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eth/downloader: add a basic block download congestion control

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This commit is contained in:
Péter Szilágyi 2015-06-03 14:39:21 +03:00
parent 9085b10508
commit c9a546c310
5 changed files with 67 additions and 55 deletions
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10
eth/downloader/downloader.go
View File

@ -27,7 +27,8 @@ const (
)
var (
blockTTL = 5 * time.Second // Time it takes for a block request to time out
blockSoftTTL = 3 * time.Second // Request completion threshold for increasing or decreasing a peer's bandwidth
blockHardTTL = 3 * blockSoftTTL // Maximum time allowance before a block request is considered expired
crossCheckCycle = time.Second // Period after which to check for expired cross checks
minDesiredPeerCount = 5 // Amount of peers desired to start syncing
)
@ -324,7 +325,7 @@ func (d *Downloader) fetchHashes(p *peer, h common.Hash) error {
glog.V(logger.Detail).Infof("Cross checking (%s) with %x/%x", active.id, origin, parent)
d.checks[origin] = &crossCheck{
expire: time.Now().Add(blockTTL),
expire: time.Now().Add(blockSoftTTL),
parent: parent,
}
active.getBlocks([]common.Hash{origin})
@ -429,6 +430,7 @@ out:
// Peer did deliver, but some blocks were off, penalize
glog.V(logger.Debug).Infof("Failed delivery for peer %s: %v\n", blockPack.peerId, err)
peer.Demote()
peer.SetIdle()
break
}
if glog.V(logger.Debug) && len(blockPack.blocks) > 0 {
@ -444,7 +446,7 @@ out:
// that badly or poorly behave are removed from the peer set (not banned).
// Bad peers are excluded from the available peer set and therefor won't be
// reused. XXX We could re-introduce peers after X time.
badPeers := d.queue.Expire(blockTTL)
badPeers := d.queue.Expire(blockHardTTL)
for _, pid := range badPeers {
// XXX We could make use of a reputation system here ranking peers
// in their performance
@ -475,7 +477,7 @@ out:
}
// Get a possible chunk. If nil is returned no chunk
// could be returned due to no hashes available.
request := d.queue.Reserve(peer, MaxBlockFetch)
request := d.queue.Reserve(peer)
if request == nil {
continue
}

