nodetool settraceprobability

Sets the probability for tracing a request.

Sets the probability for tracing any given request to value.

Probabilistic tracing identifies which queries are responsible for intermittent query performance problems. You can trace some or all statements sent to a cluster. Tracing a request usually requires at least 10 rows to be inserted.

A probability of 1.0 traces everything whereas lesser amounts (for example, 0.10) only sample a certain percentage of statements. Take care on large and active systems, as system-wide tracing will have a performance impact. Unless you are under a very light load, tracing all requests (probability 1.0) will probably overwhelm your system. Start with a small fraction, for example, 0.001 and increase only if necessary.

The trace information is stored in a system_traces keyspace that holds the sessions and events tables that can be easily queried to answer questions, such as what the most time-consuming query has been since a trace was started. Query the parameters map and thread column in the system_traces.sessions and tables for probabilistic tracing information.

Tip: To discover the current trace probability setting, use nodetool gettraceprobability.


nodetool [connection_options] settraceprobability
[--] value
Table 1. Legend
Syntax conventions Description
UPPERCASE Literal keyword.
Lowercase Not literal.


The short form and long form parameters are comma-separated.

Connection options

-h, --host hostname
-p, --port jmx_port
The JMX port number.
-pw, --password jmxpassword
-pwf, --password-file jmx_password_filepath
The filepath to the file that stores JMX authentication credentials.
-u, --username jmx_username
The user name for authenticating with secure JMX.

Command arguments

  • 0 - disables trace probability. Default.
  • number between 0 and 1 - trace probability to represent a percentage.
  • 1 - enables for all requests.


Set probability for tracing a request at 60%

nodetool settraceprobability 0.6

Enable tracing for all requests

nodetool settraceprobability 1

Disable request tracing

nodetool settraceprobability 0