github.com/sberex/go-sberex@v1.8.2-0.20181113200658-ed96ac38f7d7/swarm/network/forwarding.go

// This file is part of the go-sberex library. The go-sberex library is 
// free software: you can redistribute it and/or modify it under the terms 
// of the GNU Lesser General Public License as published by the Free 
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// The go-sberex library is distributed in the hope that it will be useful, 
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 
// General Public License <http://www.gnu.org/licenses/> for more details.

package network

import (
	"fmt"
	"math/rand"
	"time"

	"github.com/Sberex/go-sberex/log"
	"github.com/Sberex/go-sberex/swarm/storage"
)

const requesterCount = 3

/*
forwarder implements the CloudStore interface (use by storage.NetStore)
and serves as the cloud store backend orchestrating storage/retrieval/delivery
via the native bzz protocol
which uses an MSB logarithmic distance-based semi-permanent Kademlia table for
* recursive forwarding style routing for retrieval
* smart syncronisation
*/

type forwarder struct {
	hive *Hive
}

func NewForwarder(hive *Hive) *forwarder {
	return &forwarder{hive: hive}
}

// generate a unique id uint64
func generateId() uint64 {
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	return uint64(r.Int63())
}

var searchTimeout = 3 * time.Second

// forwarding logic
// logic propagating retrieve requests to peers given by the kademlia hive
func (self *forwarder) Retrieve(chunk *storage.Chunk) {
	peers := self.hive.getPeers(chunk.Key, 0)
	log.Trace(fmt.Sprintf("forwarder.Retrieve: %v - received %d peers from KΛÐΞMLIΛ...", chunk.Key.Log(), len(peers)))
OUT:
	for _, p := range peers {
		log.Trace(fmt.Sprintf("forwarder.Retrieve: sending retrieveRequest %v to peer [%v]", chunk.Key.Log(), p))
		for _, recipients := range chunk.Req.Requesters {
			for _, recipient := range recipients {
				req := recipient.(*retrieveRequestMsgData)
				if req.from.Addr() == p.Addr() {
					continue OUT
				}
			}
		}
		req := &retrieveRequestMsgData{
			Key: chunk.Key,
			Id:  generateId(),
		}
		var err error
		if p.swap != nil {
			err = p.swap.Add(-1)
		}
		if err == nil {
			p.retrieve(req)
			break OUT
		}
		log.Warn(fmt.Sprintf("forwarder.Retrieve: unable to send retrieveRequest to peer [%v]: %v", chunk.Key.Log(), err))
	}
}

// requests to specific peers given by the kademlia hive
// except for peers that the store request came from (if any)
// delivery queueing taken care of by syncer
func (self *forwarder) Store(chunk *storage.Chunk) {
	var n int
	msg := &storeRequestMsgData{
		Key:   chunk.Key,
		SData: chunk.SData,
	}
	var source *peer
	if chunk.Source != nil {
		source = chunk.Source.(*peer)
	}
	for _, p := range self.hive.getPeers(chunk.Key, 0) {
		log.Trace(fmt.Sprintf("forwarder.Store: %v %v", p, chunk))

		if p.syncer != nil && (source == nil || p.Addr() != source.Addr()) {
			n++
			Deliver(p, msg, PropagateReq)
		}
	}
	log.Trace(fmt.Sprintf("forwarder.Store: sent to %v peers (chunk = %v)", n, chunk))
}

// once a chunk is found deliver it to its requesters unless timed out
func (self *forwarder) Deliver(chunk *storage.Chunk) {
	// iterate over request entries
	for id, requesters := range chunk.Req.Requesters {
		counter := requesterCount
		msg := &storeRequestMsgData{
			Key:   chunk.Key,
			SData: chunk.SData,
		}
		var n int
		var req *retrieveRequestMsgData
		// iterate over requesters with the same id
		for id, r := range requesters {
			req = r.(*retrieveRequestMsgData)
			if req.timeout == nil || req.timeout.After(time.Now()) {
				log.Trace(fmt.Sprintf("forwarder.Deliver: %v -> %v", req.Id, req.from))
				msg.Id = uint64(id)
				Deliver(req.from, msg, DeliverReq)
				n++
				counter--
				if counter <= 0 {
					break
				}
			}
		}
		log.Trace(fmt.Sprintf("forwarder.Deliver: submit chunk %v (request id %v) for delivery to %v peers", chunk.Key.Log(), id, n))
	}
}

// initiate delivery of a chunk to a particular peer via syncer#addRequest
// depending on syncer mode and priority settings and sync request type
// this either goes via confirmation roundtrip or queued or pushed directly
func Deliver(p *peer, req interface{}, ty int) {
	p.syncer.addRequest(req, ty)
}

// push chunk over to peer
func Push(p *peer, key storage.Key, priority uint) {
	p.syncer.doDelivery(key, priority, p.syncer.quit)
}