refactor: consolidate exp backoff config into pluto_core::expbackoff

crates/app/src/sse/mod.rs

@@ -392,12 +392,12 @@ impl SseListenerActor {
 /// failure.
 async fn fetch_config(client: &EthBeaconNodeApiClient) -> Result<(DateTime<Utc>, Duration, u64)> {
     let genesis_time = (|| client.fetch_genesis_time())
-        .retry(fast_backoff())
+        .retry(pluto_core::expbackoff::fast())
         .notify(|err, _| tracing::error!(err = ?err, "Failure fetching genesis time"))
         .await?;
 
     let (slot_duration, slots_per_epoch) = (|| client.fetch_slots_config())
-        .retry(fast_backoff())
+        .retry(pluto_core::expbackoff::fast())
         .notify(|err, _| tracing::error!(err = ?err, "Failure fetching slots config"))
         .await?;
 
@@ -503,18 +503,6 @@ async fn stream_once(
     }
 }
 
-// TODO: Extract these backoff configurations into a shared module.
-
-/// Backoff used while waiting for the beacon node configuration.
-fn fast_backoff() -> ExponentialBuilder {
-    ExponentialBuilder::default()
-        .with_min_delay(Duration::from_millis(100))
-        .with_max_delay(Duration::from_secs(5))
-        .with_factor(1.6)
-        .without_max_times()
-        .with_jitter()
-}
-
 /// Backoff used between SSE reconnection attempts.
 fn reconnect_backoff() -> ExponentialBuilder {
     ExponentialBuilder::default()

crates/core/src/expbackoff.rs

@@ -0,0 +1,41 @@
+//! Exponential backoff builders mirroring Charon's `app/expbackoff` package.
+//!
+//! Charon defines two shared configurations (`app/expbackoff/expbackoff.go`):
+//! `FastConfig` (100ms base, 5s max) for quick retries, and `DefaultConfig`
+//! (1s base, 120s max) for slower loops. Both use a 1.6 multiplier and 0.2
+//! jitter and retry until the surrounding context is cancelled.
+//!
+//! Note on jitter: Charon applies a `±20%` multiplicative jitter, whereas
+//! `backon`'s [`ExponentialBuilder::with_jitter`] adds a randomized delay in
+//! `(0, base)`. This is an approximation, but it matches every existing
+//! Pluto backoff call site, so consolidating here introduces no behavioral
+//! change.
+
+use std::time::Duration;
+
+use backon::ExponentialBuilder;
+
+/// Backoff matching Charon's `expbackoff.FastConfig`: base=100ms, max=5s,
+/// multiplier=1.6, jitter≈0.2. Retries until the surrounding cancellation
+/// stops it (`without_max_times`), mirroring Go's "back off until the context
+/// is cancelled" loops.
+pub fn fast() -> ExponentialBuilder {
+    ExponentialBuilder::default()
+        .with_min_delay(Duration::from_millis(100))
+        .with_max_delay(Duration::from_secs(5))
+        .with_factor(1.6)
+        .without_max_times()
+        .with_jitter()
+}
+
+/// Backoff matching Charon's `expbackoff.DefaultConfig`: base=1s, max=120s,
+/// multiplier=1.6, jitter≈0.2. Retries until the surrounding cancellation
+/// stops it (`without_max_times`).
+pub fn default() -> ExponentialBuilder {
+    ExponentialBuilder::default()
+        .with_min_delay(Duration::from_secs(1))
+        .with_max_delay(Duration::from_secs(120))
+        .with_factor(1.6)
+        .without_max_times()
+        .with_jitter()
+}

crates/core/src/lib.rs

@@ -30,6 +30,9 @@ pub mod clock;
 /// future.
 pub mod gater;
 
+/// Exponential backoff builders mirroring Charon's `app/expbackoff`.
+pub mod expbackoff;
+
 /// parsigdb
 pub mod parsigdb;
 

crates/core/src/scheduler.rs

@@ -1,7 +1,4 @@
-use std::{
-    collections::{HashMap, hash_map::Entry},
-    time::Duration,
-};
+use std::collections::{HashMap, hash_map::Entry};
 
 use backon::{BackoffBuilder, Retryable};
 use tokio::sync;
@@ -719,39 +716,10 @@ async fn resolve_active_validators(
     Ok(validators)
 }
 
