aboutsummaryrefslogtreecommitdiffstats
path: root/eth/downloader/queue.go
blob: c53ad939e80e2677104fc81b59be2be6d6d19382 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum 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-ethereum 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 for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// Contains the block download scheduler to collect download tasks and schedule
// them in an ordered, and throttled way.

package downloader

import (
    "errors"
    "fmt"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/rcrowley/go-metrics"
    "gopkg.in/karalabe/cookiejar.v2/collections/prque"
)

var (
    blockCacheLimit = 1024 // Maximum number of blocks to cache before throttling the download
)

var (
    errNoFetchesPending = errors.New("no fetches pending")
    errStaleDelivery    = errors.New("stale delivery")
)

// fetchRequest is a currently running data retrieval operation.
type fetchRequest struct {
    Peer    *peer               // Peer to which the request was sent
    Hashes  map[common.Hash]int // [eth/61] Requested block with their insertion index (priority)
    Headers []*types.Header     // [eth/62] Requested headers, sorted by request order
    Time    time.Time           // Time when the request was made
}

// fetchResult is the assembly collecting partial results from potentially more
// than one fetcher routines, until all outstanding retrievals complete and the
// result as a whole can be processed.
type fetchResult struct {
    Pending int // Number of data fetches still pending

    Header       *types.Header
    Uncles       []*types.Header
    Transactions types.Transactions
    Receipts     types.Receipts
}

// queue represents hashes that are either need fetching or are being fetched
type queue struct {
    hashPool    map[common.Hash]int // [eth/61] Pending hashes, mapping to their insertion index (priority)
    hashQueue   *prque.Prque        // [eth/61] Priority queue of the block hashes to fetch
    hashCounter int                 // [eth/61] Counter indexing the added hashes to ensure retrieval order

    headerHead common.Hash // [eth/62] Hash of the last queued header to verify order

    blockTaskPool  map[common.Hash]*types.Header // [eth/62] Pending block (body) retrieval tasks, mapping hashes to headers
    blockTaskQueue *prque.Prque                  // [eth/62] Priority queue of the headers to fetch the blocks (bodies) for
    blockPendPool  map[string]*fetchRequest      // [eth/62] Currently pending block (body) retrieval operations
    blockDonePool  map[common.Hash]struct{}      // [eth/62] Set of the completed block (body) fetches

    receiptTaskPool  map[common.Hash]*types.Header // [eth/63] Pending receipt retrieval tasks, mapping hashes to headers
    receiptTaskQueue *prque.Prque                  // [eth/63] Priority queue of the headers to fetch the receipts for
    receiptPendPool  map[string]*fetchRequest      // [eth/63] Currently pending receipt retrieval operations
    receiptDonePool  map[common.Hash]struct{}      // [eth/63] Set of the completed receipt fetches

    resultCache  []*fetchResult // Downloaded but not yet delivered fetch results
    resultOffset uint64         // Offset of the first cached fetch result in the block-chain
    resultParts  int            // Number of fetch components required to complete an item

    lock sync.RWMutex
}

// newQueue creates a new download queue for scheduling block retrieval.
func newQueue() *queue {
    return &queue{
        hashPool:         make(map[common.Hash]int),
        hashQueue:        prque.New(),
        blockTaskPool:    make(map[common.Hash]*types.Header),
        blockTaskQueue:   prque.New(),
        blockPendPool:    make(map[string]*fetchRequest),
        blockDonePool:    make(map[common.Hash]struct{}),
        receiptTaskPool:  make(map[common.Hash]*types.Header),
        receiptTaskQueue: prque.New(),
        receiptPendPool:  make(map[string]*fetchRequest),
        receiptDonePool:  make(map[common.Hash]struct{}),
        resultCache:      make([]*fetchResult, blockCacheLimit),
    }
}

// Reset clears out the queue contents.
func (q *queue) Reset() {
    q.lock.Lock()
    defer q.lock.Unlock()

    q.hashPool = make(map[common.Hash]int)
    q.hashQueue.Reset()
    q.hashCounter = 0

    q.headerHead = common.Hash{}

    q.blockTaskPool = make(map[common.Hash]*types.Header)
    q.blockTaskQueue.Reset()
    q.blockPendPool = make(map[string]*fetchRequest)
    q.blockDonePool = make(map[common.Hash]struct{})

    q.receiptTaskPool = make(map[common.Hash]*types.Header)
    q.receiptTaskQueue.Reset()
    q.receiptPendPool = make(map[string]*fetchRequest)
    q.receiptDonePool = make(map[common.Hash]struct{})

    q.resultCache = make([]*fetchResult, blockCacheLimit)
    q.resultOffset = 0
    q.resultParts = 0
}

