Function reconnect

crates/eth-engine/src/persistence_meter.rs:368–393

Retry the subscription connection with exponential backoff (1s → 60s cap). Retries forever. This runs in the background task, not in the caller's loop, so it never directly blocks block processing.

(
    endpoint: &SubscriptionEndpoint,
)

/// Retries forever. This runs in the background task, not in the caller's
/// loop, so it never directly blocks block processing.
async fn reconnect(
    endpoint: &SubscriptionEndpoint,
) -> (Client, jsonrpsee::core::client::Subscription<BlockNumHash>) {
    let mut backoff = RECONNECT_BACKOFF;
    loop {
        match connect_and_subscribe(endpoint).await {
            Ok((client, subscription)) => {
                info!("Persistence meter: reconnected to persisted block subscription");
                return (client, subscription);
            }
            Err(error) => {
                warn!(
                    %error,
                    backoff = ?backoff,
                    "Persistence meter: reconnection failed; retrying"
                );
                tokio::time::sleep(backoff).await;
                // backoff <= MAX_RECONNECT_BACKOFF (60s); *2 fits in Duration
                #[allow(clippy::arithmetic_side_effects)]
                {
                    backoff = (backoff * 2).min(MAX_RECONNECT_BACKOFF);
                }
            }
        }
    }
}

/// Establish a fresh connection and subscribe to persisted block
/// notifications. Used both for the initial connection in