1use super::queue::BodiesRequestQueue;
2use crate::{bodies::task::TaskDownloader, metrics::BodyDownloaderMetrics};
3use alloy_consensus::BlockHeader;
4use alloy_primitives::BlockNumber;
5use futures::Stream;
6use futures_util::StreamExt;
7use reth_config::BodiesConfig;
8use reth_consensus::{Consensus, ConsensusError};
9use reth_network_p2p::{
10 bodies::{
11 client::BodiesClient,
12 downloader::{BodyDownloader, BodyDownloaderResult},
13 response::BlockResponse,
14 },
15 error::{DownloadError, DownloadResult},
16};
17use reth_primitives_traits::{size::InMemorySize, Block, SealedHeader};
18use reth_storage_api::HeaderProvider;
19use reth_tasks::{TaskSpawner, TokioTaskExecutor};
20use std::{
21 cmp::Ordering,
22 collections::BinaryHeap,
23 fmt::Debug,
24 mem,
25 ops::RangeInclusive,
26 pin::Pin,
27 sync::Arc,
28 task::{Context, Poll},
29};
30use tracing::info;
31
32#[must_use = "Stream does nothing unless polled"]
36#[derive(Debug)]
37pub struct BodiesDownloader<
38 B: Block,
39 C: BodiesClient<Body = B::Body>,
40 Provider: HeaderProvider<Header = B::Header>,
41> {
42 client: Arc<C>,
44 consensus: Arc<dyn Consensus<B, Error = ConsensusError>>,
46 provider: Provider,
48 request_limit: u64,
50 stream_batch_size: usize,
52 concurrent_requests_range: RangeInclusive<usize>,
54 max_buffered_blocks_size_bytes: usize,
56 buffered_blocks_size_bytes: usize,
58 download_range: RangeInclusive<BlockNumber>,
60 latest_queued_block_number: Option<BlockNumber>,
62 in_progress_queue: BodiesRequestQueue<B, C>,
64 buffered_responses: BinaryHeap<OrderedBodiesResponse<B>>,
66 queued_bodies: Vec<BlockResponse<B>>,
68 metrics: BodyDownloaderMetrics,
70}
71
72impl<B, C, Provider> BodiesDownloader<B, C, Provider>
73where
74 B: Block,
75 C: BodiesClient<Body = B::Body> + 'static,
76 Provider: HeaderProvider<Header = B::Header> + Unpin + 'static,
77{
78 fn next_headers_request(&self) -> DownloadResult<Option<Vec<SealedHeader<Provider::Header>>>> {
80 let start_at = match self.in_progress_queue.last_requested_block_number {
81 Some(num) => num + 1,
82 None => *self.download_range.start(),
83 };
84 let items_left = (self.download_range.end() + 1).saturating_sub(start_at);
86 let limit = items_left.min(self.request_limit);
87 self.query_headers(start_at..=*self.download_range.end(), limit)
88 }
89
90 fn query_headers(
101 &self,
102 range: RangeInclusive<BlockNumber>,
103 max_non_empty: u64,
104 ) -> DownloadResult<Option<Vec<SealedHeader<B::Header>>>> {
105 if range.is_empty() || max_non_empty == 0 {
106 return Ok(None)
107 }
108
109 let mut collected = 0;
115 let mut non_empty_headers = 0;
116 let headers = self.provider.sealed_headers_while(range.clone(), |header| {
117 let should_take = range.contains(&header.number()) &&
118 non_empty_headers < max_non_empty &&
119 collected < self.stream_batch_size;
120
121 if should_take {
122 collected += 1;
123 if !header.is_empty() {
124 non_empty_headers += 1;
125 }
126 true
127 } else {
128 false
129 }
130 })?;
131
132 Ok(Some(headers).filter(|h| !h.is_empty()))
133 }
134
135 const fn next_expected_block_number(&self) -> BlockNumber {
137 match self.latest_queued_block_number {
138 Some(num) => num + 1,
139 None => *self.download_range.start(),
140 }
141 }
142
143 #[inline]
148 fn concurrent_request_limit(&self) -> usize {
149 let num_peers = self.client.num_connected_peers();
150
151 let max_requests = num_peers.max(*self.concurrent_requests_range.start());
152
153 if num_peers < *self.concurrent_requests_range.start() {
155 return max_requests
156 }
157
158 max_requests.min(*self.concurrent_requests_range.end())
159 }
160
161 const fn has_buffer_capacity(&self) -> bool {
163 self.buffered_blocks_size_bytes < self.max_buffered_blocks_size_bytes
