Recently a number of support cases have highlighted the statistics

"ss wiredtiger concurrentTransactions read out"

"ss wiredtiger concurrentTransactions read totalTickets"

"ss wiredtiger concurrentTransactions write out"

"ss wiredtiger concurrentTransactions write totalTickets".

For example this FTDC image demonstrates a case where the write tickets are exhausted:

This statistic tends to cause confusion among both support and other engineers as it implicates the storage engine layer (it is even merged with WiredTiger stats by T2), however the storage engine doesn't maintain the ticketing system or have a concept of read/write tickets. This can lead to misdirected questions about ticket exhaustion and other issues with regards to ticketing.

As part of this work it may be worth sharing information with support as to what the ticketing system is, when it comes into affect and other related issues.