Making HTTP Requests

HTTP functions are available in the spin_sdk::outbound_http module. The function is named send_request. It takes a spin_sdk::http::Request and returns a spin_sdk::http::Response. Both of these types are specializations of the Request and Response types from the http crate, and have all their behaviour and methods; the Spin SDK maps them to the underlying Wasm interface. For example:

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

let request = http::Request::builder()
    .method("POST")
    .uri("https://example.com/users")
    .body(Some(json_text.into()))?;

let response = spin_sdk::outbound_http::send_request(request)?;
println!("Status: {}", response.status().as_str());

Notes

• The Rust SDK surfaces the idiomatic http types rather than the raw Wasm interface types. For example, the method in Rust is a string, not an enum.
• Request and response bodies are of type Option<bytes::Bytes>.

You can find a complete example for using outbound HTTP in the Spin repository on GitHub.

HTTP operations are available via the standard JavaScript fetch function. The Spin runtime maps this to the underlying Wasm interface. For example:

const response = await fetch("https://example.com/users");

Notes

• Although the underlying Spin interface is blocking, the fetch function is defined by JavaScript as async. You must await the response, but the request will always block, and the promise will resolve as soon as the request is returned.

You can find a complete example of using outbound HTTP in the JavaScript SDK repository on GitHub (TypeScript, JavaScript).

HTTP functions and classes are available in the spin_http module. The function name is http_send. The request type is Request, and the response type is Response. For example:

from spin_http import Request, Response, http_send

response = http_send(
    Request("GET", "https://random-data-api.fermyon.app/animals/json", {}, None))

Notes

• For compatibility with idiomatic Python, types do not necessarily match the underlying Wasm interface. For example, method is a string.
• Request and response bodies are bytes. (You can pass literal strings using the b prefix.) Pass None for no body.
• Request and response headers are dictionaries.
• Errors are signalled through exceptions.

You can find a complete example for using outbound HTTP in the Python SDK repository on GitHub.

HTTP functions are available in the github.com/fermyon/spin/sdk/go/http package. See Go Packages for reference documentation.. The general function is named Send, but the Go SDK also surfaces individual functions, with request-specific parameters, for the Get and Post operations. For example:

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

res1, err1 := spinhttp.Get("https://random-data-api.fermyon.app/animals/json")
res2, err2 := spinhttp.Post("https://example.com/users", "application/json", json)

request, err := http.NewRequest("PUT", "https://example.com/users/1", bytes.NewBufferString(user1))
request.Header.Add("content-type", "application/json")
res3, err3 := spinhttp.Send(req)

Notes

• In the Post function, the body is an io.Reader. The Spin SDK reads this into the underlying Wasm byte array.
• The NewRequest function is part of the standard library. The Send method adapts the standard request type to the underlying Wasm interface.
• Errors are returned through the usual Go multiple return values mechanism.

You can find a complete example for using outbound HTTP in the Spin repository on GitHub.