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@effect/platform
Advanced tools
Welcome to the documentation for @effect/platform
, a library designed for creating platform-independent abstractions (Node.js, Bun, browsers).
With @effect/platform
, you can incorporate abstract services like Terminal
or FileSystem
into your program. Later, during the assembly of the final application, you can provide specific layers for the target platform using the corresponding packages: platform-node
, platform-bun
, and platform-browser
.
This package empowers you to perform various operations, such as:
Operation | Description |
---|---|
Terminal | Reading and writing from/to standard input/output |
Command | Creating and running a command with the specified process name and an optional list of arguments |
FileSystem | Reading and writing from/to the file system |
HTTP Client | Sending HTTP requests and receiving responses |
HTTP Server | Creating HTTP servers to handle incoming requests |
HTTP Router | Routing HTTP requests to specific handlers |
KeyValueStore | Storing and retrieving key-value pairs |
PlatformLogger | Creating a logger that writes to a specified file from another string logger |
By utilizing @effect/platform
, you can write code that remains platform-agnostic, ensuring compatibility across different environments.
The @effect/platform/Terminal
module exports a single Terminal
tag, which serves as the entry point to reading from and writing to standard input and standard output.
import { Terminal } from "@effect/platform"
import { NodeRuntime, NodeTerminal } from "@effect/platform-node"
import { Effect } from "effect"
// const displayMessage: Effect.Effect<void, PlatformError, Terminal.Terminal>
const displayMessage = Effect.gen(function* (_) {
const terminal = yield* _(Terminal.Terminal)
yield* _(terminal.display("a message\n"))
})
NodeRuntime.runMain(displayMessage.pipe(Effect.provide(NodeTerminal.layer)))
// Output: "a message"
import { Terminal } from "@effect/platform"
import { NodeRuntime, NodeTerminal } from "@effect/platform-node"
import { Console, Effect } from "effect"
// const readLine: Effect.Effect<void, Terminal.QuitException, Terminal.Terminal>
const readLine = Effect.gen(function* (_) {
const terminal = yield* _(Terminal.Terminal)
const input = yield* _(terminal.readLine)
yield* _(Console.log(`input: ${input}`))
})
NodeRuntime.runMain(readLine.pipe(Effect.provide(NodeTerminal.layer)))
// Input: "hello"
// Output: "input: hello"
These simple examples illustrate how to utilize the Terminal
module for handling standard input and output in your programs. Let's use this knowledge to build a number guessing game:
import { Terminal } from "@effect/platform"
import type { PlatformError } from "@effect/platform/Error"
import { Effect, Option, Random } from "effect"
export const secret = Random.nextIntBetween(1, 100)
const parseGuess = (input: string) => {
const n = parseInt(input, 10)
return isNaN(n) || n < 1 || n > 100 ? Option.none() : Option.some(n)
}
const display = (message: string) =>
Effect.gen(function* (_) {
const terminal = yield* _(Terminal.Terminal)
yield* _(terminal.display(`${message}\n`))
})
const prompt = Effect.gen(function* (_) {
const terminal = yield* _(Terminal.Terminal)
yield* _(terminal.display("Enter a guess: "))
return yield* _(terminal.readLine)
})
const answer: Effect.Effect<
number,
Terminal.QuitException | PlatformError,
Terminal.Terminal
> = Effect.gen(function* (_) {
const input = yield* _(prompt)
const guess = parseGuess(input)
if (Option.isNone(guess)) {
yield* _(display("You must enter an integer from 1 to 100"))
return yield* _(answer)
}
return guess.value
})
const check = <A, E, R>(
secret: number,
guess: number,
ok: Effect.Effect<A, E, R>,
ko: Effect.Effect<A, E, R>
): Effect.Effect<A, E | PlatformError, R | Terminal.Terminal> =>
Effect.gen(function* (_) {
if (guess > secret) {
yield* _(display("Too high"))
return yield* _(ko)
} else if (guess < secret) {
yield* _(display("Too low"))
return yield* _(ko)
} else {
return yield* _(ok)
}
})
const end = display("You guessed it!")
const loop = (
secret: number
): Effect.Effect<
void,
Terminal.QuitException | PlatformError,
Terminal.Terminal
> =>
Effect.gen(function* (_) {
const guess = yield* _(answer)
return yield* _(
check(
secret,
guess,
end,
Effect.suspend(() => loop(secret))
)
)
})
export const game = Effect.gen(function* (_) {
yield* _(
display(
"We have selected a random number between 1 and 100. See if you can guess it in 10 turns or fewer. We'll tell you if your guess was too high or too low."
)
)
yield* _(loop(yield* _(secret)))
})
Let's run the game in Node.js:
import { NodeRuntime, NodeTerminal } from "@effect/platform-node"
import * as Effect from "effect/Effect"
import { game } from "./game.js"
NodeRuntime.runMain(game.pipe(Effect.provide(NodeTerminal.layer)))
Let's run the game in Bun:
import { BunRuntime, BunTerminal } from "@effect/platform-bun"
import * as Effect from "effect/Effect"
import { game } from "./game.js"
BunRuntime.runMain(game.pipe(Effect.provide(BunTerminal.layer)))
As an example of using the @effect/platform/Command
module, let's see how to run the TypeScript compiler tsc
:
import { Command, CommandExecutor } from "@effect/platform"
import {
NodeCommandExecutor,
NodeFileSystem,
NodeRuntime
} from "@effect/platform-node"
import { Effect } from "effect"
// const program: Effect.Effect<string, PlatformError, CommandExecutor.CommandExecutor>
const program = Effect.gen(function* (_) {
const executor = yield* _(CommandExecutor.CommandExecutor)
// Creating a command to run the TypeScript compiler
const command = Command.make("tsc", "--noEmit")
console.log("Running tsc...")
// Executing the command and capturing the output
const output = yield* _(executor.string(command))
console.log(output)
return output
})
// Running the program with the necessary runtime and executor layers
NodeRuntime.runMain(
program.pipe(
Effect.provide(NodeCommandExecutor.layer),
Effect.provide(NodeFileSystem.layer)
)
)
Here, we'll explore how to retrieve information about a running process.
import { Command, CommandExecutor } from "@effect/platform"
import {
NodeCommandExecutor,
NodeFileSystem,
NodeRuntime
} from "@effect/platform-node"
import { Effect, Stream, String } from "effect"
const runString = <E, R>(
stream: Stream.Stream<Uint8Array, E, R>
): Effect.Effect<string, E, R> =>
stream.pipe(Stream.decodeText(), Stream.runFold(String.empty, String.concat))
const program = Effect.gen(function* (_) {
const executor = yield* _(CommandExecutor.CommandExecutor)
const command = Command.make("ls")
const [exitCode, stdout, stderr] = yield* _(
// Start running the command and return a handle to the running process.
executor.start(command),
Effect.flatMap((process) =>
Effect.all(
[
// Waits for the process to exit and returns the ExitCode of the command that was run.
process.exitCode,
// The standard output stream of the process.
runString(process.stdout),
// The standard error stream of the process.
runString(process.stderr)
],
{ concurrency: 3 }
)
)
)
console.log({ exitCode, stdout, stderr })
})
NodeRuntime.runMain(
Effect.scoped(program).pipe(
Effect.provide(NodeCommandExecutor.layer),
Effect.provide(NodeFileSystem.layer)
)
)
To run a command (for example cat
) and stream its stdout
to process.stdout
follow these steps:
import { Command } from "@effect/platform"
import { NodeContext, NodeRuntime } from "@effect/platform-node"
import { Effect } from "effect"
// Create a command to run `cat` on a file and inherit stdout
const program = Command.make("cat", "./some-file.txt").pipe(
Command.stdout("inherit"),
Command.exitCode
)
// Run the command using NodeRuntime with the NodeContext layer
NodeRuntime.runMain(program.pipe(Effect.provide(NodeContext.layer)))
The @effect/platform/FileSystem
module provides a single FileSystem
tag, which acts as the gateway for interacting with the filesystem.
