MDEV-16277 tcp_nodelay session variable to enable / disable Nagle algorithm

include/violite.h

@@ -89,6 +89,7 @@ size_t	vio_write(Vio *vio, const uchar * buf, size_t size);
 int	vio_blocking(Vio *vio, my_bool onoff, my_bool *old_mode);
 my_bool	vio_is_blocking(Vio *vio);
 /* setsockopt TCP_NODELAY at IPPROTO_TCP level, when possible */
+int vio_nodelay(Vio *vio, my_bool on);
 int	vio_fastsend(Vio *vio);
 /* setsockopt SO_KEEPALIVE at SOL_SOCKET level, when possible */
 int	vio_keepalive(Vio *vio, my_bool	onoff);

sql/sql_class.h

@@ -717,6 +717,7 @@ typedef struct system_variables
   ulong session_track_transaction_info;
   my_bool session_track_schema;
   my_bool session_track_state_change;
+  my_bool tcp_nodelay;
 
   ulong threadpool_priority;
 

sql/sys_vars.cc

@@ -4039,6 +4039,16 @@ static bool fix_sql_log_bin_after_update(sys_var *self, THD *thd,
   return FALSE;
 }
 
+static bool check_session_only_variable(sys_var *self, THD *,set_var *var)
+{
+  if (unlikely(var->type == OPT_GLOBAL))
+  {
+    my_error(ER_INCORRECT_GLOBAL_LOCAL_VAR, MYF(0), self->name.str, "SESSION");
+    return true;
+  }
+  return false;
+}
+
 /**
   This function checks if the sql_log_bin can be changed,
   what is possible if:
@@ -4054,20 +4064,17 @@ static bool fix_sql_log_bin_after_update(sys_var *self, THD *thd,
 static bool check_sql_log_bin(sys_var *self, THD *thd, set_var *var)
 {
   if (check_has_super(self, thd, var))
-    return TRUE;
+    return true;
 
-  if (unlikely(var->type == OPT_GLOBAL))
+  if (check_session_only_variable(self, thd, var))
-  {
+    return true;
-    my_error(ER_INCORRECT_GLOBAL_LOCAL_VAR, MYF(0), self->name.str, "SESSION");
-    return TRUE;
-  }
 
   if (unlikely(error_if_in_trans_or_substatement(thd,
                                                  ER_STORED_FUNCTION_PREVENTS_SWITCH_SQL_LOG_BIN,
                                                  ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_SQL_LOG_BIN)))
-    return TRUE;
+    return true;
 
-  return FALSE;
+  return false;
 }
 
 static Sys_var_mybool Sys_log_binlog(	
@@ -5579,6 +5586,27 @@ static Sys_var_int Sys_keepalive_probes(
        BLOCK_SIZE(1),
        NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(NULL));
 
+
+static bool update_tcp_nodelay(sys_var *self, THD *thd,
+  enum_var_type type)
+{
+  DBUG_ASSERT(thd);
+
+  Vio *vio = thd->net.vio;
+  if (vio)
+    return (MY_TEST(vio_nodelay(vio, thd->variables.tcp_nodelay)));
+
+  return false;
+}
+
+static Sys_var_mybool Sys_tcp_nodelay(
+       "tcp_nodelay",
+       "Set option TCP_NODELAY (disable Nagle's algorithm) on socket",
+       SESSION_VAR(tcp_nodelay), CMD_LINE(OPT_ARG),
+       DEFAULT(TRUE),NO_MUTEX_GUARD, NOT_IN_BINLOG,
+       ON_CHECK(check_session_only_variable),
+       ON_UPDATE(update_tcp_nodelay));
+
 static Sys_var_charptr Sys_ignore_db_dirs(
        "ignore_db_dirs",
        "Specifies a directory to add to the ignore list when collecting "

vio/viosocket.c

@@ -435,8 +435,34 @@ int vio_socket_timeout(Vio *vio,
   DBUG_RETURN(ret);
 }
 
+/* Set TCP_NODELAY (disable Nagle's algorithm */
+int vio_nodelay(Vio *vio, my_bool on)
+{
+  int r;
+  int no_delay= MY_TEST(on);
+  DBUG_ENTER("vio_nodelay");
 
-int vio_fastsend(Vio * vio __attribute__((unused)))
+  if (vio->type == VIO_TYPE_NAMEDPIPE || vio->type == VIO_TYPE_SHARED_MEMORY)
+  {
+    DBUG_RETURN(0);
+  }
+
+  r = mysql_socket_setsockopt(vio->mysql_socket, IPPROTO_TCP, TCP_NODELAY,
+    IF_WIN((const char*), (void*)) &no_delay,
+    sizeof(no_delay));
+
+  if (r)
+  {
+    DBUG_PRINT("warning",
+     ("Couldn't set socket option for fast send, error %d",
+      socket_errno));
+     r = -1;
+  }
+  DBUG_PRINT("exit", ("%d", r));
+  DBUG_RETURN(r);
+}
+
+int vio_fastsend(Vio * vio)
 {
   int r=0;
   DBUG_ENTER("vio_fastsend");
@@ -454,18 +480,7 @@ int vio_fastsend(Vio * vio __attribute__((unused)))
   }
 #endif                                    /* IPTOS_THROUGHPUT */
   if (!r)
-  {
+    r = vio_nodelay(vio, TRUE);
-#ifdef __WIN__
-    BOOL nodelay= 1;
-#else
-    int nodelay = 1;
-#endif
-
-    r= mysql_socket_setsockopt(vio->mysql_socket, IPPROTO_TCP, TCP_NODELAY,
-                  IF_WIN((const char*), (void*)) &nodelay,
-                  sizeof(nodelay));
-
-  }
   if (r)
   {
     DBUG_PRINT("warning",