// PendingBlocks retrieves the number of block (body) requests pending for retrieval.
func (q *queue) PendingBlocks() int {
    q.lock.RLock()
    defer q.lock.RUnlock()

    return q.hashQueue.Size() + q.blockTaskQueue.Size()
}

// PendingReceipts retrieves the number of block receipts pending for retrieval.
func (q *queue) PendingReceipts() int {
    q.lock.RLock()
    defer q.lock.RUnlock()

    return q.receiptTaskQueue.Size()
}

// InFlight retrieves the number of fetch requests currently in flight.
func (q *queue) InFlight() int {
    q.lock.RLock()
    defer q.lock.RUnlock()

    return len(q.blockPendPool) + len(q.receiptPendPool)
}

// Idle returns if the queue is fully idle or has some data still inside. This
// method is used by the tester to detect termination events.
func (q *queue) Idle() bool {
    q.lock.RLock()
    defer q.lock.RUnlock()

    queued := q.hashQueue.Size() + q.blockTaskQueue.Size() + q.receiptTaskQueue.Size()
    pending := len(q.blockPendPool) + len(q.receiptPendPool)
    cached := len(q.blockDonePool) + len(q.receiptDonePool)

    return (queued + pending + cached) == 0
}

// ThrottleBlocks checks if the download should be throttled (active block (body)
// fetches exceed block cache).
func (q *queue) ThrottleBlocks() bool {
    q.lock.RLock()
    defer q.lock.RUnlock()

    // Calculate the currently in-flight block (body) requests
    pending := 0
    for _, request := range q.blockPendPool {
        pending += len(request.Hashes) + len(request.Headers)
    }
    // Throttle if more blocks (bodies) are in-flight than free space in the cache
    return pending >= len(q.resultCache)-len(q.blockDonePool)
}

// ThrottleReceipts checks if the download should be throttled (active receipt
// fetches exceed block cache).
func (q *queue) ThrottleReceipts() bool {
    q.lock.RLock()
    defer q.lock.RUnlock()

    // Calculate the currently in-flight receipt requests
    pending := 0
    for _, request := range q.receiptPendPool {
        pending += len(request.Headers)
    }
    // Throttle if more receipts are in-flight than free space in the cache
    return pending >= len(q.resultCache)-len(q.receiptDonePool)
}

// Schedule61 adds a set of hashes for the download queue for scheduling, returning
// the new hashes encountered.
func (q *queue) Schedule61(hashes []common.Hash, fifo bool) []common.Hash {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Insert all the hashes prioritized in the arrival order
    inserts := make([]common.Hash, 0, len(hashes))
    for _, hash := range hashes {
        // Skip anything we already have
        if old, ok := q.hashPool[hash]; ok {
            glog.V(logger.Warn).Infof("Hash %x already scheduled at index %v", hash, old)
            continue
        }
        // Update the counters and insert the hash
        q.hashCounter = q.hashCounter + 1
        inserts = append(inserts, hash)

        q.hashPool[hash] = q.hashCounter
        if fifo {
            q.hashQueue.Push(hash, -float32(q.hashCounter)) // Lowest gets schedules first
        } else {
            q.hashQueue.Push(hash, float32(q.hashCounter)) // Highest gets schedules first
        }
    }
    return inserts
}

