Crate toy_rpc[−][src]

A async RPC crate that mimics the golang’s net/rpc package and supports both async-std and tokio.

This crate aims at providing an easy-to-use RPC that is similar to golang’s net/rpc.

The usage is similar to that of golang’s net/rpc with functions sharing similar names and functionalities. Certain function names are changed to be more “rusty”. Because rust doesn’t come with reflection built-in, attribute macros are used to make certain methods as if they were “exported”.

Content

Breaking Changes

The most recent breaking changes will be reflected here. Change logs can be found in Change Log.

0.6.0

Breaking Changes

  • In short, this update makes the crate resemble closer to the usage of go’s net/rpc package
  • Service registration is simplified to Server::builder().register(foo_service).build(). The examples will be updated accordingly. Thus
    • service!() macro will be deprecated
    • register function now takes only one argument, which is the instance of the service
    • on the client side, the service name will just be the name of the struct. for example, to call a RPC method on struct Foo { } service, the client simply uses .async_call("Foo.<method>").await where <method> should be replaced with the RPC method
    • you can still register multiple services on the same server. However, only one object of the same type can be registered on the same server. Multiple servers are needed to have multiple objects of the same type.
  • Re-defined the custom Error type

Non-breaking changes

  • Fixed bug where client does not interpret error message correctly
  • Fixed bug with accept_websocket crashes with incorrect protocol

Crate Feature Flags

The feature flags can be put into two categories.

Choice of serialization/deserialzation

  • serde_bincode: the default codec will use bincode for serialization/deserialization
  • serde_json: the default codec will use serde_json for json serialization/deserialization
  • serde_cbor: the default codec will use serde_cbor for serialization/deserialization
  • serde_rmp: the default codec will use rmp-serde for serialization/deserialization

Choice of runtime

  • async_std_runtime: supports usage with async-std
  • tokio_runtime: supports usage with tokio
  • http_tide: enables tide integration on the server side. This also enables async_std_runtime
  • http_actix_web: enables actix-web integration on the server side. This also enables tokio_runtime
  • http_warp: enables integration with warp on the server side. This also enables tokio_runtime

Other trivial feature flags are listed below, and they are likely of no actual usage for you.

  • docs
  • std: serde/std. There is no actual usage right now.

Default Features

[features]
default = [
    "serde_bincode",
    "async_std_runtime"
]

Documentation

The following documentation is adapted based on golang’s documentation.

This crate provides access to the methods marked with #[export_impl] and #[export_method] of an object across a network connection. A server registers an object, making it visible as a service with the name of the type of the object. After the registration, the “exported” methods will be accessible remotely. A server may register multiple objects (services) of different types but may not register multiple objects of the same type.

To export a method, use #[export_method] attribute in an impl block marked with #[export_impl] attribute. This crate currently only support using #[export_impl] attribute on one impl block per type. Please note that the service name and method name is case sensitive (ie. the “exported” service and method in the example below can be remotely accessed via "ExampleService.exported_method").

use toy_rpc::macros::export_impl;
 
struct ExampleService { }

#[export_impl]
impl ExampleService {
    #[export_method]
    async fn exported_method(&self, args: ()) -> Result<String, String> {
        Ok("This is an exported method".to_string())
    }

    async fn not_exported_method(&self, args: ()) -> Result<String, String> {
        Ok("This method is NOT exported".to_string())
    }
}

The methods to export must meet the following criteria on the server side

  • the method resides in an impl block marked with #[export_impl]

  • the method is marked with #[export_method] attribute

  • the method takes one argument other than &self and returns a Result<T, E>

    • the argument must implement trait serde::Deserialize
    • the Ok type T of the result must implement trait serde::Serialize
    • the Err type E of the result must implement trait ToString

  • the method is essentially in the form

struct Service { }

#[export_impl]
impl Service {
    #[export_method]
    async fn method_name(&self, args: Req) -> Result<Res, ErrorMsg>
    where
        Req: serde::Deserialize,
        Res: serde::Serialize,
        ErrorMsg: ToString,
    {
        unimplemented!()
    }
}

Req and Res are marshaled/unmarshaled (serialized/deserialized) by serde. Realistically the Req and Res type must also be marshaled/unmarshaled on the client side, and thus Req and Res must both implement both serde::Serialize and serde::Deserialize.

The method’s argument represents the argument provided by the client caller, and the Ok type of result represents success parameters to be returned to the client caller. The Err type of result is passed back to the client as a String.

