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We wanted to capture the long running queries in Apache Cassandra cluster. What is the unit for duration and source_elapsed in sessions and events tables. Is it milliseconds or microseconds?
CREATE TABLE system_traces.sessions ( ... duration int, ... )
CREATE TABLE system_traces.events ( ... source_elapsed int, ... )
Regards,
Lavaraja.
Both duration and source_elapsed are in microseconds.
Here is a sample trace output in cqlsh:
Tracing session: 12009cc0-d588-11ea-ac98-437845cca09f
activity | timestamp | source | source_elapsed | client
--------------------------------------------------+----------------------------+----------+----------------+----------
Execute CQL3 query | 2020-08-03 22:51:38.264000 | 10.x.x.x | 0 | 10.x.x.x
Parsing INSERT INTO ... ; [CoreThread-0] | 2020-08-03 22:51:38.268000 | 10.x.x.x | 6551 | 10.x.x.x
Preparing statement [CoreThread-0] | 2020-08-03 22:51:38.270000 | 10.x.x.x | 8461 | 10.x.x.x
Determining replicas for mutation [CoreThread-0] | 2020-08-03 22:51:38.273000 | 10.x.x.x | 10746 | 10.x.x.x
Appending to commitlog [CoreThread-0] | 2020-08-03 22:51:38.274000 | 10.x.x.x | 11611 | 10.x.x.x
Adding to message_map memtable [CoreThread-0] | 2020-08-03 22:51:38.274000 | 10.x.x.x | 11840 | 10.x.x.x
Request complete | 2020-08-03 22:51:38.283161 | 10.x.x.x | 19161 | 10.x.x.x
These are the same entries in the system_traces.events table. The source_elapsed value of 19161 is equivalent to 19 milliseconds.
This is the same value as duration in the system_traces.sessions table:
SELECT session_id, duration FROM system_traces.sessions ; session_id | duration --------------------------------------+---------- 12009cc0-d588-11ea-ac98-437845cca09f | 19161
Cheers!
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