Bug #20581228: MYSQLD --HELP --VERBOSE TRIES TO LOCK FILES

Various issues are relevant to consider when running mysqld with
options --help --verbose:

1. On a loaded system, mysqld --help --verbose will initialize InnoDB in the
same way as for an ordinary start. It will try to lock the system files
present, and keeps trying for a hardcoded number of times, with a hardcoded
sleep inbetween. It will eventually fail, and this will also make mysqld
--help --verbose fail and report an error.

2. On an existing but empty datadir, InnoDB will create the system files
while initializing. These files will be left behind after mysqld --help
--verbose is finished, and will make a subsequent mysqld --initialize fail
due to the datadir not being empty.

3. On a non-existing datadir, the plugin table will not be found, and mysqld
--help --verbose will fail too.

InnoDB is initialized in order to enable reading the plugin table, which
contains the dynamic plugins. However, this is relevant only in issue 1
above. For issue 2 and 3, there is no point in initializing InnoDB since only
the builtin plugins will be listed anyway.

This patch applies the same constraint also in the first situation above.
Thus, we let mysqld --help --verbose only list options belonging to the
builtin plugins, and skip the dynamic ones. This allows us to execute
mysqld --help --verbose without initializing InnoDB and without opening the
plugin table, and this solves all three issues listed above.

Author: ssorumgard

mysql-test/r/help_verbose.result

@@ -0,0 +1,10 @@
+# There should be no errors or warnings
+Pattern "ERROR" not found
+Pattern "WARNING" not found
+# There should be no errors or warnings
+Pattern "ERROR" not found
+Pattern "WARNING" not found
+# There should be no leftovers in the datadir.
+# There should be no errors or warnings
+Pattern "ERROR" not found
+Pattern "WARNING" not found

mysql-test/t/help_verbose.test

@@ -0,0 +1,83 @@
+###########################################################################
+# Global settings
+###########################################################################
+
+--let $MESSAGES_DIR=     `select @@lc_messages_dir`
+
+###########################################################################
+# 1. Run --help --verbose on a writable datadir with another
+#    server already running.
+###########################################################################
+
+--let $BUGDIR=           $MYSQL_TMP_DIR/help_verbose_tc1
+--let $LOG_FILE =        $BUGDIR/mysqld.log
+--let $TEST_DATADIR=     `select @@datadir`
+
+--mkdir $BUGDIR
+
+--exec $MYSQLD --no-defaults --help --verbose --datadir=$TEST_DATADIR --lc-messages-dir=$MESSAGES_DIR --secure-file-priv="" > $LOG_FILE 2>&1
+
+--echo # There should be no errors or warnings
+--let SEARCH_FILE=    $LOG_FILE
+--let SEARCH_PATTERN= ERROR
+--source include/search_pattern.inc
+
+--let SEARCH_PATTERN= WARNING
+--source include/search_pattern.inc
+
+# Cleanup
+--remove_files_wildcard $BUGDIR *
+--rmdir $BUGDIR
+
+###########################################################################
+# 2. Run --help --verbose on an existing but empty datadir.
+###########################################################################
+
+--let $BUGDIR=           $MYSQL_TMP_DIR/help_verbose_tc2
+--let $LOG_FILE =        $BUGDIR/mysqld.log
+--let $TEST_DATADIR=     $BUGDIR/data
+
+--mkdir $BUGDIR
+--mkdir $TEST_DATADIR
+
+--exec $MYSQLD --no-defaults --help --verbose --datadir=$TEST_DATADIR --lc-messages-dir=$MESSAGES_DIR  --secure-file-priv="" > $LOG_FILE 2>&1
+
+--echo # There should be no errors or warnings
+--let SEARCH_FILE=    $LOG_FILE
+--let SEARCH_PATTERN= ERROR
+--source include/search_pattern.inc
+
+--let SEARCH_PATTERN= WARNING
+--source include/search_pattern.inc
+
+--echo # There should be no leftovers in the datadir.
+--list_files $TEST_DATADIR
+
+# Cleanup
+--remove_files_wildcard $BUGDIR *
+--rmdir $TEST_DATADIR
+--rmdir $BUGDIR
+
+###########################################################################
+# 3. Run --help --verbose on a non-existing datadir.
+###########################################################################
+
+--let $BUGDIR=           $MYSQL_TMP_DIR/help_verbose_tc3
+--let $LOG_FILE =        $BUGDIR/mysqld.log
+--let $TEST_DATADIR=     $BUGDIR/data
+
+--mkdir $BUGDIR
+
+--exec $MYSQLD --no-defaults --help --verbose --datadir=$TEST_DATADIR --lc-messages-dir=$MESSAGES_DIR  --secure-file-priv="" > $LOG_FILE 2>&1
+
+--echo # There should be no errors or warnings
+--let SEARCH_FILE=    $LOG_FILE
+--let SEARCH_PATTERN= ERROR
+--source include/search_pattern.inc
+
+--let SEARCH_PATTERN= WARNING
+--source include/search_pattern.inc
+
+# Cleanup
+--remove_files_wildcard $BUGDIR *
+--rmdir $BUGDIR

