# About [![AppVeyor branch](https://ci.appveyor.com/api/projects/status/wcbc0mefhap535kd?svg=true)](https://ci.appveyor.com/project/Abc-Arbitrage/zebus) [![NuGet](https://buildstats.info/nuget/Zebus)](http://www.nuget.org/packages/Zebus/) [![Join the chat at https://gitter.im/Abc-Arbitrage/Zebus](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/Abc-Arbitrage/Zebus?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)

Zebus is a lightweight peer to peer service bus, built with [CQRS](http://martinfowler.com/bliki/CQRS.html) principles in mind. It allows applications to communicate with each other in a fast and easy manner. Most of the complexity is hidden in the library and you can focus on writing code that matters to you, not debugging messaging code.

# Introduction

Zebus is **peer to peer**, so it does not depend on a broker to dispatch messages between the peers. This allows it to reach a throughput of 140k msg/s and a roundtrip latency under 500µs (have a look at the [Performance](https://github.com/Abc-Arbitrage/Zebus/wiki/Performance) page for details).

It is **resilient** thanks to the absence of a broker and an optional persistence feature that ensures that messages are not lost if a peer is down or disconnected.

It is **stable**, since we have been using it on a production environment at [Abc Arbitrage](http://www.abc-arbitrage.com/) for more than four years. Although we did not release all the necessary bricks yet so you will have to wait a few minor versions to have a fully resilient prodable product.

## Key concepts

### Peer

We call a peer any program that is connected to the bus, a peer is identified by a unique identifier called a PeerId that looks like this: `MyAmazingPeer.0` (we use this convention to identify different instances of the same service).

### Event

An event is sent by a peer to notify everyone who is interested that something happened (ex: `MyBusinessObjectWasSaved`, `AlertTriggered`...).

### Command

A command is sent to a peer asking for an action to be performed (ex: `SaveMyBusinessObjectCommand`).

### Message Handler

A class deriving from `IMessageHandler<T>` will be scanned by the bus and will be used to handle messages of the `T` kind on reception.

### Bus

The piece of code that is the point of entry to use Zebus, the methods that you will use the most are `Publish(IEvent)` and `Send(ICommand)`.

## A quick demo

On startup, the bus will scan your assemblies for message handlers and notify the other peers that you are interested by those messages. When a peer publishes a message, it will use the Directory to know who handles it and send the message directly to the correct recipients.

### Receiver

```csharp
public class MyHandler : IMessageHandler<MyEvent>
{
    public void Handle(MyEvent myEvent)
    {
        Console.WriteLine(myEvent.Value);
    }
}
```

### Sender

```csharp
public void MethodThatSends(IBus bus)
{
    bus.Publish(new MyEvent { Value = 42 });
}
```

### Event description

```csharp
[ProtoContract]
public class MyEvent : IEvent
{
    [ProtoMember(1)]
    public int Value { get; set; }
}
```

And you're set ! This is all the code you need to send an event from one machine to the other. If you want to read more about how the magic happens, have a look at the [wiki](https://github.com/Abc-Arbitrage/Zebus/wiki). Or if you want a more detailed walkthrough (what to reference, how to start the Bus...) visit the [Quick start](https://github.com/Abc-Arbitrage/Zebus/wiki/Quick-start) page.

# Requirements

On Windows, you will need to have [Microsoft Visual C++ 2015 Redistributable](https://www.microsoft.com/en-us/download/details.aspx?id=53587) installed in order to load the x86 or the x64 version of `libzmq` embedded in the project.

# Release notes

We try to stick to the [semantic versioning](http://semver.org/) principles and keep the [release notes](https://github.com/Abc-Arbitrage/Zebus/blob/master/RELEASE_NOTES.md) up to date.

# Copyright

Copyright © 2016 Abc Arbitrage Asset Management

# License

Zebus is licensed under MIT, refer to [LICENSE.md](https://github.com/Abc-Arbitrage/Zebus/blob/master/LICENSE.md) for more information.

# Tools
We use

[![resharper_icon](https://raw.githubusercontent.com/wiki/Abc-Arbitrage/Zebus/content/icon_ReSharper.png)](https://www.jetbrains.com/resharper/)