MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0

13.7.7.15 SHOW ENGINE Syntax

SHOW ENGINE engine_name {STATUS | MUTEX}

SHOW ENGINE displays operational information about a storage engine. It requires the PROCESS privilege. The statement has these variants:

SHOW ENGINE INNODB STATUS
SHOW ENGINE INNODB MUTEX
SHOW ENGINE PERFORMANCE_SCHEMA STATUS

SHOW ENGINE INNODB STATUS displays extensive information from the standard InnoDB Monitor about the state of the InnoDB storage engine. For information about the standard monitor and other InnoDB Monitors that provide information about InnoDB processing, see Section 15.17, “InnoDB Monitors”.

SHOW ENGINE INNODB MUTEX displays InnoDB mutex and rw-lock statistics.

Note

InnoDB mutexes and rwlocks can also be monitored using Performance Schema tables. See Section 15.16.2, “Monitoring InnoDB Mutex Waits Using Performance Schema”.

Mutex statistics collection is configured dynamically using the following options:

Collection of mutex statistics for SHOW ENGINE INNODB MUTEX can also be enabled by setting innodb_monitor_enable='all', or disabled by setting innodb_monitor_disable='all'.

SHOW ENGINE INNODB MUTEX output has these columns:

SHOW ENGINE INNODB MUTEX skips the mutexes and rw-locks of buffer pool blocks, as the amount of output can be overwhelming on systems with a large buffer pool. (There is one mutex and one rw-lock in each 16K buffer pool block, and there are 65,536 blocks per gigabyte.) SHOW ENGINE INNODB MUTEX also does not list any mutexes or rw-locks that have never been waited on (os_waits=0). Thus, SHOW ENGINE INNODB MUTEX only displays information about mutexes and rw-locks outside of the buffer pool that have caused at least one OS-level wait.

Use SHOW ENGINE PERFORMANCE_SCHEMA STATUS to inspect the internal operation of the Performance Schema code:

mysql> SHOW ENGINE PERFORMANCE_SCHEMA STATUS\G
...
*************************** 3. row ***************************
  Type: performance_schema
  Name: events_waits_history.size
Status: 76
*************************** 4. row ***************************
  Type: performance_schema
  Name: events_waits_history.count
Status: 10000
*************************** 5. row ***************************
  Type: performance_schema
  Name: events_waits_history.memory
Status: 760000
...
*************************** 57. row ***************************
  Type: performance_schema
  Name: performance_schema.memory
Status: 26459600
...

This statement is intended to help the DBA understand the effects that different Performance Schema options have on memory requirements.

Name values consist of two parts, which name an internal buffer and a buffer attribute, respectively. Interpret buffer names as follows:

Buffer attributes have these meanings:

In some cases, there is a direct relationship between a Performance Schema configuration parameter and a SHOW ENGINE value. For example, events_waits_history_long.count corresponds to performance_schema_events_waits_history_long_size. In other cases, the relationship is more complex. For example, events_waits_history.count corresponds to performance_schema_events_waits_history_size (the number of rows per thread) multiplied by performance_schema_max_thread_instances ( the number of threads).

SHOW ENGINE NDB STATUS.  If the server has the NDB storage engine enabled, SHOW ENGINE NDB STATUS displays cluster status information such as the number of connected data nodes, the cluster connectstring, and cluster binary log epochs, as well as counts of various Cluster API objects created by the MySQL Server when connected to the cluster. Sample output from this statement is shown here:

mysql> SHOW ENGINE NDB STATUS;
+------------+-----------------------+--------------------------------------------------+
| Type       | Name                  | Status                                           |
+------------+-----------------------+--------------------------------------------------+
| ndbcluster | connection            | cluster_node_id=7,
  connected_host=198.51.100.103, connected_port=1186, number_of_data_nodes=4,
  number_of_ready_data_nodes=3, connect_count=0                                         |
| ndbcluster | NdbTransaction        | created=6, free=0, sizeof=212                    |
| ndbcluster | NdbOperation          | created=8, free=8, sizeof=660                    |
| ndbcluster | NdbIndexScanOperation | created=1, free=1, sizeof=744                    |
| ndbcluster | NdbIndexOperation     | created=0, free=0, sizeof=664                    |
| ndbcluster | NdbRecAttr            | created=1285, free=1285, sizeof=60               |
| ndbcluster | NdbApiSignal          | created=16, free=16, sizeof=136                  |
| ndbcluster | NdbLabel              | created=0, free=0, sizeof=196                    |
| ndbcluster | NdbBranch             | created=0, free=0, sizeof=24                     |
| ndbcluster | NdbSubroutine         | created=0, free=0, sizeof=68                     |
| ndbcluster | NdbCall               | created=0, free=0, sizeof=16                     |
| ndbcluster | NdbBlob               | created=1, free=1, sizeof=264                    |
| ndbcluster | NdbReceiver           | created=4, free=0, sizeof=68                     |
| ndbcluster | binlog                | latest_epoch=155467, latest_trans_epoch=148126,
  latest_received_binlog_epoch=0, latest_handled_binlog_epoch=0,
  latest_applied_binlog_epoch=0                                                         |
+------------+-----------------------+--------------------------------------------------+

The Status column in each of these rows provides information about the MySQL server's connection to the cluster and about the cluster binary log's status, respectively. The Status information is in the form of comma-delimited set of name/value pairs.

The connection row's Status column contains the name/value pairs described in the following table.

Name Value
cluster_node_id The node ID of the MySQL server in the cluster
connected_host The host name or IP address of the cluster management server to which the MySQL server is connected
connected_port The port used by the MySQL server to connect to the management server (connected_host)
number_of_data_nodes The number of data nodes configured for the cluster (that is, the number of [ndbd] sections in the cluster config.ini file)
number_of_ready_data_nodes The number of data nodes in the cluster that are actually running
connect_count The number of times this mysqld has connected or reconnected to cluster data nodes

The binlog row's Status column contains information relating to NDB Cluster Replication. The name/value pairs it contains are described in the following table.

Name Value
latest_epoch The most recent epoch most recently run on this MySQL server (that is, the sequence number of the most recent transaction run on the server)
latest_trans_epoch The most recent epoch processed by the cluster's data nodes
latest_received_binlog_epoch The most recent epoch received by the binary log thread
latest_handled_binlog_epoch The most recent epoch processed by the binary log thread (for writing to the binary log)
latest_applied_binlog_epoch The most recent epoch actually written to the binary log

See Section 22.6, “NDB Cluster Replication”, for more information.

The remaining rows from the output of SHOW ENGINE NDB STATUS which are most likely to prove useful in monitoring the cluster are listed here by Name:

Note

SHOW ENGINE NDB STATUS returns an empty result if no operations involving NDB tables have been performed during the current session by the MySQL client accessing the SQL node on which this statement is run.