164 }
165
166 fn is_terminated(&self) -> bool {
168 let nothing_to_request = self.download_range.is_empty() ||
170 self.in_progress_queue
172 .last_requested_block_number.is_some_and(|last| last == *self.download_range.end());
173
174 nothing_to_request &&
175 self.in_progress_queue.is_empty() &&
176 self.buffered_responses.is_empty() &&
177 self.queued_bodies.is_empty()
178 }
179
180 fn clear(&mut self) {
184 self.download_range = RangeInclusive::new(1, 0);
185 self.latest_queued_block_number.take();
186 self.in_progress_queue.clear();
187 self.queued_bodies = Vec::new();
188 self.buffered_responses = BinaryHeap::new();
189 self.buffered_blocks_size_bytes = 0;
190
191 self.metrics.in_flight_requests.set(0.);
193 self.metrics.buffered_responses.set(0.);
194 self.metrics.buffered_blocks.set(0.);
195 self.metrics.buffered_blocks_size_bytes.set(0.);
196 self.metrics.queued_blocks.set(0.);
197 }
198
199 fn queue_bodies(&mut self, bodies: Vec<BlockResponse<B>>) {
201 self.latest_queued_block_number = Some(bodies.last().expect("is not empty").block_number());
202 self.queued_bodies.extend(bodies);
203 self.metrics.queued_blocks.set(self.queued_bodies.len() as f64);
204 }
205
206 fn pop_buffered_response(&mut self) -> Option<OrderedBodiesResponse<B>> {
208 let resp = self.buffered_responses.pop()?;
209 self.metrics.buffered_responses.decrement(1.);
210 self.buffered_blocks_size_bytes -= resp.size();
211 self.metrics.buffered_blocks.decrement(resp.len() as f64);
212 self.metrics.buffered_blocks_size_bytes.set(self.buffered_blocks_size_bytes as f64);
213 Some(resp)
214 }
215
216 fn buffer_bodies_response(&mut self, response: Vec<BlockResponse<B>>) {
218 let size = response.iter().map(BlockResponse::size).sum::<usize>() +
220 response.capacity() * mem::size_of::<BlockResponse<B>>();
221
222 let response = OrderedBodiesResponse { resp: response, size };
223 let response_len = response.len();
224
225 self.buffered_blocks_size_bytes += size;
226 self.buffered_responses.push(response);
227
228 self.metrics.buffered_blocks.increment(response_len as f64);
229 self.metrics.buffered_blocks_size_bytes.set(self.buffered_blocks_size_bytes as f64);
230 self.metrics.buffered_responses.set(self.buffered_responses.len() as f64);
231 }
232
233 fn try_next_buffered(&mut self) -> Option<Vec<BlockResponse<B>>> {
235 if let Some(next) = self.buffered_responses.peek() {
236 let expected = self.next_expected_block_number();
237 let next_block_range = next.block_range();
238
239 if next_block_range.contains(&expected) {
240 return self.pop_buffered_response().map(|buffered| {
241 buffered
242 .resp
243 .into_iter()
244 .skip_while(|b| b.block_number() < expected)
245 .take_while(|b| self.download_range.contains(&b.block_number()))
246 .collect()
247 })
248 }
249
250 if *next_block_range.end() < expected {
252 self.pop_buffered_response();
253 }
254 }
255 None
256 }
257
258 fn try_split_next_batch(&mut self) -> Option<Vec<BlockResponse<B>>> {
261 if self.queued_bodies.len() >= self.stream_batch_size {
262 let next_batch = self.queued_bodies.drain(..self.stream_batch_size).collect::<Vec<_>>();
263 self.queued_bodies.shrink_to_fit();
264 self.metrics.total_flushed.increment(next_batch.len() as u64);
265 self.metrics.queued_blocks.set(self.queued_bodies.len() as f64);
266 return Some(next_batch)
267 }
268 None
269 }
270
271 fn can_submit_new_request(&self) -> bool {
276 self.queued_bodies.len() < 4 * self.stream_batch_size &&
280 self.has_buffer_capacity() &&
281 self.in_progress_queue.len() < self.concurrent_request_limit()
282 }
283}
284
285impl<B, C, Provider> BodiesDownloader<B, C, Provider>
286where
287 B: Block + 'static,