Here's a list of operations that can be performed using the FileSystem
tag:
Name | Arguments | Return | Description |
---|---|---|---|
access | path: string , options?: AccessFileOptions | Effect<void, PlatformError> | Check if a file can be accessed. You can optionally specify the level of access to check for. |
copy | fromPath: string , toPath: string , options?: CopyOptions | Effect<void, PlatformError> | Copy a file or directory from fromPath to toPath . Equivalent to cp -r . |
copyFile | fromPath: string , toPath: string | Effect<void, PlatformError> | Copy a file from fromPath to toPath . |
chmod | path: string , mode: number | Effect<void, PlatformError> | Change the permissions of a file. |
chown | path: string , uid: number , gid: number | Effect<void, PlatformError> | Change the owner and group of a file. |
exists | path: string | Effect<boolean, PlatformError> | Check if a path exists. |
link | fromPath: string , toPath: string | Effect<void, PlatformError> | Create a hard link from fromPath to toPath . |
makeDirectory | path: string , options?: MakeDirectoryOptions | Effect<void, PlatformError> | Create a directory at path . You can optionally specify the mode and whether to recursively create nested directories. |
makeTempDirectory | options?: MakeTempDirectoryOptions | Effect<string, PlatformError> | Create a temporary directory. By default, the directory will be created inside the system's default temporary directory. |
makeTempDirectoryScoped | options?: MakeTempDirectoryOptions | Effect<string, PlatformError, Scope> | Create a temporary directory inside a scope. Functionally equivalent to makeTempDirectory , but the directory will be automatically deleted when the scope is closed. |
makeTempFile | options?: MakeTempFileOptions | Effect<string, PlatformError> | Create a temporary file. The directory creation is functionally equivalent to makeTempDirectory . The file name will be a randomly generated string. |
makeTempFileScoped | options?: MakeTempFileOptions | Effect<string, PlatformError, Scope> | Create a temporary file inside a scope. Functionally equivalent to makeTempFile , but the file will be automatically deleted when the scope is closed. |
open | path: string , options?: OpenFileOptions | Effect<File, PlatformError, Scope> | Open a file at path with the specified options . The file handle will be automatically closed when the scope is closed. |
readDirectory | path: string , options?: ReadDirectoryOptions | Effect<Array<string>, PlatformError> | List the contents of a directory. You can recursively list the contents of nested directories by setting the recursive option. |
readFile | path: string | Effect<Uint8Array, PlatformError> | Read the contents of a file. |
readFileString | path: string , encoding?: string | Effect<string, PlatformError> | Read the contents of a file as a string. |
readLink | path: string | Effect<string, PlatformError> | Read the destination of a symbolic link. |
realPath | path: string | Effect<string, PlatformError> | Resolve a path to its canonicalized absolute pathname. |
remove | path: string , options?: RemoveOptions | Effect<void, PlatformError> | Remove a file or directory. By setting the recursive option to true , you can recursively remove nested directories. |
rename | oldPath: string , newPath: string | Effect<void, PlatformError> | Rename a file or directory. |
sink | path: string , options?: SinkOptions | Sink<void, Uint8Array, never, PlatformError> | Create a writable Sink for the specified path . |
stat | path: string | Effect<File.Info, PlatformError> | Get information about a file at path . |
stream | path: string , options?: StreamOptions | Stream<Uint8Array, PlatformError> | Create a readable Stream for the specified path . |
symlink | fromPath: string , toPath: string | Effect<void, PlatformError> | Create a symbolic link from fromPath to toPath . |
truncate | path: string , length?: SizeInput | Effect<void, PlatformError> | Truncate a file to a specified length. If the length is not specified, the file will be truncated to length 0 . |
utimes | path: string , atime: Date | number , mtime: Date | number | Effect<void, PlatformError> | Change the file system timestamps of the file at path . |
watch | path: string | Stream<WatchEvent, PlatformError> | Watch a directory or file for changes. |
Let's explore a simple example using readFileString
:
import { FileSystem } from "@effect/platform"
import { NodeFileSystem, NodeRuntime } from "@effect/platform-node"
import { Effect } from "effect"
// const readFileString: Effect.Effect<void, PlatformError, FileSystem.FileSystem>
const readFileString = Effect.gen(function* (_) {
const fs = yield* _(FileSystem.FileSystem)
// Reading the content of the same file where this code is written
const content = yield* _(fs.readFileString("./index.ts", "utf8"))
console.log(content)
})
NodeRuntime.runMain(readFileString.pipe(Effect.provide(NodeFileSystem.layer)))
The KeyValueStore
module provides a robust and effectful interface for managing key-value pairs. It supports asynchronous operations, ensuring data integrity and consistency, and includes built-in implementations for in-memory, file system-based, and schema-validated stores.
The KeyValueStore
interface includes the following operations:
Example
import { KeyValueStore, layerMemory } from "@effect/platform/KeyValueStore"
import { Effect } from "effect"
const program = Effect.gen(function* () {
const store = yield* KeyValueStore
console.log(yield* store.size) // Outputs: 0
yield* store.set("key", "value")
console.log(yield* store.size) // Outputs: 1
const value = yield* store.get("key")
console.log(value) // Outputs: { _id: 'Option', _tag: 'Some', value: 'value' }
yield* store.remove("key")
console.log(yield* store.size) // Outputs: 0
})
Effect.runPromise(program.pipe(Effect.provide(layerMemory)))
The module provides several built-in implementations to suit different needs:
layerMemory
provides a simple, in-memory key-value store, ideal for lightweight or testing scenarios.layerFileSystem
offers a file-based store for persistent storage needs.layerSchema
enables schema-based validation for stored values, ensuring data integrity and type safety.The SchemaStore
implementation allows you to validate and parse values according to a defined schema. This ensures that all data stored in the key-value store adheres to the specified structure, enhancing data integrity and type safety.
Example
import { KeyValueStore, layerMemory } from "@effect/platform/KeyValueStore"
import { Schema } from "@effect/schema"
import { Effect } from "effect"
// Define a schema for the values
const Person = Schema.Struct({
name: Schema.String,
age: Schema.Number
})
const program = Effect.gen(function* () {
const store = (yield* KeyValueStore).forSchema(Person)
// Create a value that adheres to the schema
const value = { name: "Alice", age: 30 }
yield* store.set("user1", value)
console.log(yield* store.size) // Outputs: 1
// Retrieve and validate the value
const retrievedValue = yield* store.get("user1")
console.log(retrievedValue) // Outputs: { _id: 'Option', _tag: 'Some', value: { name: 'Alice', age: 30 } }
})
Effect.runPromise(program.pipe(Effect.provide(layerMemory)))
In this example:
Person
.Person
.An HttpClient
is a function that takes a request and produces a certain value A
in an effectful way (possibly resulting in an error E
and depending on some requirement R
).
type HttpClient<A, E, R> = (request: HttpClientRequest): Effect<A, E, R>
Generally, you'll deal with a specialization called Default
where A
, E
, and R
are predefined:
type Default = (request: HttpClientRequest): Effect<HttpClientResponse, RequestError | ResponseError, Scope>
The goal of Default
is straightforward: transform a HttpClientRequest
into a HttpClientResponse
.
