nodetool settraceprobability
Sets the probability for tracing a request.
Sets the probability for tracing a request.
Synopsis
nodetool <options> settraceprobability -- <value>
installation_location/cassandra/bin| Short | Long | Description |
|---|---|---|
-h |
--host |
Hostname or IP address. |
-p |
--port |
Port number. |
-pwf |
--password-file |
Password file path. |
-pw |
--password |
Password. |
-u |
--username |
Remote JMX agent username. |
| value | Trace probability between 0 and 1. For example: 0.2. | |
-- |
Separates an option from an argument that could be mistaken for a option. | |
Description
Probabilistic tracing is useful to determine the cause of intermittent query performance problems by identifying which queries are responsible. This option traces 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 will trace everything whereas lesser amounts (for example, 0.10) only sample a certain percentage of statements. Care should be taken on large and active systems, as system-wide tracing will have a performance impact. Unless you are under 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 two tables – sessions and events, which 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 events tables for probabilistic tracing information.
To discover the current trace probability setting, use nodetool gettraceprobability.