web3-proxy/web3_proxy/src/rpcs/blockchain.rs

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///! Keep track of the blockchain as seen by a Web3Connections.
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use super::connection::Web3Connection;
use super::connections::Web3Connections;
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use super::transactions::TxStatus;
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use crate::{
config::BlockAndRpc, jsonrpc::JsonRpcRequest, rpcs::synced_connections::SyncedConnections,
};
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use anyhow::Context;
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use dashmap::{
mapref::{entry::Entry, one::Ref},
DashMap,
};
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use derive_more::From;
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use ethers::prelude::{Block, TxHash, H256, U64};
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use hashbrown::{HashMap, HashSet};
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use serde::Serialize;
use serde_json::json;
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use std::{cmp::Ordering, fmt::Display, sync::Arc};
use tokio::sync::{broadcast, watch};
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use tracing::{debug, trace, warn};
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pub type ArcBlock = Arc<Block<TxHash>>;
pub type BlockHashesMap = Arc<DashMap<H256, ArcBlock>>;
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/// A block's hash and number.
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#[derive(Clone, Debug, Default, From, Serialize)]
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pub struct BlockId {
pub(super) hash: H256,
pub(super) num: U64,
}
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impl Display for BlockId {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{} ({})", self.num, self.hash)
}
}
impl Web3Connections {
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/// add a block to our map and it's hash to our graphmap of the blockchain
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pub fn save_block(&self, block: &ArcBlock, heaviest_chain: Option<bool>) -> anyhow::Result<()> {
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let block_hash = block.hash.as_ref().context("no block hash")?;
let block_num = block.number.as_ref().context("no block num")?;
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let _block_td = block
.total_difficulty
.as_ref()
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.context("no block total difficulty")?;
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// think more about heaviest_chain
if heaviest_chain.unwrap_or(true) {
match self.block_numbers.entry(*block_num) {
Entry::Occupied(mut x) => {
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let old_hash = x.insert(*block_hash);
if block_hash == &old_hash {
// this block has already been saved
return Ok(());
}
// TODO: what should we do?
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// TODO: if old_hash's number is > block_num, we need to remove more entries
warn!(
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"do something with the old hash? we may need to update a bunch more block numbers"
)
}
Entry::Vacant(x) => {
x.insert(*block_hash);
}
}
}
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if self.block_hashes.contains_key(block_hash) {
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// this block is already included. no need to continue
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return Ok(());
}
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let mut blockchain = self.blockchain_graphmap.write();
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if blockchain.contains_node(*block_hash) {
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// this hash is already included. we must have hit that race condition
// return now since this work was already done.
return Ok(());
}
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// TODO: theres a small race between contains_key and insert
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if let Some(_overwritten) = self.block_hashes.insert(*block_hash, block.clone()) {
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// there was a race and another thread wrote this block
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// i don't think this will happen. the blockchain.conains_node above should be enough
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// no need to continue because that other thread would have written (or soon will) write the
return Ok(());
}
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// TODO: prettier log? or probably move the log somewhere else
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trace!(%block_hash, "new block");
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blockchain.add_node(*block_hash);
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// what should edge weight be? and should the nodes be the blocks instead?
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// TODO: maybe the weight should be the block?
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// we store parent_hash -> hash because the block already stores the parent_hash
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blockchain.add_edge(block.parent_hash, *block_hash, 0);
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// TODO: prune block_numbers and block_map to only keep a configurable (256 on ETH?) number of blocks?
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Ok(())
}
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/// Get a block from caches with fallback.
/// Will query a specific node or the best available.
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/// WARNING! If rpc is specified, this may wait forever. be sure this runs with your own timeout
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pub async fn block(
&self,
hash: &H256,
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rpc: Option<&Arc<Web3Connection>>,
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) -> anyhow::Result<ArcBlock> {
// first, try to get the hash from our cache
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if let Some(block) = self.block_hashes.get(hash) {
return Ok(block.clone());
}
// block not in cache. we need to ask an rpc for it
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let request_params = (hash, false);
// TODO: if error, retry?
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let block: Block<TxHash> = match rpc {
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Some(rpc) => {
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rpc.wait_for_request_handle()
.await?
.request("eth_getBlockByHash", request_params)
.await?
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}
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None => {
// TODO: helper for method+params => JsonRpcRequest
// TODO: does this id matter?
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let request =
json!({ "id": "1", "method": "eth_getBlockByHash", "params": request_params });
let request: JsonRpcRequest = serde_json::from_value(request)?;
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let response = self.try_send_best_upstream_server(request, None).await?;
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let block = response.result.unwrap();
serde_json::from_str(block.get())?