288 C: BodiesClient<Body = B::Body> + 'static,
289 Provider: HeaderProvider<Header = B::Header> + Unpin + 'static,
290{
291 pub fn into_task(self) -> TaskDownloader<B> {
293 self.into_task_with(&TokioTaskExecutor::default())
294 }
295
296 pub fn into_task_with<S>(self, spawner: &S) -> TaskDownloader<B>
298 where
299 S: TaskSpawner,
300 {
301 TaskDownloader::spawn_with(self, spawner)
302 }
303}
304
305impl<B, C, Provider> BodyDownloader for BodiesDownloader<B, C, Provider>
306where
307 B: Block + 'static,
308 C: BodiesClient<Body = B::Body> + 'static,
309 Provider: HeaderProvider<Header = B::Header> + Unpin + 'static,
310{
311 type Block = B;
312
313 fn set_download_range(&mut self, range: RangeInclusive<BlockNumber>) -> DownloadResult<()> {
320 if range.is_empty() {
322 tracing::error!(target: "downloaders::bodies", ?range, "Bodies download range is invalid (empty)");
323 return Err(DownloadError::InvalidBodyRange { range })
324 }
325
326 let is_current_range_subset = self.download_range.contains(range.start()) &&
328 *range.end() == *self.download_range.end();
329 if is_current_range_subset {
330 tracing::trace!(target: "downloaders::bodies", ?range, "Download range already in progress");
331 return Ok(())
333 }
334
335 let count = *range.end() - *range.start() + 1; let is_next_consecutive_range = *range.start() == *self.download_range.end() + 1;
338 if is_next_consecutive_range {
339 tracing::trace!(target: "downloaders::bodies", ?range, "New download range set");
341 info!(target: "downloaders::bodies", count, ?range, "Downloading bodies");
342 self.download_range = range;
343 return Ok(())
344 }
345
346 tracing::trace!(target: "downloaders::bodies", ?range, prev_range = ?self.download_range, "Download range reset");
349 info!(target: "downloaders::bodies", count, ?range, "Downloading bodies");
350 if let Some(last_returned) = self.latest_queued_block_number &&
352 *range.start() < last_returned
353 {
354 self.metrics.out_of_order_requests.increment(1);
355 }
356 self.clear();
357 self.download_range = range;
358 Ok(())
359 }
360}
361
362impl<B, C, Provider> Stream for BodiesDownloader<B, C, Provider>
363where
364 B: Block + 'static,
365 C: BodiesClient<Body = B::Body> + 'static,
366 Provider: HeaderProvider<Header = B::Header> + Unpin + 'static,
367{
368 type Item = BodyDownloaderResult<B>;
369
370 fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
371 let this = self.get_mut();
372 if this.is_terminated() {
373 return Poll::Ready(None)
374 }
375 loop {
377 if let Some(next_batch) = this.try_split_next_batch() {
379 return Poll::Ready(Some(Ok(next_batch)))
380 }
381
382 while let Poll::Ready(Some(response)) = this.in_progress_queue.poll_next_unpin(cx) {
384 this.metrics.in_flight_requests.decrement(1.);
385 match response {
386 Ok(response) => {
387 this.buffer_bodies_response(response);
388 }
389 Err(error) => {
390 tracing::debug!(target: "downloaders::bodies", %error, "Request failed");
391 this.clear();
392 return Poll::Ready(Some(Err(error)))
393 }
394 };
395 }
396
397 let mut new_request_submitted = false;
399 'inner: while this.can_submit_new_request() {
401 match this.next_headers_request() {
402 Ok(Some(request)) => {
403 this.metrics.in_flight_requests.increment(1.);
404 this.in_progress_queue.push_new_request(
405 Arc::clone(&this.client),
406 Arc::clone(&this.consensus),
407 request,
408 );
409 new_request_submitted = true;
410 }
411 Ok(None) => break 'inner,
412 Err(error) => {
413 tracing::error!(target: "downloaders::bodies", %error, "Failed to download from next request");
414 this.clear();
415 return Poll::Ready(Some(Err(error)))
416 }
417 };
418 }
419
420 while let Some(buf_response) = this.try_next_buffered() {
