shuffle resolved IPs

programs/copier/Internals.cpp

@@ -259,7 +259,7 @@ ShardPriority getReplicasPriority(const Cluster::Addresses & replicas, const std
     res.is_remote = 1;
     for (const auto & replica : replicas)
     {
-        if (isLocalAddress(DNSResolver::instance().resolveHost(replica.host_name)))
+        if (isLocalAddress(DNSResolver::instance().resolveHostAllInOriginOrder(replica.host_name).front()))
         {
             res.is_remote = 0;
             break;

src/Access/Common/AllowedClientHosts.cpp

@@ -55,7 +55,7 @@ namespace
     {
         IPAddress addr_v6 = toIPv6(address);
 
-        auto host_addresses = DNSResolver::instance().resolveHostAll(host);
+        auto host_addresses = DNSResolver::instance().resolveHostAllInOriginOrder(host);
 
         for (const auto & addr : host_addresses)
         {

src/Client/ConnectionParameters.cpp

@@ -115,7 +115,7 @@ ConnectionParameters::ConnectionParameters(const Poco::Util::AbstractConfigurati
     /// At the same time, I want clickhouse-local to always work, regardless.
     /// TODO: get rid of glibc, or replace getaddrinfo to c-ares.
 
-    compression = config.getBool("compression", host != "localhost" && !isLocalAddress(DNSResolver::instance().resolveHost(host)))
+    compression = config.getBool("compression", host != "localhost" && !isLocalAddress(DNSResolver::instance().resolveHostAllInOriginOrder(host).front()))
                   ? Protocol::Compression::Enable : Protocol::Compression::Disable;
 
     timeouts = ConnectionTimeouts()

src/Common/DNSResolver.cpp

@@ -202,10 +202,10 @@ DNSResolver::DNSResolver() : impl(std::make_unique<DNSResolver::Impl>()), log(ge
 
 Poco::Net::IPAddress DNSResolver::resolveHost(const std::string & host)
 {
-    return pickAddress(resolveHostAll(host));
+    return pickAddress(resolveHostAll(host)); // random order -> random pick
 }
 
-DNSResolver::IPAddresses DNSResolver::resolveHostAll(const std::string & host)
+DNSResolver::IPAddresses DNSResolver::resolveHostAllInOriginOrder(const std::string & host)
 {
     if (impl->disable_cache)
         return resolveIPAddressImpl(host);
@@ -214,6 +214,13 @@ DNSResolver::IPAddresses DNSResolver::resolveHostAll(const std::string & host)
     return resolveIPAddressWithCache(impl->cache_host, host);
 }
 
+DNSResolver::IPAddresses DNSResolver::resolveHostAll(const std::string & host)
+{
+    auto addresses = resolveHostAllInOriginOrder(host);
+    std::shuffle(addresses.begin(), addresses.end(), thread_local_rng);
+    return addresses;
+}
+
 Poco::Net::SocketAddress DNSResolver::resolveAddress(const std::string & host_and_port)
 {
     if (impl->disable_cache)

src/Common/DNSResolver.h

@@ -34,6 +34,9 @@ class DNSResolver : private boost::noncopyable
     Poco::Net::IPAddress resolveHost(const std::string & host);
 
     /// Accepts host names like 'example.com' or '127.0.0.1' or '::1' and resolves all its IPs
+    /// resolveHostAllInOriginOrder returns addresses with the same order as system call returns it
+    IPAddresses resolveHostAllInOriginOrder(const std::string & host);
+    /// resolveHostAll returns addresses in random order
     IPAddresses resolveHostAll(const std::string & host);
 
     /// Accepts host names like 'example.com:port' or '127.0.0.1:port' or '[::1]:port' and resolves its IP and port

src/Coordination/KeeperStateManager.cpp

@@ -30,7 +30,7 @@ bool isLocalhost(const std::string & hostname)
 {
     try
     {
-        return isLocalAddress(DNSResolver::instance().resolveHost(hostname));
+        return isLocalAddress(DNSResolver::instance().resolveHostAllInOriginOrder(hostname).front());
     }
     catch (...)
     {

src/Interpreters/Context.cpp

@@ -3270,7 +3270,7 @@ bool checkZooKeeperConfigIsLocal(const Poco::Util::AbstractConfiguration & confi
         if (startsWith(key, "node"))
         {
             String host = config.getString(config_name + "." + key + ".host");
-            if (isLocalAddress(DNSResolver::instance().resolveHost(host)))
+            if (isLocalAddress(DNSResolver::instance().resolveHostAllInOriginOrder(host).front()))
                 return true;
         }
     }