Taking Spin for a spin

Download the spin binary along with a starter set of templates and plugins using the install.sh script hosted on this site:

$ curl -fsSL https://developer.fermyon.com/downloads/install.sh | bash

Then move the spin binary somewhere in your path, so you can run it from anywhere. For example:

$ sudo mv ./spin /usr/local/bin/spin

Download the spin binary along with a starter set of templates and plugins using the install.sh script hosted on this site:

$ curl -fsSL https://developer.fermyon.com/downloads/install.sh | bash

Then move the spin binary somewhere in your path, so you can run it from anywhere. For example:

$ sudo mv ./spin /usr/local/bin/spin

Download the Windows binary release of Spin from GitHub.

Unzip the binary release and place the spin.exe in your system path.

$ spin templates install --git https://github.com/fermyon/spin --update
Copying remote template source
Installing template redis-rust...
Installing template http-rust...
... other templates omitted ...
+------------------------------------------------------------------------+
| Name                Description                                        |
+========================================================================+
| ... other templates omitted ...                                        |
| http-rust           HTTP request handler using Rust                    |
| redis-rust          Redis message handler using Rust                   |
| ... other templates omitted ...                                        |
+------------------------------------------------------------------------+

Note: The Rust templates are in a repo that contains several other languages; they will all be installed together.

$ spin templates install --git https://github.com/fermyon/spin-js-sdk --update
Copying remote template source
Installing template http-js...
Installing template http-ts...
+------------------------------------------------------------------------+
| Name                Description                                        |
+========================================================================+
| http-js             HTTP request handler using Javascript              |
| http-ts             HTTP request handler using Typescript              |
+------------------------------------------------------------------------+

$ spin templates install --git https://github.com/fermyon/spin-python-sdk --update
Copying remote template source
Installing template http-py...
+---------------------------------------------+
| Name      Description                       |
+=============================================+
| http-py   HTTP request handler using Python |
+---------------------------------------------+

$ spin templates install --git https://github.com/fermyon/spin --update
Copying remote template source
Installing template redis-go...
Installing template http-go...
+------------------------------------------------------------------------+
| Name                Description                                        |
+========================================================================+
| ... other templates omitted ...                                        |
| http-go             HTTP request handler using (Tiny)Go                |
| redis-go            Redis message handler using (Tiny)Go               |
| ... other templates omitted ...                                        |
+------------------------------------------------------------------------+

Note: The Go templates are in a repo that contains several other languages; they will all be installed together.

You’ll need the wasm32-wasi target for Rust:

$ rustup target add wasm32-wasi

Learn more in the language guide.

You will need npm installed and on the path. npm will install any additional build tools as part of building the application.

Learn more in the language guide.

Ensure that you have Python 3.10 or later installed on your system. You can check your Python version by running:

python3 --version

If you do not have Python 3.10 or later, you can install it by following the instructions here.

You’ll install all the required Python tools as part of building the application. We’ll cover that in the Build Your Application section below. For now, there’s nothing to do here!

Learn more in the language guide.

You’ll need the TinyGo compiler, as the standard Go compiler does not yet support WASI exports. See the TinyGo installation guide.

Learn more in the language guide.

Use the spin new command and the http-rust template to scaffold a new Spin application:

$ spin new
Pick a template to start your application with:
  http-c (HTTP request handler using C and the Zig toolchain)
  http-csharp (HTTP request handler using C# (EXPERIMENTAL))
  http-go (HTTP request handler using (Tiny)Go)
  http-grain (HTTP request handler using Grain)
> http-rust (HTTP request handler using Rust)
  http-swift (HTTP request handler using SwiftWasm)
  http-zig (HTTP request handler using Zig)
  redis-go (Redis message handler using (Tiny)Go)
  redis-rust (Redis message handler using Rust)

Enter a name for your new application: hello_rust
Project description: My first Rust Spin application
HTTP path: /...

This command created a directory with the necessary files needed to build and run a Rust Spin application. Change to that directory, and look at the files. It looks very much like a normal Rust library project:

$ cd hello_rust
$ tree
.
├── .gitignore
├── Cargo.toml
├── spin.toml
└── src
    └── lib.rs

The additional spin.toml file is the manifest file, which tells Spin what events should trigger what components. In this case our trigger is HTTP, for a Web application, and we have only one component, at the route /.... This is a wildcard that matches any route:

spin_manifest_version = 2

[application]
name = "hello_rust"
version = "0.1.0"
authors = ["Your Name <your-name@example.com>"]
description = "My first Rust Spin application"

[[trigger.http]]
route = "/..."
component = "hello-rust"

[component.hello-rust]
source = "target/wasm32-wasi/release/hello_rust.wasm"
allowed_outbound_hosts = []
[component.hello-rust.build]
command = "cargo build --target wasm32-wasi --release"
watch = ["src/**/*.rs", "Cargo.toml"]

This represents a simple Spin HTTP application (triggered by an HTTP request). It has:

• A single HTTP trigger, for the /... route, associated with the hello-rust component. /... is a wildcard, meaning it will match any route. When the application gets an HTTP request that matches this route - that is, any HTTP request at all! - Spin will run the hello-rust component.
• A single component called hello-rust, whose implementation is in the associated hello_rust.wasm WebAssembly component. When, in response to the HTTP trigger, Spin runs this component, it will execute the HTTP handler in hello_rust.wasm. (We’re about to see the source code for that.)

