SvelteKit Adapter IIS

This package contains an adapter for Sveltekit that will make your project output deployable to IIS.

Usage

1. Install to your sveltekit project

From npm

pnpm add -D sveltekit-adapter-iis
#or
npm i sveltekit-adapter-iis --save-dev
#or
yarn add sveltekit-adapter-iis --dev

2. In your svelte.config.js file replace default adapter with IISAdapter

import { vitePreprocess } from '@sveltejs/kit/vite'
import IISAdapter from 'sveltekit-adapter-iis'

/** @type {import('@sveltejs/kit').Config} */
const config = {
  preprocess: vitePreprocess(),

  kit: {
    version: {
      pollInterval: 300000,
    },
    adapter: IISAdapter({
      // the hostname/port that the site will be hosted on in IIS.
      // can be changed later in web.config
      origin: 'http://localhost:80XX',
      // ... other options
    }),
  },
}

export default config

3. Build the project

pnpm build
#or
npm run build

4. Install dependencies

You should try to bundle all your dependencies as dev dependencies so that you can skip this step however not all dependencies play nice. In this case you can install just the production dependencies using your preferred package manager.

npm

npm install --omit-dev

pnpm

pnpm install --P

yarn

yarn install --production=true

bun

bun install --production

Deploy the files to IIS

Prerequisites

• IIS 7.0 or greater with IISRewrite module and iisnode installed
• Check out Setting up IIS or IIS Troubleshooting if needed.

Option 1: Direct point to output directory

• This is useful for local testing with IIS running on your machine
• You will have to stop the website and possibly IIS every time when re-building.

1 . In IIS Manager add a new Website: Sites -> Add Website...
2. Set the Physical Path to <your project>/.svelte-kit/adapter-iis.

Option 2: Copying build output elsewhere

1. create a new folder in C:/inetpub/<your project>
2. copy the contents of <your project>/.svelte-kit/adapter-iis into C:/inetpub/<your project>
3. In IIS Manager add a new Website: Sites -> Add Website...
4. Set the Physical Path to C:/inetpub/<your project>.

Setting up IIS

This is not a complete guide, but it should help.

1. Enable IIS on your local machine for testing
2. Restart your computer, check if it works by going to localhost without a port
3. Find the IIS manager program (recommended: pin it to start)
   • C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Administrative Tools
     • Internet Information Services (IIS) Manager
   • or: %windir%\system32\inetsrv\InetMgr.exe
4. Install URL Rewrite and iisnode modules
   • URLRewrite: English x64
   • iisnode: iisnode-full-vx.x.x-x64.msi
5. Restart IIS from the manager:
6. Unlock the section in global config (More information needed)
7. Set some permission to Read/Write instead of Read Only (More information needed)
8. Set up logs:
   • Set iisNodeOptions.loggingEnabled to true in the adapter options
   • (Optional) Configure a path for the logs using iisNodeOptions.logDirectory

IIS troubleshooting

• Locked section error
• URLs are not being handled by sveltekit
  • UrlRewrite rule might not be enabled
• Node executable cannot be found
  • By default the nodeExePath is set to node.exe to override this set iisNodeOptions.overrideNodeExePath.

  const config = {
    //...
    kit: {
      adapter: IISAdapter({
        iisNodeOptions: {
          nodeProcessCommandLine: 'C:\\Program Files\\nodejs\\node.exe', // or whatever the path is
        },
      }),
    },
  }

• Logs not being written, builds fail if server is running with EBUSY fs error.
  • Set up file permissions for log dir & for adapter-iis dir for IIS_USER or Everyone to allow all
  • If they are still not being written, instead of console.log, try using console.warn - it will show up in stderr logs without stopping the server.
  • IIS likes to often overwrite log files instead of creating new ones, so make sure you open+close your text editor to see the latest log contents.
• Images or scripts outside of sveltekit (e.g. Virtual Directories, or external) fail to load
  • If you are using a full url with https:// protocol, and have not set up SSL certificates in IIS, it will fail due to 'Cannot provide secure connection'
    • If the url's on the same origin, try using a relative URL
      • example: /virtual-images/image1.png instead of https://localhost:XXXX/virtual-images/image1.png
    • If the url's on a different origin, try changing it to http instead of https
      • If you're generating the url, on the URL object, you can change the protocol key
      • make sure to build it with https once deploying to production
  • You could also probably set the site to use https in IIS, in site settings.
• POST requests or form actions fail with error 403
  • Either you forgot to specify the origin option, or it is mismatched
  • Set it like this:

