bitswap

package module
v0.1.10 Latest Latest
Warning

This package is not in the latest version of its module.

 Go to latest Published: Dec 16, 2019 License: MIT Imports: 29 Imported by: 0

README

go-bitswap

Matrix IRC Discord Coverage Status Build Status

An implementation of the bitswap protocol in go!

Lead Maintainer

Dirk McCormick

Table of Contents

Background

Bitswap is the data trading module for ipfs. It manages requesting and sending blocks to and from other peers in the network. Bitswap has two main jobs:

  • to acquire blocks requested by the client from the network
  • to judiciously send blocks in its possession to other peers who want them

Bitswap is a message based protocol, as opposed to request-response. All messages contain wantlists or blocks.

A node sends a wantlist to tell peers which blocks it wants. When a node receives a wantlist it should check which blocks it has from the wantlist, and consider sending the matching blocks to the requestor.

When a node receives blocks that it asked for, the node should send out a notification called a 'Cancel' to tell its peers that the node no longer wants those blocks.

go-bitswap provides an implementation of the Bitswap protocol in go.

Install

go-bitswap requires Go >= 1.11 and can be installed using Go modules

Usage

Initializing a Bitswap Exchange
import (
  "context"
  bitswap "github.com/SJTU-OpenNetwork/go-bitswap"
  bsnet "github.com/ipfs/go-graphsync/network"
  blockstore "github.com/ipfs/go-ipfs-blockstore"
  "github.com/libp2p/go-libp2p-core/routing"
	"github.com/libp2p/go-libp2p-core/host"
)

var ctx context.Context
var host host.Host
var router routing.ContentRouting
var bstore blockstore.Blockstore

network := bsnet.NewFromIPFSHost(host, router)
exchange := bitswap.New(ctx, network, bstore)

Parameter Notes:

  1. ctx is just the parent context for all of Bitswap
  2. network is a network abstraction provided to Bitswap on top of libp2p & content routing.
  3. bstore is an IPFS blockstore
Get A Block Synchronously
var c cid.Cid
var ctx context.Context
var exchange bitswap.Bitswap

block, err := exchange.GetBlock(ctx, c)

Parameter Notes:

  1. ctx is the context for this request, which can be cancelled to cancel the request
  2. c is the content ID of the block you're requesting
Get Several Blocks Asynchronously
var cids []cid.Cid
var ctx context.Context
var exchange bitswap.Bitswap

blockChannel, err := exchange.GetBlocks(ctx, cids)

Parameter Notes:

  1. ctx is the context for this request, which can be cancelled to cancel the request
  2. cids is an slice of content IDs for the blocks you're requesting

In IPFS, content blocks are often connected to each other through a MerkleDAG. If you know ahead of time that block requests are related, Bitswap can make several optimizations internally in how it requests those blocks in order to get them faster. Bitswap provides a mechanism called a Bitswap session to manage a series of block requests as part of a single higher level operation. You should initialize a bitswap session any time you intend to make a series of block requests that are related -- and whose responses are likely to come from the same peers.

var ctx context.Context
var cids []cids.cid
var exchange bitswap.Bitswap

session := exchange.NewSession(ctx)
blocksChannel, err := session.GetBlocks(ctx, cids)
// later
var relatedCids []cids.cid
relatedBlocksChannel, err := session.GetBlocks(ctx, relatedCids)

Note that new session returns an interface with a GetBlock and GetBlocks method that have the same signature as the overall Bitswap exchange.

Tell bitswap a new block was added to the local datastore
var blk blocks.Block
var exchange bitswap.Bitswap

err := exchange.HasBlock(blk)

Implementation

The following diagram outlines the major tasks Bitswap handles, and their consituent components:

Bitswap Components

Sending Blocks

Internally, when a message with a wantlist is received, it is sent to the decision engine to be considered. The decision engine checks the CID for each block in the wantlist against local storage and creates a task for each block it finds in the peer request queue. The peer request queue is a priority queue that sorts available tasks by some metric. Currently, that metric is very simple and aims to fairly address the tasks of each peer. More advanced decision logic will be implemented in the future. Task workers pull tasks to be done off of the queue, retrieve the block to be sent, and send it off. The number of task workers is limited by a constant factor.