sql/mysqld.cc

@@ -4049,9 +4049,17 @@ a file name for --log-bin-index option", opt_binlog_index_name);
   */
   tc_log= &tc_log_dummy;
 
+  /*
+    Skip reading the plugin table when starting with --help in order
+    to also skip initializing InnoDB. This provides a simpler and more
+    uniform handling of various startup use cases, e.g. when the data
+    directory does not exist, exists but is empty, exists with InnoDB
+    system tablespaces present etc.
+  */
   if (plugin_init(&remaining_argc, remaining_argv,
                   (opt_noacl ? PLUGIN_INIT_SKIP_PLUGIN_TABLE : 0) |
-                  (opt_help ? PLUGIN_INIT_SKIP_INITIALIZATION : 0)))
+                  (opt_help ? (PLUGIN_INIT_SKIP_INITIALIZATION |
+                               PLUGIN_INIT_SKIP_PLUGIN_TABLE) : 0)))
   {
     sql_print_error("Failed to initialize plugins.");
     unireg_abort(MYSQLD_ABORT_EXIT);

sql/sql_plugin.cc

@@ -1343,7 +1343,6 @@ static void init_plugin_psi_keys(void)
 int plugin_init(int *argc, char **argv, int flags)
 {
   uint i;
-  bool is_myisam;
   st_mysql_plugin **builtins;
   st_mysql_plugin *plugin;
   st_plugin_int tmp, *plugin_ptr, **reap;
@@ -1444,11 +1443,18 @@ int plugin_init(int *argc, char **argv, int flags)
       if (register_builtin(plugin, &tmp, &plugin_ptr))
         goto err_unlock;
 
-      /* only initialize MyISAM, InnoDB and CSV at this stage */
-      is_myisam= !my_strcasecmp(&my_charset_latin1, plugin->name, "MyISAM");
+      /*
+        Only initialize MyISAM, InnoDB and CSV at this stage.
+        Note that when the --help option is supplied, InnoDB is not
+        initialized because the plugin table will not be read anyway,
+        as indicated by the flag set when the plugin_init() function
+        is called.
+      */
+      bool is_myisam= !my_strcasecmp(&my_charset_latin1, plugin->name, "MyISAM");
+      bool is_innodb= !my_strcasecmp(&my_charset_latin1, plugin->name, "InnoDB");
       if (!is_myisam &&
-          my_strcasecmp(&my_charset_latin1, plugin->name, "CSV") &&
-          my_strcasecmp(&my_charset_latin1, plugin->name, "InnoDB"))
+          (!is_innodb || opt_help) &&
+          my_strcasecmp(&my_charset_latin1, plugin->name, "CSV"))
         continue;
 
       if (plugin_ptr->state != PLUGIN_IS_UNINITIALIZED ||