Here's a simple example demonstrating how to retrieve JSON data using HttpClient
from @effect/platform
.
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { Effect } from "effect"
const req = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/posts/1"
)
// HttpClient.fetch is a Default
const res = HttpClient.fetch(req)
const json = HttpClientResponse.json(res)
Effect.runPromise(json).then(console.log)
/*
Output:
{
userId: 1,
id: 1,
title: 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit',
body: 'quia et suscipit\n' +
'suscipit recusandae consequuntur expedita et cum\n' +
'reprehenderit molestiae ut ut quas totam\n' +
'nostrum rerum est autem sunt rem eveniet architecto'
}
*/
In this example:
HttpClientRequest.get
creates a GET request to the specified URL.HttpClient.fetch
executes the request.HttpClientResponse.json
converts the response to JSON.Effect.runPromise
runs the effect and logs the result.Default | Description |
---|---|
HttpClient.fetch | Execute the request using the global fetch function |
HttpClient.fetchOk | Same as fetch but ensures only 2xx responses are treated as successes |
You can create your own Default
using the HttpClient.makeDefault
constructor.
import { HttpClient, HttpClientResponse } from "@effect/platform"
import { Effect } from "effect"
const myClient = HttpClient.makeDefault((req) =>
Effect.succeed(
HttpClientResponse.fromWeb(
req,
// Simulate a response from a server
new Response(
JSON.stringify({ userId: 1, id: 1, title: "title...", body: "body..." })
)
)
)
)
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { Console, Effect } from "effect"
const req = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/posts/1"
)
// Log the request before fetching
const tapFetch: HttpClient.HttpClient.Default = HttpClient.fetch.pipe(
HttpClient.tapRequest(Console.log)
)
const res = tapFetch(req)
const json = HttpClientResponse.json(res)
Effect.runPromise(json).then(console.log)
/*
Output:
{
_id: '@effect/platform/HttpClientRequest',
method: 'GET',
url: 'https://jsonplaceholder.typicode.com/posts/1',
urlParams: [],
hash: { _id: 'Option', _tag: 'None' },
headers: Object <[Object: null prototype]> {},
body: { _id: '@effect/platform/HttpBody', _tag: 'Empty' }
}
{
userId: 1,
id: 1,
title: 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit',
body: 'quia et suscipit\n' +
'suscipit recusandae consequuntur expedita et cum\n' +
'reprehenderit molestiae ut ut quas totam\n' +
'nostrum rerum est autem sunt rem eveniet architecto'
}
*/
You can create a HttpClientRequest
using the following provided constructors:
Constructor | Description |
---|---|
HttpClientRequest.get | Create a GET request |
HttpClientRequest.post | Create a POST request |
HttpClientRequest.patch | Create a PATCH request |
HttpClientRequest.put | Create a PUT request |
HttpClientRequest.del | Create a DELETE request |
HttpClientRequest.head | Create a HEAD request |
HttpClientRequest.options | Create an OPTIONS request |
When making HTTP requests, sometimes you need to include additional information in the request headers. You can set headers using the setHeader
function for a single header or setHeaders
for multiple headers simultaneously.
import { HttpClientRequest } from "@effect/platform"
const req = HttpClientRequest.get("https://api.example.com/data").pipe(
// Setting a single header
HttpClientRequest.setHeader("Authorization", "Bearer your_token_here"),
// Setting multiple headers
HttpClientRequest.setHeaders({
"Content-Type": "application/json; charset=UTF-8",
"Custom-Header": "CustomValue"
})
)
console.log(JSON.stringify(req.headers, null, 2))
/*
Output:
{
"authorization": "Bearer your_token_here",
"content-type": "application/json; charset=UTF-8",
"custom-header": "CustomValue"
}
*/
To include basic authentication in your HTTP request, you can use the basicAuth
method provided by HttpClientRequest
.
import { HttpClientRequest } from "@effect/platform"
const req = HttpClientRequest.get("https://api.example.com/data").pipe(
HttpClientRequest.basicAuth("your_username", "your_password")
)
console.log(JSON.stringify(req.headers, null, 2))
/*
Output:
{
"authorization": "Basic eW91cl91c2VybmFtZTp5b3VyX3Bhc3N3b3Jk"
}
*/
To include a Bearer token in your HTTP request, use the bearerToken
method provided by HttpClientRequest
.
import { HttpClientRequest } from "@effect/platform"
const req = HttpClientRequest.get("https://api.example.com/data").pipe(
HttpClientRequest.bearerToken("your_token")
)
console.log(JSON.stringify(req.headers, null, 2))
/*
Output:
{
"authorization": "Bearer your_token"
}
*/
To specify the media types that are acceptable for the response, use the accept
method provided by HttpClientRequest
.
import { HttpClientRequest } from "@effect/platform"
const req = HttpClientRequest.get("https://api.example.com/data").pipe(
HttpClientRequest.accept("application/xml")
)
console.log(JSON.stringify(req.headers, null, 2))
/*
Output:
{
"accept": "application/xml"
}
*/
To indicate that the client accepts JSON responses, use the acceptJson
method provided by HttpClientRequest
.
import { HttpClientRequest } from "@effect/platform"
const req = HttpClientRequest.get("https://api.example.com/data").pipe(
HttpClientRequest.acceptJson
)
console.log(JSON.stringify(req.headers, null, 2))
/*
Output:
{
"accept": "application/json"
}
*/
To convert a GET response to JSON:
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Console, Effect } from "effect"
const getPostAsJson = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/posts/1"
).pipe(HttpClient.fetch, HttpClientResponse.json)
NodeRuntime.runMain(
getPostAsJson.pipe(Effect.andThen((post) => Console.log(typeof post, post)))
)
/*
Output:
object {
userId: 1,
id: 1,
title: 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit',
body: 'quia et suscipit\n' +
'suscipit recusandae consequuntur expedita et cum\n' +
'reprehenderit molestiae ut ut quas totam\n' +
'nostrum rerum est autem sunt rem eveniet architecto'
}
*/
To convert a GET response to text:
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Console, Effect } from "effect"
const getPostAsText = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/posts/1"
).pipe(HttpClient.fetch, HttpClientResponse.text)
NodeRuntime.runMain(
getPostAsText.pipe(Effect.andThen((post) => Console.log(typeof post, post)))
)
/*
Output:
string {
userId: 1,
id: 1,
title: 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit',
body: 'quia et suscipit\n' +
'suscipit recusandae consequuntur expedita et cum\n' +
'reprehenderit molestiae ut ut quas totam\n' +
'nostrum rerum est autem sunt rem eveniet architecto'
}
*/
Here are some APIs you can use to convert the response:
API | Description |
---|---|
HttpClientResponse.arrayBuffer | Convert to ArrayBuffer |
HttpClientResponse.formData | Convert to FormData |
HttpClientResponse.json | Convert to JSON |
HttpClientResponse.stream | Convert to a Stream of Uint8Array |
HttpClientResponse.text | Convert to text |
HttpClientResponse.urlParamsBody | Convert to Http.urlParams.UrlParams |
A common use case when fetching data is to validate the received format. For this purpose, the HttpClient
module is integrated with @effect/schema
.
