Use a throttled logger for exceeded memory warnings

[GuptaManan100]

Description

This PR fixes the issue described in #15423.

We now create a throttled logger and use that to log the warnings for exceeding memory row count.

Related Issue(s)

• Fixes Throttle logs for exceeding of max memory rows #15423

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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[dbussink]

Does this throttle only on the exact matching len(result.Rows) or also on different lengths? And should it only throttle on exactly the same or should we also throttle if it's a slightly different value?

[frouioui]

It feels like the throttler will throttle all max memory warning regardless of the query. I think it would be more useful if we could throttle based on the query we are receiving rather than just the error.

[deepthi]

Right now it will throttle all log messages that are generated by this line. That is, it might be a different query, or it might be a different number of rows. It will only print one message a minute.
I agree that it will be nice to print one message per distinct query. That will need writing a new kind of ThrottledLogger. I don't know if that is worth it. If we believe it is, then let's do it.

[deepthi]

On second thought, maybe we should just throttle like before and focus on making sure that this is returned as a warning to the client. With mysql clients, that should be pretty easy. What do we do for grpc clients?

[frouioui]

Currently working on this PR to add a per-query throttler

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 65.64%. Comparing base (696fe0e) to head (d27dec5).
Report is 106 commits behind head on main.

Files	Patch %	Lines
go/vt/vtgate/executor.go	50.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15424      +/-   ##
==========================================
- Coverage   67.41%   65.64%   -1.78%     
==========================================
  Files        1560     1563       +3     
  Lines      192752   194405    +1653     
==========================================
- Hits       129952   127621    -2331     
- Misses      62800    66784    +3984     

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[frouioui]

Not sure if EROutOfMemory is appropriate, we can also remove the Code altogether

[deepthi]

Should be fine, because the warning we return to the client is descriptive.

[frouioui]

Validated the change with a local test by setting warnMemoryRows to 1 and running the 101 script.

mysql> show tables;
+--------------------+
| Tables_in_commerce |
+--------------------+
| corder             |
| customer           |
| product            |
+--------------------+
3 rows in set, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+--------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                              |
+---------+------+--------------------------------------------------------------------------------------+
| Warning | 1037 | "show tables" exceeds warning threshold of max memory rows: 1. Actual memory rows: 3 |
+---------+------+--------------------------------------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> 

[GuptaManan100]

LGTM!

[deepthi]

Currently working on this PR to add a per-query throttler

Just a note that we abandoned this because it seemed like too much work for log throttling.