// Schedule adds a set of headers for the download queue for scheduling, returning
// the new headers encountered.
func (q *queue) Schedule(headers []*types.Header, from uint64, receipts bool) []*types.Header {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Insert all the headers prioritized by the contained block number
    inserts := make([]*types.Header, 0, len(headers))
    for _, header := range headers {
        // Make sure chain order is honored and preserved throughout
        hash := header.Hash()
        if header.Number == nil || header.Number.Uint64() != from {
            glog.V(logger.Warn).Infof("Header #%v [%x] broke chain ordering, expected %d", header.Number, hash[:4], from)
            break
        }
        if q.headerHead != (common.Hash{}) && q.headerHead != header.ParentHash {
            glog.V(logger.Warn).Infof("Header #%v [%x] broke chain ancestry", header.Number, hash[:4])
            break
        }
        // Make sure no duplicate requests are executed
        if _, ok := q.blockTaskPool[hash]; ok {
            glog.V(logger.Warn).Infof("Header #%d [%x] already scheduled for block fetch", header.Number.Uint64(), hash[:4])
            continue
        }
        if _, ok := q.receiptTaskPool[hash]; ok {
            glog.V(logger.Warn).Infof("Header #%d [%x] already scheduled for receipt fetch", header.Number.Uint64(), hash[:4])
            continue
        }
        // Queue the header for content retrieval
        q.blockTaskPool[hash] = header
        q.blockTaskQueue.Push(header, -float32(header.Number.Uint64()))
        if receipts {
            q.receiptTaskPool[hash] = header
            q.receiptTaskQueue.Push(header, -float32(header.Number.Uint64()))
        }
        inserts = append(inserts, header)
        q.headerHead = hash
        from++
    }
    return inserts
}

// GetHeadResult retrieves the first fetch result from the cache, or nil if it hasn't
// been downloaded yet (or simply non existent).
func (q *queue) GetHeadResult() *fetchResult {
    q.lock.RLock()
    defer q.lock.RUnlock()

    if len(q.resultCache) == 0 || q.resultCache[0] == nil {
        return nil
    }
    if q.resultCache[0].Pending > 0 {
        return nil
    }
    return q.resultCache[0]
}

// TakeResults retrieves and permanently removes a batch of fetch results from
// the cache.
func (q *queue) TakeResults() []*fetchResult {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Accumulate all available results
    results := []*fetchResult{}
    for _, result := range q.resultCache {
        if result == nil || result.Pending > 0 {
            break
        }
        results = append(results, result)

        hash := result.Header.Hash()
        delete(q.blockDonePool, hash)
        delete(q.receiptDonePool, hash)
    }
    // Delete the results from the slice and let them be garbage collected
    // without this slice trick the results would stay in memory until nil
    // would be assigned to them.
    copy(q.resultCache, q.resultCache[len(results):])
    for k, n := len(q.resultCache)-len(results), len(q.resultCache); k < n; k++ {
        q.resultCache[k] = nil
    }
    q.resultOffset += uint64(len(results))

    return results
}

// Reserve61 reserves a set of hashes for the given peer, skipping any previously
// failed download.
func (q *queue) Reserve61(p *peer, count int) *fetchRequest {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Short circuit if the pool has been depleted, or if the peer's already
    // downloading something (sanity check not to corrupt state)
    if q.hashQueue.Empty() {
        return nil
    }
    if _, ok := q.blockPendPool[p.id]; ok {
        return nil
    }
    // Calculate an upper limit on the hashes we might fetch (i.e. throttling)
    space := len(q.resultCache) - len(q.blockDonePool)
    for _, request := range q.blockPendPool {
        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 proc := 0; proc < space && len(send) < count && !q.hashQueue.Empty(); proc++ {
        hash, priority := q.hashQueue.Pop()
        if p.ignored.Has(hash) {
            skip[hash.(common.Hash)] = int(priority)
        } else {
            send[hash.(common.Hash)] = int(priority)
        }
    }
    // Merge all the skipped hashes back
    for hash, index := range skip {
        q.hashQueue.Push(hash, float32(index))
    }
    // Assemble and return the block download request
    if len(send) == 0 {
        return nil
    }
    request := &fetchRequest{
        Peer:   p,
        Hashes: send,
        Time:   time.Now(),
    }
    q.blockPendPool[p.id] = request

    return request
}

// ReserveBlocks reserves a set of body fetches for the given peer, skipping any
// previously failed downloads. Beside the next batch of needed fetches, it also
// returns a flag whether empty blocks were queued requiring processing.
func (q *queue) ReserveBlocks(p *peer, count int) (*fetchRequest, bool, error) {
    noop := func(header *types.Header) bool {
        return header.TxHash == types.EmptyRootHash && header.UncleHash == types.EmptyUncleHash
    }
    return q.reserveFetch(p, count, q.blockTaskPool, q.blockTaskQueue, q.blockPendPool, q.blockDonePool, noop)
}

