I have 5 mysql servers in master-master group replication setup. (MySQL version 8.0.26) 2 nodes are having 1vCore and 2GB RAM and 20GB HDD configurations, and rest 3 nodes are having about 32GB RAM and 6vCores.
There are 5 InnoDB databases having 45 tables and mysqldump sql file is around 150MB, for all db combined.
I have following configuration for those 2 nodes of MySQL:
max_connections = 900
wait_timeout = 60
interactive_timeout = 60
log_timestamps = SYSTEM
innodb_log_buffer_size = 256M
innodb_log_file_size = 1G
innodb_write_io_threads = 16
innodb_flush_log_at_trx_commit = 0
innodb_doublewrite = 0
# Disabling other storage engines, use only InnoDB
disabled_storage_engines = "MyISAM,BLACKHOLE,FEDERATED,ARCHIVE,MEMORY"
My springboot java application is not optimised and somehow creates many connections to database for quick queries. It throws exception when max_connections are 250 or lower and works fine when it's between 600 and 900.
The problem is that these 2 nodes, always goes out of memory and the VM stops responding, and then automatically reboots. MySQL works fine after reboot and slowly it fills up the memory and same things repeats.
mysqltuner perl script suggest memory allocation based on multiplication of the max_connections and other values. But that is not practical as it will happen when server is running at full capacity.
I have tried many configurations but still the same problem is there. Here's the link of configuration that I have tried - Dedicated mysql server slow response
EDIT 1
- Also, I would like to mention that, they are acting as backup servers in group replication and application do not connect to the servers until required. The memory overflow is caused only by group replication syncing.
- The server runs normally till 5 hours then reboot itself
- After changing the flags to recommended ones by Rick James below is the mysqltuner report
MySQLTuner 1.8.1 - Major Hayden [email protected] Bug reports, feature requests, and downloads at http://mysqltuner.pl/ Run with '--help' for additional options and output filtering
[--] Skipped version check for MySQLTuner script
[OK] Logged in using credentials passed on the command line
[OK] Currently running supported MySQL version 8.0.26-0ubuntu0.20.04.2
[OK] Operating on 64-bit architecture
-------- Log file Recommendations ------------------------------------------------------------------
[OK] Log file /var/log/mysql/error.log exists
[--] Log file: /var/log/mysql/error.log(22K)
[OK] Log file /var/log/mysql/error.log is not empty
[OK] Log file /var/log/mysql/error.log is smaller than 32 Mb
[OK] Log file /var/log/mysql/error.log is readable.
[!!] /var/log/mysql/error.log contains 47 warning(s).
[!!] /var/log/mysql/error.log contains 6 error(s).
[--] 6 start(s) detected in /var/log/mysql/error.log
[--] 1) 2021-09-16T11:38:56.901372+05:30 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.26-0ubuntu0.20.04.2' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu).
[--] 2) 2021-09-16T11:38:56.901295+05:30 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '127.0.0.1' port: 33060, socket: /var/run/mysqld/mysqlx.sock
[--] 3) 2021-09-16T10:38:33.120014+05:30 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.26-0ubuntu0.20.04.2' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu).
[--] 4) 2021-09-16T10:38:33.119526+05:30 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '127.0.0.1' port: 33060, socket: /var/run/mysqld/mysqlx.sock
[--] 5) 2021-09-16T09:44:28.059734+05:30 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.26-0ubuntu0.20.04.2' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu).
[--] 6) 2021-09-16T09:44:28.059267+05:30 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '127.0.0.1' port: 33060, socket: /var/run/mysqld/mysqlx.sock
[--] 1 shutdown(s) detected in /var/log/mysql/error.log
[--] 1) 2021-09-16T11:38:40.998090+05:30 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.26-0ubuntu0.20.04.2) (Ubuntu).
-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MEMORY +MRG_MYISAM +MyISAM +PERFORMANCE_SCHEMA
[--] Data in InnoDB tables: 3.7G (Tables: 60)
[OK] Total fragmented tables: 0
-------- Analysis Performance Metrics --------------------------------------------------------------
[--] innodb_stats_on_metadata: OFF
[OK] No stat updates during querying INFORMATION_SCHEMA.
