Develop a Spin application

Prerequisites - Install the Spin CLI
Install Spin
Install the Prerequisites
- Install a Template
- Install the Tools
Create a New Spin Application From a Template
Run the Application
Next Steps

This article briefly describes how to create a new Spin application. For a more thorough guide to developing Spin applications, take a look here.

Prerequisites - Install the Spin CLI

Before developing a Spin application, you need to have the Spin CLI installed locally. Here’s a way to install the Spin CLI:

Install Spin

Download the spin binary 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 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.

Install the Prerequisites

Install a Template

The quickest and most convenient way to start a new application is to use a Spin template. Let’s install the templates for your preferred language.

$ 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.

Additional info

If you already have templates installed, you can update them by running spin templates install --git https://github.com/fermyon/spin --update.

Install the Tools

Some languages require additional tool support for Wasm.

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

$ rustup target add wasm32-wasi

Learn more in the language guide.

You’ll need the Spin js2wasm plugin:

$ spin plugins update
$ spin plugins install js2wasm --yes

Learn more in the language guide.

You’ll need the Spin py2wasm plugin:

$ spin plugins update
$ spin plugins install py2wasm --yes

Learn more in the language guide.

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

Learn more in the language guide.

Create a New Spin Application From a Template

Now you can create your very own application based on one of the templates you just installed. For this example, we’ll show how to create a HTTP application.

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 base: /
HTTP path: /...

This command created a directory with the necessary files needed to build and run a Rust Spin application. Here’s the spin.toml file, the manifest for a Spin application:

spin_manifest_version = "1"
authors = ["You <you@yourself.net>"]
description = "My first Rust Spin application"
name = "hello_rust"
trigger = { type = "http", base = "/" }
version = "0.1.0"

[[component]]
id = "hello-rust"
source = "target/wasm32-wasi/release/hello_rust.wasm"
allowed_http_hosts = []
[component.trigger]
route = "/..."
[component.build]
command = "cargo build --target wasm32-wasi --release"

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 base: /
HTTP path: /...

This command created a directory with the necessary files needed to build and run a TypeScript Spin application. Here’s the spin.toml file, the manifest for a Spin application:

spin_manifest_version = "1"
authors = ["You <you@yourself.net>"]
description = "My first TypeScript Spin application"
name = "hello_typescript"
trigger = { type = "http", base = "/" }
version = "0.1.0"

[[component]]
id = "hello-typescript"
source = "target/spin-http-js.wasm"
exclude_files = ["**/node_modules"]
[component.trigger]
route = "/..."
[component.build]
command = "npm run build"

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

$ spin new
Pick a template to start your application with:
> http-py (HTTP request handler using Python)
Enter a name for your new application: hello_python
Description: My first Python Spin application
HTTP base: /
HTTP path: /...

This command created a directory with the necessary files needed to build and run a Python Spin application. Here’s the spin.toml file, the manifest for a Spin application:

spin_manifest_version = "1"
authors = ["You <you@yourself.net>"]
description = "My first Python Spin application"
name = "hello_python"
trigger = { type = "http", base = "/" }
version = "0.1.0"

[[component]]
id = "hello-python"
source = "app.wasm"
[component.trigger]
route = "/..."
[component.build]
command = "spin py2wasm app -o app.wasm"

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 base: /
HTTP path: /...

This command created a directory with the necessary files needed to build and run a Go Spin application using the TinyGo compiler. Here’s the spin.toml file, the manifest for a Spin application:

spin_manifest_version = "1"
authors = ["You <you@yourself.net>"]
description = "My first Go Spin application"
name = "hello_go"
trigger = { type = "http", base = "/" }
version = "0.1.0"

[[component]]
id = "hello-go"
source = "main.wasm"
allowed_http_hosts = []
[component.trigger]
route = "/..."
[component.build]
command = "tinygo build -target=wasi -gc=leaking -no-debug -o main.wasm main.go"

Next, let’s build the app:

$ 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
Successfully ran the build command for the 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.

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

$ npm install

added 134 packages, and audited 135 packages in 2s

18 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 && mkdir -p target && spin js2wasm -o target/spin-http-js.wasm dist/spin.js

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
Successfully ran the build command for the Spin components.

If the build fails, check:

Are you in the hello_typescript directory?
Did you run npm install before building`?
Did you install the js2wasm plugin?

$ spin build
Executing the build command for component hello-python: spin py2wasm app -o app.wasm
Spin-compatible module built successfully
Successfully ran the build command for the Spin components.

If the build fails, check:

Are you in the hello_python directory?
Did you install the py2wasm plugin?

$ 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
Successfully ran the build command for the 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.

Run the Application

Now it’s time to spin up the application:

$ spin up
Serving http://127.0.0.1:3000
Available Routes:
  hello-rust: http://127.0.0.1:3000 (wildcard)

Additional info

Spin prints application output, and any Spin errors, to the console. To see additional diagnostic information, set the RUST_LOG environment variable for detailed logs, before running spin up, e.g., RUST_LOG=spin=debug spin up.

Spin will instantiate all components from the application manifest, and will create the router configuration for the HTTP trigger accordingly. The component can now be invoked by making requests to http://localhost:3000:

$ curl -i localhost:3000
HTTP/1.1 200 OK
foo: bar
content-length: 15

Hello, Fermyon

Next Steps

Learn how to deploy an application
To learn more about how to develop Spin applications, head over to the Spin documentation
Find known issues and file new ones with this GitHub repository