// ReserveReceipts reserves a set of receipt fetches for the given peer, skipping
// any previously failed downloads. Beside the next batch of needed fetches, it
// also returns a flag whether empty receipts were queued requiring importing.
func (q *queue) ReserveReceipts(p *peer, count int) (*fetchRequest, bool, error) {
    noop := func(header *types.Header) bool {
        return header.ReceiptHash == types.EmptyRootHash
    }
    return q.reserveFetch(p, count, q.receiptTaskPool, q.receiptTaskQueue, q.receiptPendPool, q.receiptDonePool, noop)
}

// reserveFetch reserves a set of data download operations for a given peer,
// skipping any previously failed ones. This method is a generic version used
// by the individual special reservation functions.
func (q *queue) reserveFetch(p *peer, count int, taskPool map[common.Hash]*types.Header, taskQueue *prque.Prque,
    pendPool map[string]*fetchRequest, donePool map[common.Hash]struct{}, noop func(*types.Header) bool) (*fetchRequest, bool, error) {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Short circuit if the pool has been depleted, or if the peer's already
    // downloading something (sanity check not to corrupt state)
    if taskQueue.Empty() {
        return nil, false, nil
    }
    if _, ok := pendPool[p.id]; ok {
        return nil, false, nil
    }
    // Calculate an upper limit on the items we might fetch (i.e. throttling)
    space := len(q.resultCache) - len(donePool)
    for _, request := range pendPool {
        space -= len(request.Headers)
    }
    // Retrieve a batch of tasks, skipping previously failed ones
    send := make([]*types.Header, 0, count)
    skip := make([]*types.Header, 0)

    progress := false
    for proc := 0; proc < space && len(send) < count && !taskQueue.Empty(); proc++ {
        header := taskQueue.PopItem().(*types.Header)

        // If we're the first to request this task, initialize the result container
        index := int(header.Number.Int64() - int64(q.resultOffset))
        if index >= len(q.resultCache) || index < 0 {
            return nil, false, errInvalidChain
        }
        if q.resultCache[index] == nil {
            q.resultCache[index] = &fetchResult{
                Pending: q.resultParts,
                Header:  header,
            }
        }
        // If this fetch task is a noop, skip this fetch operation
        if noop(header) {
            donePool[header.Hash()] = struct{}{}
            delete(taskPool, header.Hash())

            space, proc = space-1, proc-1
            q.resultCache[index].Pending--
            progress = true
            continue
        }
        // Otherwise if not a known unknown block, add to the retrieve list
        if p.ignored.Has(header.Hash()) {
            skip = append(skip, header)
        } else {
            send = append(send, header)
        }
    }
    // Merge all the skipped headers back
    for _, header := range skip {
        taskQueue.Push(header, -float32(header.Number.Uint64()))
    }
    // Assemble and return the block download request
    if len(send) == 0 {
        return nil, progress, nil
    }
    request := &fetchRequest{
        Peer:    p,
        Headers: send,
        Time:    time.Now(),
    }
    pendPool[p.id] = request

    return request, progress, nil
}

// Cancel61 aborts a fetch request, returning all pending hashes to the queue.
func (q *queue) Cancel61(request *fetchRequest) {
    q.cancel(request, nil, q.blockPendPool)
}

// CancelBlocks aborts a body fetch request, returning all pending hashes to the
// task queue.
func (q *queue) CancelBlocks(request *fetchRequest) {
    q.cancel(request, q.blockTaskQueue, q.blockPendPool)
}

// CancelReceipts aborts a body fetch request, returning all pending hashes to
// the task queue.
func (q *queue) CancelReceipts(request *fetchRequest) {
    q.cancel(request, q.receiptTaskQueue, q.receiptPendPool)
}

// Cancel aborts a fetch request, returning all pending hashes to the task queue.
func (q *queue) cancel(request *fetchRequest, taskQueue *prque.Prque, pendPool map[string]*fetchRequest) {
    q.lock.Lock()
    defer q.lock.Unlock()

    for hash, index := range request.Hashes {
        q.hashQueue.Push(hash, float32(index))
    }
    for _, header := range request.Headers {
        taskQueue.Push(header, -float32(header.Number.Uint64()))
    }
    delete(pendPool, request.Peer.id)
}

