fix: detect read-only errors on wrapped mysql2 errors - #692
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Summary
Read read-only diagnostics off the wrapped error's
cause, so failover triggers on MySQL as well.Description
#673 added read-only connection error detection, but the MySQL side never fired.
Every mysql2 query goes through
ClientUtils.queryWithTimeout, which re-throws the driver error as anAwsWrapperErrorand keeps the original only ascause.MySQLErrorHandlerreaderrnostraight off the error it was handed, so it saw nothing on exactly the errors it exists to classify, and a demoted writer kept failing writes.(PostgreSQL was unaffected:
pg/libhas no such wrapper and hands the driver error to the plugins as-is.)Fix: both handlers fall back to
causewhen the error itself carries no diagnostics. That fallback is what makes MySQL work; on PostgreSQL it is there so the handler keeps working if that path is ever wrapped too.By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.