  // svelte.config.js
  const config = {
    //...
    kit: {
      adapter: IISAdapter({
        origin: 'http://localhost:8010', // or whatever the site's origin is when you deploy it using IIS
      }),
    },
  }

  This sets it in web.config during building.
• Only seeing default Error Page when accessing the app remotely
  • You need to enable Detailed errors in IIS for the site.
  • Navigate to the site in IIS Manager
  • Open Error Pages
  • Click Edit Feature Settings... under the Actions menu on the right
  • Change Error Responses to Detailed Errors. This will allow Sveltekit to handle errors itself.

outputWhitelist

This adapter also provides outputWhitelist in options. This is useful when you need some extra directories on server for the app to function. You can do the following:

Use rollup-plugin-copy to copy the files

// vite.config.ts
import { resolve } from 'node:path'
import { defineConfig, normalizePath } from 'vite'
import copy from 'rollup-plugin-copy'

// your define config does not need to be a function, i think
// i did it like this to make sure thecopy plugin only runs when building
export default defineConfig(({ command }) => {
  const config = {
    // ...
    plugins: [],
  }
  if (command === 'build') {
    const copyPlugin = copy({
      targets: [
        {
          // some files you want to copy over
          src: [
            'db/*.htaccess',
            'db/schema.json',
            'db/*SCINDEX.json',
            'db/vtmeta.yml',
          ],
          dest: normalizePath(resolve('.svelte-kit', 'adapter-iis', 'db')),
        },
      ],
      hook: 'writeBundle',
    })

    config.plugins.push(copyPlugin)
  }
  return config
})

set the outputWhitelist

// svelte.config.js
const config = {
  //...
  kit: {
    adapter: IISAdapter({
      // origin, ...
      outputWhitelist: ['db'],
    }),
  },
}

Now, when building, .svelte-kit/adapter-iis/db should get preserved instead of being deleted

Using Virtual Directories

You might want to use the IIS feature 'Virtual Directory', where it maps a real directory onto a route. To make sure sveltekit doesn't block this with a 404, modify externalRoutes option in the adapter config:

// svelte.config.js
const config = {
  //...
  kit: {
    adapter: IISAdapter({
      // origin, ...
      externalRoutes: ['cdn', 'images', 'viewer'],
    }),
  },
}

Then add some virtual directories that map to cdn, images, and viewer. Re-build the app, and these routes will be taken into account in the generated web.config file.

/healthcheck route

By default, since IIS can be quite tricky to set up, the adapter adds a simple /healthcheck route, which responds with 'ok' This is useful if you want to determine that the node server is running, but your main site isn't loading for whatever reson. The route can be turned off setting the healthcheckRoute adapter option to false. (A re-build is needed to take effect.)

Handling stage specific environment variables

When providing environment variables through a .env file, the adapter will also look for any .env.{stage} files in order to create web.{stage}.config transformation files in .svelte-kit/adapter-iis. These transformation files can later be used to perform XML Transformation steps in your CI/CD pipelines based on which stage is being deployed to.

Read more about XML Transformations here: XML Transformation in Azure Pipelines

Redirecting requests to HTTPS

// svelte.config.js
const config = {
  //...
  kit: {
    adapter: IISAdapter({
      // origin, ...
      redirectToHttps: true,
    }),
  },
}

By setting the option redirectToHttps to true, a URL Rewrite rule is applied to the web.config file that redirect all non-HTTPS request to HTTPS.

httpErrors

By default IIS will take control of HTTP errors and show the default IIS [STATUS].htm for each status. If you want the SvelteKit application to handle all HTTP errors, you can specify httpErrors.existingResponse with PassThrough to let the application handle the errors.

// svelte.config.js
const config = {
  //...
  kit: {
    adapter: IISAdapter({
      // origin, ...
      httpErrors: {
        existingResponse: 'PassThrough',
      },
    }),
  },
}

Disclaimer

Note that this only works when served from the root of a domain.

So you can serve it from www.mysvelteapp.com or sub.mysvelteapp.com but it will not work from www.mysvelteapp.com/subfolder. Unfortunately this is due to how routing works with sveltekit. Adding the base property to your sveltekit config causes all of the routes to have that appended so you end up with the app living on www.mysevelteapp.com/subfolder/subfolder.

How it works

This adapter wraps adapter-node from @sveltejs/kit and uses node:http as the web server. It outputs a web.config file that rewrites incoming requests to the node:http server.

Contributions

Contributions are welcome! Please open an issue or submit a PR if you would like to help out with this project!