876 lines
36 KiB
Rust
876 lines
36 KiB
Rust
//! The syncer downloads and verifies large numbers of blocks from peers to Zebra.
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//!
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//! It is used when Zebra is a long way behind the current chain tip.
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use std::{collections::HashSet, pin::Pin, sync::Arc, task::Poll, time::Duration};
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use color_eyre::eyre::{eyre, Report};
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use futures::stream::{FuturesUnordered, StreamExt};
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use indexmap::IndexSet;
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use tokio::time::sleep;
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use tower::{
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builder::ServiceBuilder, hedge::Hedge, limit::ConcurrencyLimit, retry::Retry, timeout::Timeout,
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Service, ServiceExt,
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};
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use zebra_chain::{
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block::{self, Block},
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chain_tip::ChainTip,
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parameters::genesis_hash,
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};
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use zebra_consensus::{
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chain::VerifyChainError, BlockError, VerifyBlockError, VerifyCheckpointError,
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};
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use zebra_network as zn;
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use zebra_state as zs;
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use crate::{
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components::sync::downloads::BlockDownloadVerifyError, config::ZebradConfig, BoxError,
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};
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mod downloads;
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mod gossip;
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mod recent_sync_lengths;
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mod status;
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#[cfg(test)]
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mod tests;
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use downloads::{AlwaysHedge, Downloads};
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pub use gossip::{gossip_best_tip_block_hashes, BlockGossipError};
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pub use recent_sync_lengths::RecentSyncLengths;
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pub use status::SyncStatus;
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/// Controls the number of peers used for each ObtainTips and ExtendTips request.
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const FANOUT: usize = 3;
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/// Controls how many times we will retry each block download.
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///
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/// Failing block downloads is important because it defends against peers who
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/// feed us bad hashes. But spurious failures of valid blocks cause the syncer to
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/// restart from the previous checkpoint, potentially re-downloading blocks.
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///
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/// We also hedge requests, so we may retry up to twice this many times. Hedged
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/// retries may be concurrent, inner retries are sequential.
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const BLOCK_DOWNLOAD_RETRY_LIMIT: usize = 2;
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/// A lower bound on the user-specified lookahead limit.
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///
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/// Set to two checkpoint intervals, so that we're sure that the lookahead
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/// limit always contains at least one complete checkpoint.
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///
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/// ## Security
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///
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/// If a malicious node is chosen for an ObtainTips or ExtendTips request, it can
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/// provide up to 500 malicious block hashes. These block hashes will be
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/// distributed across all available peers. Assuming there are around 50 connected
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/// peers, the malicious node will receive approximately 10 of those block requests.
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///
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/// Malicious deserialized blocks can take up a large amount of RAM, see
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/// [`super::inbound::downloads::MAX_INBOUND_CONCURRENCY`] and #1880 for details.
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/// So we want to keep the lookahead limit reasonably small.
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///
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/// Once these malicious blocks start failing validation, the syncer will cancel all
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/// the pending download and verify tasks, drop all the blocks, and start a new
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/// ObtainTips with a new set of peers.
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pub const MIN_LOOKAHEAD_LIMIT: usize = zebra_consensus::MAX_CHECKPOINT_HEIGHT_GAP * 2;
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/// The default for the user-specified lookahead limit.
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///
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/// See [`MIN_LOOKAHEAD_LIMIT`] for details.
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pub const DEFAULT_LOOKAHEAD_LIMIT: usize = zebra_consensus::MAX_CHECKPOINT_HEIGHT_GAP * 5;
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/// The expected maximum number of hashes in an ObtainTips or ExtendTips response.
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///
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/// This is used to allow block heights that are slightly beyond the lookahead limit,
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/// but still limit the number of blocks in the pipeline between the downloader and
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/// the state.
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///
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/// See [`MIN_LOOKAHEAD_LIMIT`] for details.
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pub const MAX_TIPS_RESPONSE_HASH_COUNT: usize = 500;
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/// Controls how long we wait for a tips response to return.
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///
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/// ## Correctness
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///
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/// If this timeout is removed (or set too high), the syncer will sometimes hang.
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///
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/// If this timeout is set too low, the syncer will sometimes get stuck in a
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/// failure loop.