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Schema } from "@effect/schema"
import { Console, Effect } from "effect"
const Post = Schema.Struct({
id: Schema.Number,
title: Schema.String
})
/*
const getPostAndValidate: Effect.Effect<{
readonly id: number;
readonly title: string;
}, Http.error.HttpClientError | ParseError, never>
*/
const getPostAndValidate = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/posts/1"
).pipe(
HttpClient.fetch,
Effect.andThen(HttpClientResponse.schemaBodyJson(Post)),
Effect.scoped
)
NodeRuntime.runMain(getPostAndValidate.pipe(Effect.andThen(Console.log)))
/*
Output:
{
id: 1,
title: 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit'
}
*/
In this example, we define a schema for a post object with properties id
and title
. Then, we fetch the data and validate it against this schema using HttpClientResponse.schemaBodyJson
. Finally, we log the validated post object.
Note that we use Effect.scoped
after consuming the response. This ensures that any resources associated with the HTTP request are properly cleaned up once we're done processing the response.
It's important to note that HttpClient.fetch
doesn't consider non-200
status codes as errors by default. This design choice allows for flexibility in handling different response scenarios. For instance, you might have a schema union where the status code serves as the discriminator, enabling you to define a schema that encompasses all possible response cases.
You can use HttpClient.filterStatusOk
, or HttpClient.fetchOk
to ensure only 2xx
responses are treated as successes.
In this example, we attempt to fetch a non-existent page and don't receive any error:
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Console, Effect } from "effect"
const getText = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/non-existing-page"
).pipe(HttpClient.fetch, HttpClientResponse.text)
NodeRuntime.runMain(getText.pipe(Effect.andThen(Console.log)))
/*
Output:
{}
*/
However, if we use HttpClient.filterStatusOk
, an error is logged:
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Console, Effect } from "effect"
const getText = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/non-existing-page"
).pipe(HttpClient.filterStatusOk(HttpClient.fetch), HttpClientResponse.text)
NodeRuntime.runMain(getText.pipe(Effect.andThen(Console.log)))
/*
Output:
timestamp=... level=ERROR fiber=#0 cause="ResponseError: StatusCode error (404 GET https://jsonplaceholder.typicode.com/non-existing-page): non 2xx status code
... stack trace ...
*/
Note that you can use HttpClient.fetchOk
as a shortcut for HttpClient.filterStatusOk(HttpClient.fetch)
:
const getText = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/non-existing-page"
).pipe(HttpClient.fetchOk, HttpClientResponse.text)
You can also create your own status-based filters. In fact, HttpClient.filterStatusOk
is just a shortcut for the following filter:
const getText = HttpClientRequest.get(
"https://jsonplaceholder.typicode.com/non-existing-page"
).pipe(
HttpClient.filterStatus(
HttpClient.fetch,
(status) => status >= 200 && status < 300
),
HttpClientResponse.text
)
/*
Output:
timestamp=... level=ERROR fiber=#0 cause="ResponseError: StatusCode error (404 GET https://jsonplaceholder.typicode.com/non-existing-page): invalid status code
... stack trace ...
*/
To make a POST request, you can use the HttpClientRequest.post
function provided by the HttpClient
module. Here's an example of how to create and send a POST request:
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Console, Effect } from "effect"
const addPost = HttpClientRequest.post(
"https://jsonplaceholder.typicode.com/posts"
).pipe(
HttpClientRequest.jsonBody({
title: "foo",
body: "bar",
userId: 1
}),
Effect.andThen(HttpClient.fetch),
HttpClientResponse.json
)
NodeRuntime.runMain(addPost.pipe(Effect.andThen(Console.log)))
/*
Output:
{ title: 'foo', body: 'bar', userId: 1, id: 101 }
*/
If you need to send data in a format other than JSON, such as plain text, you can use different APIs provided by HttpClientRequest
.
In the following example, we send the data as text:
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Console, Effect } from "effect"
const addPost = HttpClientRequest.post(
"https://jsonplaceholder.typicode.com/posts"
).pipe(
HttpClientRequest.textBody(
JSON.stringify({
title: "foo",
body: "bar",
userId: 1
}),
"application/json; charset=UTF-8"
),
HttpClient.fetch,
HttpClientResponse.json
)
NodeRuntime.runMain(Effect.andThen(addPost, Console.log))
/*
Output:
{ title: 'foo', body: 'bar', userId: 1, id: 101 }
*/
A common use case when fetching data is to validate the received format. For this purpose, the HttpClient
module is integrated with @effect/schema
.
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { NodeRuntime } from "@effect/platform-node"
import { Schema } from "@effect/schema"
import { Console, Effect } from "effect"
const Post = Schema.Struct({
id: Schema.Number,
title: Schema.String
})
const addPost = HttpClientRequest.post(
"https://jsonplaceholder.typicode.com/posts"
).pipe(
HttpClientRequest.jsonBody({
title: "foo",
body: "bar",
userId: 1
}),
Effect.andThen(HttpClient.fetch),
Effect.andThen(HttpClientResponse.schemaBodyJson(Post)),
Effect.scoped
)
NodeRuntime.runMain(addPost.pipe(Effect.andThen(Console.log)))
/*
Output:
{ id: 101, title: 'foo' }
*/
To test HTTP requests, you can inject a mock fetch implementation.
import {
HttpClient,
HttpClientRequest,
HttpClientResponse
} from "@effect/platform"
import { Effect, Layer } from "effect"
import * as assert from "node:assert"
// Mock fetch implementation
const FetchTest = Layer.succeed(HttpClient.Fetch, () =>
Promise.resolve(new Response("not found", { status: 404 }))
)
// Program to test
const program = HttpClientRequest.get("https://www.google.com/").pipe(
HttpClient.fetch,
HttpClientResponse.text
)
// Test
Effect.gen(function* () {
const response = yield* program
assert.equal(response, "not found")
}).pipe(Effect.provide(FetchTest), Effect.runPromise)
This section provides a simplified explanation of key concepts within the @effect/platform
TypeScript library, focusing on components used to build HTTP servers. Understanding these terms and their relationships helps in structuring and managing server applications effectively.
HttpApp: This is an Effect
which results in a value A
. It can utilize ServerRequest
to produce the outcome A
. Essentially, an HttpApp
represents an application component that handles HTTP requests and generates responses based on those requests.
Default (HttpApp): A special type of HttpApp
that specifically produces a ServerResponse
as its output A
. This is the most common form of application where each interaction is expected to result in an HTTP response.
Server: A construct that takes a Default
app and converts it into an Effect
. This serves as the execution layer where the Default
app is operated, handling incoming requests and serving responses.
Router: A type of Default
app where the possible error outcome is RouteNotFound
. Routers are used to direct incoming requests to appropriate handlers based on the request path and method.
Handler: Another form of Default
app, which has access to both RouteContext
and ServerRequest.ParsedSearchParams
. Handlers are specific functions designed to process requests and generate responses.
