MySQL服务器最大化内存，Galera群集

Question

I have PHP ( Laravel 5.7 ) application connected to a cluster of DBs powered by Galera cluster. I am running cron job every night to clear thousands of thousands log data from DB tables. I run Delete statement of the MySQL to delete the rows in the table based on the time stamp range.

My Delete Operations looks like

DB::delete('DELETE FROM incoming_logs WHERE created_at < DATE_SUB(NOW(), INTERVAL 1 DAY)');
DB::delete('DELETE FROM provisioning_logs WHERE created_at < DATE_SUB(NOW(), INTERVAL '.Config::get('app.keep_provisioning_logs') .' DAY)');

NOTE: And these are defined in Laravel console commands and those commands scheduled in Laravel tasks.

Problem: Every time after running the cron job to delete the huge amount of data: Main memory of the DB servers max out and when I clear the cache memory manually using following command, I get my Main Memory free.

sync; echo 1 > /proc/sys/vm/drop_caches

I need to know about why cache is not being automatically re-claimed, or why after cron job my memory went out as well as I faced problem of too many connection error on MySQL.

Or is this just because my DB servers ( Total 3 DB servers under load balancer and syncing using galena) syncing real time, so when i try to delete thousands records using cron job, the server which get that delete request try to delete and maintain cache to sync with other DBs? I am not sure whats going on. Please help me with my memory maxing out problem.

My Architecture:
One Load balancer (HA proxy having three DBs under it) and galera cluster to sync data among those three DBs.

Answer 1

You are deleting half the table every night? Consider deleting an hour's worth every hour.

Do you have INDEX(created_at) ? That would help the hourly purge, though perhaps not the daily purge.

This task is an excellent one for PARTITIONing .

These, and more techniques, are discussed here .