From 5892fa2f9f5ef80e2c3593f2a20818a611e34534 Mon Sep 17 00:00:00 2001
From: Omar Mohamed Khallaf
 <51155980+OmarMohamedKhallaf@users.noreply.github.com>
Date: Wed, 27 Apr 2022 10:46:27 +0200
Subject: [PATCH] fix bug when resolving redis server hostname (#1229)

Calling `drogon::app().createRedisClient` from the resolver callback
function results in a failure because of `assert(!running_);` in
`HttpAppFrameworkImpl::createRedisClient`.

This fix uses a promise whose value is set in the callback and the
client creation is done outside the callback.
---
 lib/src/ConfigLoader.cc | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/lib/src/ConfigLoader.cc b/lib/src/ConfigLoader.cc
index 5e05b313..3c516863 100644
--- a/lib/src/ConfigLoader.cc
+++ b/lib/src/ConfigLoader.cc
@@ -554,30 +554,33 @@ static void loadRedisClients(const Json::Value &redisClients)
 {
     if (!redisClients)
         return;
+    std::promise<std::string> promise;
+    auto future = promise.get_future();
     for (auto const &client : redisClients)
     {
         auto host = client.get("host", "127.0.0.1").asString();
         trantor::Resolver::newResolver()->resolve(
-            host, [client](const trantor::InetAddress &address) {
-                auto hostIp = address.toIp();
-                auto port = client.get("port", 6379).asUInt();
-                auto password = client.get("passwd", "").asString();
-                if (password.empty())
-                {
-                    password = client.get("password", "").asString();
-                }
-                auto connNum = client.get("connection_number", 1).asUInt();
-                if (connNum == 1)
-                {
-                    connNum = client.get("number_of_connections", 1).asUInt();
-                }
-                auto name = client.get("name", "default").asString();
-                auto isFast = client.get("is_fast", false).asBool();
-                auto timeout = client.get("timeout", -1.0).asDouble();
-                auto db = client.get("db", 0).asUInt();
-                drogon::app().createRedisClient(
-                    hostIp, port, name, password, connNum, isFast, timeout, db);
+            host, [&promise](const trantor::InetAddress &address) {
+                promise.set_value(address.toIp());
             });
+        auto port = client.get("port", 6379).asUInt();
+        auto password = client.get("passwd", "").asString();
+        if (password.empty())
+        {
+            password = client.get("password", "").asString();
+        }
+        auto connNum = client.get("connection_number", 1).asUInt();
+        if (connNum == 1)
+        {
+            connNum = client.get("number_of_connections", 1).asUInt();
+        }
+        auto name = client.get("name", "default").asString();
+        auto isFast = client.get("is_fast", false).asBool();
+        auto timeout = client.get("timeout", -1.0).asDouble();
+        auto db = client.get("db", 0).asUInt();
+        auto hostIp = future.get();
+        drogon::app().createRedisClient(
+            hostIp, port, name, password, connNum, isFast, timeout, db);
     }
 }