Nuestra organización tiene una aplicación web bastante avanzada (como en muchas piezas móviles) que ha funcionado muy bien hasta hace poco, pero no se han realizado cambios notables.
Está el servidor web Apache, el servidor mySQL (procesamiento de datos) y luego otro servidor mySQL que maneja las solicitudes repetitivas del público. La afluencia de tráfico al servidor web principal casi solo afectaría al servidor SQL secundario. El servidor de solicitudes repetitivas es esclavo del servidor de procesamiento de datos, pero no se envían consultas de escritura al servidor de solicitudes repetitivas: solo lectura.
El problema al que me enfrento es que el servidor MySQL de procesamiento de datos parece aumentar aleatoriamente al 100% del uso de la CPU cuando normalmente funciona al 15-20%, incluso bajo una carga pesada. El uso del 100% de la CPU dura aproximadamente 8 segundos, a veces en períodos de 2 a 3 minutos hasta que desaparece aleatoriamente por sí solo.
No hay consultas en el registro de consultas lentas, aparte de las que se intenta procesar cuando están al 100%. Las consultas que conducen al registro son las mismas que normalmente se ejecutan sin problemas antes del pico aleatorio.
La única actividad que muestra HTOP es mySQL; tampoco hay crons programados en este servidor y no hay aumento en otras actividades de consulta durante estos momentos. La cuenta del hilo de conexión abierta se mantiene estable entre 3 y 5, y la LISTA DE PROCESOS también solo tiene entre 3 y 5 consultas antes, durante o después.
SELECT * FROM audio
WHERE associated_incident IS null
AND archive IS NULL
AND temp_skip IS null
AND length >= 3
AND (locked <> 1 or locked IS NULL)
AND timestamp > (NOW() - INTERVAL 4 HOUR)
ORDER BY `audio`.`id` DESC
LIMIT 1;
UPDATE audio SET locked=1, lockexpr = '$ulockexpr', lockuser = '$ulockuser' WHERE id = $audio_id;
La consulta anterior se ejecuta repetidamente en el software que utiliza nuestro personal, pero en un momento dado no más de 1 o 2 por segundo, pero es lo más cerca que puedo reducir el problema. Esta consulta también se mostrará en slow_query_log durante los picos altos. Pero solo para aclarar, esta consulta se utiliza durante todo el día y no siempre encontramos estos problemas.
Puedo realizar una prueba de esfuerzo del servidor con esta consulta, ejecutándolo 100 veces en 5 segundos y aun así obtener un resultado promedio de 0,002 a 0,005 segundos para un tiempo de retorno.
En /var/log/mysql tengo 8,2 Gb de archivos mysql-bin.
Sólo posibles modificaciones a my.cnf
key_buffer_size = 16M
myisam-recover-options = BACKUP
log_error = /var/log/mysql/error.log
slow_query_log = 1
slow_query_log_file = /var/log/mysql/mysql-slow.log
long_query_time = 2
server-id = 1
log_bin = /var/log/mysql/mysql-bin.log
max_binlog_size = 100M
binlog_do_db = incident_log
Todo lo demás no está especificado o comentado.
Sintonizador MySQL
>> MySQLTuner 2.1.1
* Jean-Marie Renouard <[email protected]>
* 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 from Debian maintenance account.
[OK] Currently running supported MySQL version 8.0.32-0ubuntu0.20.04.2
[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 (0B)
[--] Log file /var/log/mysql/error.log is empty. Assuming log-rotation. Use --server-log={file} for explicit file
-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MEMORY +MRG_MYISAM +MyISAM +PERFORMANCE_SCHEMA
[--] Data in InnoDB tables: 1.5G (Tables: 107)
[OK] Total fragmented tables: 0
-------- Analysis Performance Metrics --------------------------------------------------------------
[--] innodb_stats_on_metadata: OFF
[OK] No stat updates during querying INFORMATION_SCHEMA.
-------- Views Metrics -----------------------------------------------------------------------------
-------- Triggers Metrics --------------------------------------------------------------------------
-------- Routines Metrics --------------------------------------------------------------------------
-------- Security Recommendations ------------------------------------------------------------------
[--] Skipped due to unsupported feature for MySQL 8.0+
-------- CVE Security Recommendations --------------------------------------------------------------
[--] Skipped due to --cvefile option undefined
-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 12h 41m 34s (3M q [73.289 qps], 1M conn, TX: 5G, RX: 445M)
[--] Reads / Writes: 81% / 19%
[--] Binary logging is enabled (GTID MODE: OFF)
[--] Physical Memory : 1.9G
[--] Max MySQL memory : 10.1G
[--] Other process memory: 0B
[--] Total buffers: 176.0M global + 65.9M per thread (151 max threads)
[--] Performance_schema Max memory usage: 239M
[--] Galera GCache Max memory usage: 0B
[!!] Maximum reached memory usage: 10.2G (528.62% of installed RAM)
[!!] Maximum possible memory usage: 10.1G (525.28% of installed RAM)
[!!] Overall possible memory usage with other process exceeded memory
[OK] Slow queries: 0% (3/3M)
[!!] Highest connection usage: 100% (152/151)
[OK] Aborted connections: 0.09% (1203/1391547)
[!!] Name resolution is active: a reverse name resolution is made for each new connection which can reduce performance
[--] Query cache has been removed since MySQL 8.0
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 10K sorts)
[!!] Joins performed without indexes: 5915
[OK] Temporary tables created on disk: 0% (0 on disk / 8K total)
[OK] Thread cache hit rate: 94% (75K created / 1M connections)
[OK] Table cache hit rate: 99% (1M hits / 1M requests)
[OK] table_definition_cache (2000) is greater than number of tables (434)
[OK] Open file limit used: 0% (3/10K)
[OK] Table locks acquired immediately: 100% (1K immediate / 1K locks)
[OK] Binlog cache memory access: 100.00% (346520 Memory / 346520 Total)
-------- Performance schema ------------------------------------------------------------------------
[--] Performance_schema is activated.