Middleware: Functions that transform a Default
app into another Default
app. Middleware can be used to modify requests, responses, or handle tasks like logging, authentication, and more. Middleware can be applied in two ways:
Router
using router.use: Handler -> Default
which applies the middleware to specific routes.Server
using server.serve: () -> Layer | Middleware -> Layer
which applies the middleware globally to all routes handled by the server.These components are designed to work together in a modular and flexible way, allowing developers to build complex server applications with reusable components. Here's how you might typically use these components in a project:
Create Handlers: Define functions that process specific types of requests (e.g., GET, POST) and return responses.
Set Up Routers: Organize handlers into routers, where each router manages a subset of application routes.
Apply Middleware: Enhance routers or entire servers with middleware to add extra functionality like error handling or request logging.
Initialize the Server: Wrap the main router with server functionality, applying any server-wide middleware, and start listening for requests.
In this example, we will create a simple HTTP server that listens on port 3000
. The server will respond with "Hello World!" when a request is made to the root URL (/) and return a 500
error for all other paths.
Node.js Example
import { HttpRouter, HttpServer, HttpServerResponse } from "@effect/platform"
import { NodeHttpServer, NodeRuntime } from "@effect/platform-node"
import { Layer } from "effect"
import { createServer } from "node:http"
// Define the router with a single route for the root URL
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("Hello World"))
)
// Set up the application server with logging
const app = router.pipe(HttpServer.serve(), HttpServer.withLogAddress)
// Specify the port
const port = 3000
// Create a server layer with the specified port
const ServerLive = NodeHttpServer.layer(() => createServer(), { port })
// Run the application
NodeRuntime.runMain(Layer.launch(Layer.provide(app, ServerLive)))
/*
Output:
timestamp=... level=INFO fiber=#0 message="Listening on http://localhost:3000"
*/
[!NOTE] The
HttpServer.withLogAddress
middleware logs the address and port where the server is listening, helping to confirm that the server is running correctly and accessible on the expected endpoint.
Bun Example
import { HttpRouter, HttpServer, HttpServerResponse } from "@effect/platform"
import { BunHttpServer, BunRuntime } from "@effect/platform-bun"
import { Layer } from "effect"
// Define the router with a single route for the root URL
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("Hello World"))
)
// Set up the application server with logging
const app = router.pipe(HttpServer.serve(), HttpServer.withLogAddress)
// Specify the port
const port = 3000
// Create a server layer with the specified port
const ServerLive = BunHttpServer.layer({ port })
// Run the application
BunRuntime.runMain(Layer.launch(Layer.provide(app, ServerLive)))
/*
Output:
timestamp=... level=INFO fiber=#0 message="Listening on http://localhost:3000"
*/
To avoid boilerplate code for the final server setup, we'll use a helper function from the listen.ts
file:
import type { HttpPlatform, HttpServer } from "@effect/platform"
import { NodeHttpServer, NodeRuntime } from "@effect/platform-node"
import { Layer } from "effect"
import { createServer } from "node:http"
export const listen = (
app: Layer.Layer<
never,
never,
HttpPlatform.HttpPlatform | HttpServer.HttpServer
>,
port: number
) =>
NodeRuntime.runMain(
Layer.launch(
Layer.provide(
app,
NodeHttpServer.layer(() => createServer(), { port })
)
)
)
Routing refers to determining how an application responds to a client request to a particular endpoint, which is a URI (or path) and a specific HTTP request method (GET, POST, and so on).
Route definition takes the following structure:
router.pipe(HttpRouter.METHOD(PATH, HANDLER))
Where:
Router
(import type { Router } from "@effect/platform/Http/Router"
).The following examples illustrate defining simple routes.
Respond with "Hello World!"
on the homepage:
router.pipe(HttpRouter.get("/", HttpServerResponse.text("Hello World")))
Respond to POST request on the root route (/), the application's home page:
router.pipe(HttpRouter.post("/", HttpServerResponse.text("Got a POST request")))
Respond to a PUT request to the /user
route:
router.pipe(
HttpRouter.put("/user", HttpServerResponse.text("Got a PUT request at /user"))
)
Respond to a DELETE request to the /user
route:
router.pipe(
HttpRouter.del(
"/user",
HttpServerResponse.text("Got a DELETE request at /user")
)
)
To serve static files such as images, CSS files, and JavaScript files, use the HttpServerResponse.file
built-in action.
import { HttpRouter, HttpServer, HttpServerResponse } from "@effect/platform"
import { listen } from "./listen.js"
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.file("index.html"))
)
const app = router.pipe(HttpServer.serve())
listen(app, 3000)
Create an index.html
file in your project directory:
<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<title>index.html</title>
<meta name="viewport" content="width=device-width, initial-scale=1" />
</head>
<body>
index.html
</body>
</html>
Routing refers to how an application's endpoints (URIs) respond to client requests.
You define routing using methods of the HttpRouter
object that correspond to HTTP methods; for example, HttpRouter.get()
to handle GET requests and HttpRouter.post
to handle POST requests. You can also use HttpRouter.all()
to handle all HTTP methods.
These routing methods specify a Route.Handler
called when the application receives a request to the specified route (endpoint) and HTTP method. In other words, the application “listens” for requests that match the specified route(s) and method(s), and when it detects a match, it calls the specified handler.
The following code is an example of a very basic route.
// respond with "hello world" when a GET request is made to the homepage
HttpRouter.get("/", HttpServerResponse.text("Hello World"))
A route method is derived from one of the HTTP methods, and is attached to an instance of the HttpRouter
object.
The following code is an example of routes that are defined for the GET and the POST methods to the root of the app.
// GET method route
HttpRouter.get("/", HttpServerResponse.text("GET request to the homepage"))
// POST method route
HttpRouter.post("/", HttpServerResponse.text("POST request to the homepage"))
HttpRouter
supports methods that correspond to all HTTP request methods: get
, post
, and so on.
There is a special routing method, HttpRouter.all()
, used to load middleware functions at a path for all HTTP request methods. For example, the following handler is executed for requests to the route “/secret” whether using GET, POST, PUT, DELETE.
HttpRouter.all(
"/secret",
HttpServerResponse.empty().pipe(
Effect.tap(Console.log("Accessing the secret section ..."))
)
)
Route paths, when combined with a request method, define the endpoints where requests can be made. Route paths can be specified as strings according to the following type:
type PathInput = `/${string}` | "*"
[!NOTE] Query strings are not part of the route path.
Here are some examples of route paths based on strings.
This route path will match requests to the root route, /.
HttpRouter.get("/", HttpServerResponse.text("root"))
This route path will match requests to /user
.
HttpRouter.get("/user", HttpServerResponse.text("user"))
This route path matches requests to any path starting with /user
(e.g., /user
, /users
, etc.)
HttpRouter.get(
"/user*",
Effect.map(HttpServerRequest.HttpServerRequest, (req) =>
HttpServerResponse.text(req.url)
)
)
Route parameters are named URL segments that are used to capture the values specified at their position in the URL. By using a schema the captured values are populated in an object, with the name of the route parameter specified in the path as their respective keys.
Route parameters are named segments in a URL that capture the values specified at those positions. These captured values are stored in an object, with the parameter names used as keys.
