diff --git a/src/Client/ConnectionEstablisher.cpp b/src/Client/ConnectionEstablisher.cpp index 4bab643ed31..f96546846c7 100644 --- a/src/Client/ConnectionEstablisher.cpp +++ b/src/Client/ConnectionEstablisher.cpp @@ -33,12 +33,12 @@ ConnectionEstablisher::ConnectionEstablisher( { } -void ConnectionEstablisher::run(ConnectionEstablisher::TryResult & result, std::string & fail_message) +void ConnectionEstablisher::run(ConnectionEstablisher::TryResult & result, std::string & fail_message, bool force_connected) { try { ProfileEvents::increment(ProfileEvents::DistributedConnectionTries); - result.entry = pool->get(*timeouts, settings, /* force_connected = */ false); + result.entry = pool->get(*timeouts, settings, force_connected); AsyncCallbackSetter async_setter(&*result.entry, std::move(async_callback)); UInt64 server_revision = 0; diff --git a/src/Client/ConnectionEstablisher.h b/src/Client/ConnectionEstablisher.h index a3a01e63246..ff071e59aea 100644 --- a/src/Client/ConnectionEstablisher.h +++ b/src/Client/ConnectionEstablisher.h @@ -24,7 +24,13 @@ public: const QualifiedTableName * table_to_check = nullptr); /// Establish connection and save it in result, write possible exception message in fail_message. - void run(TryResult & result, std::string & fail_message); + /// The connection is returned from connection pool and it can be stale. Use force_connected flag to ensure that connection is working one. + /// NOTE: force_connected is false by default due to the following consideration ... + /// When true, it implies sending a Ping packet to another peer and, if it fails - reestablishing the connection. + /// Ping-Pong round trip can be unnecessary in case of connection is still alive. + /// So, the optimistic approach is used by default. In this case, stale connections can be handled by retrying, + /// - see ConnectionPoolWithFailover, as example + void run(TryResult & result, std::string & fail_message, bool force_connected = false); /// Set async callback that will be called when reading from socket blocks. void setAsyncCallback(AsyncCallback async_callback_) { async_callback = std::move(async_callback_); } diff --git a/src/QueryPipeline/RemoteQueryExecutor.cpp b/src/QueryPipeline/RemoteQueryExecutor.cpp index 61a512bcfc5..6f8b3931803 100644 --- a/src/QueryPipeline/RemoteQueryExecutor.cpp +++ b/src/QueryPipeline/RemoteQueryExecutor.cpp @@ -89,12 +89,12 @@ RemoteQueryExecutor::RemoteQueryExecutor( auto table_name = main_table.getQualifiedName(); ConnectionEstablisher connection_establisher(pool, &timeouts, current_settings, log, &table_name); - connection_establisher.run(result, fail_message); + connection_establisher.run(result, fail_message, /*force_connected=*/ true); } else { ConnectionEstablisher connection_establisher(pool, &timeouts, current_settings, log, nullptr); - connection_establisher.run(result, fail_message); + connection_establisher.run(result, fail_message, /*force_connected=*/ true); } std::vector connection_entries;