SHORS

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Shors - a library for creating transport layer for distributed systems built with tarantool-module. Shors contains four components: - http router - rpc router - rpc client - builtin components like: - middlewares (opentelemetry, metrics, etc) - logger

!!! Read before work with this lib

HTTP

Create http route

Use a route::Builder for create http routes. After route created just register it with http Server.

Example:

```rust use shors::transport::http::route::Builder; use shors::transport::http::{server, Request}; use shors::transport::Context; use std::error::Error;

fn makehttpendpoint() { let endpoint = Builder::new() .withmethod("GET") .withpath("/concat/a/:a/b/:b") .build( |ctx: &mut Context, request: Request| -> Result<_, Box> { let a = request .stash .get("a") .map(|s| s.asstr()) .unwrapordefault(); let b = request .stash .get("b") .map(|s| s.asstr()) .unwrapor_default();

          Ok(a.to_string() + b)
        },
      );

let s = server::Server::new(); s.register(Box::new(endpoint)); } ```

A more complex example (with groups, error handling, custom and builtin middlewares): ```rust use oncecell::sync::Lazy; use opentelemetry::sdk::export::trace::stdout; use opentelemetry::sdk::trace::Tracer; use shors::transport::http::route::Builder; use shors::transport::http::{server, Request, Response}; use shors::transport::Context; use shors::{middleware, shorserror}; use std::error::Error;

static OPENTELEMETRYTRACER: Lazy = Lazy::new(|| stdout::newpipeline().install_simple());

pub fn makehttpendpoints() { let routegroup = Builder::new() .withpath("/v1") .withmiddleware(|route| { println!("got new http request!"); route }) .withmiddleware(middleware::http::otel(&OPENTELEMETRY_TRACER)) .group();

#[derive(serde::Deserialize)] struct EchoRequest { text: String, }

let echo = routegroup .builder() .withmethod("POST") .withpath("/echo") .build( |ctx: &mut Context, request: Request| -> Result<_, Box> { let req: EchoRequest = request.parse()?; Ok(req.text) }, );

let ping = routegroup .builder() .withmethod("GET") .withpath("/ping") .build(|ctx: &mut Context, _request: Request| -> Result<_, Box> { Ok("pong") });

let s = server::Server::new(); s.register(Box::new(echo)); s.register(Box::new(ping)); } ```

RPC

Prepare

Rpc transport required exported stored procedure - rpc_handler.

Create stored procedure. Example (where RPC_SERVER is the Server instance): ```rust

[no_mangle]

pub extern "C" fn rpchandler(ctx: FunctionCtx, args: FunctionArgs) -> cint { RPC_SERVER.with(|srv| srv.handle(ctx, args)) } ```

And export it from cartridge role. Example:

lua box.schema.func.create('mylib.rpc_handler', { language = 'C', if_not_exists = true }) rawset(_G, 'rpc_handler', function(path, ctx, mp_request) return box.func['mylib.rpc_handle']:call({ path, ctx, mp_request }) end)

Create rpc routes

Working with rpc routes same as http: use route::Builder for creating rpc routes. After route created register it with rpc Server.

Complex example: ```rust use oncecell::unsync::Lazy; use shors::log::RequestIdOwner; use shors::transport::rpc::server::Server; use shors::transport::{rpc, Context}; use std::error::Error; use shors::{middleware, shorserror};

threadlocal! { pub static RPCSERVER: Lazy = Lazy::new(Server::new); }

[tarantool::proc]

fn initrpc() -> tarantool::Result<()> { let routes = rpc::route::Builder::new() .witherrorhandler(|ctx, err| { shorserror!(ctx: ctx, "rpc error {}", err); }) .withmiddleware(|route| { println!("got new rpc request!"); route }) .withmiddleware(middleware::rpc::otel(&OPENTELEMETRY_TRACER)) .group();

let sumroute = routes.builder().withpath("/sum").build( |ctx: &mut Context, req: rpc::Request| -> Result<_, Box> { let numbers = req.parse::>()?.0; Ok(numbers.intoiter().sum::()) }, );

RPCSERVER.with(|srv| { srv.register(Box::new(sumroute)); });

Ok(()) } ```

RPC client

There is a special component for interaction with remote rpc endpoints. Currently, client can call rpc endpoint in four modes: - by bucketid (vshard) - by bucketid (vshard) async (without waiting for an response) - by replicaset id (call current master) - by cartridge role (call current master)

Prepare

Rpc client require register some lua code in luaopen_ function (or in any init function).

Example: ```rust

[no_mangle]

pub unsafe extern "C" fn luaopenlibstub(l: *mut ffilua::luaState) -> cint { let lua = tlua::StaticLua::fromstatic(l); shors::initlua_functions(&lua).unwrap(); 1 } ```

Call rpc endpoint by bucket_id