-// TODO: Duplicated from `crates/p2p/src/bootnode.rs`
-fn fast_backoff() -> backon::ExponentialBuilder {
-    /// Backoff configuration constants matching Go's expbackoff.FastConfig.
-    const FAST_BASE_DELAY: Duration = Duration::from_millis(100);
-    const FAST_MAX_DELAY: Duration = Duration::from_secs(5);
-    const FAST_MULTIPLIER: f32 = 1.6;
-
-    backon::ExponentialBuilder::default()
-        .with_min_delay(FAST_BASE_DELAY)
-        .with_max_delay(FAST_MAX_DELAY)
-        .with_factor(FAST_MULTIPLIER)
-        .without_max_times()
-        .with_jitter()
-}
-
-fn default_backoff() -> backon::ExponentialBuilder {
-    /// Backoff configuration constants matching Go's expbackoff.DefaultConfig.
-    const DEFAULT_BASE_DELAY: Duration = Duration::from_secs(1);
-    const DEFAULT_MAX_DELAY: Duration = Duration::from_secs(120);
-    const DEFAULT_MULTIPLIER: f32 = 1.6;
-
-    backon::ExponentialBuilder::default()
-        .with_min_delay(DEFAULT_BASE_DELAY)
-        .with_max_delay(DEFAULT_MAX_DELAY)
-        .with_factor(DEFAULT_MULTIPLIER)
-        .without_max_times()
-        .with_jitter()
-}
-
 /// Blocks until the beacon chain has started.
 async fn wait_chain_start(client: &pluto_eth2api::BeaconNodeClient) -> Result<()> {
     let fetch = || client.api().fetch_genesis_time();
-    let backoff = fast_backoff();
+    let backoff = crate::expbackoff::fast();
     let genesis_time = fetch
         .retry(backoff)
         .notify(|err, _| tracing::error!(err = ?err, "Failure getting genesis"))
@@ -777,9 +745,9 @@ async fn wait_beacon_sync(client: &pluto_eth2api::BeaconNodeClient) -> Result<()
             .api()
             .get_syncing_status(pluto_eth2api::GetSyncingStatusRequest {})
     };
-    let fetch_backoff = fast_backoff();
+    let fetch_backoff = crate::expbackoff::fast();
 
-    let mut is_syncing_backoff = default_backoff().build();
+    let mut is_syncing_backoff = crate::expbackoff::default().build();
 
     loop {
         let response: pluto_eth2api::GetSyncingStatusResponse = fetch
@@ -1036,7 +1004,7 @@ async fn fetch_sync_committee_duties(
 
 #[cfg(test)]
 mod tests {
-    use std::collections::HashSet;
+    use std::{collections::HashSet, time::Duration};
 
     use pluto_eth2api::{
         BeaconNodeClient, GetStateValidatorsResponseResponse,

crates/p2p/src/bootnode.rs

@@ -2,7 +2,7 @@
 
 use std::time::Duration;
 
-use backon::{ExponentialBuilder, Retryable};
+use backon::Retryable;
 use libp2p::Multiaddr;
 use pluto_eth2util::enr::Record;
 use tokio_util::sync::CancellationToken;
@@ -12,11 +12,6 @@ use crate::peer::{
     AddrInfo, MutablePeer, Peer, PeerError, addr_infos_from_p2p_addrs, peer_id_from_key,
 };
 
-/// Backoff configuration constants matching Go's expbackoff.FastConfig.
-const FAST_BASE_DELAY: Duration = Duration::from_millis(100);
-const FAST_MAX_DELAY: Duration = Duration::from_secs(5);
-const FAST_MULTIPLIER: f32 = 1.6;
-
 /// Polling interval for relay address updates.
 const RELAY_POLL_INTERVAL: Duration = Duration::from_secs(120); // 2 minutes
 
@@ -235,12 +230,9 @@ async fn query_relay_addrs(
         return Err(BootnodeError::InvalidRelayUrl);
     }
 
-    // Retry with exponential backoff
-    let backoff = ExponentialBuilder::default()
-        .with_min_delay(FAST_BASE_DELAY)
-        .with_max_delay(FAST_MAX_DELAY)
-        .with_factor(FAST_MULTIPLIER)
-        .with_jitter();
+    // Retry with exponential backoff until the cancel token fires, matching
+    // Go's `queryRelayAddrs` ("It retries until the context is cancelled").
+    let backoff = pluto_core::expbackoff::fast();
 
     let fetch = || async {
         if cancel.is_cancelled() {