Getting started

Write and deploy Rust functions as web services

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The Second State FaaS service (currently in public beta) enables you to write Rust functions, and make them available as RESTful web services. Key features:

• Each Rust function is a RESTful endpoint

• Input arguments can be supplied via the HTTP request or from another URL

• Return values can be in the HTTP response body or redirected to another URL

• Stateful execution

• Finely-grained resource metering (based on Opscode)

• Much faster and lighter compared with Docker

• No-wait code start

• Access to native OS and system features

• Access to customized hardware (e.g., AI inference chips)

• Works across multiple clouds

Setup

First, let's install Rust and Node.js on the dev computer. Node.js is needed for our toolchain. If you have already done it, you can skip these steps.

# Prerequisite
$ sudo apt-get update
$ sudo apt install -y build-essential curl wget git vim libboost-all-dev

# Install rust
$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
$ source $HOME/.cargo/env

# Install nvm
$ curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
# Follow the on-screen instructions to logout and then log in

# Install node
$ nvm install v10.19.0
$ nvm use v10.19.0

The ssvmup npm module installs the Second State Virtual Machine (SSVM) into Node.js as a native addon, and provides the necessary compiler tools. Follow the steps below to install Rust and the ssvmup tool.

# Install ssvmup toolchain
$ npm install -g ssvmup # Append --unsafe-perm if permission denied

# Install the nodejs addon for SSVM
$ npm install ssvm

WebAssembly program in Rust

In this example, our Rust program appends the input string after “hello”. Let’s create a new cargo project. Since this program is intended to be called from a host application, not to run as a stand-alone executable, we will create a hello project.

$ cargo new --lib hello
$ cd hello

Edit the Cargo.toml file to add a [lib] section. It tells the compiler where to find the source code for the library and how to generate the bytecode output. We also need to add a dependency of wasm-bindgen here. It is the utility ssvmup uses to generate the JavaScript binding for the Rust WebAssembly program, which is required by the FaaS runtime.

[lib]
name = "hello_lib"
path = "src/lib.rs"
crate-type =["cdylib"]

[dependencies]
wasm-bindgen = "=0.2.61"

Below is the content of the Rust program src/lib.rs. You can see that it takes two input parameters. Let's not worry about the context at this moment. The function parameter s comes from the HTTP request when a user calls this function over the web.

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn say(context: &str, s: &str) -> String {
  let r = String::from("hello ");
  return r + &s;
}

Next, you can compile the Rust source code into WebAssembly bytecode.

$ ssvmup build --nowasi

The result are files in the pkg/ directory. the .wasm file is the WebAssembly bytecode program.

Upload the wasm file to FaaS

Use the following curl command to upload the wasm file to the FaaS service. In the beta stage, it is all FREE!

$ curl --location --request POST 'https://rpc.ssvm.secondstate.io:8081/api/executables' \
--header 'Content-Type: application/octet-stream' \
--header 'SSVM_Description: say hello' \
--data-binary 'pkg/hello_lib_bg.wasm'

It returns an ID for the wasm file in the FaaS system.

{"wasm_id":123}

Run the function

Use the following curl command to run the say() function in the wasm program. The argument s for this function call is passed in as a string in the HTTP request body.

$ curl --location --request POST 'https://rpc.ssvm.secondstate.io:8081/api/run/123/say' \
--header 'Content-Type: text/plain' \
--data-raw 'Second State FaaS'

The HTTP response body is as follows.

hello Second State FaaS

What's next

In the next article, we will learn how to give the Rust function a persistence context to customize its runtime behavior. That is where the first function parameter context comes into play.