22
eth/downloader/downloader_test.go
View File

@ -191,7 +191,7 @@ func (dl *downloadTester) badBlocksPeer(id string, td *big.Int, hash common.Hash
func TestDownload(t *testing.T) {
minDesiredPeerCount = 4
blockTTL = 1 * time.Second
blockHardTTL = 1 * time.Second
targetBlocks := 1000
hashes := createHashes(0, targetBlocks)
@ -240,7 +240,7 @@ func TestMissing(t *testing.T) {
func TestTaking(t *testing.T) {
minDesiredPeerCount = 4
blockTTL = 1 * time.Second
blockHardTTL = 1 * time.Second
targetBlocks := 1000
hashes := createHashes(0, targetBlocks)
@ -281,7 +281,7 @@ func TestInactiveDownloader(t *testing.T) {
func TestCancel(t *testing.T) {
minDesiredPeerCount = 4
blockTTL = 1 * time.Second
blockHardTTL = 1 * time.Second
targetBlocks := 1000
hashes := createHashes(0, targetBlocks)
@ -307,7 +307,7 @@ func TestCancel(t *testing.T) {
func TestThrottling(t *testing.T) {
minDesiredPeerCount = 4
blockTTL = 1 * time.Second
blockHardTTL = 1 * time.Second
targetBlocks := 16 * blockCacheLimit
hashes := createHashes(0, targetBlocks)
@ -461,7 +461,7 @@ func TestInvalidHashOrderAttack(t *testing.T) {
// Tests that if a malicious peer makes up a random hash chain and tries to push
// indefinitely, it actually gets caught with it.
func TestMadeupHashChainAttack(t *testing.T) {
blockTTL = 100 * time.Millisecond
blockSoftTTL = 100 * time.Millisecond
crossCheckCycle = 25 * time.Millisecond
// Create a long chain of hashes without backing blocks
@ -495,10 +495,10 @@ func TestMadeupHashChainDrippingAttack(t *testing.T) {
// Tests that if a malicious peer makes up a random block chain, and tried to
// push indefinitely, it actually gets caught with it.
func TestMadeupBlockChainAttack(t *testing.T) {
defaultBlockTTL := blockTTL
defaultBlockTTL := blockSoftTTL
defaultCrossCheckCycle := crossCheckCycle
blockTTL = 100 * time.Millisecond
blockSoftTTL = 100 * time.Millisecond
crossCheckCycle = 25 * time.Millisecond
// Create a long chain of blocks and simulate an invalid chain by dropping every second
@ -516,7 +516,7 @@ func TestMadeupBlockChainAttack(t *testing.T) {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, ErrCrossCheckFailed)
}
// Ensure that a valid chain can still pass sync
blockTTL = defaultBlockTTL
blockSoftTTL = defaultBlockTTL
crossCheckCycle = defaultCrossCheckCycle
tester.hashes = hashes
@ -530,10 +530,10 @@ func TestMadeupBlockChainAttack(t *testing.T) {
// attacker make up a valid hashes for random blocks, but also forges the block
// parents to point to existing hashes.
func TestMadeupParentBlockChainAttack(t *testing.T) {
defaultBlockTTL := blockTTL
defaultBlockTTL := blockSoftTTL
defaultCrossCheckCycle := crossCheckCycle
blockTTL = 100 * time.Millisecond
blockSoftTTL = 100 * time.Millisecond
crossCheckCycle = 25 * time.Millisecond
// Create a long chain of blocks and simulate an invalid chain by dropping every second
@ -550,7 +550,7 @@ func TestMadeupParentBlockChainAttack(t *testing.T) {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, ErrCrossCheckFailed)
}
// Ensure that a valid chain can still pass sync
blockTTL = defaultBlockTTL
blockSoftTTL = defaultBlockTTL
crossCheckCycle = defaultCrossCheckCycle
tester.blocks = blocks

45
eth/downloader/peer.go
View File

@ -5,10 +5,14 @@ package downloader
import (
"errors"
"math"
"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"gopkg.in/fatih/set.v0"
)
@ -27,14 +31,15 @@ type peer struct {
head common.Hash // Hash of the peers latest known block
idle int32 // Current activity state of the peer (idle = 0, active = 1)
rep int32 // Simple peer reputation (not used currently)
rep int32 // Simple peer reputation
mu sync.RWMutex
capacity int32 // Number of blocks allowed to fetch per request
started time.Time // Time instance when the last fetch was started
ignored *set.Set
ignored *set.Set // Set of hashes not to request (didn't have previously)
getHashes hashFetcherFn
getBlocks blockFetcherFn
getHashes hashFetcherFn // Method to retrieve a batch of hashes (mockable for testing)
getBlocks blockFetcherFn // Method to retrieve a batch of blocks (mockable for testing)
}
// newPeer create a new downloader peer, with specific hash and block retrieval
@ -43,6 +48,7 @@ func newPeer(id string, head common.Hash, getHashes hashFetcherFn, getBlocks blo
return &peer{
id: id,
head: head,
capacity: 1,
getHashes: getHashes,
getBlocks: getBlocks,
ignored: set.New(),
@ -52,6 +58,7 @@ func newPeer(id string, head common.Hash, getHashes hashFetcherFn, getBlocks blo
// Reset clears the internal state of a peer entity.
func (p *peer) Reset() {
atomic.StoreInt32(&p.idle, 0)
atomic.StoreInt32(&p.capacity, 1)
p.ignored.Clear()
}
@ -61,6 +68,8 @@ func (p *peer) Fetch(request *fetchRequest) error {
if !atomic.CompareAndSwapInt32(&p.idle, 0, 1) {
return errAlreadyFetching
}
p.started = time.Now()
// Convert the hash set to a retrievable slice
hashes := make([]common.Hash, 0, len(request.Hashes))
for hash, _ := range request.Hashes {
@ -72,10 +81,36 @@ func (p *peer) Fetch(request *fetchRequest) error {
}
// SetIdle sets the peer to idle, allowing it to execute new retrieval requests.
// Its block retrieval allowance will also be updated either up- or downwards,
// depending on whether the previous fetch completed in time or not.
func (p *peer) SetIdle() {
// Update the peer's download allowance based on previous performance
scale := 2.0
if time.Since(p.started) > blockSoftTTL {
scale = 0.5
}
for {
// Calculate the new download bandwidth allowance
prev := atomic.LoadInt32(&p.capacity)
next := int32(math.Max(1, math.Min(MaxBlockFetch, float64(prev)*scale)))
if scale < 1 {
glog.V(logger.Detail).Infof("%s: reducing block allowance from %d to %d", p.id, prev, next)
}
// Try to update the old value
if atomic.CompareAndSwapInt32(&p.capacity, prev, next) {
break
}
}
// Set the peer to idle to allow further block requests
atomic.StoreInt32(&p.idle, 0)
}
// Capacity retrieves the peers block download allowance based on its previously
// discovered bandwidth capacity.
func (p *peer) Capacity() int {
return int(atomic.LoadInt32(&p.capacity))
}
// Promote increases the peer's reputation.
func (p *peer) Promote() {
atomic.AddInt32(&p.rep, 1)