// Revoke cancels all pending requests belonging to a given peer. This method is
// meant to be called during a peer drop to quickly reassign owned data fetches
// to remaining nodes.
func (q *queue) Revoke(peerId string) {
    q.lock.Lock()
    defer q.lock.Unlock()

    if request, ok := q.blockPendPool[peerId]; ok {
        for hash, index := range request.Hashes {
            q.hashQueue.Push(hash, float32(index))
        }
        for _, header := range request.Headers {
            q.blockTaskQueue.Push(header, -float32(header.Number.Uint64()))
        }
        delete(q.blockPendPool, peerId)
    }
    if request, ok := q.receiptPendPool[peerId]; ok {
        for _, header := range request.Headers {
            q.receiptTaskQueue.Push(header, -float32(header.Number.Uint64()))
        }
        delete(q.receiptPendPool, peerId)
    }
}

// Expire61 checks for in flight requests that exceeded a timeout allowance,
// canceling them and returning the responsible peers for penalization.
func (q *queue) Expire61(timeout time.Duration) []string {
    return q.expire(timeout, q.blockPendPool, nil)
}

// ExpireBlocks checks for in flight block body requests that exceeded a timeout
// allowance, canceling them and returning the responsible peers for penalization.
func (q *queue) ExpireBlocks(timeout time.Duration) []string {
    return q.expire(timeout, q.blockPendPool, q.blockTaskQueue)
}

// ExpireReceipts checks for in flight receipt requests that exceeded a timeout
// allowance, canceling them and returning the responsible peers for penalization.
func (q *queue) ExpireReceipts(timeout time.Duration) []string {
    return q.expire(timeout, q.receiptPendPool, q.receiptTaskQueue)
}

// expire is the generic check that move expired tasks from a pending pool back
// into a task pool, returning all entities caught with expired tasks.
func (q *queue) expire(timeout time.Duration, pendPool map[string]*fetchRequest, taskQueue *prque.Prque) []string {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Iterate over the expired requests and return each to the queue
    peers := []string{}
    for id, request := range pendPool {
        if time.Since(request.Time) > timeout {
            // Update the metrics with the timeout
            if len(request.Hashes) > 0 {
                blockTimeoutMeter.Mark(1)
            } else {
                bodyTimeoutMeter.Mark(1)
            }
            // Return any non satisfied requests to the pool
            for hash, index := range request.Hashes {
                q.hashQueue.Push(hash, float32(index))
            }
            for _, header := range request.Headers {
                taskQueue.Push(header, -float32(header.Number.Uint64()))
            }
            peers = append(peers, id)
        }
    }
    // Remove the expired requests from the pending pool
    for _, id := range peers {
        delete(pendPool, id)
    }
    return peers
}

// Deliver61 injects a block retrieval response into the download queue.
func (q *queue) Deliver61(id string, blocks []*types.Block) (err error) {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Short circuit if the blocks were never requested
    request := q.blockPendPool[id]
    if request == nil {
        return errNoFetchesPending
    }
    blockReqTimer.UpdateSince(request.Time)
    delete(q.blockPendPool, id)

    // If no blocks were retrieved, mark them as unavailable for the origin peer
    if len(blocks) == 0 {
        for hash, _ := range request.Hashes {
            request.Peer.ignored.Add(hash)
        }
    }
    // Iterate over the downloaded blocks and add each of them
    errs := make([]error, 0)
    for _, block := range blocks {
        // Skip any blocks that were not requested
        hash := block.Hash()
        if _, ok := request.Hashes[hash]; !ok {
            errs = append(errs, fmt.Errorf("non-requested block %x", hash))
            continue
        }
        // Reconstruct the next result if contents match up
        index := int(block.Number().Int64() - int64(q.resultOffset))
        if index >= len(q.resultCache) || index < 0 {
            errs = []error{errInvalidChain}
            break
        }
        q.resultCache[index] = &fetchResult{
            Header:       block.Header(),
            Transactions: block.Transactions(),
            Uncles:       block.Uncles(),
        }
        q.blockDonePool[block.Hash()] = struct{}{}

        delete(request.Hashes, hash)
        delete(q.hashPool, hash)
    }
    // Return all failed or missing fetches to the queue
    for hash, index := range request.Hashes {
        q.hashQueue.Push(hash, float32(index))
    }
    // If none of the blocks were good, it's a stale delivery
    switch {
    case len(errs) == 0:
        return nil