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pub const TIPS_RESPONSE_TIMEOUT: Duration = Duration::from_secs(6);
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/// Controls how long we wait for a block download request to complete.
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///
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/// This timeout makes sure that the syncer doesn't hang when:
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/// - the lookahead queue is full, and
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/// - we are waiting for a request that is stuck.
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/// See [`BLOCK_VERIFY_TIMEOUT`] for details.
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///
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/// ## Correctness
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///
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/// If this timeout is removed (or set too high), the syncer will sometimes hang.
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///
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/// If this timeout is set too low, the syncer will sometimes get stuck in a
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/// failure loop.
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pub(super) const BLOCK_DOWNLOAD_TIMEOUT: Duration = Duration::from_secs(15);
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/// Controls how long we wait for a block verify request to complete.
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///
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/// This timeout makes sure that the syncer doesn't hang when:
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/// - the lookahead queue is full, and
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/// - all pending verifications:
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/// - are waiting on a missing download request,
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/// - are waiting on a download or verify request that has failed, but we have
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/// deliberately ignored the error,
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/// - are for blocks a long way ahead of the current tip, or
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/// - are for invalid blocks which will never verify, because they depend on
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/// missing blocks or transactions.
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/// These conditions can happen during normal operation - they are not bugs.
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///
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/// This timeout also mitigates or hides the following kinds of bugs:
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/// - all pending verifications:
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/// - are waiting on a download or verify request that has failed, but we have
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/// accidentally dropped the error,
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/// - are waiting on a download request that has hung inside Zebra,
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/// - are on tokio threads that are waiting for blocked operations.
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///
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/// ## Correctness
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///
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/// If this timeout is removed (or set too high), the syncer will sometimes hang.
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///
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/// If this timeout is set too low, the syncer will sometimes get stuck in a
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/// failure loop.
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pub(super) const BLOCK_VERIFY_TIMEOUT: Duration = Duration::from_secs(180);
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/// Controls how long we wait to restart syncing after finishing a sync run.
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///
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/// This delay should be long enough to:
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/// - allow zcashd peers to process pending requests. If the node only has a
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/// few peers, we want to clear as much peer state as possible. In
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/// particular, zcashd sends "next block range" hints, based on zcashd's
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/// internal model of our sync progress. But we want to discard these hints,
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/// so they don't get confused with ObtainTips and ExtendTips responses, and
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/// - allow in-progress downloads to time out.
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///
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/// This delay is particularly important on instances with slow or unreliable
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/// networks, and on testnet, which has a small number of slow peers.
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///
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/// Using a prime number makes sure that syncer fanouts don't synchronise with other crawls.
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///
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/// ## Correctness
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///
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/// If this delay is removed (or set too low), the syncer will
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/// sometimes get stuck in a failure loop, due to leftover downloads from
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/// previous sync runs.
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const SYNC_RESTART_DELAY: Duration = Duration::from_secs(67);
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/// Controls how long we wait to retry a failed attempt to download
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/// and verify the genesis block.
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///
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/// This timeout gives the crawler time to find better peers.
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///
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/// ## Security
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///
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/// If this timeout is removed (or set too low), Zebra will immediately retry
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/// to download and verify the genesis block from its peers. This can cause
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/// a denial of service on those peers.
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const GENESIS_TIMEOUT_RETRY: Duration = Duration::from_secs(5);
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/// Helps work around defects in the bitcoin protocol by checking whether
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/// the returned hashes actually extend a chain tip.
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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struct CheckedTip {
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tip: block::Hash,
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expected_next: block::Hash,
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}
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pub struct ChainSync<ZN, ZS, ZV, ZSTip>
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where
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ZN: Service<zn::Request, Response = zn::Response, Error = BoxError>
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+ Send
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+ Sync
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+ Clone
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+ 'static,
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ZN::Future: Send,
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ZS: Service<zs::Request, Response = zs::Response, Error = BoxError>
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+ Send
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+ Sync
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+ Clone
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+ 'static,
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ZS::Future: Send,
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ZV: Service<Arc<Block>, Response = block::Hash, Error = BoxError>
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+ Send
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+ Sync
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+ Clone
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+ 'static,
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ZV::Future: Send,
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ZSTip: ChainTip + Clone + Send + 'static,
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{
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// Configuration
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/// The genesis hash for the configured network
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genesis_hash: block::Hash,
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/// The configured lookahead limit, after applying the minimum limit.
