2020-06-22 19:24:53 -07:00
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use color_eyre::eyre::{eyre, Report};
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use futures::stream::{FuturesUnordered, StreamExt};
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use std::{collections::HashSet, iter, time::Duration};
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use tokio::time::delay_for;
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use tower::{Service, ServiceExt};
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use tracing_futures::Instrument;
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use zebra_chain::{block::BlockHeaderHash, types::BlockHeight};
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2020-06-22 22:31:26 -07:00
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use zebra_network as zn;
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use zebra_state as zs;
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2020-06-22 19:24:53 -07:00
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pub struct Syncer<ZN, ZS>
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where
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2020-06-22 22:31:26 -07:00
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ZN: Service<zn::Request>,
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2020-06-22 19:24:53 -07:00
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{
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pub peer_set: ZN,
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// TODO(jlusby): add validator
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pub state: ZS,
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pub prospective_tips: HashSet<BlockHeaderHash>,
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pub block_requests: FuturesUnordered<ZN::Future>,
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pub downloading: HashSet<BlockHeaderHash>,
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pub downloaded: HashSet<BlockHeaderHash>,
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pub fanout: NumReq,
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}
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impl<ZN, ZS> Syncer<ZN, ZS>
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where
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ZN: Service<zn::Request, Response = zn::Response, Error = Error> + Send + Clone + 'static,
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ZN::Future: Send,
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ZS: Service<zs::Request, Response = zs::Response, Error = Error> + Send + Clone + 'static,
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ZS::Future: Send,
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{
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pub async fn run(&mut self) -> Result<(), Report> {
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loop {
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info!("populating prospective tips list");
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self.obtain_tips().await?;
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// ObtainTips Step 6
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//
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// If there are any prospective tips, call ExtendTips. Continue this step until there are no more prospective tips.
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while !self.prospective_tips.is_empty() {
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info!("extending prospective tips");
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self.extend_tips().await?;
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// TODO(jlusby): move this to a background task and check it for errors after each step.
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self.process_blocks().await?;
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}
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delay_for(Duration::from_secs(15)).await;
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}
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}
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/// Given a block_locator list fan out request for subsequent hashes to
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/// multiple peers
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async fn obtain_tips(&mut self) -> Result<(), Report> {
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// ObtainTips Step 1
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//
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// Query the current state to construct the sequence of hashes: handled by
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// the caller
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//
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// TODO(jlusby): get the block_locator from the state
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let block_locator = vec![super::GENESIS];
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let mut tip_futs = FuturesUnordered::new();
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// ObtainTips Step 2
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//
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// Make a FindBlocksByHash request to the network F times, where F is a
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// fanout parameter, to get resp1, ..., respF
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for _ in 0..self.fanout {
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let req = self.peer_set.ready_and().await.map_err(|e| eyre!(e))?.call(
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zn::Request::FindBlocks {
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known_blocks: block_locator.clone(),
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stop: None,
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},
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);
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tip_futs.push(req);
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}
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let mut download_set = HashSet::new();
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while let Some(res) = tip_futs.next().await {
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match res.map_err::<Report, _>(|e| eyre!(e)) {
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2020-06-22 22:31:26 -07:00
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Ok(zn::Response::BlockHeaderHashes(hashes)) => {
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if hashes.is_empty() {
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tracing::debug!("skipping empty response");
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2020-06-22 19:24:53 -07:00
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continue;
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}
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// ObtainTips Step 3
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//
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// For each response, starting from the beginning of the
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// list, prune any block hashes already included in the
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// state, stopping at the first unknown hash to get resp1',
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// ..., respF'. (These lists may be empty).
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2020-06-22 22:31:26 -07:00
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let mut first_unknown = 0;
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for (i, &hash) in hashes.iter().enumerate() {
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let depth = self
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.state
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.ready_and()
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.await
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.map_err(|e| eyre!(e))?
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.call(zebra_state::Request::GetDepth { hash })
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.await
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.map_err(|e| eyre!(e))?;
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if let zs::Response::Depth(None) = depth {
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first_unknown = i;
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break;
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}
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}
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2020-06-22 22:31:26 -07:00
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if first_unknown == hashes.len() {
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tracing::debug!("no new hashes, even though we gave our tip?");
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continue;
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}
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let unknown_hashes = &hashes[first_unknown..];
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download_set.extend(unknown_hashes);
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2020-06-22 19:24:53 -07:00
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// ObtainTips Step 4
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//
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// Combine the last elements of each list into a set; this
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// is the set of prospective tips.
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let new_tip = *unknown_hashes
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.last()
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.expect("already checked first_unknown < hashes.len()");
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let _ = self.prospective_tips.insert(new_tip);
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}
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Ok(r) => tracing::error!("unexpected response {:?}", r),
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Err(e) => tracing::error!("{:?}", e),
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}
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}
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// ObtainTips Step 5
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//
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// Combine all elements of each list into a set, and queue
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// download and verification of those blocks.
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self.request_blocks(download_set.into_iter().collect())
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.await?;
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Ok(())
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}
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async fn extend_tips(&mut self) -> Result<(), Report> {
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// Extend Tips 1
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//
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// remove all prospective tips and iterate over them individually
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let tips = std::mem::take(&mut self.prospective_tips);
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let mut download_set = HashSet::new();
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for tip in tips {
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// ExtendTips Step 2
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//
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// Create a FindBlocksByHash request consisting of just the
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// prospective tip. Send this request to the network F times
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for _ in 0..self.fanout {
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let res = self
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.peer_set
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.ready_and()
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.await
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.map_err(|e| eyre!(e))?
