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Upgrading Uber's MySQL Fleet

(www.uber.com)
234 points benocodes | 2 comments | 14 Oct 24 12:08 UTC | HN request time: 0s | source
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tiffanyh ◴[14 Oct 24 12:36 UTC] No.41836942[source]▶
Why upgrade to v8.0 (old LTS) and not v8.4 (current LTS)?

Especially given that end-of-support is only 18-months from now (April 2026) … when end-of-support of v5.7 is what drive them to upgrade in the first place.

https://en.m.wikipedia.org/wiki/MySQL

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hu3 ◴[14 Oct 24 12:50 UTC] No.41837038[source]▶
The upgrade initiative started somewhere in 2023 according to the article.

MySQL 8.4 was released in April 30, 2024.

Their criteria for a "battle tested" MySQL version is probably much more rigorous than the average CRUD shop.

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paulryanrogers ◴[14 Oct 24 13:09 UTC] No.41837173[source]▶
Considering several versions of 8.0 had a crashing bug if you renamed a table, waiting is probably the right choice.
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blindriver ◴[14 Oct 24 14:45 UTC] No.41838032[source]▶
You’re not renaming tables when you’re at scale.
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abhorrence ◴[14 Oct 24 15:04 UTC] No.41838215[source]▶
Sure you do! It's how online schema changes tend to be done, e.g. https://docs.percona.com/percona-toolkit/pt-online-schema-ch... describes doing an atomic rename as the last step.
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yen223 ◴[14 Oct 24 17:29 UTC] No.41839727[source]▶
You aren't renaming tables at scale because there are 27 downstream services that will break if you even think about fixing the name of the revnue_dolars table, and it's not in anyone's OKR to fix it
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paulryanrogers ◴[14 Oct 24 21:08 UTC] No.41842030[source]▶
Take a closer look at how some min downtime tools work. They often use a drop-swap strategy to replace an old table name with a new one that has schema changes.

There are sometimes temporary views to keep the old and new code working during gradual transitions.

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1. blindriver ◴[16 Oct 24 17:21 UTC] No.41861496[source]▶
You clearly have not worked at global companies with concerns that go beyond “can I do it?”. I’ve used percona and I’ve used these tools before and percona is great. But when you’re at scale something as trivial as a table name change is not something you ever do because it’s not worth the risk of taking your entire site down. Just use the existing name no matter how bad it is.
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2. paulryanrogers ◴[18 Oct 24 11:34 UTC] No.41878403[source]▶
Are we talking about the same Pt-online-ddl-change?

It certainly has a drop-swap approach which does a table rename, even though the resulting table ends up with the same name as before.

That's how I encountered the MySQL table-rename-crash bug.