10
eth/downloader/queue.go
View File

@ -203,7 +203,7 @@ func (q *queue) TakeBlocks() []*Block {
// Reserve reserves a set of hashes for the given peer, skipping any previously
// failed download.
func (q *queue) Reserve(p *peer, max int) *fetchRequest {
func (q *queue) Reserve(p *peer) *fetchRequest {
q.lock.Lock()
defer q.lock.Unlock()
@ -215,11 +215,17 @@ func (q *queue) Reserve(p *peer, max int) *fetchRequest {
if _, ok := q.pendPool[p.id]; ok {
return nil
}
// Calculate an upper limit on the hashes we might fetch (i.e. throttling)
space := len(q.blockCache) - len(q.blockPool)
for _, request := range q.pendPool {
space -= len(request.Hashes)
}
// Retrieve a batch of hashes, skipping previously failed ones
send := make(map[common.Hash]int)
skip := make(map[common.Hash]int)
for len(send) < max && !q.hashQueue.Empty() {
capacity := p.Capacity()
for len(send) < space && len(send) < capacity && !q.hashQueue.Empty() {
hash, priority := q.hashQueue.Pop()
if p.ignored.Has(hash) {
skip[hash.(common.Hash)] = int(priority)

31
eth/downloader/queue_test.go
View File

@ -1,8 +1,6 @@
package downloader
import (
"testing"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"gopkg.in/fatih/set.v0"
@ -30,32 +28,3 @@ func createBlocksFromHashSet(hashes *set.Set) []*types.Block {
return blocks
}
func TestChunking(t *testing.T) {
queue := newQueue()
peer1 := newPeer("peer1", common.Hash{}, nil, nil)
peer2 := newPeer("peer2", common.Hash{}, nil, nil)
// 99 + 1 (1 == known genesis hash)
hashes := createHashes(0, 99)
queue.Insert(hashes)
chunk1 := queue.Reserve(peer1, 99)
if chunk1 == nil {
t.Errorf("chunk1 is nil")
t.FailNow()
}
chunk2 := queue.Reserve(peer2, 99)
if chunk2 == nil {
t.Errorf("chunk2 is nil")
t.FailNow()
}
if len(chunk1.Hashes) != 99 {
t.Error("expected chunk1 hashes to be 99, got", len(chunk1.Hashes))
}
if len(chunk2.Hashes) != 1 {
t.Error("expected chunk1 hashes to be 1, got", len(chunk2.Hashes))
}
}