Marine Rust SDK

The marine-rs-sdk empowers developers to write services suitable for peer hosting in peer-to-peer networks using the Marine Virtual Machine by enabling the wasm32-wasi compile target for Marine. For an introduction to writing services with the marine-rs-sdk, see the Developing Modules And Services section.

API

The procedural macros [marine] and [marine_test] are the two primary features provided by the SDK. The [marine] macro can be applied to a function, external block or structure. The [marine_test] macro, on the other hand, allows the use of the familiar cargo test to execute tests over the actual Wasm module generated from the service code.

Function Export

Applying the [marine] macro to a function results in its export, which means that it can be called from other modules or AIR scripts. For the function to be compatible with this macro, its arguments must be of the ftype, which is defined as follows:

ftype = bool, u8, u16, u32, u64, i8, i16, i32, i64, f32, f64, String ftype = ftype | Vec<ftype> ftype = ftype | Record<ftype>

In other words, the arguments must be one of the types listed below:

  • one of the following Rust basic types: bool, u8, u16, u32, u64, i8, i16, i32, i64, f32, f64, String

  • a vector of elements of the above types

  • a vector composed of vectors of the above type, where recursion is acceptable, e.g. the type Vec<Vec<Vec<u8>>> is permissible

  • a record, where all fields are of the basic Rust types

  • a record, where all fields are of any above types or other records

The return type of a function must follow the same rules, but currently only one return type is possible.

See the example below of an exposed function with a complex type signature and return value:

// export TestRecord as a public data structure bound by
// the IT type constraints
#[marine]
pub struct TestRecord {
pub field_0: i32,
pub field_1: Vec<Vec<u8>>,
}
// export foo as a public function bound by the
// IT type contraints
#[marine] #
pub fn foo(arg_1: Vec<Vec<Vec<Vec<TestRecord>>>>, arg_2: String) -> Vec<Vec<Vec<Vec<TestRecord>>>> {
unimplemented!()
}

Function Export Requirements

  • wrap a target function with the [marine] macro

  • function arguments must by of ftype

  • the function return type also must be of ftype

Function Import

The [marine] macro can also wrap an extern block. In this case, all functions declared in it are considered imported functions. If there are imported functions in some module, say, module A, then:

  • There should be another module, module B, that exports the same functions. The name of module B is indicated in the link macro (see examples below).

  • Module B should be loaded to Marine by the moment the loading of module A starts. Module A cannot be loaded if at least one imported function is absent in Marine.

See the examples below for wrapped extern block usage:

Example 1
Example 2
Example 1
#[marine]
pub struct TestRecord {
pub field_0: i32,
pub field_1: Vec<Vec<u8>>,
}
// wrap the extern block with the marine macro to expose the function
// as an import to the Marine VM
#[marine]
#[link(wasm_import_module = "some_module")]
extern "C" {
pub fn foo(arg: Vec<Vec<Vec<Vec<TestRecord>>>>, arg_2: String) -> Vec<Vec<Vec<Vec<TestRecord>>>>;
}
Example 2
[marine]
#[link(wasm_import_module = "some_module")]
extern "C" {
pub fn foo(arg: Vec<Vec<Vec<Vec<u8>>>>) -> Vec<Vec<Vec<Vec<u8>>>>;
}

Function import requirements

  • wrap an extern block with the function(s) to be imported with the [marine] macro

  • all function(s) arguments must be of the ftype type

  • the return type of the function(s) must be ftype

Structures

Finally, the [marine] macro can wrap a struct making possible to use it as a function argument or return type. Note that

  • only macro-wrapped structures can be used as function arguments and return types

  • all fields of the wrapped structure must be public and of the ftype.

  • it is possible to have inner records in the macro-wrapped structure and to import wrapped structs from other crates

See the example below for wrapping struct:

Example 1
Example 2
Example 3
Example 1
#[marine]
pub struct TestRecord0 {
pub field_0: i32,
}
#[marine]
pub struct TestRecord1 {
pub field_0: i32,
pub field_1: String,
pub field_2: Vec<u8>,
pub test_record_0: TestRecord0,
}
#[marine]
pub struct TestRecord2 {
pub test_record_0: TestRecord0,
pub test_record_1: TestRecord1,
}
#[marine]
fn foo(mut test_record: TestRecord2) -> TestRecord2 { unimplemented!(); }
Example 2
#[fce]
pub struct TestRecord0 {
pub field_0: i32,
}
#[fce]
pub struct TestRecord1 {
pub field_0: i32,
pub field_1: String,
pub field_2: Vec<u8>,
pub test_record_0: TestRecord0,
}
#[fce]
pub struct TestRecord2 {
pub test_record_0: TestRecord0,
pub test_record_1: TestRecord1,
}
#[fce]
#[link(wasm_import_module = "some_module")]
extern "C" {
fn foo(mut test_record: TestRecord2) -> TestRecord2;
}
Example 3
mod data_crate {
use fluence::marine;
#[marine]
pub struct Data {
pub name: String,
pub data: f64,
}
}
use data_crate::Data;
use fluence::marine;
fn main() {}
#[marine]
fn some_function() -> Data {
Data {
name: "example".into(),
data: 1.0,
}
}

