Bug#32550019 Missing check for ndb_schema_result leads to schema dist

timeout

Problem:
Random test failure in util_table_drop.test with message "Schema
distribution timeout". This test checks that dropping the ndb_schema,
ndb_schema_result and ndb_apply_status tables from NDB are handled
gracefull by the ndbcluster plugin.

Analysis:
When dropping of ndb_schema_result table occurs during a DDL query, the
DDL query will hang until the schema distribution timeout is later
detected. Detecting timeout is a good fall back mechanicm but the
dropped table should be detected immediately since event subscription is
setup on the ndb_schema_result table.

Fix:
Change the schema distribution client to check that ndb_schema_result
table is available and event subscriptions are active, this is done both
when preparing and while waiting for replies to arrive.

This patch also fixes the root cause of "Bug#33318201 Mysqld crashes
when coordinator receive stale schema event " and the testcase for that
bug is removed as no longer possible to provoke.

Change-Id: Ib5d9c65f8710c27d56946b09d8a38e7fc8946fde

Author: blaudden

mysql-test/suite/ndbcluster/stale_schema_event.cnf

@@ -1177,7 +1177,8 @@ bool Ndb_schema_dist_client::log_schema_op_impl(
     }
 
     // Check if schema distribution is still ready.
-    if (m_share->have_event_operation() == false) {
+    if (m_share->have_event_operation() == false ||
+        m_result_share->have_event_operation() == false) {
       // This case is unlikely, but there is small race between
       // clients first check for schema distribution ready and schema op
       // registered in the coordinator(since the message is passed
@@ -4272,11 +4273,6 @@ class Ndb_schema_event_handler {
     // take the GSL properly
     assert(!m_thd_ndb->check_option(Thd_ndb::IS_SCHEMA_DIST_PARTICIPANT));
 
-    // Sleep here will make other mysql server in same cluster setup to create
-    // the schema result table in NDB before this mysql server. This also makes
-    // the create table in the connection thread to acquire GSL before the
-    // Binlog thread
-    DBUG_EXECUTE_IF("ndb_bi_sleep_before_gsl", sleep(1););
     // Protect the setup with GSL(Global Schema Lock)
     Ndb_global_schema_lock_guard global_schema_lock_guard(m_thd);
     if (global_schema_lock_guard.lock()) {

mysql-test/suite/ndbcluster/stale_schema_event.result

@@ -138,6 +138,19 @@ bool Ndb_schema_dist_client::prepare(const char *db, const char *tabname) {
     return false;
   }
 
+  // Acquire reference also on mysql.ndb_schema_result
+  m_result_share = NDB_SHARE::acquire_reference(
+      Ndb_schema_result_table::DB_NAME.c_str(),
+      Ndb_schema_result_table::TABLE_NAME.c_str(), m_share_reference.c_str());
+  if (m_result_share == nullptr ||
+      m_result_share->have_event_operation() == false) {
+    // The mysql.ndb_schema_result hasn't been created or not setup yet ->
+    // schema distribution is not ready
+    push_warning(m_thd, Sql_condition::SL_WARNING, ER_GET_ERRMSG,
+                 "Schema distribution is not ready (ndb_schema_result)");
+    return false;
+  }
+
   if (unlikely(m_ddl_blocked)) {
     // If a data node gets upgraded after this MySQL Server is upgraded, this
     // MySQL Server will not be aware of the upgrade due to Bug#30930132.
@@ -286,6 +299,10 @@ Ndb_schema_dist_client::~Ndb_schema_dist_client() {
     // Release the reference to mysql.ndb_schema table
     NDB_SHARE::release_reference(m_share, m_share_reference.c_str());
   }
+  if (m_result_share) {
+    // Release the reference to mysql.ndb_schema_result table
+    NDB_SHARE::release_reference(m_result_share, m_share_reference.c_str());
+  }
 
   if (m_thd_ndb) {
     // Inform Applier that one schema distribution has completed
@@ -373,9 +390,9 @@ bool Ndb_schema_dist_client::log_schema_op(const char *query,
     return false;
   }
 
-  // Require that m_share has been initialized to reference the
-  // schema distribution table
+  // Require that references to schema distribution tables has been initialized
   ndbcluster::ndbrequire(m_share);
+  ndbcluster::ndbrequire(m_result_share);
 
   // Check that prepared keys match
   if (!m_prepared_keys.check_key(db, table_name)) {

mysql-test/suite/ndbcluster/stale_schema_event.test

@@ -130,6 +130,7 @@ class Ndb_schema_dist_client {
   class THD *const m_thd;
   class Thd_ndb *const m_thd_ndb;
   struct NDB_SHARE *m_share{nullptr};
+  struct NDB_SHARE *m_result_share{nullptr};
   const std::string m_share_reference;
   class Prepared_keys {
     using Key = std::pair<std::string, std::string>;