From 53d09eb00f29fe5c7a8a14fa22ce6cfc64bb0b14 Mon Sep 17 00:00:00 2001
From: Jonathan Davies <jpds@protonmail.com>
Date: Sat, 4 Mar 2023 16:16:10 +0000
Subject: [PATCH 1/2] block/repair.rs: Added function and time_next_run_scrub
 with a random element of 10 days to SCRUB_INTERVAL to help balance scrub load
 across cluster.

---
 src/block/repair.rs | 48 ++++++++++++++++++++++++++++++++++-----------
 1 file changed, 37 insertions(+), 11 deletions(-)

diff --git a/src/block/repair.rs b/src/block/repair.rs
index d4593dbf..10d46291 100644
--- a/src/block/repair.rs
+++ b/src/block/repair.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 use std::time::Duration;
 
 use async_trait::async_trait;
+use rand::Rng;
 use serde::{Deserialize, Serialize};
 use tokio::fs;
 use tokio::select;
@@ -19,8 +20,8 @@ use garage_util::tranquilizer::Tranquilizer;
 
 use crate::manager::*;
 
-// Full scrub every 30 days
-const SCRUB_INTERVAL: Duration = Duration::from_secs(3600 * 24 * 30);
+// Full scrub every 25 days with a random element of 10 days mixed in below
+const SCRUB_INTERVAL: Duration = Duration::from_secs(3600 * 24 * 25);
 // Scrub tranquility is initially set to 4, but can be changed in the CLI
 // and the updated version is persisted over Garage restarts
 const INITIAL_SCRUB_TRANQUILITY: u32 = 4;
@@ -175,13 +176,30 @@ pub struct ScrubWorker {
 pub struct ScrubWorkerPersisted {
 	pub tranquility: u32,
 	pub(crate) time_last_complete_scrub: u64,
+	pub(crate) time_next_run_scrub: u64,
 	pub(crate) corruptions_detected: u64,
 }
+
+fn randomize_next_scrub_run_time() -> u64 {
+	// Take SCRUB_INTERVAL and mix in a random interval of 10 days to attempt to
+	// balance scrub load across different cluster nodes.
+
+	let next_run_timestamp = now_msec()
+		+ SCRUB_INTERVAL
+			.saturating_add(Duration::from_secs(
+				rand::thread_rng().gen_range(0..3600 * 24 * 10),
+			))
+			.as_millis() as u64;
+
+	next_run_timestamp
+}
+
 impl garage_util::migrate::InitialFormat for ScrubWorkerPersisted {}
 impl Default for ScrubWorkerPersisted {
 	fn default() -> Self {
 		ScrubWorkerPersisted {
 			time_last_complete_scrub: 0,
+			time_next_run_scrub: randomize_next_scrub_run_time(),
 			tranquility: INITIAL_SCRUB_TRANQUILITY,
 			corruptions_detected: 0,
 		}
@@ -279,12 +297,13 @@ impl Worker for ScrubWorker {
 	}
 
 	fn status(&self) -> WorkerStatus {
-		let (corruptions_detected, tranquility, time_last_complete_scrub) =
+		let (corruptions_detected, tranquility, time_last_complete_scrub, time_next_run_scrub) =
 			self.persister.get_with(|p| {
 				(
 					p.corruptions_detected,
 					p.tranquility,
 					p.time_last_complete_scrub,
+					p.time_next_run_scrub,
 				)
 			});
 
@@ -302,10 +321,16 @@ impl Worker for ScrubWorker {
 				s.freeform = vec![format!("Scrub paused, resumes at {}", msec_to_rfc3339(*rt))];
 			}
 			ScrubWorkerState::Finished => {
-				s.freeform = vec![format!(
-					"Last scrub completed at {}",
-					msec_to_rfc3339(time_last_complete_scrub)
-				)];
+				s.freeform = vec![
+					format!(
+						"Last scrub completed at {}",
+						msec_to_rfc3339(time_last_complete_scrub),
+					),
+					format!(
+						"Next scrub scheduled for {}",
+						msec_to_rfc3339(time_next_run_scrub)
+					),
+				];
 			}
 		}
 		s
@@ -334,8 +359,10 @@ impl Worker for ScrubWorker {
 						.tranquilizer
 						.tranquilize_worker(self.persister.get_with(|p| p.tranquility)))
 				} else {
-					self.persister
-						.set_with(|p| p.time_last_complete_scrub = now_msec())?;
+					self.persister.set_with(|p| {
+						p.time_last_complete_scrub = now_msec();
+						p.time_next_run_scrub = randomize_next_scrub_run_time();
+					})?;
 					self.work = ScrubWorkerState::Finished;
 					self.tranquilizer.clear();
 					Ok(WorkerState::Idle)
@@ -350,8 +377,7 @@ impl Worker for ScrubWorker {
 			ScrubWorkerState::Running(_) => return WorkerState::Busy,
 			ScrubWorkerState::Paused(_, resume_time) => (*resume_time, ScrubWorkerCommand::Resume),
 			ScrubWorkerState::Finished => (
-				self.persister.get_with(|p| p.time_last_complete_scrub)
-					+ SCRUB_INTERVAL.as_millis() as u64,
+				self.persister.get_with(|p| p.time_next_run_scrub),
 				ScrubWorkerCommand::Start,
 			),
 		};

From 148b66b843be7f79f15b0a3805f38a0c3e944214 Mon Sep 17 00:00:00 2001
From: Jonathan Davies <jpds@protonmail.com>
Date: Mon, 6 Mar 2023 12:31:03 +0000
Subject: [PATCH 2/2] block/manager.rs: Display scrub-next-run.

---
 src/block/manager.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/block/manager.rs b/src/block/manager.rs
index 051a9f93..bfa66069 100644
--- a/src/block/manager.rs
+++ b/src/block/manager.rs
@@ -185,6 +185,9 @@ impl BlockManager {
 		vars.register_ro(&self.scrub_persister, "scrub-last-completed", |p| {
 			p.get_with(|x| msec_to_rfc3339(x.time_last_complete_scrub))
 		});
+		vars.register_ro(&self.scrub_persister, "scrub-next-run", |p| {
+			p.get_with(|x| msec_to_rfc3339(x.time_next_run_scrub))
+		});
 		vars.register_ro(&self.scrub_persister, "scrub-corruptions_detected", |p| {
 			p.get_with(|x| x.corruptions_detected)
 		});