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lookahead_limit: usize,
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// Services
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/// A network service which is used to perform ObtainTips and ExtendTips
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/// requests.
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///
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/// Has no retry logic, because failover is handled using fanout.
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tip_network: Timeout<ZN>,
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/// A service which downloads and verifies blocks, using the provided
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/// network and verifier services.
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downloads: Pin<
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Box<
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Downloads<
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Hedge<ConcurrencyLimit<Retry<zn::RetryLimit, Timeout<ZN>>>, AlwaysHedge>,
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Timeout<ZV>,
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ZSTip,
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>,
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>,
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>,
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/// The cached block chain state.
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state: ZS,
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// Internal sync state
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/// The tips that the syncer is currently following.
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prospective_tips: HashSet<CheckedTip>,
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/// The lengths of recent sync responses.
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recent_syncs: RecentSyncLengths,
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}
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/// Polls the network to determine whether further blocks are available and
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/// downloads them.
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///
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/// This component is used for initial block sync, but the `Inbound` service is
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/// responsible for participating in the gossip protocols used for block
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/// diffusion.
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impl<ZN, ZS, ZV, ZSTip> ChainSync<ZN, ZS, ZV, ZSTip>
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where
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ZN: Service<zn::Request, Response = zn::Response, Error = BoxError>
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+ Send
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+ Sync
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+ Clone
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+ 'static,
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ZN::Future: Send,
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ZS: Service<zs::Request, Response = zs::Response, Error = BoxError>
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+ Send
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+ Sync
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+ Clone
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+ 'static,
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ZS::Future: Send,
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ZV: Service<Arc<Block>, Response = block::Hash, Error = BoxError>
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+ Send
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+ Sync
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+ Clone
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+ 'static,
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ZV::Future: Send,
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ZSTip: ChainTip + Clone + Send + 'static,
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{
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/// Returns a new syncer instance, using:
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/// - chain: the zebra-chain `Network` to download (Mainnet or Testnet)
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/// - peers: the zebra-network peers to contact for downloads
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/// - verifier: the zebra-consensus verifier that checks the chain
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/// - state: the zebra-state that stores the chain
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/// - latest_chain_tip: the latest chain tip from `state`
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///
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/// Also returns a [`SyncStatus`] to check if the syncer has likely reached the chain tip.
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pub fn new(
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config: &ZebradConfig,
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peers: ZN,
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verifier: ZV,
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state: ZS,
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latest_chain_tip: ZSTip,
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) -> (Self, SyncStatus) {
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let tip_network = Timeout::new(peers.clone(), TIPS_RESPONSE_TIMEOUT);
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// The Hedge middleware is the outermost layer, hedging requests
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// between two retry-wrapped networks. The innermost timeout
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// layer is relatively unimportant, because slow requests will
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// probably be pre-emptively hedged.
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//
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// The Hedge goes outside the Retry, because the Retry layer
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// abstracts away spurious failures from individual peers
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// making a less-fallible network service, and the Hedge layer
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// tries to reduce latency of that less-fallible service.
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//
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// XXX add ServiceBuilder::hedge() so this becomes
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// ServiceBuilder::new().hedge(...).retry(...)...
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let block_network = Hedge::new(
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ServiceBuilder::new()
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.concurrency_limit(config.sync.max_concurrent_block_requests)
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.retry(zn::RetryLimit::new(BLOCK_DOWNLOAD_RETRY_LIMIT))
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.timeout(BLOCK_DOWNLOAD_TIMEOUT)
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.service(peers),
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AlwaysHedge,
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20,
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0.95,
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2 * SYNC_RESTART_DELAY,
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);
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// We apply a timeout to the verifier to avoid hangs due to missing earlier blocks.