The server may handle requests on a single connection by calling serve_conn, and it may handle multiple connections by creating a TcpListener and call accept. HTTP integration is accomplished with WebSocket and currently supports actix-web, warp, and tide.

A client wishing to use the service establishes a TcpStream connection and then creates Client over the connection. The convenience function dial performs this step for raw TCP socket connection, and dial_http performs this for an HTTP connection. A Client with HTTP connection or socket connection has three methods, call, async_call, and spawn_task, to specify the service and method to call and the argument. Please note that the service and method name is case sensitive, and following Rust’s naming convention, the service name should be in CamelCase, for example, if a service is defined as pub struct FooBar {}, the client needs to use async_call("FooBar.echo").await to make the remote call.

  • call method is synchronous and waits for the remote call to complete and then returns the result in a blocking manner.
  • async_call is the async versions of call and call_http, respectively. Because they are async functions, they must be called with .await to be executed.
  • spawn_task method spawns an async task and returns a JoinHandle. The result can be obtained using the JoinHandle. Please note that async_std::task::JoinHandle and tokio::task::JoinHandle behave slightly differently. Executing .await on async_std::task::JoinHandle returns Result<Res, toy_rpc::error::Error>. However, executing .await on tokio::task::JoinHandle returns `Result<Result<Res, toy_rpc::Error>, tokio::task::JoinError>.
  • A client stub trait is generated automatically which allows usage such as client.foo_bar().echo("data").await where foo_bar() represents a call to the FooBar{} service while echo() represents the RPC method for the FooBar{} service. More details can be found below

Unless an explicity codec is set up (with serve_codec method, HTTP is NOT supported yet), the default codec specified by one of the following features tags (serde_bincode, serde_json serde_cbor, serde_rmp) will be used to marshal/unmarshal data.

async-std and tokio

Starting from version 0.5.0-beta.2, you can use toy-rpc with either runtime by choosing the corresponding feature flag (async_std_runtime, tokio_runtime).

HTTP integrations

Similar to choosing the runtimes, toy-rpc supports integration with actix-web, tide, and warp by choosing the corresponding feature flag (http_actix_web, http_tide, http_warp). Starting from version 0.5.0-beta.0 the integration is implemented using WebSocket as the transport protocol, and the DEFAULT_RPC_SERVER=_rpc_ is appended to the path you supply to the HTTP framework. The client side support is now based on async_tungstenite. Please note that toy-rpc versions >=0.5.0-beta.0 are NOT compatible with versions <0.5.0-beta.0. The examples below are also updated to reflect the changes.

Client Stub

The #[export_impl] macro now also generates client stubs that internally uses async_call. For example, if the Example {} service is registered on the server with the echo(&self, arg: u32) method. If you want to call the echo() RPC method on the Example {} service, you can conveniently use client.example().echo(3).await.unwrap(). The generated stub follows the snake case, for example - if a service is defined as pub struct Foo {}, the generated stub will be foo() - if a service is defined as pub struct FooBar {}, the generated stub will be foo_bar() - if a service is defined asx pub struct FooBarService {}, the generated stub will be foo_bar_service()

pub mod rpc {
    use toy_rpc::macros::export_impl;
    use serde::{Serialize, Deserialze};

    pub struct Example { }
     
    #[export_impl]   
    impl Example {
        pub async fn echo(&self, arg: u32) -> Result<u32, String> {
            Ok(arg)
        }
    }
}
 
// import everything from the `rpc` mod to include the generated client stub
use rpc::*;
 
#[async_std::main] 
async fn main() {
    let addr = "127.0.0.1:23333";
    let client = Client::dial(addr).await.unwrap();
 
    // The generated client stub will provide a function `example()`
    // for convenience.
    // The line below is equivalent to `let reply = client.async_call("Example.echo", 3).await.unwrap();`
    let reply = client.example().echo(3).await.unwrap();
    println!("Reply: {}", reply);
}

Examples

A few simple examples are shown below. More examples can be found in the examples directory in the repo. All examples here will assume the follwing RPC service definition below.

