MySQL: What does event `/io/table/sql/handler` mean?

Yesterday I experienced a MySQL incident

• the load was extremely high

• All select statements takes more than 3 times time than usual.

• All insert statements takes 10+ times time than usual.

The MySQL performance monitor tool shows:

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there are lots of /io/table/sql/handler has been generated during the period of incident.

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lots of active threads within the period of incident.

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lots of blocked thread within the period of incident.

Questions

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What does /io/table/sql/handler mean?

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Do you know the possible root cause?

From documentation of solorwinds


.../sql/handler = work has been delegated to a storage engine


examples:

• io/table/sql/handler = storage engine is processing an I/O request against a table

• lock/table/sql/handler = storage engine is processing a table lock operation

Reference

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See the MySQL reference manual for more information on Wait Instrument naming (look at the section for "Wait Instrumented Components"):

https://dev.mysql.com/doc/refman/5.6/en/performance-schema-instrument-naming.html

StackExchange Database Administrators Q#220859, answer score: 6