eth/fetcher: fix timer reset bug, add initial tests

2 files changed, 207 insertions, 3 deletions

diff --git a/eth/fetcher/fetcher.go b/eth/fetcher/fetcher.go
index 19c53048c..a8d1f2fb5 100644
--- a/eth/fetcher/fetcher.go
+++ b/eth/fetcher/fetcher.go
@@ -149,7 +149,8 @@ func (f *Fetcher) loop() {
 				break
 			}
 			if len(announced) == 0 {
-				fetch.Reset(arriveTimeout)
+				glog.V(logger.Detail).Infof("Scheduling fetch in %v, at %v", arriveTimeout-time.Since(notification.time), notification.time.Add(arriveTimeout))
+				fetch.Reset(arriveTimeout - time.Since(notification.time))
 			}
 			announced[notification.hash] = append(announced[notification.hash], notification)
 
@@ -181,11 +182,12 @@ func (f *Fetcher) loop() {
 			if len(announced) > 0 {
 				nearest := time.Now()
 				for _, announces := range announced {
-					if nearest.Before(announces[0].time) {
+					if nearest.After(announces[0].time) {
 						nearest = announces[0].time
 					}
 				}
-				fetch.Reset(arriveTimeout + time.Since(nearest))
+				glog.V(logger.Detail).Infof("Rescheduling fetch in %v, at %v", arriveTimeout-time.Since(nearest), nearest.Add(arriveTimeout))
+				fetch.Reset(arriveTimeout - time.Since(nearest))
 			}
 
