MySQL Query Cache Invalidation with comment_propagation

[zmariscal]

Current Behaviour:
When enabling comment_propagation for the mysql2 adapter, we noticed that it invalidates MySQL's query cache. It appears to be potentially linked to a known MySQL issue documented here: MySQL Bug #40986. The specific line in the codebase possibly implicated in this behavior can be found here.

Expected Behaviour:
At the very least, there should be documentation outlining the implications of enabling comment_propagation.

Steps to Reproduce:

Datadog.configure do |c|
    c.tracing.instrument :mysql2, comment_propagation: "full"

Environment:

• ddtrace version: 1.20.0
• Ruby version: 3.2.0

[TonyCTHsu]

Thanks @zmariscal , I will have a look!

[marcotc]

From MySQL Bug #40986:

'/* */'-style comments are fine and do not affect caching.

This is possibly a workaround.

[zmariscal]

Any update on this issue? Anything I can do to help?

[TonyCTHsu]

From MySQL Bug #40986:

'/* */'-style comments are fine and do not affect caching.

This is possibly a workaround.

This is the current implementation. I am forwarding this to our DBM team.

[sethsamuel]

Hi @zmariscal, which version of MySQL are you querying and is it self-hosted, Aurora, etc?

[zmariscal]

Hi @zmariscal, which version of MySQL are you querying and is it self-hosted, Aurora, etc?

The AWS Engine version is as follows: 5.7.mysql_aurora.2.11.2

[sethsamuel]

Ok, thanks for the report. We've opened a ticket and will get back to you when we know more