Bug#30152258 MYSQLDUMP HANG ON DUMP_TABLESPACES WHEN DISK DATA TABLES

EXIST

Hang occurs in acquire_lock() when querying for information about the
tablespace. The problem only occurs on participant mysqld after a table
in the tablespace has been dropped. The root cause is that a MDL lock on
the tablespace in TRANSACTIONAL scope has not been released while
dropping the table on participant.

Fix by releasing all MDL locks aquired by called functions in
TRANSACTIONAL or STATEMENT scope. This is done by extending the
Ndb_dd_client to release all new MDL locks taken in TRANSACTIONAL and
STATEMENT scope in addition to the EXPLICIT scope locks it already
releases. Move the release of EXPLICIT MDL locks to after rollback.

Change-Id: I5a47b22f7298a1a82aedb9c360a50510a060be8c

Author: blaudden

mysql-test/suite/ndb_ddl/drop_table_release_mdl.result

@@ -0,0 +1,34 @@
+# Create logfile group, tablespace, and table in the tablespace
+CREATE LOGFILE GROUP lg1
+ADD UNDOFILE 'lg1_undofile.dat'
+  INITIAL_SIZE 1M
+UNDO_BUFFER_SIZE = 1M
+ENGINE NDB;
+CREATE TABLESPACE ts1
+ADD DATAFILE 'ts1_datafile.dat'
+  USE LOGFILE GROUP lg1
+INITIAL_SIZE 2M
+ENGINE NDB;
+CREATE TABLE t10 (
+a INT PRIMARY KEY,
+b VARCHAR(255)
+) ENGINE NDB
+TABLESPACE ts1
+STORAGE DISK;
+# Drop the table, this caused problem on participant which didn't
+# release an MDL lock in TRANSACTIONAL scope
+DROP TABLE t10;
+# mysqld2> Run query accessing the tablespace where t10 was located
+SELECT LOGFILE_GROUP_NAME, FILE_NAME, TOTAL_EXTENTS, INITIAL_SIZE, ENGINE, EXTRA
+FROM INFORMATION_SCHEMA.FILES
+WHERE FILE_TYPE = 'UNDO LOG'
+    AND FILE_NAME IS NOT NULL
+AND LOGFILE_GROUP_NAME IS NOT NULL
+ORDER BY LOGFILE_GROUP_NAME;
+LOGFILE_GROUP_NAME	FILE_NAME	TOTAL_EXTENTS	INITIAL_SIZE	ENGINE	EXTRA
+lg1	./lg1_undofile.dat	262144	1048576	ndbcluster	UNDO_BUFFER_SIZE=1048576
+# Cleanup
+ALTER TABLESPACE ts1
+DROP DATAFILE 'ts1_datafile.dat';
+DROP TABLESPACE ts1;
+DROP LOGFILE GROUP lg1 ENGINE NDB;

mysql-test/suite/ndb_ddl/drop_table_release_mdl.test

@@ -0,0 +1,41 @@
+--source connect.inc
+
+--echo # Create logfile group, tablespace, and table in the tablespace
+CREATE LOGFILE GROUP lg1
+  ADD UNDOFILE 'lg1_undofile.dat'
+  INITIAL_SIZE 1M
+  UNDO_BUFFER_SIZE = 1M
+  ENGINE NDB;
+
+CREATE TABLESPACE ts1
+  ADD DATAFILE 'ts1_datafile.dat'
+  USE LOGFILE GROUP lg1
+  INITIAL_SIZE 2M
+  ENGINE NDB;
+
+CREATE TABLE t10 (
+  a INT PRIMARY KEY,
+  b VARCHAR(255)
+) ENGINE NDB
+  TABLESPACE ts1
+  STORAGE DISK;
+
+--echo # Drop the table, this caused problem on participant which didn't
+--echo # release an MDL lock in TRANSACTIONAL scope
+DROP TABLE t10;
+
+--connection mysqld2
+--echo # mysqld2> Run query accessing the tablespace where t10 was located
+SELECT LOGFILE_GROUP_NAME, FILE_NAME, TOTAL_EXTENTS, INITIAL_SIZE, ENGINE, EXTRA
+  FROM INFORMATION_SCHEMA.FILES
+  WHERE FILE_TYPE = 'UNDO LOG'
+    AND FILE_NAME IS NOT NULL
+    AND LOGFILE_GROUP_NAME IS NOT NULL
+  ORDER BY LOGFILE_GROUP_NAME;
+
+--echo # Cleanup
+--connection mysqld1
+ALTER TABLESPACE ts1
+  DROP DATAFILE 'ts1_datafile.dat';
+DROP TABLESPACE ts1;
+DROP LOGFILE GROUP lg1 ENGINE NDB;

