From f11bd80d2a0b8ba0c108deab1293daa31109ce5f Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Mon, 5 Apr 2021 20:33:24 +0200
Subject: Keep old data

---
 src/rpc/membership.rs | 24 ++++++++++++++++++++----
 src/util/persister.rs | 12 +++++++++++-
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/src/rpc/membership.rs b/src/rpc/membership.rs
index 330c154f..f8223420 100644
--- a/src/rpc/membership.rs
+++ b/src/rpc/membership.rs
@@ -582,7 +582,7 @@ impl System {
 					.map(|ip| (*ip, None))
 					.collect::<Vec<_>>();
 
-				match self.persist_status.load() {
+				match self.persist_status.load_async().await {
 					Ok(peers) => {
 						bp2.extend(peers.iter().map(|x| (x.addr, Some(x.id))));
 					}
@@ -653,9 +653,25 @@ impl System {
 	async fn update_status(self: &Arc<Self>, updaters: &Updaters, status: Status) {
 		if status.hash != self.status.borrow().hash {
 			info!("Persisting new peer list");
-			let serializable_status = status.to_serializable_membership(&self);
-			self.persist_status.save_async(&serializable_status).await
-				.expect("Unable to persist peer list");
+
+			let mut list = status.to_serializable_membership(&self);
+
+			// Combine with old peer list to make sure no peer is lost
+			match self.persist_status.load_async().await {
+				Ok(old_list) => {
+					for pp in old_list {
+						if !list.iter().any(|np| pp.id == np.id) {
+							list.push(pp);
+						}
+					}
+				}
+				_ => (),
+			}
+
+			if list.len() > 0 {
+				self.persist_status.save_async(&list).await
+					.expect("Unable to persist peer list");
+			}
 		}
 
 		let status = Arc::new(status);
diff --git a/src/util/persister.rs b/src/util/persister.rs
index f4e8cd72..93b7cdf4 100644
--- a/src/util/persister.rs
+++ b/src/util/persister.rs
@@ -1,7 +1,7 @@
 use std::io::{Read, Write};
 use std::path::PathBuf;
 
-use tokio::io::AsyncWriteExt;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
 use serde::{Deserialize, Serialize};
 
@@ -51,6 +51,16 @@ where
 		Ok(())
 	}
 
+	pub async fn load_async(&self) -> Result<T, Error> {
+		let mut file = tokio::fs::File::open(&self.path).await?;
+
+		let mut bytes = vec![];
+		file.read_to_end(&mut bytes).await?;
+
+		let value = rmp_serde::decode::from_read_ref(&bytes[..])?;
+		Ok(value)
+	}
+
 	pub async fn save_async(&self, t: &T) -> Result<(), Error> {
 		let bytes = rmp_to_vec_all_named(t)?;
 
-- 
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