```rust let lua = tarantool::lua_state();

let params = vec![2, 3, 4];
let resp = rpc::client::Builder::new(&lua)
    .shard_endpoint("/add")
    .call(&mut Context::background(), bucket_id, &params)?;

```

Call rpc endpoint by bucket_id async

```rust let lua = tarantool::lua_state();

rpc::client::Builder::new(&lua)
    .async_shard_endpoint("/ping")
    .call(&mut Context::background(), bucket_id, &())?;

```

Call rpc endpoint by replicaset uuid

```rust let lua = tarantool::lua_state();

let params = vec![2, 3, 4];
let resp = rpc::client::Builder::new(&lua)
    .replicaset_endpoint("/add")
    .prefer_replica()
    .call(&mut Context::background(), rs_uuid, &params)?;

```

Call rpc endpoint by cartridge role

NOTE: calling rpc endpoint by role require register exported rpc_handler stored procedure as exported role method. For example:

lua return { role_name = 'app.roles.stub', ... rpc_handler = function(path, ctx, mp_request) return box.func['libstub.rpc_handle']:call({ path, ctx, mp_request }) end, }

Call example: ```rust let lua = tarantool::lua_state();

let resp = rpc::client::Builder::new(&lua)
  .role_endpoint("app.roles.stub", "/ping")
  .call(&mut Context::background(), &())?;

```

Builtin middlewares

• http server
  • debug - print debug information in debug logs
  • otel - opentelemetry tracing
  • otelconditional - opentelemetry tracing, disabled if http-header with-trace not set
  • accesslogs - nginx like access logs
• rpc server
  • debug - print debug information in debug logs
  • otel - opentelemetry tracing
  • record_latency - record route latency as prometheus metric
• rpc client
  • otel - opentelemetry tracing
  • retry - retry call on server side errors
  • record_latency - record call latency as prometheus metric

Testing

Unit

bash make unit-test

Integration

bash (cd tests/testapplication/ && cartridge build) make int-test

Request pipeline (actual for 0.1.x version)

!NOTE text bellow not actual for shors v 0.2.0+

Shors use vshard/cartridge API underline for make remote requests. Both cartridge and vshard api is a LUA api. So, look at pipeline of shors rpc request:

Client side

• Rust side: 1) sender create an instance of rpc::client::Client 2) sender use rpc::client::Client::call method with rust structure that represent request payload 3) rust structure serialize into LUA table (using tarantool::tlua - Push trait)
• LUA side: 1) calling vshard or cartridge method with LUA table derived from previous step 2) vshard or cartridge api calling iproto 3) iproto serialize LUA table into msgpack and send it into server side

Server side

• LUA side: 1) received message from iproto, message representation is a tarantool tuple 2) call function-handler in rust using internal routes table
• Rust side: 1) Call .decode method on rpc::Request to restore the request

So serialization/deserialization scheme looks like this: rust structure -> lua table -> msgpack representation -> rust structure

There is a problem in this scheme: what if we use enum in fields of initial rust structure? For example ```rust #[derive(Debug, Deserialize, Serialize, tlua::Push)] enum Value { String(String), Code(String), }

[derive(Debug, Deserialize, Serialize, tlua::Push)]

struct Foo { bar: Value, } let example = Foo{ bar: Value::Code("abc".to_string()) }; tarantool::tlua will serialize this struct in lua table like this: lua { bar = "abc" } ```

So as you see, information about which enum variant using is lost. In the future, when we serialize this LUA table into msgpack and then deserialize it into a rust structure, we will get a serde error. Serde expect some type information for deserializing, but there is no. In this example if LUA table looks like: lua { bar = {"Code" = "abc"} } Deserialization will be success and no errors occurred.

How we can fix this? Currently most generic approach is an implement tlua::Push trait for enum. For this example (note, this is example implementation, don't create hashmap at production code): ```rust impl tlua::Push for Value where L: tlua::AsLua, { type Err = TuplePushError;

fn pushtolua(&self, lua: L) -> Result, (Self::Err, L)> { let mut hm = HashMap::::new(); match self { Value::String(s) => hm.insert("String".tostring(), s.tostring()), Value::Code(s) => hm.insert("Code".tostring(), s.tostring()), }; hm.pushtolua(lua) } }

impl tlua::PushOne for Value where L: tlua::AsLua {} ```