From 2314baf0d381e8ec05b03cdb40a3fc4881483e2a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C4=99drzej=20Stuczy=C5=84ski?=
 <jedrzej.stuczynski@gmail.com>
Date: Fri, 29 Jan 2021 10:17:37 +0000
Subject: [PATCH] Allowing for a single topology refresh failure (#505)

---
 clients/client-core/src/client/topology_control.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/clients/client-core/src/client/topology_control.rs b/clients/client-core/src/client/topology_control.rs
index 016e33f7a6..7e70636d21 100644
--- a/clients/client-core/src/client/topology_control.rs
+++ b/clients/client-core/src/client/topology_control.rs
@@ -153,6 +153,8 @@ pub struct TopologyRefresher {
     validator_client: validator_client::Client,
     topology_accessor: TopologyAccessor,
     refresh_rate: Duration,
+
+    was_latest_valid: bool,
 }
 
 impl TopologyRefresher {
@@ -167,6 +169,7 @@ impl TopologyRefresher {
             validator_client,
             topology_accessor,
             refresh_rate: cfg.refresh_rate,
+            was_latest_valid: true,
         }
     }
 
@@ -187,6 +190,16 @@ impl TopologyRefresher {
         trace!("Refreshing the topology");
         let new_topology = self.get_current_compatible_topology().await;
 
+        if new_topology.is_none() && self.was_latest_valid {
+            // if we failed to grab this topology, but the one before it was alright, let's assume
+            // validator had a tiny hiccup and use the old data
+            warn!("we're going to keep on using the old topology for this iteration");
+            self.was_latest_valid = false;
+            return;
+        } else if new_topology.is_some() {
+            self.was_latest_valid = true;
+        }
+
         self.topology_accessor
             .update_global_topology(new_topology)
             .await;