Requesting Blocks

The want manager handles client requests for new blocks. The 'WantBlocks' method is invoked for each block (or set of blocks) requested. The want manager ensures that connected peers are notified of the new block that we want by sending the new entries to a message queue for each peer. The message queue will loop while there is work available and:

  1. Ensure it has a connection to its peer
  2. grab the message to be sent
  3. Send the message If new messages are added while the loop is in steps 1 or 3, the messages are combined into one to avoid having to keep an actual queue and send multiple messages. The same process occurs when the client receives a block and sends a cancel message for it.
Sessions

Sessions track related requests for blocks, and attempt to optimize transfer speed and reduce the number of duplicate blocks sent across the network. The basic optimization of sessions is to limit asks for blocks to the peers most likely to have that block and most likely to respond quickly. This is accomplished by tracking who responds to each block request, and how quickly they respond, and then optimizing future requests with that information. Sessions try to distribute requests amongst peers such that there is some duplication of data in the responses from different peers, for redundancy, but not too much.

Finding Providers

When bitswap can't find a connected peer who already has the block it wants, it falls back to querying a content routing system (a DHT in IPFS's case) to try to locate a peer with the block.

Bitswap routes these requests through the ProviderQueryManager system, which rate-limits these requests and also deduplicates in-process requests.

Providing

As a bitswap client receives blocks, by default it announces them on the provided content routing system (again, a DHT in most cases). This behaviour can be disabled by passing bitswap.ProvideEnabled(false) as a parameter when initializing Bitswap. IPFS currently has its own experimental provider system (go-ipfs-provider) which will eventually replace Bitswap's system entirely.

Contribute

PRs are welcome!

Small note: If editing the Readme, please conform to the standard-readme specification.

License

MIT © Juan Batiz-Benet

Documentation

Overview

Package bitswap implements the IPFS exchange interface with the BitSwap bilateral exchange protocol.

Index

Constants

This section is empty.

Variables

View Source 
var (
	// HasBlockBufferSize is the buffer size of the channel for new blocks
	// that need to be provided. They should get pulled over by the
	// provideCollector even before they are actually provided.
	// TODO: Does this need to be this large givent that?
	HasBlockBufferSize = 256
)
View Source 
var TaskWorkerCount = 8

TaskWorkerCount is the total number of simultaneous threads sending outgoing messages

View Source 
var TicketWorkerCount = 4

TicketWorkerCount is the total number of si,ultaneous threads sending outgoing messages TODO: Judge the number of ticketworkers - Riften

Functions

func New 

func New(parent context.Context, network bsnet.BitSwapNetwork,
	bstore blockstore.Blockstore, options ...Option) exchange.Interface

New initializes a BitSwap instance that communicates over the provided BitSwapNetwork. This function registers the returned instance as the network delegate. Runs until context is cancelled or bitswap.Close is called.

Types

type Bitswap 

type Bitswap struct {
	// contains filtered or unexported fields
}

Bitswap instances implement the bitswap protocol.

func (*Bitswap) Close 

func (bs *Bitswap) Close() error

Close is called to shutdown Bitswap

func (*Bitswap) GetBlock 

func (bs *Bitswap) GetBlock(parent context.Context, k cid.Cid) (blocks.Block, error)

GetBlock attempts to retrieve a particular block from peers within the deadline enforced by the context.

func (*Bitswap) GetBlocks 

func (bs *Bitswap) GetBlocks(ctx context.Context, keys []cid.Cid) (<-chan blocks.Block, error)

GetBlocks returns a channel where the caller may receive blocks that correspond to the provided |keys|. Returns an error if BitSwap is unable to begin this request within the deadline enforced by the context.

