docs/operating-scylla/nodetool-commands/settraceprobability.rst
settraceprobability - <value> - Sets the probability for tracing a request. Value is trace probability between 0 and 1. 0 the trace will never happen and 1 the trace will always happen.
Anything in between is a percentage of the time, converted into a decimal. For example, 60% would be 0.6.
This command is useful to determine the cause of intermittent query performance problems by identifying which queries are responsible.
It can trace some or all the queries sent to the cluster, setting the probability to 1.0 will trace everything, set to a lower number will reduce the traced queries.
Use caution when setting the settraceprobability high, it can affect active systems, as system-wide tracing will have a performance impact.
Trace information is stored under system_traces keyspace for more information you can read our CQL tracing in ScyllaDB_ blog
.. _CQL tracing in ScyllaDB: https://www.scylladb.com/2016/08/04/cql-tracing/
For example, to set the probability to 10%:
.. code-block:: shell
nodetool settraceprobability 0.1
gettraceprobability </operating-scylla/nodetool-commands/gettraceprobability/> - Nodetool Reference