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let verifier = Timeout::new(verifier, BLOCK_VERIFY_TIMEOUT);
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assert!(
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config.sync.lookahead_limit >= MIN_LOOKAHEAD_LIMIT,
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"configured lookahead limit {} too low, must be at least {}",
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config.sync.lookahead_limit,
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MIN_LOOKAHEAD_LIMIT
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);
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let (sync_status, recent_syncs) = SyncStatus::new();
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let new_syncer = Self {
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genesis_hash: genesis_hash(config.network.network),
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lookahead_limit: config.sync.lookahead_limit,
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tip_network,
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downloads: Box::pin(Downloads::new(
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block_network,
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verifier,
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latest_chain_tip,
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config.sync.lookahead_limit,
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)),
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state,
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prospective_tips: HashSet::new(),
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recent_syncs,
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};
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(new_syncer, sync_status)
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}
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#[instrument(skip(self))]
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pub async fn sync(mut self) -> Result<(), Report> {
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// We can't download the genesis block using our normal algorithm,
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// due to protocol limitations
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self.request_genesis().await?;
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// Distinguishes a restart from a start, so we don't sleep when starting
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// the sync process, but we can keep restart logic in one place.
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let mut started_once = false;
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'sync: loop {
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if started_once {
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tracing::info!(timeout = ?SYNC_RESTART_DELAY, "waiting to restart sync");
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self.prospective_tips = HashSet::new();
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self.downloads.cancel_all();
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self.update_metrics();
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sleep(SYNC_RESTART_DELAY).await;
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} else {
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started_once = true;
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}
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tracing::info!("starting sync, obtaining new tips");
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if let Err(e) = self.obtain_tips().await {
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tracing::warn!(?e, "error obtaining tips");
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continue 'sync;
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}
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self.update_metrics();
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while !self.prospective_tips.is_empty() {
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// Check whether any block tasks are currently ready:
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while let Poll::Ready(Some(rsp)) = futures::poll!(self.downloads.next()) {
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match rsp {
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Ok(hash) => {
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tracing::trace!(?hash, "verified and committed block to state");
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}
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Err(e) => {
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if Self::should_restart_sync(e) {
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continue 'sync;
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}
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}
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}
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}
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self.update_metrics();
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// If we have too many pending tasks, wait for some to finish.
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//
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// Starting to wait is interesting, but logging each wait can be
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// very verbose.
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if self.downloads.in_flight() > self.lookahead_limit {
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tracing::info!(
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tips.len = self.prospective_tips.len(),
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in_flight = self.downloads.in_flight(),
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lookahead_limit = self.lookahead_limit,
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"waiting for pending blocks",
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);
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}
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while self.downloads.in_flight() > self.lookahead_limit {
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tracing::trace!(
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tips.len = self.prospective_tips.len(),
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in_flight = self.downloads.in_flight(),
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lookahead_limit = self.lookahead_limit,
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"waiting for pending blocks",
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);
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match self.downloads.next().await.expect("downloads is nonempty") {
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Ok(hash) => {
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tracing::trace!(?hash, "verified and committed block to state");
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}
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Err(e) => {
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if Self::should_restart_sync(e) {
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continue 'sync;
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}
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}
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}
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self.update_metrics();
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}
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// Once we're below the lookahead limit, we can keep extending the tips.
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tracing::info!(
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tips.len = self.prospective_tips.len(),
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in_flight = self.downloads.in_flight(),
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lookahead_limit = self.lookahead_limit,
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"extending tips",
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);
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if let Err(e) = self.extend_tips().await {
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tracing::warn!(?e, "error extending tips");
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continue 'sync;
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}
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self.update_metrics();
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}
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tracing::info!("exhausted prospective tip set");
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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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#[instrument(skip(self))]
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async fn obtain_tips(&mut self) -> Result<(), Report> {
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let block_locator = self
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.state
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.ready()
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.await
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.map_err(|e| eyre!(e))?
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.call(zebra_state::Request::BlockLocator)
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.await
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.map(|response| match response {
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zebra_state::Response::BlockLocator(block_locator) => block_locator,
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_ => unreachable!(
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"GetBlockLocator request can only result in Response::BlockLocator"
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),
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})
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.map_err(|e| eyre!(e))?;
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tracing::info!(tip = ?block_locator.first().unwrap(), "trying to obtain new chain tips");
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tracing::debug!(?block_locator, "got block locator");
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let mut requests = FuturesUnordered::new();
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for attempt in 0..FANOUT {
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if attempt > 0 {
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// Let other tasks run, so we're more likely to choose a different peer.
