The NDB management client's
CLUSTERLOG STATISTICS command can provide a
number of useful statistics in its output. Counters providing
information about the state of the cluster are updated at
5-second reporting intervals by the transaction coordinator (TC)
and the local query handler (LQH), and written to the cluster
log.
Transaction coordinator statistics. Each transaction has one transaction coordinator, which is chosen by one of the following methods:
In a round-robin fashion
By communication proximity
Local query handler statistics (Operations).
There is 1 cluster event per local query handler block (that
is, 1 per data node process). Operations are recorded in the
LQH where the data they are operating on resides.
A single transaction may operate on data stored in multiple LQH blocks.
Process scheduler statistics. In addition to the statistics reported by the transaction coordinator and local query handler, each ndbd process has a scheduler which also provides useful metrics relating to the performance of a MySQL Cluster. This scheduler runs in an infinite loop; during each loop the scheduler performs the following tasks:
Read any incoming messages from sockets into a job buffer.
Check whether there are any timed messages to be executed; if so, put these into the job buffer as well.
Execute (in a loop) any messages in the job buffer.
Send any distributed messages that were generated by executing the messages in the job buffer.
Wait for any new incoming messages.
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
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