From 624379680a1d70cded63c51153f1b5ce74c3f9a3 Mon Sep 17 00:00:00 2001
From: Marcin Kulik <m@ku1ik.com>
Date: Sun, 1 Jun 2025 22:47:36 +0200
Subject: [PATCH] Add jitter to exponential backoff in forwarder reconnection

---
 Cargo.lock       | 1 +
 Cargo.toml       | 1 +
 src/forwarder.rs | 9 +++++++--
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index a89bca2..6786b33 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -95,6 +95,7 @@ dependencies = [
  "config",
  "futures-util",
  "nix 0.30.1",
+ "rand",
  "reqwest",
  "rgb",
  "rust-embed",
diff --git a/Cargo.toml b/Cargo.toml
index 4b9ffbc..8d9617f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,6 +41,7 @@ url = "2.5.0"
 tokio-tungstenite = { version = "0.26.2", default-features = false, features = ["connect", "rustls-tls-native-roots"] }
 rustls = { version = "0.23.26", default-features = false, features = ["aws_lc_rs"] }
 tokio-util = "0.7.10"
+rand = "0.9.1"
 
 [build-dependencies]
 clap = { version = "4.5.37", features = ["derive"] }
diff --git a/src/forwarder.rs b/src/forwarder.rs
index ef0beba..6f81b46 100644
--- a/src/forwarder.rs
+++ b/src/forwarder.rs
@@ -5,6 +5,7 @@ use std::time::Duration;
 use anyhow::{anyhow, bail};
 use axum::http::Uri;
 use futures_util::{SinkExt, Stream, StreamExt};
+use rand::Rng;
 use tokio::net::TcpStream;
 use tokio::time::{interval, sleep, timeout};
 use tokio_stream::wrappers::errors::BroadcastStreamRecvError;
@@ -23,7 +24,8 @@ use crate::stream::Subscriber;
 const PING_INTERVAL: u64 = 15;
 const PING_TIMEOUT: u64 = 10;
 const SEND_TIMEOUT: u64 = 10;
-const MAX_RECONNECT_DELAY: u64 = 5000;
+const RECONNECT_DELAY_BASE: u64 = 500;
+const RECONNECT_DELAY_CAP: u64 = 10_000;
 
 pub async fn forward<N: Notifier>(
     url: url::Url,
@@ -224,7 +226,10 @@ fn handle_close_frame(frame: Option<CloseFrame>) -> anyhow::Result<()> {
 }
 
 fn exponential_delay(attempt: usize) -> u64 {
-    (2_u64.pow(attempt as u32) * 500).min(MAX_RECONNECT_DELAY)
+    let mut rng = rand::rng();
+    let base = (RECONNECT_DELAY_BASE * 2_u64.pow(attempt as u32)).min(RECONNECT_DELAY_CAP);
+
+    rng.random_range(..base)
 }
 
 fn ws_result(m: Result<Vec<u8>, BroadcastStreamRecvError>) -> anyhow::Result<Message> {