eG Monitoring
 

Measures reported by MySQLCluInnoTptest

InnoDB uses asynchronous disk I/O where possible, by creating a number of threads to handle I/O operations, while permitting other database operations to proceed while the I/O is still in progress. If InnoDB determines that there is a high probability of data being needed soon, it performs read-ahead operations to bring that data into the buffer pool so that it is available in memory. Making a few large read requests for contiguous data can be more efficient than making several small, spread-out requests. There are two read-ahead heuristics in InnoDB:

  • In sequential read-ahead, if InnoDB notices that the access pattern to a segment in the tablespace is sequential, it posts in advance a batch of reads of database pages to the I/O system.

  • In random read-ahead, if InnoDB notices that some area in a tablespace seems to be in the process of being fully read into the buffer pool, it posts the remaining reads to the I/O system.

If the rows in the InnoDB of each node in the MySQL Cluster database server cannot be read through, then, the data should be catered to the users from the disks which is an expensive operation. To avoid such unwanted disk reads/writes, administrators should keep track on the efficiency of the InnoDB tables, figure out how well the rows in the tables are inserted, deleted etc. The MySQLCluInnoTptest helps administrators in this regard!

This test tracks the load on the InnoDB tables of each node on the target of the MySQL cluster database server and reports which type of operations (reads or writes or inserts or updates or deletes) are contributing to the workload of the InnoDB tables. The test additionally reports the random/sequential read-aheads initiated by the InnoDB tables. Capacity planning and clustering decisions can be taken based on insights provided by this test.

Outputs of the test : One set of results for each node in the MySQL cluster database server being monitored

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Read_requests Indicates the number of physical reads of a key block from disk into the MyISAM key cache on this node. Number If the value of this measure is increasing at a steady pace, then administrators should consider reconfiguring the key_buffer_size value.
Read_request_rate Indicates the number of physical reads of a key block from disk into the MyISAM key cache on this node per second during the last measurement period. Reads/second A consistent increase in the value of this measure could indicate a potential overload.
Write_requests Indicates the number of physical writes of a key block from the MyISAM key cache on this node to disk. Number  
Write_request_rate Indicates the number of physical writes of a key block from the MyISAM key cache on this node to disk per second during the last measurement period. Writes/second A consistent increase in the value of this measure could indicate a potential overload.
Ahead_Rnd Indicates the number of “random” read-aheads initiated by InnoDB on this node during the last measurement period. Number  
Ahead_Sql Indicates the number of “sequential” read-aheads initiated by InnoDB on this node during the last measurement period. Number  
Wait_for_free_buffer Indicates the number of buffer pool waits captured on this node during the last measurement period. Number Normally, writes to the InnoDB buffer pool happen in the background. When InnoDB needs to read or create a page and no clean pages are available, InnoDB flushes some dirty pages first and waits for that operation to finish. This measure accounts the instances of such waits.

A consistently high value for this measure indicates that the innodb_ buffer_pool_size value should be reconfigured with appropriate value.
Rows_inserted Indicates the number of rows inserted into the Innodb tables on this node during the last measurement period. Number  
Rows_updated Indicates the number of rows updated in the InnoDB tables on this node during the last measurement period. Number  
Rows_deleted Indicates the number of rows deleted from the InnoDB tables during the last measurement period. Number  
Rows_read Indicates the number of rows read from the InnoDB tables on this node during the last measurement period. Number  
Rows_insert_rate Indicates the rate at which rows were inserted into InnoDB tables during the last measurement period. Inserts/second  
Rows_update_rate Indicates the rate at which rows were updated in the InnoDB tables on this node during the last measurement period. Updates/second  
Rows_delete_rate Indicates the rate at which rows were deleted from the InnoDB tables on this node during the last measurement period. Deletes/second  
Rows_read_rate Indicates the rate at which rows were read from the InnoDB tables on this node during the last measurement period. Reads/second