For example:
Route path: /users/:userId/books/:bookId
Request URL: http://localhost:3000/users/34/books/8989
params: { "userId": "34", "bookId": "8989" }
To define routes with parameters, include the parameter names in the path and use a schema to validate and parse these parameters, as shown below.
import { HttpRouter, HttpServer, HttpServerResponse } from "@effect/platform"
import { Schema } from "@effect/schema"
import { Effect } from "effect"
import { listen } from "./listen.js"
// Define the schema for route parameters
const Params = Schema.Struct({
userId: Schema.String,
bookId: Schema.String
})
// Create a router with a route that captures parameters
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/users/:userId/books/:bookId",
HttpRouter.schemaPathParams(Params).pipe(
Effect.flatMap((params) => HttpServerResponse.json(params))
)
)
)
const app = router.pipe(HttpServer.serve())
listen(app, 3000)
The methods on HttpServerResponse
object in the following table can send a response to the client, and terminate the request-response cycle. If none of these methods are called from a route handler, the client request will be left hanging.
Method | Description |
---|---|
empty | Sends an empty response. |
formData | Sends form data. |
html | Sends an HTML response. |
raw | Sends a raw response. |
setBody | Sets the body of the response. |
stream | Sends a streaming response. |
text | Sends a plain text response. |
Use the HttpRouter
object to create modular, mountable route handlers. A Router
instance is a complete middleware and routing system, often referred to as a "mini-app."
The following example shows how to create a router as a module, define some routes, and mount the router module on a path in the main app.
Create a file named birds.ts
in your app directory with the following content:
import { HttpRouter, HttpServerResponse } from "@effect/platform"
export const birds = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("Birds home page")),
HttpRouter.get("/about", HttpServerResponse.text("About birds"))
)
In your main application file, load the router module and mount it.
import { HttpRouter, HttpServer } from "@effect/platform"
import { birds } from "./birds.js"
import { listen } from "./listen.js"
// Create the main router and mount the birds router
const router = HttpRouter.empty.pipe(HttpRouter.mount("/birds", birds))
const app = router.pipe(HttpServer.serve())
listen(app, 3000)
When you run this code, your application will be able to handle requests to /birds
and /birds/about
, serving the respective responses defined in the birds
router module.
In this section, we'll build a simple "Hello World" application and demonstrate how to add three middleware functions: myLogger
for logging, requestTime
for displaying request timestamps, and validateCookies
for validating incoming cookies.
Here is an example of a basic "Hello World" application with middleware.
myLogger
This middleware logs "LOGGED" whenever a request passes through it.
const myLogger = HttpMiddleware.make((app) =>
Effect.gen(function* () {
console.log("LOGGED")
return yield* app
})
)
To use the middleware, add it to the router using HttpRouter.use()
:
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { Effect } from "effect"
import { listen } from "./listen.js"
const myLogger = HttpMiddleware.make((app) =>
Effect.gen(function* () {
console.log("LOGGED")
return yield* app
})
)
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("Hello World"))
)
const app = router.pipe(HttpRouter.use(myLogger), HttpServer.serve())
listen(app, 3000)
With this setup, every request to the app will log "LOGGED" to the terminal. Middleware execute in the order they are loaded.
requestTime
Next, we'll create a middleware that records the timestamp of each HTTP request and provides it via a service called RequestTime
.
class RequestTime extends Context.Tag("RequestTime")<RequestTime, number>() {}
const requestTime = HttpMiddleware.make((app) =>
Effect.gen(function* () {
return yield* app.pipe(Effect.provideService(RequestTime, Date.now()))
})
)
Update the app to use this middleware and display the timestamp in the response:
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { Context, Effect } from "effect"
import { listen } from "./listen.js"
class RequestTime extends Context.Tag("RequestTime")<RequestTime, number>() {}
const requestTime = HttpMiddleware.make((app) =>
Effect.gen(function* () {
return yield* app.pipe(Effect.provideService(RequestTime, Date.now()))
})
)
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/",
Effect.gen(function* () {
const requestTime = yield* RequestTime
const responseText = `Hello World<br/><small>Requested at: ${requestTime}</small>`
return yield* HttpServerResponse.html(responseText)
})
)
)
const app = router.pipe(HttpRouter.use(requestTime), HttpServer.serve())
listen(app, 3000)
Now, when you make a request to the root path, the response will include the timestamp of the request.
validateCookies
Finally, we'll create a middleware that validates incoming cookies. If the cookies are invalid, it sends a 400 response.
Here's an example that validates cookies using an external service:
class CookieError {
readonly _tag = "CookieError"
}
const externallyValidateCookie = (testCookie: string | undefined) =>
testCookie && testCookie.length > 0
? Effect.succeed(testCookie)
: Effect.fail(new CookieError())
const cookieValidator = HttpMiddleware.make((app) =>
Effect.gen(function* () {
const req = yield* HttpServerRequest.HttpServerRequest
yield* externallyValidateCookie(req.cookies.testCookie)
return yield* app
}).pipe(
Effect.catchTag("CookieError", () =>
HttpServerResponse.text("Invalid cookie")
)
)
)
Update the app to use the cookieValidator
middleware:
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerRequest,
HttpServerResponse
} from "@effect/platform"
import { Effect } from "effect"
import { listen } from "./listen.js"
class CookieError {
readonly _tag = "CookieError"
}
const externallyValidateCookie = (testCookie: string | undefined) =>
testCookie && testCookie.length > 0
? Effect.succeed(testCookie)
: Effect.fail(new CookieError())
const cookieValidator = HttpMiddleware.make((app) =>
Effect.gen(function* () {
const req = yield* HttpServerRequest.HttpServerRequest
yield* externallyValidateCookie(req.cookies.testCookie)
return yield* app
}).pipe(
Effect.catchTag("CookieError", () =>
HttpServerResponse.text("Invalid cookie")
)
)
)
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("Hello World"))
)
const app = router.pipe(HttpRouter.use(cookieValidator), HttpServer.serve())
listen(app, 3000)
Test the middleware with the following commands:
curl -i http://localhost:3000
curl -i http://localhost:3000 --cookie "testCookie=myvalue"
curl -i http://localhost:3000 --cookie "testCookie="
This setup validates the testCookie
and returns "Invalid cookie" if the validation fails, or "Hello World" if it passes.
Middleware functions are powerful tools that allow you to modify the request-response cycle. Middlewares can be applied at various levels to achieve different scopes of influence:
At the route level, middlewares are applied to specific endpoints, allowing for targeted modifications or enhancements such as logging, authentication, or parameter validation for a particular route.
Example
Here's a practical example showing how to apply middleware at the route level:
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { Effect } from "effect"
import { listen } from "./listen.js"
// Middleware constructor that logs the name of the middleware
const withMiddleware = (name: string) =>
HttpMiddleware.make((app) =>
Effect.gen(function* () {
console.log(name) // Log the middleware name when the route is accessed
return yield* app // Continue with the original application flow
})
)
const router = HttpRouter.empty.pipe(
// Applying middleware to route "/a"
HttpRouter.get("/a", HttpServerResponse.text("a").pipe(withMiddleware("M1"))),
// Applying middleware to route "/b"
HttpRouter.get("/b", HttpServerResponse.text("b").pipe(withMiddleware("M2")))
)
const app = router.pipe(HttpServer.serve())
listen(app, 3000)
Testing the Middleware
You can test the middleware by making requests to the respective routes and observing the console output:
# Test route /a
curl -i http://localhost:3000/a
# Expected console output: M1
# Test route /b
curl -i http://localhost:3000/b
# Expected console output: M2
Applying middleware at the router level is an efficient way to manage common functionalities across multiple routes within your application. Middleware can handle tasks such as logging, authentication, and response modifications before reaching the actual route handlers.