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//
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// TODO: move fanouts into the PeerSet, so we always choose different peers (#2214)
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tokio::task::yield_now().await;
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}
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let ready_tip_network = self.tip_network.ready().await;
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requests.push(tokio::spawn(ready_tip_network.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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}
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let mut download_set = IndexSet::new();
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while let Some(res) = requests.next().await {
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match res
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.expect("panic in spawned obtain tips request")
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.map_err::<Report, _>(|e| eyre!(e))
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{
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Ok(zn::Response::BlockHashes(hashes)) => {
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tracing::trace!(?hashes);
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// zcashd sometimes appends an unrelated hash at the start
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// or end of its response.
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//
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// We can't discard the first hash, because it might be a
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// block we want to download. So we just accept any
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// out-of-order first hashes.
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// We use the last hash for the tip, and we want to avoid bad
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// tips. So we discard the last hash. (We don't need to worry
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|
// about missed downloads, because we will pick them up again
|
|
// in ExtendTips.)
|
|
let hashes = match hashes.as_slice() {
|
|
[] => continue,
|
|
[rest @ .., _last] => rest,
|
|
};
|
|
|
|
let mut first_unknown = None;
|
|
for (i, &hash) in hashes.iter().enumerate() {
|
|
if !self.state_contains(hash).await? {
|
|
first_unknown = Some(i);
|
|
break;
|
|
}
|
|
}
|
|
|
|
tracing::debug!(hashes.len = ?hashes.len(), ?first_unknown);
|
|
|
|
let unknown_hashes = if let Some(index) = first_unknown {
|
|
&hashes[index..]
|
|
} else {
|
|
continue;
|
|
};
|
|
|
|
tracing::trace!(?unknown_hashes);
|
|
|
|
let new_tip = if let Some(end) = unknown_hashes.rchunks_exact(2).next() {
|
|
CheckedTip {
|
|
tip: end[0],
|
|
expected_next: end[1],
|
|
}
|
|
} else {
|
|
tracing::debug!("discarding response that extends only one block");
|
|
continue;
|
|
};
|
|
|
|
// Make sure we get the same tips, regardless of the
|
|
// order of peer responses
|
|
if !download_set.contains(&new_tip.expected_next) {
|
|
tracing::debug!(?new_tip,
|
|
"adding new prospective tip, and removing existing tips in the new block hash list");
|
|
self.prospective_tips
|
|
.retain(|t| !unknown_hashes.contains(&t.expected_next));
|
|
self.prospective_tips.insert(new_tip);
|
|
} else {
|
|
tracing::debug!(
|
|
?new_tip,
|
|
"discarding prospective tip: already in download set"
|
|
);
|
|
}
|
|
|
|
// security: the first response determines our download order
|
|
//
|
|
// TODO: can we make the download order independent of response order?
|
|
let prev_download_len = download_set.len();
|
|
download_set.extend(unknown_hashes);
|
|
let new_download_len = download_set.len();
|
|
let new_hashes = new_download_len - prev_download_len;
|
|
tracing::debug!(new_hashes, "added hashes to download set");
|
|
metrics::histogram!("sync.obtain.response.hash.count", new_hashes as f64);
|
|
}
|
|
Ok(_) => unreachable!("network returned wrong response"),
|
|
// We ignore this error because we made multiple fanout requests.
|
|
Err(e) => tracing::debug!(?e),
|
|
}
|
|
}
|
|
|
|
tracing::debug!(?self.prospective_tips);
|
|
|
|
// Check that the new tips we got are actually unknown.