The examples here will also need some other dependencies

[dependencies]
# you may need to change feature flags for different examples
toy-rpc = { version = "0.6.0" }

# optional depending on the choice of runtime or http framework for different examples
async-std = { version = "1.9.0", features = ["attributes"] }
tokio = { version = "1.4.0", features = ["rt", "rt-multi-thread", "macros", "net", "sync"] }
tide = "0.16.0"
actix-web = "3.3.2"
warp = "0.3.0"

# other dependencies needed for the examples here
async-trait = "0.1.42"
env_logger = "0.8.2"
log = "0.4.14"
serde = { version = "1.0.123", features = ["derive"] }

Example Service Definition

pub mod rpc {
    use serde::{Serialize, Deserialize};
    use toy_rpc::macros::export_impl;
    use async_trait::async_trait;
 
    // uncomment the line below for the examples that use tokio runtime
    // use tokio::sync::Mutex; 
     
    // uncomment the line below for the examples that use async-std runtime
    // use async_std::sync::Mutex; 

    pub struct ExampleService {
        pub counter: Mutex<i32>
    }

    #[derive(Debug, Serialize, Deserialize)]
    pub struct ExampleRequest {
        pub a: u32,
    }
     
    #[derive(Debug, Serialize, Deserialize)]
    pub struct ExampleResponse {
        a: u32,
    }

    #[async_trait]
    trait Rpc {
        async fn echo(&self, req: ExampleRequest) -> Result<ExampleResponse, String>;
    }

    #[async_trait]
    #[export_impl]
    impl Rpc for ExampleService {
        #[export_method]
        async fn echo(&self, req: ExampleRequest) -> Result<ExampleResponse, String> {
            let mut counter = self.counter.lock().await;
            *counter += 1;

            let res = ExampleResponse{ a: req.a };
            Ok(res)
        }
    }
}

RPC over TCP with async-std

This example will assume the RPC service defined above, and you may need to uncomment the line use async_std::sync::Mutex; in the RPC service definition for this example.

The default feature flags will work with the example below.

server.rs

use async_std::net::TcpListener;
use async_std::sync::{Arc, Mutex};
use async_std::task;
use toy_rpc::macros::service;
use toy_rpc::Server;

use crate::rpc; // assume the rpc module can be found here

#[async_std::main]
async fn main() {
    env_logger::init();

    let addr = "127.0.0.1:8080";
    let example_service = Arc::new(
        rpc::ExampleService {
            counter: Mutex::new(0),
        }
    );

    // notice that the`service!()` macro is no longer needed
    let server = Server::builder()
        .register(example_service) 
        .build();

    let listener = TcpListener::bind(addr).await.unwrap();
    println!("Starting listener at {}", &addr);

    let handle = task::spawn(async move {
        server.accept(listener).await.unwrap();
    });
    handle.await;
}

client.rs

use toy_rpc::Client;
use toy_rpc::error::Error;

// import everything from the `rpc` mod to include generated client stub
use crate::rpc::*; // assume the rpc module can be found here

#[async_std::main]
async fn main() {
    let addr = "127.0.0.1:8080";
    let client = Client::dial(addr).await.unwrap();

    let args = ExampleRequest{a: 1};
     
    // Use synchronous call
    let reply: Result<rpc::ExampleResponse, Error> = client.call("Example.echo", &args);
    println!("{:?}", reply);
     
    // or use the generated client stub for `ExampleService`
    let reply = client.example_service().echo(&args).await;
    println!("{:?}", reply);
    client.close().await;
}

RPC over TCP with tokio

This example will assume the RPC service defined above and you may need to uncomment the line use tokio::sync::Mutex; in the RPC service definition for this example.

The default feature flags will NOT work for this example, and you need to change the feature flags.

[dependencies]
toy_rpc = { version = "0.6.0", default-features = false, features = ["serde_bincode", "tokio_runtime"] }

server.rs

use std::sync::Arc;
use tokio::net::TcpListener;
use tokio::sync::Mutex;
use tokio::task;
use toy_rpc::macros::service;
use toy_rpc::Server;

use crate::rpc; // assume the rpc module can be found here

#[tokio::main]
async fn main() {
    env_logger::init();

    let addr = "127.0.0.1:8080";
    let example_service = Arc::new(
        rpc::ExampleService {
            counter: Mutex::new(0),
        }
    );

    // notice that the second argument in `service!()` macro is a path
    let server = Server::builder()
        .register(example_service)
        .build();

    let listener = TcpListener::bind(addr).await.unwrap();
    println!("Starting listener at {}", &addr);

    let handle = task::spawn(async move {
        server.accept(listener).await.unwrap();
    });

    // tokio JoinHandle returns an extra result
    handle.await.unwrap();
}

client.rs

use toy_rpc::Client;
use toy_rpc::error::Error;