Example
Here's how you can structure and apply middleware across different routers using the @effect/platform
library:
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { Effect } from "effect"
import { listen } from "./listen.js"
// Middleware constructor that logs the name of the middleware
const withMiddleware = (name: string) =>
HttpMiddleware.make((app) =>
Effect.gen(function* () {
console.log(name) // Log the middleware name when a route is accessed
return yield* app // Continue with the original application flow
})
)
// Define Router1 with specific routes
const router1 = HttpRouter.empty.pipe(
HttpRouter.get("/a", HttpServerResponse.text("a")), // Middleware M4, M3, M1 will apply
HttpRouter.get("/b", HttpServerResponse.text("b")), // Middleware M4, M3, M1 will apply
// Apply Middleware at the router level
HttpRouter.use(withMiddleware("M1")),
HttpRouter.get("/c", HttpServerResponse.text("c")) // Middleware M4, M3 will apply
)
// Define Router2 with specific routes
const router2 = HttpRouter.empty.pipe(
HttpRouter.get("/d", HttpServerResponse.text("d")), // Middleware M4, M2 will apply
HttpRouter.get("/e", HttpServerResponse.text("e")), // Middleware M4, M2 will apply
HttpRouter.get("/f", HttpServerResponse.text("f")), // Middleware M4, M2 will apply
// Apply Middleware at the router level
HttpRouter.use(withMiddleware("M2"))
)
// Main router combining Router1 and Router2
const router = HttpRouter.empty.pipe(
HttpRouter.mount("/r1", router1),
// Apply Middleware affecting all routes under /r1
HttpRouter.use(withMiddleware("M3")),
HttpRouter.get("/g", HttpServerResponse.text("g")), // Only Middleware M4 will apply
HttpRouter.mount("/r2", router2),
// Apply Middleware affecting all routes
HttpRouter.use(withMiddleware("M4"))
)
// Configure the application with the server middleware
const app = router.pipe(HttpServer.serve())
listen(app, 3000)
Testing the Middleware
To ensure that the middleware is working as expected, you can test it by making HTTP requests to the defined routes and checking the console output for middleware logs:
# Test route /a under router1
curl -i http://localhost:3000/r1/a
# Expected console output: M4 M3 M1
# Test route /c under router1
curl -i http://localhost:3000/r1/c
# Expected console output: M4 M3
# Test route /d under router2
curl -i http://localhost:3000/r2/d
# Expected console output: M4 M2
# Test route /g under the main router
curl -i http://localhost:3000/g
# Expected console output: M4
Applying middleware at the server level allows you to introduce certain functionalities, such as logging, authentication, or general request processing, that affect every request handled by the server. This ensures that all incoming requests, regardless of the route, pass through the applied middleware, making it an essential feature for global error handling, logging, or authentication.
Example
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { Effect } from "effect"
import { listen } from "./listen.js"
// Middleware constructor that logs the name of the middleware
const withMiddleware = (name: string) =>
HttpMiddleware.make((app) =>
Effect.gen(function* () {
console.log(name) // Log the middleware name when the route is accessed
return yield* app // Continue with the original application flow
})
)
const router = HttpRouter.empty.pipe(
HttpRouter.get("/a", HttpServerResponse.text("a").pipe(withMiddleware("M1"))),
HttpRouter.get("/b", HttpServerResponse.text("b")),
HttpRouter.use(withMiddleware("M2")),
HttpRouter.get("/", HttpServerResponse.text("root"))
)
const app = router.pipe(HttpServer.serve(withMiddleware("M3")))
listen(app, 3000)
Testing the Middleware
To confirm the middleware is functioning as intended, you can send HTTP requests to the defined routes and check the console for middleware logs:
# Test route /a and observe the middleware logs
curl -i http://localhost:3000/a
# Expected console output: M3 M2 M1 - Middleware M3 (server-level), M2 (router-level), and M1 (route-level) apply.
# Test route /b and observe the middleware logs
curl -i http://localhost:3000/b
# Expected console output: M3 M2 - Middleware M3 (server-level) and M2 (router-level) apply.
# Test route / and observe the middleware logs
curl -i http://localhost:3000/
# Expected console output: M3 M2 - Middleware M3 (server-level) and M2 (router-level) apply.
Middleware functions are simply functions that transform a Default
app into another Default
app. This flexibility allows for stacking multiple middleware functions, much like composing functions in functional programming. The flow
function from the Effect
library facilitates this by enabling function composition.
Example
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { Effect, flow } from "effect"
import { listen } from "./listen.js"
// Middleware constructor that logs the middleware's name when a route is accessed
const withMiddleware = (name: string) =>
HttpMiddleware.make((app) =>
Effect.gen(function* () {
console.log(name) // Log the middleware name
return yield* app // Continue with the original application flow
})
)
// Setup routes and apply multiple middlewares using flow for function composition
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/a",
HttpServerResponse.text("a").pipe(
flow(withMiddleware("M1"), withMiddleware("M2"))
)
),
HttpRouter.get("/b", HttpServerResponse.text("b")),
// Apply combined middlewares to the entire router
HttpRouter.use(flow(withMiddleware("M3"), withMiddleware("M4"))),
HttpRouter.get("/", HttpServerResponse.text("root"))
)
// Apply combined middlewares at the server level
const app = router.pipe(
HttpServer.serve(flow(withMiddleware("M5"), withMiddleware("M6")))
)
listen(app, 3000)
Testing the Middleware Composition
To verify that the middleware is functioning as expected, you can send HTTP requests to the routes and check the console for the expected middleware log output:
# Test route /a to see the output from multiple middleware layers
curl -i http://localhost:3000/a
# Expected console output: M6 M5 M4 M3 M2 M1
# Test route /b where fewer middleware are applied
curl -i http://localhost:3000/b
# Expected console output: M6 M5 M4 M3
# Test the root route to confirm top-level middleware application
curl -i http://localhost:3000/
# Expected console output: M6 M5
Middleware | Description |
---|---|
Logger | Provides detailed logging of all requests and responses, aiding in debugging and monitoring application activities. |
xForwardedHeaders | Manages X-Forwarded-* headers to accurately maintain client information such as IP addresses and host names in proxy scenarios. |
The HttpMiddleware.logger
middleware enables logging for your entire application, providing insights into each request and response. Here's how to set it up:
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { listen } from "./listen.js"
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("Hello World"))
)
// Apply the logger middleware globally
const app = router.pipe(HttpServer.serve(HttpMiddleware.logger))
listen(app, 3000)
/*
curl -i http://localhost:3000
timestamp=... level=INFO fiber=#0 message="Listening on http://0.0.0.0:3000"
timestamp=... level=INFO fiber=#19 message="Sent HTTP response" http.span.1=8ms http.status=200 http.method=GET http.url=/
timestamp=... level=INFO fiber=#20 cause="RouteNotFound: GET /favicon.ico not found
at ...
