MariaDB configuration for many updates, writes

Question

Based on few tutorials that I show I created the following MariaDB configuration for my server. Server has 32 GB ram, SSD, 8 cores and is dedicated to run MySQL. The biggest table has about 1,5 million rows, and we are running updates every second. So I am trying to create an optimal configuration for writing. A simple update record sometimes need 2-3 seconds. Should I change something to increase update queries speed?

[mysqld]
# MyISAM
key_buffer_size                = 32M
myisam_recover                 = FORCE,BACKUP

# SAFETY
innodb                         = FORCE
innodb_strict_mode             = 1
max_allowed_packet             = 16M
max_connect_errors             = 1000000
skip_name_resolve

# BINARY LOGGING
expire_logs_days               = 14
sync_binlog                    = 1

# CACHES AND LIMITS
max_connections                = 500
max_heap_table_size            = 32M
open_files_limit               = 65535
query_cache_type               = 0
query_cache_size               = 0
table_definition_cache         = 4096
table_open_cache               = 10240
thread_cache_size              = 50
tmp_table_size                 = 32M

# INNODB
innodb_buffer_pool_size        = 12G
innodb_buffer_pool_instances   = 12
innodb_flush_method            = O_DIRECT
innodb_flush_log_at_trx_commit = 1
innodb_file_per_table          = 1
innodb_log_files_in_group      = 2
innodb_log_file_size           = 1G

# LOGGING
log_error                      = /var/lib/mysql/srv.defrop.com.err
slow_query_log                 = 1
slow_query_log_file            = /var/lib/mysql/mysql-slow.log
long_query_time = 2

# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links                 = 0

#custom
performance_schema = on

Example log of query

# Time: 190415 10:36:59
# User@Host: defrop_defdb[defrop_defdb] @ localhost []
# Thread_id: 2420  Schema: defrop_defrop  QC_hit: No
# Query_time: 2.404021  Lock_time: 0.000053  Rows_sent: 0  Rows_examined: 2
# Rows_affected: 1
SET timestamp=1555317419;
UPDATE `backlinks` 
SET
`backlinks`.`crawler_id` = '10.0.0.28', 
`backlinks`.`used_time`=NOW() 
WHERE
`backlinks`.`campaign_id`=710
AND `backlinks`.`googlebot_id` IS NULL 
AND `backlinks`.`used_time` IS NULL 
LIMIT 1;

Answer 1

If the server is solely used by MariaDB then you can dedicate 16-24 GB of RAM to the DB service (now it is limited to the 12 GB). That allows to make bigger InnoDB pools. If your tables/indexes are fit into the RAM then your service need no expensive additional disk I/O.

You can reduce the max_connections variable to the reasonable value but that require clients to release the connections immediately after use. That can decrease the buffers consumption and overall peak RAM requirements.

Also you have to set up the join_buffer_size, sort_buffer_size, read_buffer_size and read_rnd_buffer_size variables to the appropriate values to ensure your queries do not use on-disk temporary tables for the intermediate datasets. But that values shouldn't be too big as far as they are defined for each connection and cumulative RAM consumption can reach (max_connections * all_buffers) + innodb_buffer_pool_size and even more.

The good starting point is the
SET @@global.slow_launch_time = 0.5, @@global.slow_query_log = 1; This command will start logging of the queries running for more than 0.5 second for further analysis. If the global variable log_queries_not_using_indexes is set to 1 then queries with no indexes will also be logged there. As far as your DB isn't too big it's more probable that slowdown is caused by poor indexing than bad server configuration.