NB: Your request remains open until the context expires. To conserve resources, provide a context with a reasonably short deadline (ie. not one that lasts throughout the lifetime of the server)

func (*Bitswap) GetWantlist 

func (bs *Bitswap) GetWantlist() []cid.Cid

GetWantlist returns the current local wantlist.

func (*Bitswap) HasBlock 

func (bs *Bitswap) HasBlock(blk blocks.Block) error

HasBlock announces the existence of a block to this bitswap service. The service will potentially notify its peers.

func (*Bitswap) IsOnline 

func (bs *Bitswap) IsOnline() bool

IsOnline is needed to match go-ipfs-exchange-interface

func (*Bitswap) LedgerForPeer 

func (bs *Bitswap) LedgerForPeer(p peer.ID) *decision.Receipt

LedgerForPeer returns aggregated data about blocks swapped and communication with a given peer.

func (*Bitswap) NewSession 

func (bs *Bitswap) NewSession(ctx context.Context) exchange.Fetcher

NewSession generates a new Bitswap session. You should use this, rather that calling Bitswap.GetBlocks, any time you intend to do several related block requests in a row. The session returned will have it's own GetBlocks method, but the session will use the fact that the requests are related to be more efficient in its requests to peers. If you are using a session from go-blockservice, it will create a bitswap session automatically.

func (*Bitswap) PeerConnected 

func (bs *Bitswap) PeerConnected(p peer.ID)

PeerConnected is called by the network interface when a peer initiates a new connection to bitswap.

func (*Bitswap) PeerDisconnected 

func (bs *Bitswap) PeerDisconnected(p peer.ID)

PeerDisconnected is called by the network interface when a peer closes a connection

func (*Bitswap) ReceiveError 

func (bs *Bitswap) ReceiveError(err error)

ReceiveError is called by the network interface when an error happens at the network layer. Currently just logs error.

func (*Bitswap) ReceiveMessage 

func (bs *Bitswap) ReceiveMessage(ctx context.Context, p peer.ID, incoming bsmsg.BitSwapMessage)

ReceiveMessage is called by the network interface when a new message is received.

func (*Bitswap) Stat 

func (bs *Bitswap) Stat() (*Stat, error)

Stat returns aggregated statistics about bitswap operations

func (*Bitswap) WantlistForPeer 

func (bs *Bitswap) WantlistForPeer(p peer.ID) []cid.Cid

WantlistForPeer returns the currently understood list of blocks requested by a given peer.

type Option 

type Option func(*Bitswap)

Option defines the functional option type that can be used to configure bitswap instances

func ProvideEnabled 

func ProvideEnabled(enabled bool) Option

ProvideEnabled is an option for enabling/disabling provide announcements

func ProviderSearchDelay 

func ProviderSearchDelay(newProvSearchDelay time.Duration) Option

ProviderSearchDelay overwrites the global provider search delay

func RebroadcastDelay 

func RebroadcastDelay(newRebroadcastDelay delay.D) Option

RebroadcastDelay overwrites the global provider rebroadcast delay

type Stat 

type Stat struct {
	ProvideBufLen    int
	Wantlist         []cid.Cid
	Peers            []string
	BlocksReceived   uint64
	DataReceived     uint64
	BlocksSent       uint64
	DataSent         uint64
	DupBlksReceived  uint64
	DupDataReceived  uint64
	MessagesReceived uint64
}

Stat is a struct that provides various statistics on bitswap operations

Source Files

View all Source files

Directories

Path Synopsis
Package decision implements the decision engine for the bitswap service.
 Package decision implements the decision engine for the bitswap service.
pb
Package wantlist implements an object for bitswap that contains the keys that a given peer wants.
 Package wantlist implements an object for bitswap that contains the keys that a given peer wants.

Jump to

Keyboard shortcuts

? : This menu
/ : Search site
f or F : Jump to
y or Y : Canonical URL
go.dev uses cookies from Google to deliver and enhance the quality of its services and to analyze traffic. Learn more.