MySQL :: MySQL NDB Cluster 8.0 Release Notes :: Changes in MySQL NDB Cluster 8.0.36 (2024-01-16, General Availability)

NDB Cluster APIs: An event buffer overflow in the NDB API could cause a timeout while waiting for DROP TABLE. (Bug #35655162)

References: See also: Bug #35662083.

When a node failure is detected, transaction coordinator (TC) instances check their own transactions to determine whether they need handling to ensure completion, implemented by checking whether each transaction involves the failed node, and if so, marking it for immediate timeout handling. This causes the transaction to be either rolled forward (commit) or back (abort), depending on whether it had started committing, using the serial commit protocol. When the TC was in the process of getting permission to commit (CS_PREPARE_TO_COMMIT), sending commit requests (CS_COMMITTING), or sending completion requests (CS_COMPLETING), timeout handling waited until the transaction was in a stable state before commencing the serial commit protocol.

Prior to the fix for Bug#22602898, all timeouts during CS_COMPLETING or CS_COMMITTING resulted in switching to the serial commit-complete protocol, so skipping the handling in any of the three states cited previously did not stop the prompt handling of the node failure. It was found later that this fix removed the blanket use of the serial commit-complete protocol for commit-complete timeouts, so that when handling for these states was skipped, no node failure handling action was taken, with the result that such transactions hung in a commit or complete phase, blocking checkpoints.

The fix for Bug#22602898 removed this stable state handling to avoid it accidentally triggering, but this change also stopped it from triggering when needed in this case where node failure handling found a transaction in a transient state. We solve this problem by modifying CS_COMMIT_SENT and CS_COMPLETE_SENT stable state handling to perform node failure processing if a timeout has occurred for a transaction with a failure number different from the current latest failure number, ensuring that all transactions involving the failed node are in fact eventually handled. (Bug #36028828)

References: See also: Bug #22602898.

Removed a possible race condition between start_clients_thread() and update_connections(), due to both of these seeing the same transporter in the DISCONNECTING state. Now we make sure that disconnection is in fact completed before we set indicating that that the transporter has disconnected, so that update_connections() cannot close the NdbSocket before it has been completely shut down. (Bug #36009860)

When a transporter was overloaded, the send thread did not yield to the CPU as expected, instead retrying the transporter repeatedly until reaching the hard-coded 200 microsecond timeout. (Bug #36004838)

The QMGR block's GSN_ISOLATE_ORD signal handling was modified by the fix for a previous issue to handle the larger node bitmap size necessary for supporting up to 144 data nodes. It was observed afterwards that it was possible that the original sender was already shut down when ISOLATE_ORD was processed, in which case its node version might have been reset to zero, causing the inline bitmap path to be taken, resulting in incorrect processing.

The signal handler now checks to decide whether the incoming signal uses a long section to represent nodes to isolate, and to act accordingly. (Bug #36002814)

References: See also: Bug #30529132.

A MySQL server disconnected from schema distribution was unable to set up event operations because the table columns could not be found in the event. This could be made to happen by using ndb_drop_table or another means to drop a table directly from NDB that had been created using the MySQL server.

We fix this by making sure in such cases that we properly invalidate the NDB table definition from the dictionary cache. (Bug #35948153)

Messages like Metadata: Failed to submit table 'mysql.ndb_apply_status' for synchronization were submitted to the error log each minute, which filled up the log unnecessarily, since mysql.ndb_apply_status is a utility table managed by the binary logging thread, with no need to be checked for changes. (Bug #35925503)

The DBSPJ function releaseGlobal() is responsible for releasing excess pages maintained in m_free_page_list; this function iterates over the list, releases the objects, and after 16 iterations takes a realtime break. In parallel with the realtime break, DBSPJ spawned a new invocation of releaseGlobal() by sending a CONTINUEB signal to itself with a delay, which could lead to an overflow of the Long-Time Queue since there is no control over the number of signals being sent.

We fix this by not sending the extra delayed CONTINUEB signal when a realtime break is taken. (Bug #35919302)

API node failure handling during a data node restart left its subscriptions behind. (Bug #35899768)

Removed the file storage/ndb/tools/restore/consumer_restorem.cpp, which was unused. (Bug #35894084)

Removed unnecessary output printed by ndb_print_backup_file. (Bug #35869988)

Removed a possible accidental read or write on a reused file descriptor in the transporter code. (Bug #35860854)

When a timed read function such as read_socket(), readln_socket(), NdbSocket::read(), or NdbSocket::readln() was called using an invalid socket it returned 0, indicating a timeout, rather than the expected -1, indicating an unrecoverable failure. This was especially apparent when using the poll() function, which, as a result of this issue, did not treat an invalid socket appropriately, but rather simply never fired any event for that socket. (Bug #35860646)

