Quanlong Huang created IMPALA-11409:
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Summary: Skip UpdateCatalogMetrics if another thead is on-going in
it
Key: IMPALA-11409
URL: https://issues.apache.org/jira/browse/IMPALA-11409
Project: IMPALA
Issue Type: Improvement
Components: Backend
Reporter: Quanlong Huang
Assignee: Quanlong Huang
Impala coordinator tracks local metrics of the catalog, e.g. number of
dbs/tables. When use_local_catalog is enabled, it also tracks the cache
metrics, e.g. cache hit/miss count/rate.
These metrics are updated at the end of each statement, even for simple
statements like "USE <db>", "SET var=xxx", "SELECT 1". The catalog update
thread will also update the metrics in the end.
These metrics are global metrics of the local catalog cache. They are not
specifit to a simple statement. It's a waste to update the metrics concurrently.
We've seen "hanging issues" that all statements, including the catalog update
thread, are slowly executing the UpdateCatalogMetrics() function. See details
in the attached jstack dump.
Indeed, if one thread is running the UpdateCatalogMetrics() function, the other
threads can skip it and move forward.
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