From 5a865b687c35b9ccdc1a4197bc1cef347fd45d36 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Max=20Neunh=C3=B6ffer?= <max@arangodb.com>
Date: Wed, 5 Sep 2018 21:14:07 +0200
Subject: [PATCH] Wait 2s after switching server mode before answering. (#6393)

This is needed because the change is propagated via the agency and the
heartbeat, which only happens once per second.
---
 arangod/Cluster/ServerState.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arangod/Cluster/ServerState.cpp b/arangod/Cluster/ServerState.cpp
index 02bf76b241..6ca1f93813 100644
--- a/arangod/Cluster/ServerState.cpp
+++ b/arangod/Cluster/ServerState.cpp
@@ -794,6 +794,10 @@ Result ServerState::propagateClusterReadOnly(bool mode) {
     if (!r.successful()) {
       return Result(TRI_ERROR_CLUSTER_AGENCY_COMMUNICATION_FAILED, r.errorMessage());
     }
+    // This is propagated to all servers via the heartbeat, which happens
+    // once per second. So to ensure that every server has taken note of
+    // the change, we delay here for 2 seconds.
+    std::this_thread::sleep_for(std::chrono::seconds(2));
   }
   setReadOnly(mode);
   return Result();