|
|
for hash in &download_set {
|
|
tracing::debug!(?hash, "checking if state contains hash");
|
|
if self.state_contains(*hash).await? {
|
|
return Err(eyre!("queued download of hash behind our chain tip"));
|
|
}
|
|
}
|
|
|
|
let new_downloads = download_set.len();
|
|
tracing::debug!(new_downloads, "queueing new downloads");
|
|
metrics::gauge!("sync.obtain.queued.hash.count", new_downloads as f64);
|
|
|
|
// security: use the actual number of new downloads from all peers,
|
|
// so the last peer to respond can't toggle our mempool
|
|
self.recent_syncs.push_obtain_tips_length(new_downloads);
|
|
|
|
self.request_blocks(download_set).await?;
|
|
|
|
Ok(())
|
|
}
|
|
|
|
#[instrument(skip(self))]
|
|
async fn extend_tips(&mut self) -> Result<(), Report> {
|
|
let tips = std::mem::take(&mut self.prospective_tips);
|
|
|
|
let mut download_set = IndexSet::new();
|
|
tracing::info!(tips = ?tips.len(), "trying to extend chain tips");
|
|
for tip in tips {
|
|
tracing::debug!(?tip, "asking peers to extend chain tip");
|
|
let mut responses = FuturesUnordered::new();
|
|
for attempt in 0..FANOUT {
|
|
if attempt > 0 {
|
|
// Let other tasks run, so we're more likely to choose a different peer.
|
|
//
|
|
// TODO: move fanouts into the PeerSet, so we always choose different peers (#2214)
|
|
tokio::task::yield_now().await;
|
|
}
|
|
|
|
let ready_tip_network = self.tip_network.ready().await;
|
|
responses.push(tokio::spawn(ready_tip_network.map_err(|e| eyre!(e))?.call(
|
|
zn::Request::FindBlocks {
|
|
known_blocks: vec![tip.tip],
|
|
stop: None,
|
|
},
|
|
)));
|
|
}
|
|
while let Some(res) = responses.next().await {
|
|
match res
|
|
.expect("panic in spawned extend tips request")
|
|
.map_err::<Report, _>(|e| eyre!(e))
|
|
{
|
|
Ok(zn::Response::BlockHashes(hashes)) => {
|
|
tracing::debug!(first = ?hashes.first(), len = ?hashes.len());
|
|
tracing::trace!(?hashes);
|
|
|
|
// zcashd sometimes appends an unrelated hash at the
|
|
// start or end of its response. Check the first hash
|
|
// against the previous response, and discard mismatches.
|
|
let unknown_hashes = match hashes.as_slice() {
|
|
[expected_hash, rest @ ..] if expected_hash == &tip.expected_next => {
|
|
rest
|
|
}
|
|
// If the first hash doesn't match, retry with the second.
|
|
[first_hash, expected_hash, rest @ ..]
|
|
if expected_hash == &tip.expected_next =>
|
|
{
|
|
tracing::debug!(?first_hash,
|
|
?tip.expected_next,
|
|
?tip.tip,
|
|
"unexpected first hash, but the second matches: using the hashes after the match");
|
|
rest
|
|
}
|
|
// We ignore these responses
|
|
[] => continue,
|
|
[single_hash] => {
|
|
tracing::debug!(?single_hash,
|
|
?tip.expected_next,
|
|
?tip.tip,
|
|
"discarding response containing a single unexpected hash");
|
|
continue;
|
|
}
|
|
[first_hash, second_hash, rest @ ..] => {
|
|
tracing::debug!(?first_hash,
|
|
?second_hash,
|
|
rest_len = ?rest.len(),
|
|
?tip.expected_next,
|
|
?tip.tip,
|
|
"discarding response that starts with two unexpected hashes");
|
|
continue;
|
|
}
|
|
};
|
|
|
|
// We use the last hash for the tip, and we want to avoid
|
|
// bad tips. So we discard the last hash. (We don't need
|
|
// to worry about missed downloads, because we will pick
|
|
// them up again in the next ExtendTips.)
|
|
let unknown_hashes = match unknown_hashes {
|
|
[] => continue,
|
|
[rest @ .., _last] => rest,
|
|
};
|
|
|
|
let new_tip = if let Some(end) = unknown_hashes.rchunks_exact(2).next() {
|
|
CheckedTip {
|
|
tip: end[0],
|
|
expected_next: end[1],
|
|
}
|
|
} else {
|
|
tracing::debug!("discarding response that extends only one block");
|
|
continue;
|
|
};
|
|
|
|
tracing::trace!(?unknown_hashes);
|
|
|
|
// Make sure we get the same tips, regardless of the
|
|
// order of peer responses
|
|
if !download_set.contains(&new_tip.expected_next) {
|
|
tracing::debug!(?new_tip,
|
|
"adding new prospective tip, and removing any existing tips in the new block hash list");
|
|
self.prospective_tips
|
|
.retain(|t| !unknown_hashes.contains(&t.expected_next));
|
|
self.prospective_tips.insert(new_tip);
|
|
} else {
|
|
tracing::debug!(
|
|
?new_tip,
|
|
"discarding prospective tip: already in download set"
|
|
);
|
|
}
|
|
|
|
// security: the first response determines our download order
|
|
//
|
|
// TODO: can we make the download order independent of response order?
