statd for MariaDB Xpand
A Xpand instance obtains statistics using
/opt/clustrix/bin/statd.py), a cluster-wide statistics aggregation and tracking mechanism. The resulting statistics are used for the graphical displays within the XpandGUI Administration UI and may also be queried directly using SQL.
statd script runs on each node but only active instance is on the node with the highest node ID and collects statistics from internal system tables and populates the tables in the
current: table and index read and write stats collected every 5 minutes
history: table and index read and write stats aggregated into 5 minute stats with stats older than one day rolled into hourly stats, kept for 7 days
current: query stats collected every minute
history: query stats aggregated into 5 minute stats, with stats older than one day rolled into hourly stats, kept for 7 days
current: cluster stats collected every 30 seconds
history: cluster stats aggregated into 5 minute stats, with stats older than one day rolled into hourly stats, kept for 7 days.
The frequency of statistics gathering is tunable via the
statd_config table (see below), but we recommend to leave them with their default values.
In addition, the
statd_metadata table contains the current and historical statd IDs and names that can be used to join back to the statd_
Querying statd Statistics
sql> SELECT name, value FROM clustrix_statd.statd_current NATURAL JOIN clustrix_statd.statd_metadata WHERE name LIKE '%nodes_in_quorum%' ORDER BY name;
sql> SELECT timestamp, value, name FROM clustrix_statd.statd_history NATURAL JOIN clustrix_statd.statd_metadata WHERE name LIKE 'clustrix.cpu.load_avg%' AND timestamp BETWEEN '2019-01-01 09:30:01' AND '2019-05-15 10:30:01' ORDER BY timestamp, name;
The query below looks at queries that have high average rows read between the specified timestamps as queries that read many rows may be candidates for optimizing.
sql> SELECT sum(exec_count) as exec_count, round(avg(avg_rows_read)) as avg_rows_read, sum(rows_read) as rows_read, round(avg(avg_exec_ms)) as avg_exec_ms, left(statement,60) FROM clustrix_statd.qpc_history WHERE timestamp BETWEEN '2019-06-01 00:00:00' AND '2019-06-01 23:59:59' GROUP BY 5 ORDER by 2 desc LIMIT 20;
The query below looks at tables and indexes that have the most reads over the last 24 hours:
sql> SELECT Sum(reads) AS reads, Sum(writes) AS writes, DATABASE, `table`, `index`, total_replicas FROM clustrix_statd.hotness_history WHERE timestamp >now() - INTERVAL 1 day AND DATABASE NOT IN ('clustrix_statd', '_replication', 'clustrix_ui', 'system', 'clustrix_dbi') GROUP BY `table`, `index` ORDER BY 1 desc LIMIT 50;
There are numerous statistics collected for your cluster. Use the following query to determine all available statd statistics:
sql> SELECT name FROM clustrix_statd.statd_metadata ORDER BY name;
The following tables highlight useful statistics. For additional information, see "
statd Metrics for MariaDB Xpand.
The statistics for both queries per second (qps) and transactions per second (tps) will be the same if explicit transactions were not used.
Indicates average CPU load across all CPU cores per node: and load of busiest and least busy CPU core in the cluster.
Note that core 0 is reserved for certain activities and thus will often reflect a lower CPU utilization relative to other cores, which will intern affect these averages. To see more types of cpu stats available:
SELECT name, value FROM statd_current NATURAL JOIN statd_metadata WHERE name LIKE '%clustrix.cpu%' ORDER BY name;
Provide execution counters for each operation.
Provide the total time spent executing each operation.
Taking the delta of Com_
SELECT name, value FROM statd_current NATURAL JOIN statd_metadata WHERE name LIKE '%clustrix.stats.Com%' ORDER BY name;
The statistics for number of sessions executing.
Size of the slave relay log in bytes.
Seconds behind master.
Nodes participating in current group.
All the nodes the cluster knows about, including down/unavailable.
Number of Rebalancer actions in progress for a given type.
The following statistics are kept as percentages and are thus in the range of 0-100
Average percentage of permanent space allocated across the disks in the system.
Highest percentage of permanent space allocated across all the disks in the system.
Lowest percentage of permanent space allocated across all the disks in the system.
Tuning the Frequency of statd Collection
Increasing frequency of
statd collection can impact the performance of your cluster.
The frequency of statistics collection is configurable within the
statd_config table. Contact MariaDB Support for assistance in modifying these values.
sql> select * from statd_config order by name; +---------------------------------------+-------+ | name | value | +---------------------------------------+-------+ | qpc_current_interval_s | 60 | | qpc_history_interval_s | 300 | | qpc_history_top_n | 100 | | qpc_rollup_interval_s | 3600 | | repartition_history_interval_s | 43200 | | SpaceUsedBreakdown_current_interval_s | 900 | | stats_current_interval_s | 30 | | stats_history_interval_s | 300 | +---------------------------------------+-------+ 8 rows in set (0.00 sec)
statd_history tables are partition tables and data older than 7 days are dropped. If you need to longer data retention, you can have a cron job to extract the data accordingly and store it elsewhere.
Third Party Plugins
For additional information about using third party plugins, see: