bunbun-worker/README.md

<center> <h1> BunBun-Worker </h1> </center>

`bunbun-worker` is a panic-safe multithreaded job-runner server/client library for rust. It supports [RPC](https://wikipedia.org/wiki/Remote_procedure_call) and regular (non-rpc) calls. As of right now only [rabbitmq](https://www.rabbitmq.com/) is supported but [gRPC](https://grpc.io/) will be added too.

> ❗ Disclaimer  
> This crate is still under development, meaning api's may change on every commit...

# Introduction

`bunbun-worker` was made to provide a way for microservices written in rust to communicate to each other by dispatching jobs that may return data and those who don't.

### Rpc

Remote procedure call, as it's name says is a message that can be sent to a remote microservice to be processed and the result to be returned. In `bunbun-worker` it's implemented by the following example:

```mermaid
sequenceDiagram
    ServiceA->>+ServiceB: Hey, could you do this job for me?
    Note right of ServiceB: ServiceB does the job
    ServiceB->>+ServiceA: Sure, here is the data result
```

1. ServiceA creates a callback queue that the response shall be sent to.
2. ServiceA sends a json job message to an **already declared** queue on a rabbitmq server.
3. ServiceB is listening on that queue for messages and spawns a new thread for each received.
4. Once ServiceB has finished the work, using the received messages header it responds to the callback queue with the correlation-id.

### Non-rpc

In `bunbun-worker` regular jobs are called _non-rpc_ jobs, indicating that the response is not awaited.

## Installation

Get directly from crates.io

```toml
[dependencies]
bunbun-worker = { version = "0.1.1" }
```

or get it directly from source

```toml
[dependencies]
bunbun-worker = { git = "https://git.4o1x5.dev/4o1x5/bunbun-worker", branch = "master" }
```

## Usage

Here is a basic implementation of an RPC job in bunbun-worker

```rust
// server

// First let's create a state that will be used inside a job.
// Imagine this holding a database connection, some context that may need to be changed. Anything really
#[derive(Clone, Debug)]
pub struct State {
    pub something: String,
}

/// Second, let's create a job, with field that can be serialized/deserialized into JSON
/// This is what the server will receive from a client and will do the job based on these properties
#[derive(Deserialize, Serialize, Clone, Debug)]
pub struct EmailJob {
    send_to: String,
    contents: String,
}
// We also create a result for it, since it's an RPC job
#[derive(Deserialize, Serialize, Clone, Debug, PartialEq)]
pub struct EmailJobResult {
    contents: String,
}
// And an error type so know if the other end errored out, what to do.
#[derive(Deserialize, Serialize, Clone, Debug)]
pub enum EmailJobResultError {
    Errored,
}

/// After all this we implement a Jobrunner/Taskrunner to the type, so when the listener receives it, it can run this piece of code.
impl RPCServerTask for EmailJob {
    type ErroredResult = EmailJobResultError;
    type Result = EmailJobResult;
    type State = State;
    fn run(
        self,
        state: Self::State,
    ) -> futures::prelude::future::BoxFuture<'static, Result<Self::Result, Self::ErroredResult>>
    {
        Box::pin(async move {
            tracing::info!("Sent email to {}", self.send_to);
            tokio::time::sleep(Duration::from_secs(2)).await;
            return Ok(EmailJobResult {
                contents: self.contents.clone(),
            });
        })
    }
}
// Finally, we can define an async main function to run the listener in.
#[tokio::main]
async fn main(){
    // Define a listener, with a hard-limit of 100 jobs at once.
    let mut listener =
        BunBunWorker::new(env::var("AMQP_SERVER_URL").unwrap(), 100.into()).await;
    // Add the defined sturct to the worker
    listener
        .add_rpc_consumer::<EmailJob>(
            "email-emailjob-v1.0.0", // queue name
            State {
                something: "test".into(), // putting our state into a Arc<Mutex<S>> for thread safety
            },
        )
        .await;
    tracing::debug!("Starting listener");
    // Starting the listener
    listener.start_all_listeners().await;
}
```

Instal `futures_util` for the client

```
cargo add futures_util
```

```rust
// client

// Define the same structs we did. These are DTO's after all..
#[derive(Deserialize, Serialize, Clone, Debug)]
pub struct EmailJob {
    send_to: String,
    contents: String,
}
#[derive(Deserialize, Serialize, Clone, Debug, PartialEq)]
pub struct EmailJobResult {
    contents: String,
}
#[derive(Deserialize, Serialize, Clone, Debug)]
pub enum EmailJobResultError {
    Errored,
}
// Now we implement the clientside task for it. This reduces generics when defining the calling..
impl RPCClientTask for EmailJob {
    type ErroredResult = EmailJobResultError;
    type Result = EmailJobResult;
}

#[tokio::main]
async fn main(){
// Define a client
  let mut client = BunBunClient::new(env::var("AMQP_SERVER_URL").unwrap().as_str())
      .await
      .unwrap();
  // Make a call
  let result = client
      .rpc_call::<EmailJob>(
            // Define the job
          EmailJob {
              send_to: "someone".into(),
              contents: "something".into(),
          },
          "email-emailjob-v1.0.0", // the queue name
      )
      .await
      .unwrap();
}
```

# Limitations

1. Currently some `unwrap()`'s are called inside the code and may results in panics (not in the job-runner).
2. No TLS support
3. No settings, and very limited API
4. The rabbitmq RPC logic is very basic with no message-versioning (aside using different queue names (see [usage](#usage)) )

# Bugs department

Since the code is hosted on a private git instance (as of right now) any bugs shall be discussed in [4o1x5's project room](https://matrix.to/#/#projects:4o1x5.dev).

## License

Licensed under [GNU AFFERO GENERAL PUBLIC LICENSE](https://www.gnu.org/licenses/agpl-3.0.en.html)

### Contribution

Currently this library does not accept any contributors, as it's hosted on a private git server.

# Credits

This package was made with the help of-

- [This readme template you are reading right now](https://github.com/webern/cargo-readme/blob/master/README.md)
- [Lapin, an extensive easy to use rabbitmq client](https://crates.io/crates/lapin)