|
|
let prev_download_len = download_set.len();
|
|
download_set.extend(unknown_hashes);
|
|
let new_download_len = download_set.len();
|
|
let new_hashes = new_download_len - prev_download_len;
|
|
tracing::debug!(new_hashes, "added hashes to download set");
|
|
metrics::histogram!("sync.extend.response.hash.count", new_hashes as f64);
|
|
}
|
|
Ok(_) => unreachable!("network returned wrong response"),
|
|
// We ignore this error because we made multiple fanout requests.
|
|
Err(e) => tracing::debug!(?e),
|
|
}
|
|
}
|
|
}
|
|
|
|
let new_downloads = download_set.len();
|
|
tracing::debug!(new_downloads, "queueing new downloads");
|
|
metrics::gauge!("sync.extend.queued.hash.count", new_downloads as f64);
|
|
|
|
// security: use the actual number of new downloads from all peers,
|
|
// so the last peer to respond can't toggle our mempool
|
|
self.recent_syncs.push_extend_tips_length(new_downloads);
|
|
|
|
self.request_blocks(download_set).await?;
|
|
|
|
Ok(())
|
|
}
|
|
|
|
/// Download and verify the genesis block, if it isn't currently known to
|
|
/// our node.
|
|
async fn request_genesis(&mut self) -> Result<(), Report> {
|
|
// Due to Bitcoin protocol limitations, we can't request the genesis
|
|
// block using our standard tip-following algorithm:
|
|
// - getblocks requires at least one hash
|
|
// - responses start with the block *after* the requested block, and
|
|
// - the genesis hash is used as a placeholder for "no matches".
|
|
//
|
|
// So we just download and verify the genesis block here.
|
|
while !self.state_contains(self.genesis_hash).await? {
|
|
tracing::info!("starting genesis block download and verify");
|
|
self.downloads
|
|
.download_and_verify(self.genesis_hash)
|
|
.await
|
|
.map_err(|e| eyre!(e))?;
|
|
match self.downloads.next().await.expect("downloads is nonempty") {
|
|
Ok(hash) => tracing::trace!(?hash, "verified and committed block to state"),
|
|
Err(e) => {
|
|
tracing::warn!(?e, "could not download or verify genesis block, retrying");
|
|
tokio::time::sleep(GENESIS_TIMEOUT_RETRY).await;
|
|
}
|
|
}
|
|
}
|
|
|
|
Ok(())
|
|
}
|
|
|
|
/// Queue download and verify tasks for each block that isn't currently known to our node
|
|
async fn request_blocks(&mut self, hashes: IndexSet<block::Hash>) -> Result<(), Report> {
|
|
tracing::debug!(hashes.len = hashes.len(), "requesting blocks");
|
|
for hash in hashes.into_iter() {
|
|
self.downloads.download_and_verify(hash).await?;
|
|
}
|
|
|
|
Ok(())
|
|
}
|
|
|
|
/// Returns `true` if the hash is present in the state, and `false`
|
|
/// if the hash is not present in the state.
|
|
///
|
|
/// BUG: check if the hash is in any chain (#862)
|
|
/// Depth only checks the main chain.
|
|
async fn state_contains(&mut self, hash: block::Hash) -> Result<bool, Report> {
|
|
match self
|
|
.state
|
|
.ready()
|
|
.await
|
|
.map_err(|e| eyre!(e))?
|
|
.call(zebra_state::Request::Depth(hash))
|
|
.await
|
|
.map_err(|e| eyre!(e))?
