feat(scanner): add BlockListener with mpsc fan-in + reconnect#32
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) The bot's heartbeat. One `BlockListener` per configured chain subscribes to `newHeads` over WebSocket and forwards each block into a shared mpsc channel that the scanning pipeline will consume. - New `crates/charon-scanner/src/listener.rs`: - `ChainEvent::NewBlock { chain, number, timestamp }` — enum shape so future event kinds (protocol logs, oracle updates) land without changing channel types - `BlockListener::run` loops `run_once`, reconnecting with exponential backoff (1s → 30s cap) on any subscription/transport error - Per-block structured log: `chain=<name> block=<n> timestamp=<t>` - Clean shutdown when the receiver drops - CLI `listen` subcommand now: - Spawns a listener per `[chain.<name>]` in config - Drains the shared channel at `debug!` level - Exits on Ctrl-C or when all listeners terminate - Adds `futures-util` as a workspace dep for `SubscriptionStream::next()` Verified against BSC mainnet: `cargo run -- listen` streamed 304 blocks in 2m16s with zero warnings — subscription stable, reconnect logic dormant (no drops seen).
This was referenced Apr 22, 2026
…et supervision, metrics
- Reconnect backoff now adds 0-25% random jitter before each sleep to
avoid correlated retry storms against a single RPC endpoint when
many listeners disconnect at the same instant.
- BlockListener::publish uses try_send instead of a blocking await on
the mpsc sender; a full channel drops the block with a warn log and
a charon_listener_dropped_events_total counter increment, keeping the
WS drain loop responsive so the transport never buffers past its
server-side limit.
- Track last_seen block per chain. On reconnect, fetch the current head
and backfill every block between last_seen + 1 and head - 1 via
get_block_by_number, emitting ChainEvent::NewBlock { backfill: true }
so downstream consumers see the same heartbeat during disconnect
windows.
- CLI run_listen now spawns listeners into a tokio::task::JoinSet and a
supervise() helper drains join results, logging per-chain task panics
or errors and triggering shutdown when every listener exits. Ctrl-C
also aborts outstanding listeners.
- Per-block log downgraded from info to debug (BSC ~3 s = 28,800
info lines/day otherwise). Add charon_listener_connects_total,
charon_listener_disconnects_total, charon_blocks_received_total,
charon_listener_dropped_events_total counters for PR #50.
- Workspace adds rand and metrics deps; ChainEvent is #[non_exhaustive]
and carries a backfill flag.
Closes #92 #93 #94 #95 #96
This was referenced Apr 23, 2026
Closed
Closed
# Conflicts: # crates/charon-cli/src/main.rs # crates/charon-scanner/Cargo.toml # crates/charon-scanner/src/lib.rs
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Closes #8
The bot's heartbeat. One
BlockListenerper configured chain subscribes tonewHeadsover WebSocket and forwards each block into a shared mpsc channel the scanning pipeline consumes.ChainEvent::NewBlock { chain, number, timestamp }enum — shape admits future event kinds (protocol logs, oracle updates) without changing channel typesBlockListener::runloopsrun_once, reconnecting with exponential backoff (1s → 30s cap) on any subscription/transport errorchain=<name> block=<n> timestamp=<t>listenspawns one listener per[chain.<name>], drains the shared channel, exits on Ctrl-C or when all listeners terminatefutures-utilas a workspace dep forSubscriptionStream::next()Live-verified on BSC:
cargo run -- listenstreamed 304 blocks in 2m16s, zero warnings.Depends on #7 (
feat/06-chainprovider-ws).