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Time that queue operations have to wait for disk access
--
Average Read/Write time
Time it takes to finish disk access operations (latency)
--
Read/Write bandwidth
Data transfer from and towards your disk
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General mysql metrics
mysql -E -e "select variable_value from information_schema.session_status where variable_name = 'uptime'";
# max connections
MariaDB [(none)]> show status like 'max_used_connections';
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| Max_used_connections | 1 |
+----------------------+-------+
1 row in set (0.001 sec)
MariaDB [(none)]> show variables like 'max_connections';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_connections | 151 |
+-----------------+-------+
1 row in set (0.001 sec)
mysqladmin status
# you will find uptime here in seconds
Metric
Comments
Suggested Alert
Uptime
Seconds since the server was started. We can use this to detect respawns.
When uptime is < 180. (seconds)
Threads_connected
Number of clients currently connected. If none or too high, something is wrong.
None
Max_used_connections
Max number of connections at a time since server started. (max_used_connections / max_connections) indicates if you could run out soon of connection slots.
When connections usage is > 85%.
Aborted_connects
Number of failed connection attempts. When growing over a period of time either some credentials are wrong or we are being attacked. show status like 'Aborted_connects'
When aborted connects/min > 3.
InnoDB
Metric
Coments
Suggested Alert
Innodb_row_lock_waits
Number of times InnoDB had to wait before locking a row.
None
Innodb_buffer_pool_wait_free
Number of times InnoDB had to wait for memory pages to be flushed. If too high, innodb_buffer_pool_size is too small for current write load.
None
Query tracking
Metric
Comments
Suggested Alert
Slow_queries
Number of queries that took more than long_query_time seconds to execute. Slow queries generate excessive disk reads, memory and CPU usage. Check slow_query_log to find them.
None
Select_full_join
Number of full joins needed to answer queries. If too high, improve your indexing or database schema.
None
Created_tmp_disk_tables
Number of temporary tables (typically for joins) stored on slow spinning disks, instead of faster RAM.
None
(Full table scans) Handler_read% Number of times the system reads the first row of a table index. (if 0 a table scan is done - because no key was read). Sequential reads might indicate a faulty index. None
Track Errors
journalctl -u mariadb | grep -i Error
Replication
show slaves status \G
# These are important values for slaves
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Seconds_Behind_Master: 0
Galera
see monitoring galera
External Tools
Monitoring with pmm (Percona Management Monitoring)