 		case filter := <-f.filter:
diff --git a/eth/fetcher/fetcher_test.go b/eth/fetcher/fetcher_test.go
new file mode 100644
index 000000000..e29f9c7cd
--- /dev/null
+++ b/eth/fetcher/fetcher_test.go
@@ -0,0 +1,202 @@
+package fetcher
+
+import (
+	"encoding/binary"
+	"errors"
+	"math/big"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+var (
+	knownHash   = common.Hash{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
+	unknownHash = common.Hash{2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2}
+	bannedHash  = common.Hash{3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3}
+
+	genesis = createBlock(1, common.Hash{}, knownHash)
+)
+
+// idCounter is used by the createHashes method the generate deterministic but unique hashes
+var idCounter = int64(2) // #1 is the genesis block
+
+// createHashes generates a batch of hashes rooted at a specific point in the chain.
+func createHashes(amount int, root common.Hash) (hashes []common.Hash) {
+	hashes = make([]common.Hash, amount+1)
+	hashes[len(hashes)-1] = root
+
+	for i := 0; i < len(hashes)-1; i++ {
+		binary.BigEndian.PutUint64(hashes[i][:8], uint64(idCounter))
+		idCounter++
+	}
+	return
+}
+
+// createBlock assembles a new block at the given chain height.
+func createBlock(i int, parent, hash common.Hash) *types.Block {
+	header := &types.Header{Number: big.NewInt(int64(i))}
+	block := types.NewBlockWithHeader(header)
+	block.HeaderHash = hash
+	block.ParentHeaderHash = parent
+	return block
+}
+
+// copyBlock makes a deep copy of a block suitable for local modifications.
+func copyBlock(block *types.Block) *types.Block {
+	return createBlock(int(block.Number().Int64()), block.ParentHeaderHash, block.HeaderHash)
+}
+
+// createBlocksFromHashes assembles a collection of blocks, each having a correct
+// place in the given hash chain.
+func createBlocksFromHashes(hashes []common.Hash) map[common.Hash]*types.Block {
+	blocks := make(map[common.Hash]*types.Block)
+	for i := 0; i < len(hashes); i++ {
+		parent := knownHash
+		if i < len(hashes)-1 {
+			parent = hashes[i+1]
+		}
+		blocks[hashes[i]] = createBlock(len(hashes)-i, parent, hashes[i])
+	}
+	return blocks
+}
+
+// fetcherTester is a test simulator for mocking out local block chain.
+type fetcherTester struct {
+	fetcher *Fetcher
+
+	ownHashes []common.Hash                // Hash chain belonging to the tester
+	ownBlocks map[common.Hash]*types.Block // Blocks belonging to the tester
+}
+
+// newTester creates a new fetcher test mocker.
+func newTester() *fetcherTester {
+	tester := &fetcherTester{
+		ownHashes: []common.Hash{knownHash},
+		ownBlocks: map[common.Hash]*types.Block{knownHash: genesis},
+	}
+	tester.fetcher = New(tester.hasBlock, tester.importBlock)
+	tester.fetcher.Start()
+
+	return tester
+}
+
+// hasBlock checks if a block is pres	ent in the testers canonical chain.
+func (f *fetcherTester) hasBlock(hash common.Hash) bool {
+	_, ok := f.ownBlocks[hash]
+	return ok
+}
+
+// importBlock injects a new blocks into the simulated chain.
+func (f *fetcherTester) importBlock(peer string, block *types.Block) error {
+	if _, ok := f.ownBlocks[block.ParentHash()]; !ok {
+		return errors.New("unknown parent")
+	}
+	f.ownHashes = append(f.ownHashes, block.Hash())
+	f.ownBlocks[block.Hash()] = block
+	return nil
+}
+
+// peerFetcher retrieves a fetcher associated with a simulated peer.
+func (f *fetcherTester) makeFetcher(blocks map[common.Hash]*types.Block) blockRequesterFn {
+	// Copy all the blocks to ensure they are not tampered with
+	closure := make(map[common.Hash]*types.Block)
+	for hash, block := range blocks {
+		closure[hash] = copyBlock(block)
+	}
+	// Create a function that returns blocks from the closure
+	return func(hashes []common.Hash) error {
+		// Gather the blocks to return
+		blocks := make([]*types.Block, 0, len(hashes))
+		for _, hash := range hashes {
+			if block, ok := closure[hash]; ok {
+				blocks = append(blocks, block)
+			}
+		}
+		// Return on a new thread
+		go f.fetcher.Filter(blocks)
+
+		return nil
+	}
+}
+
+// Tests that a fetcher accepts block announcements and initiates retrievals for
+// them, successfully importing into the local chain.
+func TestSequentialAnnouncements(t *testing.T) {
+	// Create a chain of blocks to import
+	targetBlocks := 24
+	hashes := createHashes(targetBlocks, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	// Iteratively announce blocks until all are imported
+	for i := len(hashes) - 1; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
+		time.Sleep(50 * time.Millisecond)
+	}
+	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
+	}
+}
+
+// Tests that if blocks are announced by multiple peers (or even the same buggy
+// peer), they will only get downloaded at most once.
+func TestConcurrentAnnouncements(t *testing.T) {
+	// Create a chain of blocks to import
+	targetBlocks := 24
+	hashes := createHashes(targetBlocks, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	// Assemble a tester with a built in counter for the requests
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	counter := uint32(0)
+	wrapper := func(hashes []common.Hash) error {
+		atomic.AddUint32(&counter, uint32(len(hashes)))
+		return fetcher(hashes)
+	}
+	// Iteratively announce blocks until all are imported
+	for i := len(hashes) - 1; i >= 0; i-- {
+		tester.fetcher.Notify("first", hashes[i], time.Now().Add(-arriveTimeout), wrapper)
+		tester.fetcher.Notify("second", hashes[i], time.Now().Add(-arriveTimeout+time.Millisecond), wrapper)
+		tester.fetcher.Notify("second", hashes[i], time.Now().Add(-arriveTimeout-time.Millisecond), wrapper)
+
+		time.Sleep(50 * time.Millisecond)
+	}
+	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
+	}
+	// Make sure no blocks were retrieved twice
+	if int(counter) != targetBlocks {
+		t.Fatalf("retrieval count mismatch: have %v, want %v", counter, targetBlocks)
+	}
+}
+
+// Tests that announcements arriving while a previous is being fetched still
+// results in a valid import.
+func TestOverlappingAnnouncements(t *testing.T) {
+	// Create a chain of blocks to import
+	targetBlocks := 24
+	hashes := createHashes(targetBlocks, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	// Iteratively announce blocks, but overlap them continuously
+	delay, overlap := 50*time.Millisecond, time.Duration(5)
+	for i := len(hashes) - 1; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout+overlap*delay), fetcher)
+		time.Sleep(delay)
+	}
+	time.Sleep(overlap * delay)
+
+	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
+	}
+}