    case len(errs) == 1 && (errs[0] == errInvalidChain || errs[0] == errInvalidBlock):
        return errs[0]

    case len(errs) == len(request.Headers):
        return errStaleDelivery

    default:
        return fmt.Errorf("multiple failures: %v", errs)
    }
}

// DeliverBlocks injects a block (body) retrieval response into the results queue.
func (q *queue) DeliverBlocks(id string, txLists [][]*types.Transaction, uncleLists [][]*types.Header) error {
    reconstruct := func(header *types.Header, index int, result *fetchResult) error {
        if types.DeriveSha(types.Transactions(txLists[index])) != header.TxHash || types.CalcUncleHash(uncleLists[index]) != header.UncleHash {
            return errInvalidBody
        }
        result.Transactions = txLists[index]
        result.Uncles = uncleLists[index]
        return nil
    }
    return q.deliver(id, q.blockTaskPool, q.blockTaskQueue, q.blockPendPool, q.blockDonePool, bodyReqTimer, len(txLists), reconstruct)
}

// DeliverReceipts injects a receipt retrieval response into the results queue.
func (q *queue) DeliverReceipts(id string, receiptList [][]*types.Receipt) error {
    reconstruct := func(header *types.Header, index int, result *fetchResult) error {
        if types.DeriveSha(types.Receipts(receiptList[index])) != header.ReceiptHash {
            return errInvalidReceipt
        }
        result.Receipts = receiptList[index]
        return nil
    }
    return q.deliver(id, q.receiptTaskPool, q.receiptTaskQueue, q.receiptPendPool, q.receiptDonePool, receiptReqTimer, len(receiptList), reconstruct)
}

// deliver injects a data retrieval response into the results queue.
func (q *queue) deliver(id string, taskPool map[common.Hash]*types.Header, taskQueue *prque.Prque, pendPool map[string]*fetchRequest,
    donePool map[common.Hash]struct{}, reqTimer metrics.Timer, results int, reconstruct func(header *types.Header, index int, result *fetchResult) error) error {
    q.lock.Lock()
    defer q.lock.Unlock()

    // Short circuit if the data was never requested
    request := pendPool[id]
    if request == nil {
        return errNoFetchesPending
    }
    reqTimer.UpdateSince(request.Time)
    delete(pendPool, id)

    // If no data items were retrieved, mark them as unavailable for the origin peer
    if results == 0 {
        for hash, _ := range request.Headers {
            request.Peer.ignored.Add(hash)
        }
    }
    // Assemble each of the results with their headers and retrieved data parts
    errs := make([]error, 0)
    for i, header := range request.Headers {
        // Short circuit assembly if no more fetch results are found
        if i >= results {
            break
        }
        // Reconstruct the next result if contents match up
        index := int(header.Number.Int64() - int64(q.resultOffset))
        if index >= len(q.resultCache) || index < 0 || q.resultCache[index] == nil {
            errs = []error{errInvalidChain}
            break
        }
        if err := reconstruct(header, i, q.resultCache[index]); err != nil {
            errs = []error{err}
            break
        }
        donePool[header.Hash()] = struct{}{}
        q.resultCache[index].Pending--

        // Clean up a successful fetch
        request.Headers[i] = nil
        delete(taskPool, header.Hash())
    }
    // Return all failed or missing fetches to the queue
    for _, header := range request.Headers {
        if header != nil {
            taskQueue.Push(header, -float32(header.Number.Uint64()))
        }
    }
    // If none of the blocks were good, it's a stale delivery
    switch {
    case len(errs) == 0:
        return nil

    case len(errs) == 1 && (errs[0] == errInvalidChain || errs[0] == errInvalidBody || errs[0] == errInvalidReceipt):
        return errs[0]

    case len(errs) == len(request.Headers):
        return errStaleDelivery

    default:
        return fmt.Errorf("multiple failures: %v", errs)
    }
}

// Prepare configures the result cache to allow accepting and caching inbound
// fetch results.
func (q *queue) Prepare(offset uint64, parts int) {
    q.lock.Lock()
    defer q.lock.Unlock()

    if q.resultOffset < offset {
        q.resultOffset = offset
    }
    q.resultParts = parts
}