421 this.queue_bodies(buf_response);
422 }
423
424 this.buffered_responses.shrink_to_fit();
426
427 if !new_request_submitted {
428 break
429 }
430 }
431
432 if this.in_progress_queue.is_empty() {
434 if this.queued_bodies.is_empty() {
435 return Poll::Ready(None)
436 }
437 let batch_size = this.stream_batch_size.min(this.queued_bodies.len());
438 let next_batch = this.queued_bodies.drain(..batch_size).collect::<Vec<_>>();
439 this.queued_bodies.shrink_to_fit();
440 this.metrics.total_flushed.increment(next_batch.len() as u64);
441 this.metrics.queued_blocks.set(this.queued_bodies.len() as f64);
442 return Poll::Ready(Some(Ok(next_batch)))
443 }
444
445 Poll::Pending
446 }
447}
448
449#[derive(Debug)]
450struct OrderedBodiesResponse<B: Block> {
451 resp: Vec<BlockResponse<B>>,
452 size: usize,
454}
455
456impl<B: Block> OrderedBodiesResponse<B> {
457 #[inline]
458 const fn len(&self) -> usize {
459 self.resp.len()
460 }
461
462 #[inline]
466 const fn size(&self) -> usize {
467 self.size
468 }
469}
470
471impl<B: Block> OrderedBodiesResponse<B> {
472 fn first_block_number(&self) -> u64 {
477 self.resp.first().expect("is not empty").block_number()
478 }
479
480 fn block_range(&self) -> RangeInclusive<u64> {
485 self.first_block_number()..=self.resp.last().expect("is not empty").block_number()
486 }
487}
488
489impl<B: Block> PartialEq for OrderedBodiesResponse<B> {
490 fn eq(&self, other: &Self) -> bool {
491 self.first_block_number() == other.first_block_number()
492 }
493}
494
495impl<B: Block> Eq for OrderedBodiesResponse<B> {}
496
497impl<B: Block> PartialOrd for OrderedBodiesResponse<B> {
498 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
499 Some(self.cmp(other))
500 }
501}
502
503impl<B: Block> Ord for OrderedBodiesResponse<B> {
504 fn cmp(&self, other: &Self) -> Ordering {
505 self.first_block_number().cmp(&other.first_block_number()).reverse()
506 }
507}
508
509#[derive(Debug, Clone)]
511pub struct BodiesDownloaderBuilder {
512 pub request_limit: u64,
514 pub stream_batch_size: usize,
516 pub max_buffered_blocks_size_bytes: usize,
518 pub concurrent_requests_range: RangeInclusive<usize>,
520}
521
522impl BodiesDownloaderBuilder {
523 pub fn new(config: BodiesConfig) -> Self {
526 Self::default()
527 .with_stream_batch_size(config.downloader_stream_batch_size)
528 .with_request_limit(config.downloader_request_limit)
529 .with_max_buffered_blocks_size_bytes(config.downloader_max_buffered_blocks_size_bytes)
530 .with_concurrent_requests_range(
531 config.downloader_min_concurrent_requests..=
532 config.downloader_max_concurrent_requests,
533 )
534 }
535}
536
537impl Default for BodiesDownloaderBuilder {
538 fn default() -> Self {
539 Self {
540 request_limit: 200,
541 stream_batch_size: 1_000,
542 max_buffered_blocks_size_bytes: 2 * 1024 * 1024 * 1024, concurrent_requests_range: 5..=100,
544 }
545 }
546}
547
548impl BodiesDownloaderBuilder {
549 pub const fn with_request_limit(mut self, request_limit: u64) -> Self {
551 self.request_limit = request_limit;
552 self
553 }
554
555 pub const fn with_stream_batch_size(mut self, stream_batch_size: usize) -> Self {
557 self.stream_batch_size = stream_batch_size;
558 self
559 }
560
561 pub const fn with_concurrent_requests_range(
563 mut self,
564 concurrent_requests_range: RangeInclusive<usize>,
565 ) -> Self {
566 self.concurrent_requests_range = concurrent_requests_range;
567 self
568 }
569
570 pub const fn with_max_buffered_blocks_size_bytes(
572 mut self,
573 max_buffered_blocks_size_bytes: usize,
574 ) -> Self {
575 self.max_buffered_blocks_size_bytes = max_buffered_blocks_size_bytes;
576 self
577 }
578
579 pub fn build<B, C, Provider>(
581 self,
582 client: C,