Learn more about the manifest here.

Now let’s have a look at the code. Below is the complete source code for a Spin HTTP component written in Rust — a regular Rust function that takes an HTTP request as a parameter and returns an HTTP response, and it is annotated with the http_component macro which identifies it as the entry point for HTTP requests:

use spin_sdk::http::{IntoResponse, Request, Response};
use spin_sdk::http_component;

/// A simple Spin HTTP component.
#[http_component]
fn handle_hello_rust(req: Request) -> anyhow::Result<impl IntoResponse> {
    println!("Handling request to {:?}", req.header("spin-full-url"));
    Ok(Response::builder()
        .status(200)
        .header("content-type", "text/plain")
        .body("Hello, Fermyon")
        .build())
}

Use the spin new command and the http-ts template to scaffold a new Spin application. (If you prefer JavaScript to TypeScript, the http-js template is very similar.):

$ spin new
Pick a template to start your application with:
  http-js (HTTP request handler using Javascript)
> http-ts (HTTP request handler using Typescript)
Enter a name for your new application: hello_typescript
Project description: My first TypeScript Spin application
HTTP path: /...

This command created a directory with the necessary files needed to build and run a TypeScript Spin application. Change to that directory, and look at the files. It looks similar to a lot of NPM projects:

$ cd hello_typescript
$ tree
.
├── package.json
├── README.md
├── spin.toml
├── src
│   └── index.ts
├── tsconfig.json
└── webpack.config.js

The additional spin.toml file is the manifest file, which tells Spin what events should trigger what components. In this case our trigger is HTTP, for a Web application, and we have only one component, at the route /.... This is a wildcard that matches any route:

spin_manifest_version = 2

[application]
name = "hello_typescript"
version = "0.1.0"
authors = ["Your Name <your-name@example.com>"]
description = "My first TypeScript Spin application"

[[trigger.http]]
route = "/..."
component = "hello-typescript"

[component.hello-typescript]
source = "target/hello-typescript.wasm"
exclude_files = ["**/node_modules"]
[component.hello-typescript.build]
command = "npm run build"

This represents a simple Spin HTTP application (triggered by an HTTP request). It has:

• A single HTTP trigger, for the /... route, associated with the hello-typescript component. /... is a wildcard, meaning it will match any route. When the application gets an HTTP request that matches this route - that is, any HTTP request at all! - Spin will run the hello-typescript component.
• A single component called hello-typescript, whose implementation is in the associated hello-typescript.wasm WebAssembly component. When, in response to the HTTP trigger, Spin runs this component, it will execute the HTTP handler in hello-typescript.wasm. (We’re about to see the source code for that.)

Learn more about the manifest here.

Now let’s have a look at the code. Below is the complete source code for a Spin HTTP component written in TypeScript — a regular function named handleRequest that takes an HTTP request as a parameter and returns an HTTP response. (The JavaScript version looks slightly different, but is still a function with the same signature.) The Spin integration looks for the handler function by name when building your application into a Wasm module:

import { ResponseBuilder } from "@fermyon/spin-sdk";

export async function handler(req: Request, res: ResponseBuilder) {
    console.log(req);
    res.send("hello universe");
}

You can install the Spin template for Python HTTP handlers from the spin-python-sdk repository using the following command:

$ spin templates install --git https://github.com/fermyon/spin-python-sdk --update

The above command will install the http-py template and produce an output similar to the following:

Copying remote template source
Installing template http-py...
Installed 1 template(s)

+---------------------------------------------+
| Name      Description                       |
+=============================================+
| http-py   HTTP request handler using Python |
+---------------------------------------------+

Please note: For more information about managing Spin templates, see the templates guide.