It was possible for the readln_socket() function in storage/ndb/src/common/util/socket_io.cpp to read one character too many from the buffer passed to it as an argument. (Bug #35857936)

It was possible for ssl_write() to receive a smaller send buffer on retries than expected due to consolidate() calculating how many full buffers could fit into it. Now we pre-pack these buffers prior to consolidation. (Bug #35846435)

During online table reorganization, rows that are moved to new fragments are tagged for later deletion in the copy phase. This tagging involves setting the REORG_MOVED bit in the tuple header; this affects the tuple header checksum which must therefore be recalculated after it is modified. In some cases this is calculated before REORG_MOVED is set, which can result in later access to the same tuple failing with a tuple header checksum mismatch. This issue was observed when executing ALTER TABLE REORGANIZE PARTITION concurrently with a table insert of blob values, and appears to have been a side effect of the introduction of configurable query threads in MySQL 8.0.23.

Now we make sure in such cases that REORG_MOVED is set before the checksum is calculated. (Bug #35783683)

Following a node connection failure, the transporter registry's error state was not cleared before initiating a reconnect, which meant that the error causing the connection to be disconnected originally might still be set; this was interpreted as a failure to reconnect. (Bug #35774109)

When encountering an ENOMEM (end of memory) error, the TCP transporter continued trying to send subsequent buffers which could result in corrupted data or checksum failures.

We fix this by removing the ENOMEM handling from the TCP transporter, and waiting for sufficient memory to become available instead. (Bug #35700332)

Setup of the binary log injector sometimes deadlocked with concurrent DDL. (Bug #35673915)

The slow disconnection of a data node while a management server was unavailable could sometimes interfere with the rolling restart process. This became especially apparent when the cluster was hosted by NDB Operator, and the old mgmd pod did not recognize the IP address change of the restarted data node pod; this was visible as discrepancies in the output of SHOW STATUS on different management nodes.

We fix this by making sure to clear any cached address when connecting to a data node so that the data node's new address (if any) is used instead. (Bug #35667611)

The maximum permissible value for the oldest restorable global checkpoint ID is MAX_INT32 (4294967295). Such an ID greater than this value causes the data node to shut down, requiring a backup and restore on a cluster started with --initial.

Now, approximately 90 days before this limit is reached under normal usage, an appropriate warning is issued, allowing time to plan the required corrective action. (Bug #35641420)

References: See also: Bug #35749589.

Transactions whose size exceeded binlog_cache_size caused duplicate warnings. (Bug #35441583)

Table map entries for some tables were written in the binary log, even though log_replica_updates was set to OFF. (Bug #35199996)

The NDB source code is now formatted according to the rules used by clang-format, which it aligns it in this regard with the rest of the MySQL sources. (Bug #33517923)

During setup of utility tables, the schema event handler sometimes hung waiting for the global schema lock (GSL) to become available. This could happen when the physical tables had been dropped from the cluster, or when the connection was lost for some other reason. Now we use a try lock when attempting to acquire the GSL in such cases, thus causing another setup check attempt to be made at a later time if the global schema lock is not available. (Bug #32550019, Bug #35949017)

Subscription reports were sent out too early by SUMA during a node restart, which could lead to schema inconsistencies between cluster SQL nodes. In addition, an issue with the ndbinfo restart_info table meant that restart phases for nodes that did not belong to any node group were not always reported correctly. (Bug #30930132)

Online table reorganization inserts rows from existing table fragments into new table fragments; then, after committing the inserted rows, it deletes the original rows. It was found that the inserts caused SUMA triggers to fire, and binary logging to occur, which led to the following issues:

Inconsistent behavior, since DDL is generally logged as one or more statements, if at all, rather than by row-level effect.
It was incorrect, since only writes were logged, but not deletes.
It was unsafe since tables with blobs did not receive associated the row changes required to form valid binary log events.
It used CPU and other resources needlessly.

For tables with no blob columns, this was primarily a performance issue; for tables having blob columns, it was possible for this behavior to result in unplanned shutdowns of mysqld processes performing binary logging and perhaps even data corruption downstream. (Bug #19912988)

References: See also: Bug #16028096, Bug #34843617.

NDB API events are buffered to match the rates of production and consumption by user code. When the maximum size set to avoid unbounded memory usage when the rate is mismatched for an extended time was reached, event buffering stopped until the buffer usage dropped below a lower threshold; this manifested as an inability to find the container for latest epoch in when handling NODE_FAILREP events. To fix this problem, we add a TE_OUT_OF_MEMORY event to the buffer to inform the consumer that there may be missing events.

Changes in MySQL NDB Cluster 8.0.36 (2024-01-16, General Availability)

Compilation Notes

Bugs Fixed