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.call(zn::Request::FindBlocks {
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known_blocks: vec![tip],
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stop: None,
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})
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.await;
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match res.map_err::<Report, _>(|e| eyre!(e)) {
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2020-06-24 12:19:34 -07:00
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Ok(zn::Response::BlockHeaderHashes(mut hashes)) => {
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let new_tip = if let Some(tip) = hashes.pop() {
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tip
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} else {
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tracing::debug!("skipping empty response");
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continue;
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2020-06-24 12:19:34 -07:00
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};
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2020-06-22 19:24:53 -07:00
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// ExtendTips Step 3
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//
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// For each response, check whether the first hash in the
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// response is the genesis block; if so, discard the response.
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// It indicates that the remote peer does not have any blocks
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// following the prospective tip.
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// TODO(jlusby): reject both main and test net genesis blocks
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2020-06-24 12:19:34 -07:00
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match hashes.first() {
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Some(&super::GENESIS) => {
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tracing::debug!("skipping response that does not extend the tip");
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continue;
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}
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Some(_) | None => {}
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}
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// ExtendTips Step 4
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//
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// Combine the last elements of the remaining responses into
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// a set, and add this set to the set of prospective tips.
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let _ = self.prospective_tips.insert(new_tip);
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download_set.extend(hashes);
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}
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2020-06-22 22:31:26 -07:00
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Ok(r) => tracing::error!("unexpected response {:?}", r),
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Err(e) => tracing::error!("{:?}", e),
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}
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}
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}
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2020-06-24 12:19:34 -07:00
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self.prospective_tips
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.retain(|tip| !download_set.contains(tip));
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// ExtendTips Step 5
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//
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// Combine all elements of the remaining responses into a
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// set, and queue download and verification of those blocks
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self.request_blocks(
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download_set
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.into_iter()
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.chain(self.prospective_tips.iter().cloned())
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.collect(),
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)
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.await?;
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2020-06-22 19:24:53 -07:00
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Ok(())
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}
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/// Queue downloads for each block that isn't currently known to our node
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async fn request_blocks(&mut self, mut hashes: Vec<BlockHeaderHash>) -> Result<(), Report> {
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hashes.retain(|hash| !self.known_block(hash));
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for chunk in hashes.chunks(10usize) {
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self.queue_download(chunk).await?;
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}
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Ok(())
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}
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/// Drive block downloading futures to completion and dispatch downloaded
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/// blocks to the validator
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async fn process_blocks(&mut self) -> Result<(), Report> {
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info!(in_flight = self.block_requests.len(), "processing blocks");
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while let Some(res) = self.block_requests.next().await {
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match res.map_err::<Report, _>(|e| eyre!(e)) {
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2020-06-22 22:31:26 -07:00
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Ok(zn::Response::Blocks(blocks)) => {
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info!(count = blocks.len(), "received blocks");
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for block in blocks {
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let hash = block.as_ref().into();
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assert!(
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self.downloading.remove(&hash),
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"all received blocks should be explicitly requested and received once"
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);
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let _ = self.downloaded.insert(hash);
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self.validate_block(block).await?;
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}
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}
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Ok(_) => continue,
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Err(e) => {
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error!("{:?}", e);
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}
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}
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}
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Ok(())
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}
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/// Validate a downloaded block using the validator service, inserting the
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/// block into the state if successful
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#[tracing::instrument(skip(self))]
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async fn validate_block(
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&mut self,
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block: std::sync::Arc<zebra_chain::block::Block>,
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) -> Result<(), Report> {
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let fut = self
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.state
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.ready_and()
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.await
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.map_err(|e| eyre!(e))?
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2020-06-22 22:31:26 -07:00
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.call(zs::Request::AddBlock { block });
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2020-06-22 19:24:53 -07:00
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let _handle = tokio::spawn(
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async move {
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match fut.await.map_err::<Report, _>(|e| eyre!(e)) {
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Ok(_) => {}
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Err(report) => error!("{:?}", report),
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}
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}
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.in_current_span(),
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);
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Ok(())
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}
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/// Returns true if the block is being downloaded or has been downloaded
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fn known_block(&self, hash: &BlockHeaderHash) -> bool {
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self.downloading.contains(hash) || self.downloaded.contains(hash)
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}
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/// Queue a future to download a set of blocks from the network
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async fn queue_download(&mut self, chunk: &[BlockHeaderHash]) -> Result<(), Report> {
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let set = chunk.iter().cloned().collect();
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let request = self
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.peer_set
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.ready_and()
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.await
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.map_err(|e| eyre!(e))?
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2020-06-22 22:31:26 -07:00
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.call(zn::Request::BlocksByHash(set));
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2020-06-22 19:24:53 -07:00
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self.downloading.extend(chunk);
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self.block_requests.push(request);
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Ok(())
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}
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}
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2020-06-23 09:41:49 -07:00
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/// Get the heights of the blocks for constructing a block_locator list
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#[allow(dead_code)]
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pub fn block_locator_heights(tip_height: BlockHeight) -> impl Iterator<Item = BlockHeight> {
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iter::successors(Some(1u32), |h| h.checked_mul(2))
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.flat_map(move |step| tip_height.0.checked_sub(step))
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.map(BlockHeight)
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.chain(iter::once(BlockHeight(0)))
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}
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type Error = Box<dyn std::error::Error + Send + Sync + 'static>;
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type NumReq = u32;
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