This command created a directory with the necessary files needed to build and run a Python Spin application. Change to that directory, and look at the files. It contains a minimal Python application:

$ spin new -t http-py hello-python --accept-defaults

Once the component is created, we can change into the hello-python directory, create and activate a virtual environment and then install the component’s requirements:

$ cd hello-python

Create a virtual environment directory (we are still inside the Spin app directory):

# python<version> -m venv <virtual-environment-name>
$ python3 -m venv venv-dir

Activate the virtual environment (this command depends on which operating system you are using):

# macOS & Linux command to activate
$ source venv-dir/bin/activate

If you are using Windows, use the following commands:

C:\Work> python3 -m venv venv
C:\Work> venv\Scripts\activate

The (venv-dir) will prefix your terminal prompt now:

(venv-dir) user@123-456-7-8 hello-python %

The requirements.txt, by default, contains the references to the spin-sdk and componentize-py packages. These can be installed in your virtual environment using the following command:

$ pip3 install -r requirements.txt 
Collecting spin-sdk==3.1.0 (from -r requirements.txt (line 1))
  Using cached spin_sdk-3.1.0-py3-none-any.whl.metadata (16 kB)
Collecting componentize-py==0.13.3 (from -r requirements.txt (line 2))
  Using cached componentize_py-0.13.3-cp37-abi3-macosx_10_12_x86_64.whl.metadata (3.4 kB)
Using cached spin_sdk-3.1.0-py3-none-any.whl (94 kB)
Using cached componentize_py-0.13.3-cp37-abi3-macosx_10_12_x86_64.whl (38.8 MB)
Installing collected packages: spin-sdk, componentize-py
Successfully installed componentize-py-0.13.3 spin-sdk-3.1.0

Structure of a Python Component

The hello-python directory structure created by the Spin http-py template is shown below:

├── app.py
├── spin.toml
└── requirements.txt 

The additional spin.toml file is the manifest file, which tells Spin what events should trigger what components. In this case our trigger is HTTP, for a Web application, and we have only one component, at the route /.... This is a wildcard that matches any route.

spin_manifest_version = 2

[application]
name = "hello-python"
version = "0.1.0"
authors = ["Your Name <your-name@example.com>"]
description = "My first Python Spin application"

[[trigger.http]]
route = "/..."
component = "hello-python"

[component.hello-python]
source = "app.wasm"
[component.hello-python.build]
command = "componentize-py -w spin-http componentize app -o app.wasm"

This represents a simple Spin HTTP application (triggered by an HTTP request). It has:

• A single HTTP trigger, for the /... route, associated with the hello-python component. /... is a wildcard, meaning it will match any route. When the application gets an HTTP request that matches this route - that is, any HTTP request at all! - Spin will run the hello-python component.
• A single component called hello-python, whose implementation is in the associated app.wasm WebAssembly component. When, in response to the HTTP trigger, Spin runs this component, it will execute the HTTP handler in app.wasm. (We’re about to see the source code for that.)

Learn more about the manifest here.

Now let’s have a look at the code. Below is the complete source code for a Spin HTTP component written in Python — a regular function named handle_request that takes an HTTP request as a parameter and returns an HTTP response.

from spin_sdk.http import IncomingHandler, Request, Response

class IncomingHandler(IncomingHandler):
    def handle_request(self, request: Request) -> Response:
        return Response(
            200,
            {"content-type": "text/plain"},
            bytes("Hello from the Python SDK!", "utf-8")
        )

Use the spin new command and the http-go template to scaffold a new Spin application.

$ spin new
Pick a template to start your application with:
  http-c (HTTP request handler using C and the Zig toolchain)
  http-empty (HTTP application with no components)
> http-go (HTTP request handler using (Tiny)Go)
  http-grain (HTTP request handler using Grain)
  http-php (HTTP request handler using PHP)
  http-rust (HTTP request handler using Rust)
Enter a name for your new application: hello_go
Description: My first Go Spin application
HTTP path: /...

This command created a directory with the necessary files needed to build and run a Go Spin application using the TinyGo compiler. Change to that directory, and look at the files. It looks very much like a normal Go project:

$ cd hello_go
$ tree
.
├── go.mod
├── go.sum
├── main.go
└── spin.toml

The additional spin.toml file is the manifest file, which tells Spin what events should trigger what components. In this case our trigger is HTTP, for a Web application, and we have only one component, at the route /.... This is a wildcard that matches any route.

spin_manifest_version = 2

[application]
name = "hello_go"
version = "0.1.0"
authors = ["Your Name <your-name@example.com>"]
description = "My first Go Spin application"

[[trigger.http]]
route = "/..."
component = "hello-go"

[component.hello-go]
source = "main.wasm"
allowed_outbound_hosts = []
[component.hello-go.build]
command = "tinygo build -target=wasi -gc=leaking -no-debug -o main.wasm main.go"

This represents a simple Spin HTTP application (triggered by an HTTP request). It has:

• A single HTTP trigger, for the /... route, associated with the hello-go component. /... is a wildcard, meaning it will match any route. When the application gets an HTTP request that matches this route - that is, any HTTP request at all! - Spin will run the hello-go component.
• A single component called hello-go, whose implementation is in the associated main.wasm WebAssembly component. When, in response to the HTTP trigger, Spin runs this component, it will execute the HTTP handler in main.wasm. (We’re about to see the source code for that.)

