Fluence Compute Engine

FCE is intended to run various Wasm binaries. At now, it is in the heavily developing phase.

Installation

• Clone this project
• cargo install --path <path-to-project/tools/cli>

Usage

• fce build in Rust project

HOW TO: Create App with FCE Modules

Recommendations:

• Modules architecture should be upwards from effectors (WASI modules) that will work with local binaries, local storage and syscalls to pure modules that perform business logic.
• Splitting app to small FCE modules are easier to support, reuse and distribute
• Each module for its own task (npm like)

Module project structure

• Init simple rust project cargo init --bin

• Config.toml:

[[bin]]
name = "wasm_application"
path = "src/main.rs"

[dependencies]
// logger - if you'll use logging
fluence = { git = "https://github.com/fluencelabs/rust-sdk", features = ["logger"] }

• Methods that will be used outside this module marked with #[fce]

use fluence::fce;

#[fce]
pub fn get(url: String) -> String {
...
}

• Multiple arguments with primitive Rust types and only one return argument could be used

• Build project with fce build

• Copy wasm file from target/wasm32-wasi/debug to directory with other modules

• To import other wasm modules to your project use similar code:

#[fce]
#[link(wasm_import_module = "wasm_curl.wasm")]
extern "C" {
    #[link_name = "get"]
    pub fn curl_get(url: String) -> String;
}

#[fce]
#[link(wasm_import_module = "wasm_local_storage.wasm")]
extern "C" {
    #[link_name = "get"]
    pub fn curl_get(url: String) -> String;
}

Combine modules to Application

• Create simple Rust project
• Create Config.toml to describe existed wasm modules and give accesses to host binaries and local storage if needed:

core_modules_dir = "wasm/artifacts/modules"

[[core_module]]
    name = "wasm_local_storage_with_curl.wasm"
    mem_pages_count = 100    

   [core_module.imports]
    curl = "/usr/bin/curl"

    [core_module.wasi]
    envs = []
    preopened_files = ["./wasm/artifacts"]
    mapped_dirs = { "tmp" = "./wasm/artifacts" }

core_modules_dir - path to directory with all modules. All subsequent paths will be relative to this path

[[core_module]] - modules list

name - wasm file name in core_modules_dir

mem_pages_count - a maximum number of Wasm memory pages that loaded module can use. Each Wasm pages is 65536 bytes long

[core_module.imports] - list of available imports

curl = "/usr/bin/curl" - gives possibility to call binary file /usr/bin/curl as method curl in Rust code

Import example:

#[link(wasm_import_module = "host")]
extern "C" {
    fn curl(ptr: i32, size: i32) -> i32;
}

It is not possible for now to use String as arguments. Use tweek for this:

fn call_curl(cmd: String) -> String {
    unsafe {
        // TODO: better error handling
        match curl(cmd.as_ptr() as _, cmd.len() as _) {
            0 => String::from_raw_parts(
                fluence::internal::get_result_ptr() as _,
                fluence::internal::get_result_size(),
                fluence::internal::get_result_size(),
            ),
            _ => "host ipfs call failed".to_string(),
        }
    }
}

Call binary with arguments: call_curl("-vvv ya.ru")

[core_module.wasi] - this block manages communication with the "outside" world env - environment variables. Usage: std::env::var("IPFS_ADDR") preopened_files - list of available directories for loaded modules mapped_dirs - mapping between paths

Working with files as usual:

fs::write(PathBuf::from("/tmp/somefile"), vec!(1,2,3));
fs::read(...);