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# Go Micro [![GoDoc](https://godoc.org/github.com/micro/go-micro?status.svg)](https://godoc.org/github.com/micro/go-micro) [![Travis CI](https://travis-ci.org/micro/go-micro.svg?branch=master)](https://travis-ci.org/micro/go-micro)
Go Micro is a pluggable RPC based microservice library which provides the fundamental building blocks for writing distributed applications. It is part of the [Micro](https://github.com/micro/micro) toolchain. It supports Proto-RPC and JSON-RPC as the request/response protocol out of the box and defaults to Consul for discovery.
Go Micro is a pluggable RPC based microservice library which provides the fundamental building blocks for writing distributed applications. It is part of the [Micro](https://github.com/micro/micro) toolkit. It supports Proto-RPC and JSON-RPC as the request/response protocol out of the box and defaults to Consul for discovery.
Every aspect of go-micro is pluggable.
The Micro philosophy is "batteries included" with a pluggable architecture. We provide sane defaults but everything can be swapped out.
An example service can be found in [**examples/service**](https://github.com/micro/go-micro/tree/master/examples/service). The [**examples**](https://github.com/micro/go-micro/tree/master/examples) directory contains many more examples for using things such as middleware/wrappers, selector filters, pub/sub and code generation.
Join the community to learn more:
- [Mailing List](https://groups.google.com/forum/#!forum/micro-services)
- [Slack](https://micro-services.slack.com) : [auto-invite](http://micro-invites.herokuapp.com/)
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By default go-micro only provides a single implementation of each interface. Plugins can be found at [github.com/micro/go-plugins](https://github.com/micro/go-plugins). Contributions welcome!
## Prerequisites
## How does it work?
Consul is the default discovery mechanism provided in go-micro. Discovery is however pluggable so you can used etcd, kubernetes, zookeeper, etc.
Go Micro is a framework that addresses the fundamental requirements to write microservices.
Let's dig into the core components.
### Registry
The registry provides a service discovery mechanism to resolve names to addresses. It can be backed by consul, etcd, zookeeper, dns, gossip, etc.
Services should register using the registry on startup and deregister on shutdown. Services can optionally provide an expiry TTL and reregister
on an interval to ensure liveness and that the service is cleaned up if it dies.
### Selector
The selector is a load balancing abstraction which builds on the registry. It allows services to be "filtered" using filter functions and "selected"
using a choice of algorithms such as random, roundrobin, leastconn, etc. The selector is leveraged by the Client when making requests. The client
will use the selector rather than the registry as it provides that built in mechanism of load balancing.
### Transport
The transport is the interface for synchronous request/response communication between services. It's akin to the golang net package but provides
a higher level abstraction which allows us to switch out communication mechanisms e.g http, rabbitmq, websockets, NATS. The transport also
supports bidirectional streaming. This is powerful for client side push to the server.
### Broker
The broker provides an interface to a message broker for asynchronous pub/sub communication. This is one of the fundamental requirements of an event
driven architecture and microservices. By default we use an inbox style point to point HTTP system to minimise the number of dependencies required
to get started. However there are many message broker implementations available in go-plugins e.g RabbitMQ, NATS, NSQ, Google Cloud Pub Sub.
### Codec
The codec is used for encoding and decoding messages before transporting them across the wire. This could be json, protobuf, bson, msgpack, etc.
Where this differs from most other codecs is that we actually support the RPC format here as well. So we have JSON-RPC, PROTO-RPC, BSON-RPC, etc.
It separates encoding from the client/server and provides a powerful method for integrating other systems such as gRPC, Vanadium, etc.
### Server
The server is the building block for writing a service. Here you can name your service, register request handlers, add middeware, etc. The service
builds on the above packages to provide a unified interface for serving requests. The built in server is an RPC system. In the future there maybe
other implementations. The server also allows you to define multiple codecs to serve different encoded messages.
### Client
The client provides an interface to make requests to services. Again like the server, it builds on the other packages to provide a unified interface
for finding services by name using the registry, load balancing using the selector, making synchronous requests with the transport and asynchronous
messaging using the broker.
The above components are combined at the top-level of micro as a **Service**.
## Getting Started
This is a quick getting started guide with the greeter service example.
### Prerequisites
There's just one prerequisite. We need a service discovery system to resolve service names to their address.
The default discovery mechanism used in go-micro is Consul. Discovery is however pluggable so you can used
etcd, kubernetes, zookeeper, etc. Other implementations can be found in [go-plugins](https://github.com/micro/go-plugins).
### Install Consul
[https://www.consul.io/intro/getting-started/install.html](https://www.consul.io/intro/getting-started/install.html)
## Getting Started
### Run Consul
```
$ consul agent -server -bootstrap-expect 1 -data-dir /tmp/consul