Learn more about the manifest here.

Now let’s have a look at the code. Below is the complete source code for a Spin HTTP component written in Go. Notice where the work is done. The main function is empty (and Spin never calls it). Instead, the init function sets up a callback, and passes that callback to spinhttp.Handle to register it as the handler for HTTP requests. You can learn more about this structure in the Go language guide.

package main

import (
        "fmt"
        "net/http"

        spinhttp "github.com/fermyon/spin/sdk/go/v2/http"
)

func init() {
        spinhttp.Handle(func(w http.ResponseWriter, r *http.Request) {
                w.Header().Set("Content-Type", "text/plain")
                fmt.Fprintln(w, "Hello Fermyon!")
        })
}

func main() {}

$ spin build
Executing the build command for component hello-rust: cargo build --target wasm32-wasi --release
    Updating crates.io index
    Updating git repository `https://github.com/fermyon/spin`
    Updating git repository `https://github.com/bytecodealliance/wit-bindgen`
   Compiling anyhow v1.0.69
   Compiling version_check v0.9.4
   # ...
   Compiling spin-sdk v0.10.0 
   Compiling hello-rust v0.1.0 (/home/ivan/testing/start/hello_rust)
    Finished release [optimized] target(s) in 11.94s
Finished building all Spin components

If the build fails, check:

• Are you in the hello_rust directory?
• Did you successfully install the wasm32-wasi target?
• Is your version of Rust up to date (cargo --version)? The Spin SDK needs Rust 1.64 or above.

If you would like to know what build command Spin runs for a component, you can find it in the manifest, in the component.(id).build section:

[component.hello-rust.build]
command = "cargo build --target wasm32-wasi --release"

You can always run this command manually; spin build is a shortcut to save you having to remember it.

As normal for NPM projects, before you build for the first time, you must run npm install:

$ npm install

added 141 packages, and audited 142 packages in 13s

20 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities

Then run spin build:

$ spin build
Executing the build command for component hello-typescript: npm run build

> hello-typescript@1.0.0 build
> npx webpack --mode=production && npx mkdirp target && npx j2w -i dist.js -d combined-wit -n combined -o target/hello-typescript.wasm

asset spin.js 4.57 KiB [emitted] (name: main)
runtime modules 670 bytes 3 modules
./src/index.ts 2.85 KiB [built] [code generated]
webpack 5.75.0 compiled successfully in 1026 ms

Starting to build Spin compatible module
Preinitiating using Wizer
Optimizing wasm binary using wasm-opt
Spin compatible module built successfully
Finished building all Spin components

If the build fails, check:

• Are you in the hello_typescript directory?
• Did you run npm install before building`?

If you would like to know what build command Spin runs for a component, you can find it in the manifest, in the component.(id).build section:

[component.hello-typescript.build]
command = "npm run build"

You can always run this command manually; spin build is a shortcut.

As a standard practice for Python, create and activate a virtual env:

If you are on a Mac/linux based operating system use the following commands:

$ python3 -m venv venv
$ source venv/bin/activate

If you are using Windows, use the following commands:

C:\Work> python3 -m venv venv
C:\Work> venv\Scripts\activate

Install componentize-py and spin-sdk packages

$ pip3 install -r requirements.txt

Then run:

$ spin build
Executing the build command for component hello-python: "componentize-py -w spin-http componentize app -o app.wasm"
Finished building all Spin components

If the build fails, check:

• Are you in the hello-python directory?
• Did you install the requirements?
• Is your virtual environment still activated?

If you would like to know what build command Spin runs for a component, you can find it in the manifest, in the component.(id).build section:

[component.hello-python.build]
command = "componentize-py -w spin-http componentize app -o app.wasm"

You can always run this command manually; spin build is a shortcut.

$ spin build
Executing the build command for component hello-go: tinygo build -target=wasi -gc=leaking -no-debug -o main.wasm main.go
go: downloading github.com/fermyon/spin/sdk/go v0.10.0
Finished building all Spin components

If the build fails, check:

• Are you in the hello_go directory?
• Did you successfully install TinyGo?
• Are your versions of Go and TinyGo up to date? The Spin SDK needs TinyGo 0.27 or above.
• Set Environment Variable CGO_ENABLED=1. (Since the Go SDK is built using CGO, it requires the CGO_ENABLED=1 environment variable to be set.)

If you would like to know what build command Spin runs for a component, you can find it in the manifest, in the component.(id).build section:

[component.hello-go.build]
command = "tinygo build -target=wasi -gc=leaking -no-debug -o main.wasm main.go"

You can always run this command manually; spin build is a shortcut to save you having to remember it.