Reports of database issues - aborted connections and (hopefully) small amounts of data loss + a possible fix using the new DBD::MariaDB Perl database driver

[taniwallach]

See: https://webwork.maa.org/moodle/mod/forum/discuss.php?d=4958

Original symptom were rare cases of students getting the error Unable to retrieve your permissions, perhaps due to a collision between your request and that of another user (or possibly unfinished request of yours).

That same symptom on my server led to my attempt at patching some of the LTI code at: #1150 and the discussion there got into the issue of the DB logs reporting warnings like

2020-11-09  5:21:50 16 [Warning] Aborted connection 16 to db: 'webwork' user: 'webworkWrite' host: '172.22.0.4' (Got timeout reading communication packets)

@dlglin reported in the forum thread that he encountered such problems when his site tried to use a new externally hosted database.

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Based on some preliminary tests, it seems that using the newer DBD::MariaDB database driver instead of the older DBD:mysql may help resolve this problem.

Using the new driver requires making some changes to the WW code, as explained in #1150 (comment). Changes to allow initial testing are pretty minimal.

Packages are available for several Linux distributions:

• https://repology.org/project/perl:dbd-mariadb/packages
• https://repology.org/project/perl:dbd-mariadb/versions
• http://ftp.us2.freshrpms.net/linux/rpm2html/search.php?query=perl(DBD%3A%3AMariaDB)
  but not for CentOS/RHEL.

Some comments about building the driver on CentOS 7 are in perl5-dbi/DBD-MariaDB#150