Increase default maxAllowedPacket size.

[methane]

Description

• Increase default maxAllowedPacket as MySQL default.
• ErrPacketTooLarge message mention client config rather than server config.

Fixes #1355.

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

[shogo82148]

LGTM

[agnivade]

FWIW we should have kept the default to be the same and let users change it via the query param. Changing the default to be higher is a breaking change for customers who have not changed their server side setting.

Please consider reverting this to be the original value of 4MB. This is causing a breaking change from our side: mattermost/mattermost#23394 (comment)

[methane]

I'm sorry about changing it in 1.7.1. I had to wait 1.8.
But decreasing it is also backward breaking change. Strict zero backward incompatibility is impossible, because some value/behavior might be bug for some users but feature for another users.

Please advocate to use larger max_allowed_packet when user might send more than 4MB blob.

[agnivade]

Keeping the default to be the same, and letting users "fix" the issue by changing the query param would have been the best way to keep full backward compatibility and fix the issue as well.

And then if you want to change the default, cut a 2.0 release.

[methane]

Keeping the default to be the same, and letting users "fix" the issue by changing the query param would have been the best way to keep full backward compatibility and fix the issue as well.

It may break people using v1.7.1 with default parameters.

Keeping the default to be the same, and letting users "fix" the issue by changing the query param would have been the best way to keep full backward compatibility and fix the issue as well.

And then if you want to change the default, cut a 2.0 release.

It is totally nonsense, like this comic.

We need to break small part every release, even in bugfix release.

We release v2 when we need to change/remove public APIs.

If you can not allow such a small behavior change, you must pin the exact version.

[agnivade]

It may break people using v1.7.1 with default parameters.

I don't see how. If the parameter is unset, it would still use the original value.

[methane]

I don't understand what you're saying...

[sjmudd]

@agnivade : Also FWIW as I brought this up a 4MB query size is tiny. The original problem was the fact that the go driver error message said the server's setting was wrong (it wasn't) and also the 4 MB default size is tiny. This has nothing to do with blobs, just large queries can easily grow over this size.

• MySQL 5.7 will be EOL in October and is very old. The setting dates back to 5.6 in 2013 where it moved from 1 MB to 4 MB
• MariaDB uses 16 MB by default.