// import everything from the `rpc` mod to include generated client stub
use crate::rpc::*; // assume the rpc module can be found here

#[tokio::main]
async fn main() {
    let addr = "127.0.0.1:8080";
    let client = Client::dial(addr).await.unwrap();

    let args = rpc::ExampleRequest{a: 1};
 
    // Use synchronous call
    let reply: Result<rpc::ExampleResponse, Error> = client.call("Example.echo", &args);
    println!("{:?}", reply);
     
    // or use the generated client stub for `ExampleService`
    let reply = client.example_service().echo(&args).await;
    println!("{:?}", reply);
    client.close().await;

    client.close().await;
}

HTTP integration with tide

This example will assume the RPC service defined above and you may need to uncomment the line use async_std::sync::Mutex; in the RPC service definition for this example.

An example client to use with HTTP can be found in a separate example here. The default feature flags will NOT work with this example, and you need to change the feature flags.

toy_rpc = { version = "0.6.0", default-features = false, features = ["serde_bincode", "http_tide"] }

server.rs

use async_std::sync::{Arc, Mutex};
use toy_rpc::macros::service;
use toy_rpc::Server;

use crate::rpc; // assume the rpc module can be found here

#[async_std::main]
async fn main() -> tide::Result<()> {
    env_logger::init();

    let addr = "127.0.0.1:8080";
    let example_service = Arc::new(
        rpc::ExampleService {
            counter: Mutex::new(0),
        }
    );

    let server = Server::builder()
        .register(example_service)
        .build();

    let mut app = tide::new();
    app.at("/rpc/").nest(server.handle_http());
    // with `http_tide`, the line above can also be replaced with the line below
    //app.at("/rpc/").nest(server.into_endpoint());

    app.listen(addr).await?;
    Ok(())
}

HTTP integration with actix-web

This example will assume the RPC service defined above and you may need to uncomment the line use tokio::sync::Mutex; in the RPC service definition for this example.

An example client to use with HTTP can be found in a another example here. The default feature flags will NOT work with this example, and you need to change the feature flags.

toy_rpc = { version = "0.6.0", default-features = false, features = ["serde_bincode", "http_actix_web"] }

server.rs

use std::sync::Arc;
use tokio::sync::Mutex;
use actix_web::{App, HttpServer, web};
use toy_rpc::macros::service;
use toy_rpc::Server;

use crate::rpc; // assume the rpc module can be found here

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    env_logger::init();

    let addr = "127.0.0.1:8080";
    let example_service = Arc::new(
        rpc::ExampleService {
            counter: Mutex::new(0),
        }
    );

    let server = Server::builder()
        .register(example_service)
        .build();

    let app_data = web::Data::new(server);

    HttpServer::new(
        move || {
            App::new()
                .service(
                    web::scope("/rpc/")
                        .app_data(app_data.clone())
                        .configure(Server::handle_http())
                        // with `http_actix_web`, the line above can also be replaced with the line below
                        //.configure(Server::scope_config)
                )
        }
    )
    .bind(addr)?
    .run()
    .await
}

HTTP integration with warp

This example will assume the RPC service defined above and you may need to uncomment the line use tokio::sync::Mutex; in the RPC service definition for this example.

An example client to use with HTTP can be found in a another example here. The default feature flags will NOT work with this example, and you need to change the feature flags.

toy_rpc = { version = "0.6.0", default-features = false, features = ["serde_bincode", "http_warp"] }

server.rs

use warp::Filter;
use std::sync::Arc;
use tokio::sync::Mutex;
use toy_rpc::macros::service;
use toy_rpc::Server;

use crate::rpc; // assume the rpc module can be found here

#[tokio::main]
async fn main() {
    env_logger::init();
    let example_service = Arc::new(
        rpc::ExampleService {
            counter: Mutex::new(0),
        }
    );

    let server = Server::builder()
        .register(example_service)
        .build();

    let routes = warp::path("rpc")
        .and(server.handle_http());

    // RPC will be served at "ws://127.0.0.1:8080/rpc/_rpc_"
    warp::serve(routes).run(([127, 0, 0, 1], 8080)).await;
}

RPC client for HTTP

This example will assume the RPC service defined above. The default feature flags will work with this example. However, you may also use client with any runtime or http feature flag.

