Freighter

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Backends ​

Backends are the servers for the load-balancer to balance.

The Backend struct ​

Freighter options asks for an array of the provided Backend struct. This struct contains information about your backend. It also tracks its state and periodically pings to check its health after Freighter starts listening.

go
// Backend is representation of an actual running backend.
type Backend struct {
	ID           string
	Metadata     interface{} // Metadata to be set by user
	URL          *url.URL
	alive        bool
	mutex        sync.RWMutex
	ReverseProxy *httputil.ReverseProxy
}

To create a instance of this struct, use the provided NewBackend function.

go
b1 := pool.NewBackend(&url.URL{
  Host: ":8080",
  Scheme: "http",
}, nil)

b2 := pool.NewBackend(&url.URL{
  Host: ":8082",
  Scheme: "http",
}, nil)

b3 := pool.NewBackend(&url.URL{
  Host: ":8083",
  Scheme: "http",
}, nil)

Metadata ​

It is possible to add metadata to these Backend instances. This is helpful as we often need to know more than just the URL of the backend while choosing a peer for an incoming request.

For example, we might want to use a strategy which forwards more requests to backends with higher processing power which makes a lot of sense. To do this, along with the setting the required strategy we will have to store more information about the backends as their metadata.

go
type MyMetadata struct {
  MaxReqsInQueue int
}

b := pool.NewBackend(&url.URL{
  Host: ":8083",
  Scheme: "http",
}, MyMetadata{
  MaxReqsInQueue: 100
})