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19.7.4 NDB Log Messages »
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19.7.3.3. Using CLUSTERLOG STATISTICS

The NDB management client's CLUSTERLOG STATISTICS command can provide a number of useful statistics in its output. The following statistics are reported by the transaction coordinator:

Statistic Description (Number of...)
Trans. Count Transactions attempted with this node as coordinator
Commit Count Transactions committed with this node as coordinator
Read Count Primary key reads (all)
Simple Read Count Primary key reads reading the latest committed value
Write Count Primary key writes (includes all INSERT, UPDATE, and DELETE operations)
AttrInfoCount Data words used to describe all reads and writes received
Concurrent Operations All concurrent operations ongoing at the moment the report is taken
Abort Count Transactions with this node as coordinator that were aborted
Scans Scans (all)
Range Scans Index scans

The ndbd process has a scheduler that runs in an infinite loop. During each loop scheduler performs the following tasks:

  1. Read any incoming messages from sockets into a job buffer.

  2. Check whether there are any timed messages to be executed; if so, put these into the job buffer as well.

  3. Execute (in a loop) any messages in the job buffer.

  4. Send any distributed messages that were generated by executing the messages in the job buffer.

  5. Wait for any new incoming messages.

The number of loops executed in the third step is reported as the Mean Loop Counter. This statistic increases in size as the utilisation of the TCP/IP buffer improves. You can use this to monitor performance as you add new processes to the cluster.

The Mean send size and Mean receive size statistics allow you to gauge the efficiency of writes and reads (respectively) between nodes. These values are given in bytes. Higher values mean a lower cost per byte sent or received; the maximum is 64k.

To cause all cluster log statistics to be logged, you can use the following command in the NDB management client: 

ndb_mgm> ALL CLUSTERLOG STATISTICS=15

Note

Setting the threshold for STATISTICS to 15 causes the cluster log to become very verbose, and to gow quite rapidly in size, in direct proportion to the number of cluster nodes and the amount of activity on the cluster.