micro/network/proxy/mucp/mucp.go

// Package mucp transparently forwards the incoming request using a go-micro client.
package mucp

import (
	"context"
	"io"
	"strings"

	"github.com/micro/go-micro/client"
	rselect "github.com/micro/go-micro/client/selector/router"
	"github.com/micro/go-micro/codec"
	"github.com/micro/go-micro/codec/bytes"
	"github.com/micro/go-micro/config/options"
	"github.com/micro/go-micro/network/proxy"
	"github.com/micro/go-micro/network/router"
	"github.com/micro/go-micro/server"
)

// Proxy will transparently proxy requests to an endpoint.
// If no endpoint is specified it will call a service using the client.
type Proxy struct {
	// embed options
	options.Options

	// Endpoint specified the fixed service endpoint to call.
	Endpoint string

	// The client to use for outbound requests
	Client client.Client
}

// read client request and write to server
func readLoop(r server.Request, s client.Stream) error {
	// request to backend server
	req := s.Request()

	for {
		// get data from client
		//  no need to decode it
		body, err := r.Read()
		if err == io.EOF {
			return nil
		}

		if err != nil {
			return err
		}

		// get the header from client
		hdr := r.Header()
		msg := &codec.Message{
			Type:   codec.Request,
			Header: hdr,
			Body:   body,
		}

		// write the raw request
		err = req.Codec().Write(msg, nil)
		if err == io.EOF {
			return nil
		} else if err != nil {
			return err
		}
	}
}

// ServeRequest honours the server.Router interface
func (p *Proxy) ServeRequest(ctx context.Context, req server.Request, rsp server.Response) error {
	// set default client
	if p.Client == nil {
		p.Client = client.DefaultClient
	}

	opts := []client.CallOption{}

	// service name
	service := req.Service()
	endpoint := req.Endpoint()

	// call a specific backend
	if len(p.Endpoint) > 0 {
		// address:port
		if parts := strings.Split(p.Endpoint, ":"); len(parts) > 1 {
			opts = append(opts, client.WithAddress(p.Endpoint))
			// use as service name
		} else {
			service = p.Endpoint
		}
	}

	// read initial request
	body, err := req.Read()
	if err != nil {
		return err
	}

	// create new request with raw bytes body
	creq := p.Client.NewRequest(service, endpoint, &bytes.Frame{body}, client.WithContentType(req.ContentType()))

	// create new stream
	stream, err := p.Client.Stream(ctx, creq, opts...)
	if err != nil {
		return err
	}
	defer stream.Close()

	// create client request read loop
	go readLoop(req, stream)

	// get raw response
	resp := stream.Response()

	// create server response write loop
	for {
		// read backend response body
		body, err := resp.Read()
		if err == io.EOF {
			return nil
		} else if err != nil {
			return err
		}

		// read backend response header
		hdr := resp.Header()

		// write raw response header to client
		rsp.WriteHeader(hdr)

		// write raw response body to client
		err = rsp.Write(body)
		if err == io.EOF {
			return nil
		} else if err != nil {
			return err
		}
	}

	return nil
}

// NewSingleHostProxy returns a proxy which sends requests to a single backend
func NewSingleHostProxy(endpoint string) *Proxy {
	return &Proxy{
		Options:  options.NewOptions(),
		Endpoint: endpoint,
	}
}

// NewProxy returns a new proxy which will route based on mucp headers
func NewProxy(opts ...options.Option) proxy.Proxy {
	p := new(Proxy)
	p.Options = options.NewOptions(opts...)
	p.Options.Init(options.WithString("mucp"))

	// get endpoint
	ep, ok := p.Options.Values().Get("proxy.endpoint")
	if ok {
		p.Endpoint = ep.(string)
	}

	// get client
	c, ok := p.Options.Values().Get("proxy.client")
	if ok {
		p.Client = c.(client.Client)
	}

	// get router
	r, ok := p.Options.Values().Get("proxy.router")
	if ok {
		// set the router in the client
		p.Client.Init(
			// pass new selector as an option to the client
			client.Selector(rselect.NewSelector(
				// set the router in the selector
				rselect.WithRouter(r.(router.Router)),
			)),
		)
	}

	return p
}