583 consensus: Arc<dyn Consensus<B, Error = ConsensusError>>,
584 provider: Provider,
585 ) -> BodiesDownloader<B, C, Provider>
586 where
587 B: Block,
588 C: BodiesClient<Body = B::Body> + 'static,
589 Provider: HeaderProvider<Header = B::Header>,
590 {
591 let Self {
592 request_limit,
593 stream_batch_size,
594 concurrent_requests_range,
595 max_buffered_blocks_size_bytes,
596 } = self;
597 let metrics = BodyDownloaderMetrics::default();
598 let in_progress_queue = BodiesRequestQueue::new(metrics.clone());
599 BodiesDownloader {
600 client: Arc::new(client),
601 consensus,
602 provider,
603 request_limit,
604 stream_batch_size,
605 max_buffered_blocks_size_bytes,
606 concurrent_requests_range,
607 in_progress_queue,
608 metrics,
609 download_range: RangeInclusive::new(1, 0),
610 latest_queued_block_number: None,
611 buffered_responses: Default::default(),
612 queued_bodies: Default::default(),
613 buffered_blocks_size_bytes: 0,
614 }
615 }
616}
617
618#[cfg(test)]
619mod tests {
620 use super::*;
621 use crate::{
622 bodies::test_utils::{insert_headers, zip_blocks},
623 test_utils::{generate_bodies, TestBodiesClient},
624 };
625 use alloy_primitives::B256;
626 use assert_matches::assert_matches;
627 use reth_consensus::test_utils::TestConsensus;
628 use reth_provider::test_utils::create_test_provider_factory;
629 use reth_testing_utils::generators::{self, random_block_range, BlockRangeParams};
630 use std::collections::HashMap;
631
632 #[tokio::test]
635 async fn streams_bodies_in_order() {
636 let factory = create_test_provider_factory();
638 let (headers, mut bodies) = generate_bodies(0..=19);
639
640 insert_headers(&factory, &headers);
641
642 let client = Arc::new(
643 TestBodiesClient::default().with_bodies(bodies.clone()).with_should_delay(true),
644 );
645
646 let mut downloader = BodiesDownloaderBuilder::default()
647 .build::<reth_ethereum_primitives::Block, _, _>(
648 client.clone(),
649 Arc::new(TestConsensus::default()),
650 factory,
651 );
652 downloader.set_download_range(0..=19).expect("failed to set download range");
653
654 assert_matches!(
655 downloader.next().await,
656 Some(Ok(res)) => assert_eq!(res, zip_blocks(headers.iter(), &mut bodies))
657 );
658 assert_eq!(client.times_requested(), 1);
659 }
660
661 #[tokio::test]
664 async fn requests_correct_number_of_times() {
665 let factory = create_test_provider_factory();
667 let mut rng = generators::rng();
668 let blocks = random_block_range(
669 &mut rng,
670 0..=199,
671 BlockRangeParams { parent: Some(B256::ZERO), tx_count: 1..2, ..Default::default() },
672 );
673
674 let headers = blocks.iter().map(|block| block.clone_sealed_header()).collect::<Vec<_>>();
675 let bodies = blocks
676 .into_iter()
677 .map(|block| (block.hash(), block.into_body()))
678 .collect::<HashMap<_, _>>();
679
680 insert_headers(&factory, &headers);
681
682 let request_limit = 10;
683 let client = Arc::new(TestBodiesClient::default().with_bodies(bodies.clone()));
684
685 let mut downloader = BodiesDownloaderBuilder::default()
686 .with_request_limit(request_limit)
687 .build::<reth_ethereum_primitives::Block, _, _>(
688 client.clone(),
689 Arc::new(TestConsensus::default()),
690 factory,
691 );
692 downloader.set_download_range(0..=199).expect("failed to set download range");
693
694 let _ = downloader.collect::<Vec<_>>().await;
695 assert_eq!(client.times_requested(), 20);
696 }
697
698 #[tokio::test]
701 async fn streams_bodies_in_order_after_range_reset() {
702 let factory = create_test_provider_factory();
704 let (headers, mut bodies) = generate_bodies(0..=99);
705
706 insert_headers(&factory, &headers);
707
708 let stream_batch_size = 20;
709 let request_limit = 10;