}
};
let block = Arc::new(block);
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// the block was fetched using eth_getBlockByHash, so it should have all fields
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self.save_block(&block, None)?;
Ok(block)
}
/// Convenience method to get the cannonical block at a given block height.
pub async fn block_hash(&self, num: &U64) -> anyhow::Result<H256> {
let block = self.cannonical_block(num).await?;
let hash = block.hash.unwrap();
Ok(hash)
}
/// Get the heaviest chain's block from cache or backend rpc
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pub async fn cannonical_block(&self, num: &U64) -> anyhow::Result<ArcBlock> {
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// we only have blocks by hash now
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// maybe save them during save_block in a blocks_by_number DashMap<U64, Vec<ArcBlock>>
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// if theres multiple, use petgraph to find the one on the main chain (and remove the others if they have enough confirmations)
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// first, try to get the hash from our cache
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if let Some(block_hash) = self.block_numbers.get(num) {
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let block = self
.block_hashes
.get(&block_hash)
.expect("block_numbers gave us this hash");
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return Ok(block.clone());
}
// block not in cache. we need to ask an rpc for it
// but before we do any queries, be sure the requested block num exists
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let head_block_num = self
.head_block_num()
.ok_or_else(|| anyhow::anyhow!("no servers in sync"))?;
if num > &head_block_num {
// TODO: i'm seeing this a lot when using ethspam. i dont know why though. i thought we delayed publishing
// TODO: instead of error, maybe just sleep and try again?
return Err(anyhow::anyhow!(
"Head block is #{}, but #{} was requested",
head_block_num,
num
));
}
// TODO: helper for method+params => JsonRpcRequest
let request = json!({ "jsonrpc": "2.0", "id": "1", "method": "eth_getBlockByNumber", "params": (num, false) });
let request: JsonRpcRequest = serde_json::from_value(request)?;
// TODO: if error, retry?
let response = self
.try_send_best_upstream_server(request, Some(num))
.await?;
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let raw_block = response.result.context("no block result")?;
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let block: Block<TxHash> = serde_json::from_str(raw_block.get())?;
let block = Arc::new(block);
// the block was fetched using eth_getBlockByNumber, so it should have all fields and be on the heaviest chain
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self.save_block(&block, Some(true))?;
Ok(block)
}
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pub(super) async fn process_incoming_blocks(
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&self,
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block_receiver: flume::Receiver<BlockAndRpc>,
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// TODO: head_block_sender should be a broadcast_sender like pending_tx_sender
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head_block_sender: watch::Sender<ArcBlock>,
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pending_tx_sender: Option<broadcast::Sender<TxStatus>>,
) -> anyhow::Result<()> {
// TODO: indexmap or hashmap? what hasher? with_capacity?
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// TODO: this will grow unbounded. prune old heads on this at the same time we prune the graph?
let mut connection_heads = HashMap::new();
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while let Ok((new_block, rpc)) = block_receiver.recv_async().await {
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self.process_block_from_rpc(
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&mut connection_heads,
new_block,
rpc,
&head_block_sender,
&pending_tx_sender,
)
.await?;
}
// TODO: if there was an error, we should return it
warn!("block_receiver exited!");
Ok(())
}
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/// `connection_heads` is a mapping of rpc_names to head block hashes.
/// self.blockchain_map is a mapping of hashes to the complete Block<TxHash>.
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/// TODO: return something?
async fn process_block_from_rpc(
&self,
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connection_heads: &mut HashMap<String, H256>,
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rpc_head_block: ArcBlock,
rpc: Arc<Web3Connection>,
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head_block_sender: &watch::Sender<ArcBlock>,
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pending_tx_sender: &Option<broadcast::Sender<TxStatus>>,
) -> anyhow::Result<()> {
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// add the block to connection_heads
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let rpc_block_id = match (rpc_head_block.hash, rpc_head_block.number) {
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(Some(rpc_head_hash), Some(rpc_head_num)) => {
if rpc_head_num == U64::zero() {
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debug!(%rpc, "still syncing");
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connection_heads.remove(&rpc.name);
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None
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} else {
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connection_heads.insert(rpc.name.to_owned(), rpc_head_hash);
// we don't know if its on the heaviest chain yet
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self.save_block(&rpc_head_block, Some(false))?;
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Some(BlockId {
hash: rpc_head_hash,
num: rpc_head_num,
})
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}
}
_ => {
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warn!(%rpc, ?rpc_head_block, "Block without number or hash!");
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connection_heads.remove(&rpc.name);
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// don't return yet! self.synced_connections likely needs an update
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None
}
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};
// iterate the known heads to find the highest_work_block
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let mut checked_heads = HashSet::new();
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let mut highest_work_block: Option<Ref<H256, ArcBlock>> = None;
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for rpc_head_hash in connection_heads.values() {
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if checked_heads.contains(rpc_head_hash) {
// we already checked this head from another rpc
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continue;
}
// don't check the same hash multiple times
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checked_heads.insert(rpc_head_hash);
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let rpc_head_block = self.block_hashes.get(rpc_head_hash).unwrap();
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match &rpc_head_block.total_difficulty {
None => {
// no total difficulty. this is a bug
unimplemented!("block is missing total difficulty");
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}
Some(td) => {
// if this is the first block we've tried
// or if this rpc's newest block has a higher total difficulty
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if highest_work_block.is_none()
|| td
> highest_work_block
.as_ref()
.expect("there should always be a block here")
.total_difficulty
.as_ref()
.expect("there should always be total difficulty here")
{
highest_work_block = Some(rpc_head_block);
}
}
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}
}
// clone to release the read lock on self.block_hashes
if let Some(mut maybe_head_block) = highest_work_block.map(|x| x.clone()) {
// track rpcs on this heaviest chain so we can build a new SyncedConnections
let mut heavy_rpcs: Vec<&Arc<Web3Connection>> = vec![];
// a running total of the soft limits covered by the heavy rpcs
let mut heavy_sum_soft_limit: u32 = 0;
// TODO: also track heavy_sum_hard_limit?