at http.server GET" http.span.2=4ms http.status=500 http.method=GET http.url=/favicon.ico
*/
To disable the logger for specific routes, you can use HttpMiddleware.withLoggerDisabled
:
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerResponse
} from "@effect/platform"
import { listen } from "./listen.js"
// Create the router with routes that will and will not have logging
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("Hello World")),
HttpRouter.get(
"/no-logger",
HttpServerResponse.text("no-logger").pipe(HttpMiddleware.withLoggerDisabled)
)
)
// Apply the logger middleware globally
const app = router.pipe(HttpServer.serve(HttpMiddleware.logger))
listen(app, 3000)
/*
curl -i http://localhost:3000/no-logger
timestamp=2024-05-19T09:53:29.877Z level=INFO fiber=#0 message="Listening on http://0.0.0.0:3000"
*/
This middleware handles X-Forwarded-*
headers, useful when your app is behind a reverse proxy or load balancer and you need to retrieve the original client's IP and host information.
import {
HttpMiddleware,
HttpRouter,
HttpServer,
HttpServerRequest,
HttpServerResponse
} from "@effect/platform"
import { Effect } from "effect"
import { listen } from "./listen.js"
// Create a router and a route that logs request headers and remote address
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/",
Effect.gen(function* () {
const req = yield* HttpServerRequest.HttpServerRequest
console.log(req.headers)
console.log(req.remoteAddress)
return yield* HttpServerResponse.text("Hello World")
})
)
)
// Set up the server with xForwardedHeaders middleware
const app = router.pipe(HttpServer.serve(HttpMiddleware.xForwardedHeaders))
listen(app, 3000)
/*
curl -H "X-Forwarded-Host: 192.168.1.1" -H "X-Forwarded-For: 192.168.1.1" http://localhost:3000
timestamp=... level=INFO fiber=#0 message="Listening on http://0.0.0.0:3000"
{
host: '192.168.1.1',
'user-agent': 'curl/8.6.0',
accept: '*\/*',
'x-forwarded-host': '192.168.1.1',
'x-forwarded-for': '192.168.1.1'
}
{ _id: 'Option', _tag: 'Some', value: '192.168.1.1' }
*/
Below is an example illustrating how to catch and manage errors that occur during the execution of route handlers:
import { HttpRouter, HttpServer, HttpServerResponse } from "@effect/platform"
import { Effect } from "effect"
import { listen } from "./listen.js"
// Define routes that might throw errors or fail
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/throw",
Effect.sync(() => {
throw new Error("BROKEN") // This will intentionally throw an error
})
),
HttpRouter.get("/fail", Effect.fail("Uh oh!")) // This will intentionally fail
)
// Configure the application to handle different types of errors
const app = router.pipe(
Effect.catchTags({
RouteNotFound: () =>
HttpServerResponse.text("Route Not Found", { status: 404 })
}),
Effect.catchAllCause((cause) =>
HttpServerResponse.text(cause.toString(), { status: 500 })
),
HttpServer.serve()
)
listen(app, 3000)
You can test the error handling setup with curl
commands by trying to access routes that trigger errors:
# Accessing a route that does not exist
curl -i http://localhost:3000/nonexistent
# Accessing the route that throws an error
curl -i http://localhost:3000/throw
# Accessing the route that fails
curl -i http://localhost:3000/fail
Validation is a critical aspect of handling HTTP requests to ensure that the data your server receives is as expected. We'll explore how to validate headers and cookies using the @effect/platform
and @effect/schema
libraries, which provide structured and robust methods for these tasks.
Headers often contain important information needed by your application, such as content types, authentication tokens, or session data. Validating these headers ensures that your application can trust and correctly process the information it receives.
import {
HttpRouter,
HttpServer,
HttpServerRequest,
HttpServerResponse
} from "@effect/platform"
import { Schema } from "@effect/schema"
import { Effect } from "effect"
import { listen } from "./listen.js"
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/",
Effect.gen(function* () {
// Define the schema for expected headers and validate them
const headers = yield* HttpServerRequest.schemaHeaders(
Schema.Struct({ test: Schema.String })
)
return yield* HttpServerResponse.text("header: " + headers.test)
}).pipe(
// Handle parsing errors
Effect.catchTag("ParseError", (e) =>
HttpServerResponse.text(`Invalid header: ${e.message}`)
)
)
)
)
const app = router.pipe(HttpServer.serve())
listen(app, 3000)
You can test header validation using the following curl
commands:
# Request without the required header
curl -i http://localhost:3000
# Request with the valid header
curl -i -H "test: myvalue" http://localhost:3000
Cookies are commonly used to maintain session state or user preferences. Validating cookies ensures that the data they carry is intact and as expected, enhancing security and application integrity.
Here's how you can validate cookies received in HTTP requests:
import {
Cookies,
HttpRouter,
HttpServer,
HttpServerRequest,
HttpServerResponse
} from "@effect/platform"
import { Schema } from "@effect/schema"
import { Effect } from "effect"
import { listen } from "./listen.js"
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/",
Effect.gen(function* () {
const cookies = yield* HttpServerRequest.schemaCookies(
Schema.Struct({ test: Schema.String })
)
return yield* HttpServerResponse.text("cookie: " + cookies.test)
}).pipe(
Effect.catchTag("ParseError", (e) =>
HttpServerResponse.text(`Invalid cookie: ${e.message}`)
)
)
)
)
const app = router.pipe(HttpServer.serve())
listen(app, 3000)
Validate the cookie handling with the following curl
commands:
# Request without any cookies
curl -i http://localhost:3000
# Request with the valid cookie
curl -i http://localhost:3000 --cookie "test=myvalue"
The native request object depends on the platform you are using, and it is not directly modeled in @effect/platform
. Instead, you need to refer to the specific platform package you are working with, such as @effect/platform-node
or @effect/platform-bun
.
Here is an example using Node.js:
import {
HttpRouter,
HttpServer,
HttpServerRequest,
HttpServerResponse
} from "@effect/platform"
import { NodeHttpServer, NodeHttpServerRequest } from "@effect/platform-node"
import { Effect } from "effect"
import { listen } from "./listen.js"
const router = HttpRouter.empty.pipe(
HttpRouter.get(
"/",
Effect.gen(function* () {
const req = yield* HttpServerRequest.HttpServerRequest
const raw = NodeHttpServerRequest.toIncomingMessage(req)
console.log(raw)
return HttpServerResponse.empty()
})
)
)
listen(HttpServer.serve(router), 3000)
The toWebHandler
function converts a Default
(i.e. a type of HttpApp
that specifically produces a ServerResponse
as its output) into a web handler that can process Request
objects and return Response
objects.
import { HttpApp, HttpRouter, HttpServerResponse } from "@effect/platform"
// Define the router with some routes
const router = HttpRouter.empty.pipe(
HttpRouter.get("/", HttpServerResponse.text("content 1")),
HttpRouter.get("/foo", HttpServerResponse.text("content 2"))
)
// Convert the router to a web handler
// const handler: (request: Request) => Promise<Response>
const handler = HttpApp.toWebHandler(router)
// Test the handler with a request
const response = await handler(new Request("http://localhost:3000/foo"))
console.log(await response.text()) // Output: content 2
FAQs
Unified interfaces for common platform-specific services
The npm package @effect/platform receives a total of 539,197 weekly downloads. As such, @effect/platform popularity was classified as popular.
We found that @effect/platform demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
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