Structure passing requirements

  • wrap a structure with the [marine] macro

  • all structure fields must be of the ftype

  • the structure must be pointed to without preceding package import in a function signature, i.eStructureName but not package_name::module_name::StructureName

  • wrapped structs can be imported from crates

Call Parameters

There is a special API function fluence::get_call_parameters() that returns an instance of the CallParameters structure defined as follows:

pub struct CallParameters {
/// Peer id of the AIR script initiator.
pub init_peer_id: String,
/// Id of the current service.
pub service_id: String,
/// Id of the service creator.
pub service_creator_peer_id: String,
/// Id of the host which run this service.
pub host_id: String,
/// Id of the particle which execution resulted a call this service.
pub particle_id: String,
/// Security tetraplets which described origin of the arguments.
pub tetraplets: Vec<Vec<SecurityTetraplet>>,
}

CallParameters are especially useful in constructing authentication services:

// auth.rs
use fluence::{marine, CallParameters};
use::marine;
pub fn is_owner() -> bool {
let meta = marine::get_call_parameters();
let caller = meta.init_peer_id;
let owner = meta.service_creator_peer_id;
caller == owner
}
#[marine]
pub fn am_i_owner() -> bool {
is_owner()
}

MountedBinaryResult

Due to the inherent limitations of Wasm modules, such as a lack of sockets, it may be necessary for a module to interact with its host to bridge such gaps, e.g. use a https transport provider like curl. In order for a Wasm module to use a host's curl capabilities, we need to provide access to the binary, which at the code level is achieved through the Rust extern block:

// Importing a linked binary, curl, to a Wasm module
#![allow(improper_ctypes)]
use fluence::marine;
use fluence::module_manifest;
use fluence::MountedBinaryResult;
module_manifest!();
pub fn main() {}
#[marine]
pub fn curl_request(curl_cmd: Vec<String>) -> MountedBinaryResult {
let response = curl(curl_cmd);
response
}
#[marine]
#[link(wasm_import_module = "host")]
extern "C" {
fn curl(cmd: Vec<String>) -> MountedBinaryResult;
}

The above code creates a "curl adapter", i.e., a Wasm module that allows other Wasm modules to use the the curl_request function, which calls the imported curl binary in this case, to make http calls. Please note that we are wrapping the extern block with the [marine]macro and introduce a Marine-native data structure MountedBinaryResult as the linked-function return value.

Please not that if you want to use curl_request with testing, see below, the curl call needs to be marked unsafe, e.g.:

let response = unsafe { curl(curl_cmd) };

since cargo does not access to the marine macro to handle unsafe.

MountedBinaryResult itself is a Marine-compatible struct containing a binary's return process code, error string and stdout and stderr as byte arrays:

#[marine]
#[derive(Clone, PartialEq, Default, Eq, Debug, Serialize, Deserialize)]
pub struct MountedBinaryResult {
/// Return process exit code or host execution error code, where SUCCESS_CODE means success.
pub ret_code: i32,
/// Contains the string representation of an error, if ret_code != SUCCESS_CODE.
pub error: String,
/// The data that the process wrote to stdout.
pub stdout: Vec<u8>,
/// The data that the process wrote to stderr.
pub stderr: Vec<u8>,
}

MountedBinaryResult then can be used on a variety of match or conditional tests.

Testing

Since we are compiling to a wasm32-wasi target with ftype constrains, the basic cargo test is not all that useful or even usable for our purposes. To alleviate that limitation, Fluence has introduced the [marine-test] macro that does a lot of the heavy lifting to allow developers to use cargo test as intended. That is, [marine-test] macro generates the necessary code to call Marine, one instance per test function, based on the Wasm module and associated configuration file so that the actual test function is run against the Wasm module not the native code.

Let's have a look at an implementation example:

use fluence::marine;
use fluence::module_manifest;
module_manifest!();
pub fn main() {}
#[marine]
pub fn greeting(name: String) -> String { # 1
format!("Hi, {}", name)
}
#[cfg(test)]
mod tests {
use fluence_test::marine_test; # 2
#[marine_test(config_path = "../Config.toml", modules_dir = "../artifacts")] # 3
fn empty_string() {
let actual = greeting.greeting(String::new()); # 4
assert_eq!(actual, "Hi, ");
}
#[marine_test(config_path = "../Config.toml", modules_dir = "../artifacts")]
fn non_empty_string() {
let actual = greeting.greeting("name".to_string());
assert_eq!(actual, "Hi, name");
}
}
  1. We wrap a basic greeting function with the [marine] macro which results in the greeting.wasm module

  2. We wrap our tests as usual with [cfg(test)] and import the fluencetest crate. Do not import super or the local crate.

  3. Instead, we apply the [marine_test] to each of the test functions by providing the path to the config file, e.g., Config.toml, and the directory containing the Wasm module we obtained after compiling our project with marine build. It is imperative that project compilation proceeds the test runner otherwise there won't be the required Wasm file.

