerfile. The cron service calls endpoints on my SvelteKit application. This works fine using the public domain of the app service using HTTPS, but when attempting to use private networking it doesn't work. In my app service, I've configured the server to listen on 0.0.0.0 with Railway's injected port. This builds well and logs Listening on 0.0.0.0:8080, so I know it's working.

vite.config.ts:

import { sveltekit } from '@sveltejs/kit/vite';
import { defineConfig } from 'vite';

export default defineConfig({
    plugins: [sveltekit()],
    optimizeDeps: {
        include: ['src/lib/components/**/*.svelte', 'src/routes/**/*.svelte']
    },

    /* Railway requires http:// to be used for private networking, as well as a port to specified. This is injected automatically during run time.

    https://docs.railway.app/guides/public-networking#port-variable
    https://docs.railway.app/guides/private-networking
    
    */
    server: {
        port: Number(process.env.PORT),
        host: process.env.HOST || '0.0.0.0'
    }
});

vite.config.ts:

import { sveltekit } from '@sveltejs/kit/vite';
import { defineConfig } from 'vite';

export default defineConfig({
    plugins: [sveltekit()],
    optimizeDeps: {
        include: ['src/lib/components/**/*.svelte', 'src/routes/**/*.svelte']
    },

    /* Railway requires http:// to be used for private networking, as well as a port to specified. This is injected automatically during run time.

    https://docs.railway.app/guides/public-networking#port-variable
    https://docs.railway.app/guides/private-networking
    
    */
    server: {
        port: Number(process.env.PORT),
        host: process.env.HOST || '0.0.0.0'
    }
});

26 Replies

Percy•3w ago

Project ID: 95e92fe0-66e9-4eed-86df-2cdc05218e79

Budi•3w ago

95e92fe0-66e9-4eed-86df-2cdc05218e79

Budi•3w ago

Here's my cron-service.ts, which also deploys with no problems.

cron-service.ts:

...
const CRON_SECRET = process.env.CRON_SECRET;
const NODE_ENV = process.env.NODE_ENV || 'development';
const PORT = process.env.PORT;

/* Railway requires http:// to be used for private networking, as well as a port to specified. This is injected automatically during run time.

https://docs.railway.app/guides/public-networking#port-variable
https://docs.railway.app/guides/private-networking

*/
const ORIGIN =
    NODE_ENV === 'production'
        ? `http://${process.env.MAIN_APP_PRIVATE_DOMAIN}:${PORT}`
        : `${process.env.MAIN_APP_DEV_ORIGIN}`;
...

cron-service.ts:

...
const CRON_SECRET = process.env.CRON_SECRET;
const NODE_ENV = process.env.NODE_ENV || 'development';
const PORT = process.env.PORT;

/* Railway requires http:// to be used for private networking, as well as a port to specified. This is injected automatically during run time.

https://docs.railway.app/guides/public-networking#port-variable
https://docs.railway.app/guides/private-networking

*/
const ORIGIN =
    NODE_ENV === 'production'
        ? `http://${process.env.MAIN_APP_PRIVATE_DOMAIN}:${PORT}`
        : `${process.env.MAIN_APP_DEV_ORIGIN}`;
...

Unfortunately, my logs show a connection error

Error executing test cron job: request to http://sveltecareers.railway.internal:8080/api/cron-tester failed, reason: connect ECONNREFUSED fd12:3663:d458::e6:bba7:55ec:8080

. Any idea why this is happening? I believe the ports line up and I'm making a HTTP request. A collorary question is how to access the ${{sveltecareers.PORT}} variable as described in https://docs.railway.app/guides/private-networking#use-internal-hostname-and-port. I cannot access the main app service's PORT variable from the cron-schedule service. I've worked around that by referencing process.env.PORT directly in the cron-service.ts assuming that the injected PORT would be the same, which it appears to be (8080). Thanks! Loving the platform so far.

Railway Docs

Private Networking | Railway Docs

Documentation for Railway

Brody•3w ago

the injected port would be the same, but its never good to assume that, you would want to set a PORT service variable on the SvelteKit service so that you can reference it on the cron service. as for the ECONNREFUSED error, remove the server config, and then simply set a HOST service variable to :: since the private network is IPv6 only.

Budi•3w ago

Thanks for the quick response @Brody! When setting the PORT service variable on the SvelteKit service, is there any way to retrieve this as a Railway provided variable? Or is PORT only made available during runtime, but not in the GUI? I wasn't able to select it from the dropdown in the service variables menu. Do I have to set a fixed port, like 8080 now that I know that's the injected one? I don't understand what you mean with setting a HOST service. Do you mean to remove the server property I had defined from the vite.config.ts altogether?

Brody•3w ago

yeah you are right, its only available during runtime, you can just set a fixed port in the UI though.

Budi•3w ago

Ah sorry I think I'm grokking now. You're suggesting I set a HOST service variable. On the SvelteKit Railway service or the cron service?

Brody•3w ago

yes, service variable, on the SvelteKit service and also remove the server property in the config file, its not needed

Budi•3w ago

OK so summarizing: On the SvelteKit service I remove the service prop from the vite.config.ts. I set a fixed PORT service variable to 8080 instead, and a HOST service variable to ::. This allows me to retrieve these on the cron service, where I define the full private origin as: http://${{sveltecareers.RAILWAY_PRIVATE_DOMAIN}}${{sveltecareers.HOST}}${{sveltecareers.PORT}}. Is that right?

Brody•3w ago

you got most correct. the url should be made like this http://${{sveltecareers.RAILWAY_PRIVATE_DOMAIN}}:${{sveltecareers.PORT}} the HOST variable is just set so that the server knows to listen on IPv6 is all

Budi•3w ago

Ah I see. But I don't need to specify this in vite for the SvelteKit build, because Railway will inject this during run time? Do I not use double colons in the private origin? Just single colon?

Brody•3w ago

yeah the SvelteKit server will look for and use a HOST variable

Budi•3w ago

(First time doing private networking on any hosting service and I'm new to IP standards like IPv6, so bear with me 😅)

Brody•3w ago

not sure what you mean, simply set HOST=:: in the SvelteKit service, no need to overthink this right now

Budi•3w ago

Funny, today I learned that https:// always defaults to port 443. And that explains why I need to define a port when using http://. OK got it, thanks Brody. Will work on implementing this r/n.

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Private networking in SvelteKit app