(The latest deployment of DiscussionTools permalinks backend to group1 wikis T315353#8392662 has resulted in some new errors, although a lot less numerous this time. It really is a gift that keeps on giving.)

There are a few occurrences of: [optimistically assuming that they share a root cause]

• "Lock wait timeout exceeded; try restarting transaction"
• "Deadlock found when trying to get lock; try restarting transaction"

…usually followed by:

• "Cannot execute query from MediaWiki\Extension\DiscussionTools\Hooks\DataUpdatesHooks::onRevisionDataUpdates while transaction status is ERROR"

All of them are for queries like "INSERT INTO discussiontools_items / discussiontools_item_ids" from MediaWiki\Extension\DiscussionTools\ThreadItemStore::insertThreadItems.

Logstash links:

• "Deadlock found when trying to get lock; try restarting transaction" AND "ThreadItemStore::insertThreadItems"
  
• "Lock wait timeout exceeded; try restarting transaction" AND "ThreadItemStore::insertThreadItems"
  

The error rate is relatively unalarming, but I'd like to learn why this is happening and what we can do about it.