[--] Memory used by Performance_schema: 239.2M
[--] Sys schema is installed.
-------- ThreadPool Metrics ------------------------------------------------------------------------
[--] ThreadPool stat is disabled.
-------- MyISAM Metrics ----------------------------------------------------------------------------
[--] MyISAM Metrics are disabled since MySQL 8.0.
-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 0
[OK] InnoDB File per table is activated
[!!] InnoDB buffer pool / data size: 128.0M / 1.5G
[!!] Ratio InnoDB log file size / InnoDB Buffer pool size (75%): 48.0M * 2 / 128.0M should be equal to 25%
[OK] InnoDB buffer pool instances: 1
[--] Number of InnoDB Buffer Pool Chunk: 1 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: 99.87% (403976971 hits / 404504329 total)
[!!] InnoDB Write Log efficiency: 59.62% (1713194 hits / 2873563 total)
[OK] InnoDB log waits: 0.00% (0 waits / 1160369 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:
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 persistent connections to reduce connection usage
Configure your accounts with ip or subnets only, then update your configuration with skip-name-resolve=1
We will suggest raising the 'join_buffer_size' until JOINs not using indexes are found.
See https://dev.mysql.com/doc/internals/en/join-buffer-size.html
(specially the conclusions at the bottom of the page).
Buffer Key MyISAM set to 0, no MyISAM table detected
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 ***
max_connections (> 151)
wait_timeout (< 28800)
interactive_timeout (< 28800)
skip-name-resolve=1
join_buffer_size (> 256.0K, or always use indexes with JOINs)
key_buffer_size=0
innodb_buffer_pool_size (>= 1.5G) if possible.
innodb_log_file_size should be (=16M) if possible, so InnoDB total log file size equals 25% of buffer pool size.
Abierto a todos los consejos.
Ediciones:
mysql> SHOW TABLE STATUS WHERE name LIKE "audio";
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment |
| audio | InnoDB | 10 | Dynamic | 969276 | 164 | 159039488 | 0 | 90898432 | 7340032 | 1644653 | 2023-04-13 14:41:27 | 2023-04-17 14:56:21 | NULL | utf8mb4_0900_ai_ci | NULL | | |
PHP
$sql = "SELECT * FROM audio
WHERE associated_incident IS null
AND archive IS NULL
AND temp_skip IS null
AND length >= 3
AND (locked <> 1 or locked IS NULL)
ORDER BY `audio`.`id` DESC
LIMIT 1;
";
$result = mysqli_query($conn, $sql) or die(mysqli_error());
$audio = mysqli_fetch_assoc($result);
if ($audio) {
$audio_id = $audio['id'];
$audio_timestamp = $audio['timestamp'];
$audio_hash = $audio['hash'];
$audio_length = $audio['length'];
$ulockexpr = date("Y-m-d H:i:s", strtotime('+ 5min'));
$ulockuser = $_SESSION['login_user'];
$sql_lock = "UPDATE audio SET locked=1, lockexpr = '$ulockexpr', lockuser = '$ulockuser' WHERE id = $audio_id";
Respuesta1
Cambie a innodb_buffer_pool_size = 500M: el antiguo valor predeterminado de 128 millones es terriblemente bajo.
Si eso SELECTse hace para encontrar una fila en la que trabajar y luego lo hace UPDATE, entonces use una transacción:
START TRANSACTION;
SELECT ... FROM audio ... FOR UPDATE;
... process ...
UPDATE audio SET ... WHERE id = ...;
COMMIT;
Esto START - FOR UPDATE - COMMITevitará que dos hilos agarren el mismo elemento para trabajar.
Considere usar ORDER BY timestamp DESCen lugar de ORDER BY id DESC.
Esta configuración puede ser necesaria para ver la declaración ofensiva:
log_slow_admin_statements = ON
¿Qué índices hay sobre la mesa? Por favor proporcione SHOW CREATE TABLE.
Baje [sí, baje] max_connectionsa solo 50. Yreduzca la configuración de Apache para que no genere más de 40 niños simultáneos. Veo ese Max_used_connectionsgolpe max_connections. Cuando esto sucede, MySQL funcionará hasta que el problema desaparezca. Reducir el límite permitirá que comience a relajarse antes.