Server Config

You can configure the behavior of the server via the server field of app declaration:

JavaScript

main.wasp

app MyApp {
  title: "My app",
  // ...
  server: {
    setupFn: import { mySetupFunction } from "@src/myServerSetupCode.js",
    middlewareConfigFn: import { myMiddlewareConfigFn } from "@src/myServerSetupCode.js"
  }
}

TypeScript

main.wasp

app MyApp {
  title: "My app",
  // ...
  server: {
    setupFn: import { mySetupFunction } from "@src/myServerSetupCode.js",
    middlewareConfigFn: import { myMiddlewareConfigFn } from "@src/myServerSetupCode.js"
  }
}

Setup Function

Adding a Custom Route

As an example, adding a custom route would look something like:

JavaScript

src/myServerSetupCode.ts

export const mySetupFunction = async ({ app }) => {
  addCustomRoute(app)
}

function addCustomRoute(app) {
  app.get('/customRoute', (_req, res) => {
    res.send('I am a custom route')
  })
}

TypeScript

src/myServerSetupCode.ts

import { ServerSetupFn } from 'wasp/server'
import { Application } from 'express'

export const mySetupFunction: ServerSetupFn = async ({ app }) => {
  addCustomRoute(app)
}

function addCustomRoute(app: Application) {
  app.get('/customRoute', (_req, res) => {
    res.send('I am a custom route')
  })
}

Storing Some Values for Later Use

In case you want to store some values for later use, or to be accessed by the Operations you do that in the setupFn function.

Dummy example of such function and its usage:

JavaScript

src/myServerSetupCode.js

let someResource = undefined

export const mySetupFunction = async () => {
  // Let's pretend functions setUpSomeResource and startSomeCronJob
  // are implemented below or imported from another file.
  someResource = await setUpSomeResource()
  startSomeCronJob()
}

export const getSomeResource = () => someResource

src/queries.js

import { getSomeResource } from './myServerSetupCode.js'

...

export const someQuery = async (args, context) => {
  const someResource = getSomeResource()
  return queryDataFromSomeResource(args, someResource)
}

TypeScript

src/myServerSetupCode.ts

import { type ServerSetupFn } from 'wasp/server'

let someResource = undefined

export const mySetupFunction: ServerSetupFn = async () => {
  // Let's pretend functions setUpSomeResource and startSomeCronJob
  // are implemented below or imported from another file.
  someResource = await setUpSomeResource()
  startSomeCronJob()  
}

export const getSomeResource = () => someResource

src/queries.ts

import { type SomeQuery } from 'wasp/server/operations'
import { getSomeResource } from './myServerSetupCode.js'

...

export const someQuery: SomeQuery<...> = async (args, context) => {
  const someResource = getSomeResource()
  return queryDataFromSomeResource(args, someResource)
}

note

The recommended way is to put the variable in the same module where you defined the setup function and then expose additional functions for reading those values, which you can then import directly from Operations and use.

This effectively turns your module into a singleton whose construction is performed on server start.

Read more about server setup function below.

Middleware Config Function

You can configure the global middleware via the middlewareConfigFn. This will modify the middleware stack for all operations and APIs.

Read more about middleware config function below.

API Reference

JavaScript

main.wasp

app MyApp {
  title: "My app",
  // ...
  server: {
    setupFn: import { mySetupFunction } from "@src/myServerSetupCode.js",
    middlewareConfigFn: import { myMiddlewareConfigFn } from "@src/myServerSetupCode.js"
  }
}

TypeScript

main.wasp

app MyApp {
  title: "My app",
  // ...
  server: {
    setupFn: import { mySetupFunction } from "@src/myServerSetupCode.js",
    middlewareConfigFn: import { myMiddlewareConfigFn } from "@src/myServerSetupCode.js"
  }
}

app.server is a dictionary with the following fields:

• setupFn: ExtImport

  setupFn declares a function that will be executed on server start. This function is expected to be async and will be awaited before the server starts accepting any requests.

  It allows you to do any custom setup, e.g. setting up additional database/websockets or starting cron/scheduled jobs.

  The setupFn function receives the express.Application and the http.Server instances as part of its context. They can be useful for setting up any custom server logic.

  JavaScript

  src/myServerSetupCode.js

  export const mySetupFunction = async () => {
    await setUpSomeResource()
  }

  TypeScript

  Types for the setup function and its context are as follows:

  wasp/server

  export type ServerSetupFn = (context: ServerSetupFnContext) => Promise<void>
  
  export type ServerSetupFnContext = {
    app: Application // === express.Application
    server: Server // === http.Server
  }

  src/myServerSetupCode.ts

  import { type ServerSetupFn } from 'wasp/server'
  
  export const mySetupFunction: ServerSetupFn = async () => {
    await setUpSomeResource()
  }

• middlewareConfigFn: ExtImport

  The import statement to an Express middleware config function. This is a global modification affecting all operations and APIs. See more in the configuring middleware section.