710 let client = Arc::new(
711 TestBodiesClient::default().with_bodies(bodies.clone()).with_should_delay(true),
712 );
713 let mut downloader = BodiesDownloaderBuilder::default()
714 .with_stream_batch_size(stream_batch_size)
715 .with_request_limit(request_limit)
716 .build::<reth_ethereum_primitives::Block, _, _>(
717 client.clone(),
718 Arc::new(TestConsensus::default()),
719 factory,
720 );
721
722 let mut range_start = 0;
723 while range_start < 100 {
724 downloader.set_download_range(range_start..=99).expect("failed to set download range");
725
726 assert_matches!(
727 downloader.next().await,
728 Some(Ok(res)) => assert_eq!(res, zip_blocks(headers.iter().skip(range_start as usize).take(stream_batch_size), &mut bodies))
729 );
730 assert!(downloader.latest_queued_block_number >= Some(range_start));
731 range_start += stream_batch_size as u64;
732 }
733 }
734
735 #[tokio::test]
738 async fn can_download_new_range_after_termination() {
739 let factory = create_test_provider_factory();
741 let (headers, mut bodies) = generate_bodies(0..=199);
742
743 insert_headers(&factory, &headers);
744
745 let client = Arc::new(TestBodiesClient::default().with_bodies(bodies.clone()));
746
747 let mut downloader = BodiesDownloaderBuilder::default()
748 .with_stream_batch_size(100)
749 .build::<reth_ethereum_primitives::Block, _, _>(
750 client.clone(),
751 Arc::new(TestConsensus::default()),
752 factory,
753 );
754
755 downloader.set_download_range(0..=99).expect("failed to set download range");
757 assert_matches!(
758 downloader.next().await,
759 Some(Ok(res)) => assert_eq!(res, zip_blocks(headers.iter().take(100), &mut bodies))
760 );
761
762 assert!(downloader.next().await.is_none());
764
765 downloader.set_download_range(100..=199).expect("failed to set download range");
767 assert_matches!(
768 downloader.next().await,
769 Some(Ok(res)) => assert_eq!(res, zip_blocks(headers.iter().skip(100), &mut bodies))
770 );
771 }
772
773 #[tokio::test]
775 async fn can_download_after_exceeding_limit() {
776 let factory = create_test_provider_factory();
778 let (headers, mut bodies) = generate_bodies(0..=199);
779
780 insert_headers(&factory, &headers);
781
782 let client = Arc::new(TestBodiesClient::default().with_bodies(bodies.clone()));
783
784 let mut downloader = BodiesDownloaderBuilder::default()
787 .with_stream_batch_size(10)
788 .with_request_limit(1)
789 .with_max_buffered_blocks_size_bytes(1)
790 .build::<reth_ethereum_primitives::Block, _, _>(
791 client.clone(),
792 Arc::new(TestConsensus::default()),
793 factory,
794 );
795
796 downloader.set_download_range(0..=199).expect("failed to set download range");
798 let mut header = 0;
799 while let Some(Ok(resp)) = downloader.next().await {
800 assert_eq!(resp, zip_blocks(headers.iter().skip(header).take(resp.len()), &mut bodies));
801 header += resp.len();
802 }
803 }
804
805 #[tokio::test]
807 async fn can_tolerate_empty_responses() {
808 let factory = create_test_provider_factory();
810 let (headers, mut bodies) = generate_bodies(0..=99);
811
812 insert_headers(&factory, &headers);
813
814 let client = Arc::new(
816 TestBodiesClient::default().with_bodies(bodies.clone()).with_empty_responses(2),
817 );
818
819 let mut downloader = BodiesDownloaderBuilder::default()
820 .with_request_limit(3)
821 .with_stream_batch_size(100)
822 .build::<reth_ethereum_primitives::Block, _, _>(
823 client.clone(),
824 Arc::new(TestConsensus::default()),
825 factory,
826 );
827
828 downloader.set_download_range(0..=99).expect("failed to set download range");
830 assert_matches!(
831 downloader.next().await,
832 Some(Ok(res)) => assert_eq!(res, zip_blocks(headers.iter().take(100), &mut bodies))
833 );
834 }
835}