decouple olap tx timeout from oltp tx timeout

[maxenglander]

Description

Since workload=olap bypasses the query timeouts (--queryserver-config-query-timeout) and also row limits, the natural assumption is that it also bypasses the transaction timeout.

This is not the case, e.g. for a tablet where the --queryserver-config-transaction-timeout is 10.

This PR

• Adds new CLI flag and YAML field to independently configure TX timeouts for OLAP workloads --queryserver-config-olap-transaction-timeout with a default value of 0 seconds, disabling OLAP TX timeouts.
• Decouples TX kill interval from OLTP TX timeout via new CLI flag and YAML field --queryserver-config-transaction-killer-interval defaulting to 3 seconds.

One subtlety is that the timeout that is applied to the transaction is based on the value of the workload setting at the beginning of the transaction. If the workload is changed mid-transaction, that may change the timeout applied to queries within the transaction, but it won't change the transaction timeout.

Demo

Using (new) default values), connected to VTGate.

mysql> set workload=oltp;
Query OK, 0 rows affected (0.00 sec)

mysql> begin ; select 1 from data limit 1; select sleep(35); commit;
Query OK, 0 rows affected (0.00 sec)

+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.01 sec)

ERROR 1317 (70100): target: dst.-.primary: vttablet: (errno 2013) due to context deadline exceeded, elapsed time: 30.00055243s, killing query ID 106 (CallerID: maxenglander)
ERROR 1317 (70100): target: dst.-.primary: vttablet: rpc error: code = Aborted desc = transaction 1659665741215176173: ended at 2022-08-05 02:18:29.360 UTC (unlocked closed connection) (CallerID: maxenglander)
mysql> set workload=olap;
Query OK, 0 rows affected (0.01 sec)

mysql> begin ; select 1 from data limit 1; select sleep(35); commit;
Query OK, 0 rows affected (0.00 sec)

+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.01 sec)

+-----------+
| sleep(35) |
+-----------+
|         0 |
+-----------+
1 row in set (35.00 sec)

Query OK, 0 rows affected (0.01 sec)

Breaking changes

Currently OLAP transactions are killed after --queryserver-config-transaction-timeout seconds. With this PR, OLAP transactions are killed after --queryserver-config-olap-transaction-timeout seconds (default value 0 means transactions are not timed out).

Currently OLTP and OLAP transactions are evaluated for killing every --queryserver-config-transaction-timeout seconds divided by 10. With this PR, OLAP and OLTP transactions are evaluated for killing every --queryserver-config-transaction-killer-interval seconds.

Related Issue(s)

#10945

Checklist

• [ ] "Backport me!" label has been added if this change should be backported
• [ ] Tests were added or are not required
• [ ] Documentation was added or is not required

Deployment Notes

[vitess-bot[bot]]

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[deepthi]

@maxenglander we'll get this reviewed. Can you add notes to the 15_0_0_summary.md file and resolve the conflicts in the meantime?

[maxenglander]

@deepthi conflicts resolved and release notes added

[maxenglander]

@harshit-gangal I implemented the one outstanding suggestion I found (timeout => conn.timeout), sorry for missing that until now. Also reverted the unrelated fmt changes (used git commit --no-verify).