Description

Mysql connections to external logstore are not reused/cached, so the amount of mysql connections is increasing.
This can best be seen during automated course backup. Every database reading creates a new database connection. This connections are terminated when backup process is finished.

Suggested solution

Use a global variable $DBEXT like $DB, where the external mysql connection is cached.

Reproduction

Setup external database

1. Create a database other than your Moodle database.
2. Create a table in the above database identical to the logstore_standard in your Moodle database.

Configuration of external database

1. Go to Site administration ► Plugins ► Logging ► Manage log stores
2. Enable External database log
3. Go to settings for the external logstore
4. Enter your external database and table details and save
5. Click on "Test connection" and make sure you can successfully connect to the database table.

Configuration of automated backups

1. Go to Site administration ► Courses ► Backups ► Automated backup setup
2. Set backup_auto_active to "Enabled"
3. Set backup_auto_logs to "Yes"

Observe mysql process while backup is running

1. Perform an automated backup on cli: php admin/cli/automated_backups.php
2. While backup is running, observer the processes on Mysql console / PHPMyAdmin: show processlist;