  4. The target of our tests is the pub fn greeting function. Since we are calling the function from the Wasm module we must prefix the function name with the module namespace -- greeting in this example case.

Now that we have our Wasm module and tests in place, we can proceed with cargo test --release. Note that using the releasevastly improves the import speed of the necessary Wasm modules.

Features

The SDK has two useful features: logger and debug.

Logger

Using logging is a simple way to assist in debugging without deploying the module(s) to a peer-to-peer network node. The logger feature allows you to use a special logger that is based at the top of the log crate.

To enable logging please specify the logger feature of the Fluence SDK in Config.toml and add the log crate:

[dependencies]
log = "0.4.14"
fluence = { version = "0.6.9", features = ["logger"] }

The logger should be initialized before its usage. This can be done in the main function as shown in the example below.

use fluence::marine;
use fluence::WasmLogger;
pub fn main() {
WasmLogger::new()
// with_log_level can be skipped,
// logger will be initialized with Info level in this case.
.with_log_level(log::Level::Info)
.build()
.unwrap();
}
#[marine]
pub fn put(name: String, file_content: Vec<u8>) -> String {
log::info!("put called with file name {}", file_name);
unimplemented!()
}

In addition to the standard log creation features, the Fluence logger allows the so-called target map to be configured during the initialization step. This allows you to filter out logs by logging_mask, which can be set for each module in the service configuration. Let's consider an example:

const TARGET_MAP: [(&str, i64); 4] = [
("instruction", 1 << 1),
("data_cache", 1 << 2),
("next_peer_pks", 1 << 3),
("subtree_complete", 1 << 4),
];
pub fn main() {
use std::collections::HashMap;
use std::iter::FromIterator;
let target_map = HashMap::from_iter(TARGET_MAP.iter().cloned());
fluence::WasmLogger::new()
.with_target_map(target_map)
.build()
.unwrap();
}
#[marine]
pub fn foo() {
log::info!(target: "instruction", "this will print if (logging_mask & 1) != 0");
log::info!(target: "data_cache", "this will print if (logging_mask & 2) != 0");
}

Here, an array called TARGET_MAP is defined and provided to a logger in the main function of a module. Each entry of this array contains a string (a target) and a number that represents the bit position in the 64-bit mask logging_mask. When you write a log message request log::info!, its target must coincide with one of the strings (the targets) defined in the TARGET_MAP array. The log will be printed if logging_mask for the module has the corresponding target bit set.

REPL also uses the log crate to print logs from Wasm modules. Log messages will be printed ifRUST_LOG environment variable is specified.

Debug

The application of the second feature is limited to obtaining some of the internal details of the IT execution. Normally, this feature should not be used by a backend developer. Here you can see example of such details for the greeting service compiled with the debug feature:

# running the greeting service compiled with debug feature
~ $ RUST_LOG="info" fce-repl Config.toml
Welcome to the Fluence FaaS REPL
app service's created with service id = e5cfa463-ff50-4996-98d8-4eced5ac5bb9
elapsed time 40.694769ms
1> call greeting greeting "user"
[greeting] sdk.allocate: 4
[greeting] sdk.set_result_ptr: 1114240
[greeting] sdk.set_result_size: 8
[greeting] sdk.get_result_ptr, returns 1114240
[greeting] sdk.get_result_size, returns 8
[greeting] sdk.get_result_ptr, returns 1114240
[greeting] sdk.get_result_size, returns 8
[greeting] sdk.deallocate: 0x110080 8
result: String("Hi, user")
elapsed time: 222.675µs

The most important information these logs relates to the allocate/deallocate function calls. The sdk.allocate: 4 line corresponds to passing the 4-byte user string to the Wasm module, with the memory allocated inside the module and the string is copied there. Whereas sdk.deallocate: 0x110080 8 refers to passing the 8-byte resulting string Hi, user to the host side. Since all arguments and results are passed by value, deallocate is called to delete unnecessary memory inside the Wasm module.

Module Manifest

The module_manifest! macro embeds the Interface Type (IT), SDK and Rust project version as well as additional project and build information into Wasm module. For the macro to be usable, it needs to be imported and initialized in the main.rs file:

// main.rs
use fluence::marine;
use fluence::module_manifest; // import manifest macro
module_manifest!(); // initialize macro
fn main() {}
#[marine]
fn some_function() {}
}

Using the Marine CLI, we can inspect a module's manifest with marine info:

mbp16~/localdev/struct-exp(main|) % marine info -i artifacts/*.wasm
it version: 0.20.1
sdk version: 0.6.0
authors: The Fluence Team
version: 0.1.0
description: foo-wasm, a Marine wasi module
repository:
build time: 2021-06-11 21:08:59.855352 +00:00 UTC