I am not sure if load alerts are useful for these servers. These servers are not production facing; as long as the replication processes are running and the replication lag is not greater than X seconds, I don't mind what the load average is.

However, for dbbackup1, there's definitely a performance issue: https://grafana.miraheze.org/d/_9zrwMHmk/mariadb-replication?viewPanel=16&orgId=1&from=1615442601928&to=1615939976899&var-interval=$__auto_interval_interval&var-host=dbbackup1.miraheze.org:9105... what's causing this? Perhaps two clusters on one VPS, running on HDDs (since SSDs are too expensive), is not possible?

Downtimed dbbackup[12] Current Load.

Investigating load on dbbackup1.

Analysing the queries from a binlog (c4):
mysqlbinlog mysql-bin.001818 | grep '::' > ~/analyse-queries-T6984.txt
(any query that has '::' in it usually includes the PHP caller as SQL comments)

Output:

$ awk '{print $4}' analyse-queries-T6984.txt | sort | uniq -c | sort -nr | head -15
   5437 UpdateExternalLinks::execute
   5164 SqlBagOStuff::deleteServerObjectsExpiringBefore
   3736 WikiPage::archiveRevisions
   2859 SET
   2346 LinksUpdate::incrTableUpdate
   1873 SiteStatsUpdate::doUpdate
   1814 CheckUserHooks::updateCheckUserData
   1807 RecentChange::save
   1799 LinksDeletionUpdate::doIncrementalUpdate
   1728 LinksUpdate::updateLinksTimestamp
   1609 ManualLogEntry::insert
   1527 SqlBagOStuff::updateTable
   1142 MediaWiki\User\UserOptionsManager::saveOptions
    934 WikiPage::doDeleteArticleBatched
    934 SearchMySQL::delete

@Paladox I have disabled c4 replication on dbbackup1, but the lag is not decreasing. It looks like dbbackup1 still doesn't have enough room to replicate a full database cluster. Do you see room for improvements?

In T6984#138318, @Southparkfan wrote:

@Paladox I have disabled c4 replication on dbbackup1, but the lag is not decreasing. It looks like dbbackup1 still doesn't have enough room to replicate a full database cluster. Do you see room for improvements?

Hi, I don't see any room for improvements without spending. I don't think hdds are suitable for DBs as they are just too slow.

I much prefer your other suggestion of using mysql backup which means we at least have a stable backup even if its not a replica.