storage/ndb/plugin/ndb_dd_client.cc

@@ -34,7 +34,6 @@
 #include "sql/dd/properties.h"
 #include "sql/dd/types/schema.h"
 #include "sql/dd/types/table.h"
-#include "sql/mdl.h"            // MDL_*
 #include "sql/query_options.h"  // OPTION_AUTOCOMMIT
 #include "sql/sql_class.h"      // THD
 #include "sql/sql_trigger.h"    // remove_all_triggers_from_perfschema
@@ -52,7 +51,9 @@
 #include "storage/ndb/plugin/ndb_thd.h"
 
 Ndb_dd_client::Ndb_dd_client(THD *thd)
-    : m_thd(thd), m_client(thd->dd_client()) {
+    : m_thd(thd),
+      m_client(thd->dd_client()),
+      m_save_mdl_locks(thd->mdl_context.mdl_savepoint()) {
   disable_autocommit();
 
   // Create dictionary client auto releaser, stored as
@@ -63,9 +64,6 @@ Ndb_dd_client::Ndb_dd_client(THD *thd)
 }
 
 Ndb_dd_client::~Ndb_dd_client() {
-  // Automatically release acquired MDL locks
-  mdl_locks_release();
-
   // Automatically restore the option_bits in THD if they have
   // been modified
   if (m_save_option_bits) m_thd->variables.option_bits = m_save_option_bits;
@@ -75,6 +73,9 @@ Ndb_dd_client::~Ndb_dd_client() {
     if (!m_comitted) rollback();
   }
 
+  // Release MDL locks
+  mdl_locks_release();
+
   // Free the dictionary client auto releaser
   dd::cache::Dictionary_client::Auto_releaser *ar =
       (dd::cache::Dictionary_client::Auto_releaser *)m_auto_releaser;
@@ -328,9 +329,12 @@ bool Ndb_dd_client::mdl_locks_acquire_exclusive(const char *schema_name,
 }
 
 void Ndb_dd_client::mdl_locks_release() {
+  // Release MDL locks acquired in EXPLICIT scope
   for (MDL_ticket *ticket : m_acquired_mdl_tickets) {
     m_thd->mdl_context.release_lock(ticket);
   }
+  // Release new MDL locks acquired in TRANSACTIONAL and STATEMENT scope
+  m_thd->mdl_context.rollback_to_savepoint(m_save_mdl_locks);
 }
 
 void Ndb_dd_client::disable_autocommit() {

storage/ndb/plugin/ndb_dd_client.h

@@ -34,6 +34,7 @@
 #include "my_inttypes.h"
 #include "sql/dd/object_id.h"
 #include "sql/dd/string_type.h"
+#include "sql/mdl.h"
 
 namespace dd {
 typedef String_type sdi_t;
@@ -85,7 +86,11 @@ class Ndb_dd_client {
   class THD *const m_thd;
   dd::cache::Dictionary_client *m_client;
   void *m_auto_releaser;  // Opaque pointer
+  // List of MDL locks taken in EXPLICIT scope by Ndb_dd_client
   std::vector<class MDL_ticket *> m_acquired_mdl_tickets;
+  // MDL savepoint which allows releasing MDL locks taken by called
+  // functions in TRANSACTIONAL and STATEMENT scope
+  const MDL_savepoint m_save_mdl_locks;
   ulonglong m_save_option_bits{0};
   bool m_comitted{false};
   bool m_auto_rollback{true};