|
|
{
|
|
zs::Response::Depth(Some(_)) => Ok(true),
|
|
zs::Response::Depth(None) => Ok(false),
|
|
_ => unreachable!("wrong response to depth request"),
|
|
}
|
|
}
|
|
|
|
fn update_metrics(&mut self) {
|
|
metrics::gauge!(
|
|
"sync.prospective_tips.len",
|
|
self.prospective_tips.len() as f64
|
|
);
|
|
metrics::gauge!(
|
|
"sync.downloads.in_flight",
|
|
self.downloads.in_flight() as f64
|
|
);
|
|
}
|
|
|
|
/// Return if the sync should be restarted based on the given error
|
|
/// from the block downloader and verifier stream.
|
|
fn should_restart_sync(e: BlockDownloadVerifyError) -> bool {
|
|
match e {
|
|
// Structural matches
|
|
BlockDownloadVerifyError::Invalid(VerifyChainError::Checkpoint(
|
|
VerifyCheckpointError::AlreadyVerified { .. },
|
|
)) => {
|
|
tracing::debug!(error = ?e, "block was already verified, possibly from a previous sync run, continuing");
|
|
false
|
|
}
|
|
BlockDownloadVerifyError::Invalid(VerifyChainError::Block(
|
|
VerifyBlockError::Block {
|
|
source: BlockError::AlreadyInChain(_, _),
|
|
},
|
|
)) => {
|
|
tracing::debug!(error = ?e, "block is already in chain, possibly from a previous sync run, continuing");
|
|
false
|
|
}
|
|
BlockDownloadVerifyError::CancelledDuringDownload
|
|
| BlockDownloadVerifyError::CancelledDuringVerification => {
|
|
tracing::debug!(error = ?e, "block verification was cancelled, continuing");
|
|
false
|
|
}
|
|
BlockDownloadVerifyError::BehindTipHeightLimit => {
|
|
tracing::debug!(
|
|
error = ?e,
|
|
"block height is behind the current state tip, \
|
|
assuming the syncer will eventually catch up to the state, continuing"
|
|
);
|
|
false
|
|
}
|
|
|
|
// String matches
|
|
BlockDownloadVerifyError::Invalid(VerifyChainError::Block(
|
|
VerifyBlockError::Commit(ref source),
|
|
)) if format!("{:?}", source).contains("block is already committed to the state") => {
|
|
// TODO: improve this by checking the type (#2908)
|
|
tracing::debug!(error = ?e, "block is already committed, possibly from a previous sync run, continuing");
|
|
false
|
|
}
|
|
BlockDownloadVerifyError::DownloadFailed(ref source)
|
|
if format!("{:?}", source).contains("NotFound") =>
|
|
{
|
|
// TODO: improve this by checking the type (#2908)
|
|
// restart after a certain number of NotFound errors?
|
|
tracing::debug!(error = ?e, "block was not found, possibly from a peer that doesn't have the block yet, continuing");
|
|
false
|
|
}
|
|
|
|
_ => {
|
|
// download_and_verify downcasts errors from the block verifier
|
|
// into VerifyChainError, and puts the result inside one of the
|
|
// BlockDownloadVerifyError enumerations. This downcast could
|
|
// become incorrect e.g. after some refactoring, and it is difficult
|
|
// to write a test to check it. The test below is a best-effort
|
|
// attempt to catch if that happens and log it.
|
|
// TODO: add a proper test and remove this
|
|
// https://github.com/ZcashFoundation/zebra/issues/2909
|
|
let err_str = format!("{:?}", e);
|
|
if err_str.contains("AlreadyVerified")
|
|
|| err_str.contains("AlreadyInChain")
|
|
|| err_str.contains("Cancelled")
|
|
|| err_str.contains("BehindTipHeight")
|
|
|| err_str.contains("block is already committed to the state")
|
|
|| err_str.contains("NotFound")
|
|
{
|
|
tracing::error!(?e,
|
|
"a BlockDownloadVerifyError that should have been filtered out was detected, \
|
|
which possibly indicates a programming error in the downcast inside \
|
|
zebrad::components::sync::downloads::Downloads::download_and_verify"
|
|
)
|
|
}
|
|
|
|
tracing::warn!(?e, "error downloading and verifying block");
|
|
true
|
|
}
|
|
}
|
|
}
|
|
}
|