Update clusters in SYSTEM DROP DNS query. [#CLICKHOUSE-3478]

dbms/src/Interpreters/Context.cpp

@@ -1348,15 +1348,21 @@ std::shared_ptr<Cluster> Context::tryGetCluster(const std::string & cluster_name
 }
 
 
+void Context::reloadClusterConfig()
+{
+    std::lock_guard<std::mutex> lock(shared->clusters_mutex);
+    auto & config = shared->clusters_config ? *shared->clusters_config : getConfigRef();
+    shared->clusters = std::make_unique<Clusters>(config, settings);
+}
+
+
 Clusters & Context::getClusters() const
 {
+    std::lock_guard<std::mutex> lock(shared->clusters_mutex);
+    if (!shared->clusters)
     {
-        std::lock_guard<std::mutex> lock(shared->clusters_mutex);
-        if (!shared->clusters)
-        {
-            auto & config = shared->clusters_config ? *shared->clusters_config : getConfigRef();
-            shared->clusters = std::make_unique<Clusters>(config, settings);
-        }
+        auto & config = shared->clusters_config ? *shared->clusters_config : getConfigRef();
+        shared->clusters = std::make_unique<Clusters>(config, settings);
     }
 
     return *shared->clusters;

dbms/src/Interpreters/Context.h

@@ -318,6 +318,7 @@ public:
     Clusters & getClusters() const;
     std::shared_ptr<Cluster> getCluster(const std::string & cluster_name) const;
     std::shared_ptr<Cluster> tryGetCluster(const std::string & cluster_name) const;
+    void reloadClusterConfig();
     void setClustersConfig(const ConfigurationPtr & config);
 
     Compiler & getCompiler();

dbms/src/Interpreters/InterpreterSystemQuery.cpp

@@ -75,6 +75,8 @@ BlockIO InterpreterSystemQuery::execute()
             break;
         case Type::DROP_DNS_CACHE:
             DNSCache::instance().drop();
+            /// Reinitialize clusters to update their resolved_addresses
+            context.reloadClusterConfig();
             break;
         case Type::DROP_MARK_CACHE:
             context.dropMarkCache();

dbms/tests/integration/test_system_queries/test.py

@@ -9,6 +9,7 @@ from contextlib import contextmanager
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from helpers.cluster import ClickHouseCluster
 from helpers.test_tools import TSV
+from helpers.client import QueryRuntimeException
 
 
 @pytest.fixture(scope="module")
@@ -24,10 +25,12 @@ def started_cluster():
         instance.query('CREATE DATABASE dictionaries ENGINE = Dictionary')
         instance.query('CREATE TABLE dictionary_source (id UInt64, value UInt8) ENGINE = Memory')
         #print instance.query('SELECT * FROM system.dictionaries FORMAT Vertical')
+        print "Started ", instance.ip_address
 
         yield cluster
 
     finally:
+        pass
         cluster.shutdown()
 
 
@@ -54,13 +57,21 @@ def test_SYSTEM_RELOAD_DICTIONARY(started_cluster):
 def test_DROP_DNS_CACHE(started_cluster):
     instance = cluster.instances['ch1']
 
-    with pytest.raises(Exception):
-        instance.query("SELECT * FROM remote('aperol', 'system', 'one')")
+    instance.exec_in_container(['bash', '-c', 'echo 127.255.255.255 lost_host > /etc/hosts'], privileged=True, user='root')
 
-    instance.exec_in_container(['bash', '-c', 'echo 127.0.0.1 aperol >> /etc/hosts'], privileged=True, user='root')
+    with pytest.raises(QueryRuntimeException):
+        instance.query("SELECT * FROM remote('lost_host', 'system', 'one')")
+
+    instance.query("CREATE TABLE distributed_lost_host (dummy UInt8) ENGINE = Distributed(lost_host_cluster, 'system', 'one')")
+    with pytest.raises(QueryRuntimeException):
+        instance.query("SELECT * FROM distributed_lost_host")
+
+    instance.exec_in_container(['bash', '-c', 'echo 127.0.0.1 lost_host > /etc/hosts'], privileged=True, user='root')
     instance.query("SYSTEM DROP DNS CACHE")
 
-    instance.query("SELECT * FROM remote('aperol', 'system', 'one')")
+    instance.query("SELECT * FROM remote('lost_host', 'system', 'one')")
+    instance.query("SELECT * FROM distributed_lost_host")
+    assert TSV(instance.query("SELECT DISTINCT host_name, host_address FROM system.clusters")) == TSV("lost_host\t127.0.0.1\n")
 
 
 if __name__ == '__main__':