// check the highest work block for a set of rpcs that can serve our request load
// if it doesn't have enough rpcs for our request load, check the parent block
// TODO: loop for how many parent blocks? we don't want to serve blocks that are too far behind. probably different per chain
// TODO: this loop is pretty long. any way to clean up this code?
for _ in 0..3 {
let maybe_head_hash = maybe_head_block
.hash
.as_ref()
.expect("blocks here always need hashes");
// find all rpcs with maybe_head_block as their current head
for (conn_name, conn_head_hash) in connection_heads.iter() {
if conn_head_hash != maybe_head_hash {
continue;
}
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if let Some(rpc) = self.conns.get(conn_name) {
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heavy_rpcs.push(rpc);
heavy_sum_soft_limit += rpc.soft_limit;
} else {
warn!("connection missing")
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}
}
if heavy_sum_soft_limit < self.min_sum_soft_limit
|| heavy_rpcs.len() < self.min_synced_rpcs
{
// not enough rpcs yet. check the parent
if let Some(parent_block) = self.block_hashes.get(&maybe_head_block.parent_hash)
{
trace!(
child=%maybe_head_hash, parent=%parent_block.hash.unwrap(), "avoiding thundering herd",
);
maybe_head_block = parent_block.clone();
continue;
} else {
warn!(
"no parent to check. soft limit only {}/{} from {}/{} rpcs: {}%",
heavy_sum_soft_limit,
self.min_sum_soft_limit,
heavy_rpcs.len(),
self.min_synced_rpcs,
heavy_sum_soft_limit * 100 / self.min_sum_soft_limit
);
break;
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}
}
// success! this block has enough soft limit and nodes on it (or on later blocks)
let conns = heavy_rpcs.into_iter().cloned().collect();
let heavy_block = maybe_head_block;
let heavy_hash = heavy_block.hash.expect("head blocks always have hashes");
let heavy_num = heavy_block.number.expect("head blocks always have numbers");
debug_assert_ne!(heavy_num, U64::zero());
let heavy_block_id = BlockId {
hash: heavy_hash,
num: heavy_num,
};
let new_synced_connections = SyncedConnections {
head_block_id: Some(heavy_block_id.clone()),
conns,
};
let old_synced_connections = self
.synced_connections
.swap(Arc::new(new_synced_connections));
let num_connection_heads = connection_heads.len();
let total_conns = self.conns.len();
// TODO: if the rpc_head_block != heavy, log something somewhere in here
match &old_synced_connections.head_block_id {
None => {
debug!(block=%heavy_block_id, %rpc, "first consensus head");
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self.save_block(&rpc_head_block, Some(true))?;
head_block_sender.send(heavy_block)?;
}
Some(old_block_id) => {
match heavy_block_id.num.cmp(&old_block_id.num) {
Ordering::Equal => {
// multiple blocks with the same fork!
if heavy_block_id.hash == old_block_id.hash {
// no change in hash. no need to use head_block_sender
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debug!(head=%heavy_block_id, %rpc, "con block")
} else {
// hash changed
// TODO: better log
warn!(heavy=%heavy_block_id, %rpc, "fork detected");
// todo!("handle equal by updating the cannonical chain");
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self.save_block(&rpc_head_block, Some(true))?;
head_block_sender.send(heavy_block)?;
}
}
Ordering::Less => {
// this is unlikely but possible
// TODO: better log
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warn!(head=%heavy_block_id, %rpc, "chain rolled back");
self.save_block(&rpc_head_block, Some(true))?;
// todo!("handle less by removing higher blocks from the cannonical chain");
head_block_sender.send(heavy_block)?;
}
Ordering::Greater => {
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debug!(head=%heavy_block_id, %rpc, "new block");
// todo!("handle greater by adding this block to and any missing parents to the cannonical chain");
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self.save_block(&rpc_head_block, Some(true))?;
head_block_sender.send(heavy_block)?;
}
}
}
}
return Ok(());
}
// if we get here, something is wrong. clear synced connections
let empty_synced_connections = SyncedConnections::default();
let old_synced_connections = self
.synced_connections
.swap(Arc::new(empty_synced_connections));
// TODO: log different things depending on old_synced_connections
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}
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Ok(())
}
}