-------- Security Recommendations ------------------------------------------------------------------
[--] Skipped due to unsupported feature for MySQL 8
-------- CVE Security Recommendations --------------------------------------------------------------
[--] Skipped due to --cvefile option undefined
-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 13m 22s (34 q [0.042 qps], 33 conn, TX: 68K, RX: 619M)
[--] Reads / Writes: 0% / 100%
[--] Binary logging is enabled (GTID MODE: ON)
[--] Physical Memory : 1.9G
[--] Max MySQL memory : 7.0G
[--] Other process memory: 0B
[--] Total buffers: 680.0M global + 65.1M per thread (100 max threads)
[--] P_S Max memory usage: 72B
[--] Galera GCache Max memory usage: 0B
[OK] Maximum reached memory usage: 810.3M (40.77% of installed RAM)
[!!] Maximum possible memory usage: 7.0G (362.00% of installed RAM)
[!!] Overall possible memory usage with other process exceeded memory
[OK] Slow queries: 0% (0/34)
[OK] Highest usage of available connections: 2% (2/100)
[!!] Aborted connections: 9.09% (3/33)
[!!] name resolution is active : a reverse name resolution is made for each new connection and can reduce performance
[--] Query cache have been removed in MySQL 8
[OK] No Sort requiring temporary tables
[OK] No joins without indexes
[OK] Temporary tables created on disk: 0% (0 on disk / 5 total)
[OK] Thread cache hit rate: 96% (1 created / 33 connections)
[OK] Table cache hit rate: 99% (413K hits / 414K requests)
[OK] table_definition_cache(2000) is upper than number of tables(391)
[OK] Open file limit used: 0% (9/10K)
[OK] Table locks acquired immediately: 100% (5 immediate / 5 locks)
[OK] Binlog cache memory access: 98.63% (199686 Memory / 202457 Total)
-------- Performance schema ------------------------------------------------------------------------
[--] Memory used by P_S: 72B
[--] Sys schema is installed.
-------- ThreadPool Metrics ------------------------------------------------------------------------
[--] ThreadPool stat is disabled.
-------- MyISAM Metrics ----------------------------------------------------------------------------
[--] MyISAM Metrics are disabled on last MySQL versions.
-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 0
[OK] InnoDB File per table is activated
[!!] InnoDB buffer pool / data size: 640.0M/3.7G
[!!] Ratio InnoDB log file size / InnoDB Buffer pool size (320 %): 1.0G * 2/640.0M should be equal to 25%
[OK] InnoDB buffer pool instances: 1
[--] Number of InnoDB Buffer Pool Chunk : 5 for 1 Buffer Pool Instance(s)
[OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances
[OK] InnoDB Read buffer efficiency: 99.95% (5081504 hits/ 5083928 total)
[!!] InnoDB Write Log efficiency: 72.9% (1546641 hits/ 2121634 total)
[OK] InnoDB log waits: 0.00% (0 waits / 574993 writes)
-------- Aria Metrics ------------------------------------------------------------------------------
[--] Aria Storage Engine not available.
-------- TokuDB Metrics ----------------------------------------------------------------------------
[--] TokuDB is disabled.
-------- XtraDB Metrics ----------------------------------------------------------------------------
[--] XtraDB is disabled.
-------- Galera Metrics ----------------------------------------------------------------------------
[--] Galera is disabled.
-------- Replication Metrics -----------------------------------------------------------------------
[--] Galera Synchronous replication: NO
[--] No replication slave(s) for this server.
[--] Binlog format: ROW
[--] XA support enabled: ON
[--] Semi synchronous replication Master: Not Activated
[--] Semi synchronous replication Slave: Not Activated
[--] This is a standalone server
-------- Recommendations ---------------------------------------------------------------------------
General recommendations:
Control warning line(s) into /var/log/mysql/error.log file
Control error line(s) into /var/log/mysql/error.log file
MySQL was started within the last 24 hours - recommendations may be inaccurate
Reduce your overall MySQL memory footprint for system stability
Dedicate this server to your database for highest performance.
Reduce or eliminate unclosed connections and network issues
Configure your accounts with ip or subnets only, then update your configuration with skip-name-resolve=1
Before changing innodb_log_file_size and/or innodb_log_files_in_group read this: https://bit.ly/2TcGgtU
Variables to adjust:
*** MySQL's maximum memory usage is dangerously high ***
*** Add RAM before increasing MySQL buffer variables ***
innodb_buffer_pool_size (>= 3.7G) if possible.
innodb_log_file_size should be (=80M) if possible, so InnoDB total log files size equals to 25% of buffer pool size.