All HTTP examples assumes that the RPC server is found at “127.0.0.1/rpc/” endpoint.

use toy_rpc::Client;
use toy_rpc::error::Error;

use crate::rpc; // assume the rpc module can be found here

// choose the runtime attribute accordingly
//#[tokio::main]
#[async_std::main]
async fn main() {
    // note that the url scheme is "ws"
    let addr = "ws://127.0.0.1:8080/rpc/";
    let client = Client::dial_http(addr).await.unwrap();

    let args = rpc::ExampleRequest{a: 1};
    // Use synchronous call
    let reply: Result<rpc::ExampleResponse, Error> = client.call("Example.echo", &args);
    println!("{:?}", reply);
     
    // or use the generated client stub for `ExampleService`
    let reply = client.example_service().echo(&args).await;
    println!("{:?}", reply);

    client.close().await;
}

Change Log

0.6.0

Breaking Changes

  • In short, this update makes the crate resemble closer to the usage of go’s net/rpc package
  • Service registration is simplified to Server::builder().register(foo_service).build(). The examples will be updated accordingly. Thus
    • service!() macro will be deprecated
    • register function now takes only one argument, which is the instance of the service
    • on the client side, the service name will just be the name of the struct. for example, to call a RPC method on struct Foo { } service, the client simply uses .async_call("Foo.<method>").await where <method> should be replaced with the RPC method
    • you can still register multiple services on the same server. However, only one object of the same type can be registered on the same server. Multiple servers are needed to have multiple objects of the same type.
  • Re-defined the custom Error type

Non-breaking changes

  • Fixed bug where client does not interpret error message correctly
  • Fixed bug with accept_websocket crashes with incorrect protocol

0.5.4

  • Handlers are now stored as a fn pointer as opposed to a trait object.

0.5.3

  • The #[export_impl] macro now generates client stub functions by generating a new trait for toy_rpc::Client.

0.5.0

Breaking changes

  • HTTP integration is now accomplished using WebSocket with async_tungstenite, and thus HTTP connections of versions <0.5.0 are not compatible with versions >=0.5.0.
  • The custom binary transport protocol now includes a magic byte at the beginning, making versions <0.5.0 NOT compatible with versions >= 0.5.0;
  • toy_rpc::error::Error changed from struct-like variants to simple enum variants
  • Changes to feature flags
    • “logging” feature flag is removed
    • “surf” feature flag is removed
    • “tide” is changed to “http_tide”
    • “actix-web” is changed to “http_actix_web”
    • added “http_warp” feature flag
    • added “async_std_runtime”
    • added “tokio_runtime”

Non-breaking changes

  • Removed Stream and Sink impl from the custom binary transport protocol Frame

0.4.5

  • Added Sink implementation for the custom binary transport protocol Frame

0.4.4

  • Modified traits CodecRead, CodecWrite, ServerCodec, ClientCodec to no longer return number of bytes written
  • The number of bytes written for header and body will be logged separately

0.4.3

  • Removed previously unused NoneError
  • Unified call, async_call and spawn_task for socket client and HTTP client. The call_http, async_call_http, and spawn_task_http methods are kept for compatibility.

0.4.2

  • Temporary fix of spawn_task() and spawn_task_http() with Arc<Mutex<_>> until lifetime with async task is figured out. As a result, Client no longer needs to be declared mut.

0.4.1

  • Updated documentation

0.4.0

  • Added actix-web feature flag to support integration with actix-web

0.3.1

  • Added serde_rmp features flag
  • Updated and corrected examples in the documentation

0.3.0

  • Added serde_cbor feature flag
  • Changed bincode feature flag to serde_bincode

Future Plan

The following items are in no particular order.

  • improve error handling (sort of done)
  • improve documentation
  • improve logging message
  • support other I/O connection
  • more tests

Re-exports

pub use server::Server;
pub use server::ServerBuilder;
pub use crate::client::async_std::Client;
pub use error::Error;
pub use serde;
pub use erased_serde;
pub use lazy_static;

Modules

client

There are two Client struct defined, one for feature = "async_std_runtime" and the other for feature = "tokio_runtime".

codec

ServerCodec and ClientCodec are defined in this module, and they are implemented for the DefaultCodec Default codec implementations are feature gated behind the following features serde_bincode, serde_json, serde_cbor, serde_rmp.

error

Custom errors

macros

Re-export of proc_macros defined in toy_rpc_macros

message

Custom definition of rpc request and response headers

server

RPC server. There is only one Server defined, but some methods have different implementations depending on the runtime feature flag

service

Service builder and registration

transport

Custom binary transport and WebSocket integration

util