nodetool toppartitions

Samples database reads and writes and reports the most active partitions.

Samples the activity in a table during the specified duration and reports the most active partitions.


nodetool [connection_options] toppartitions
[-a samplers] [-k num_partitions] [-s size] [--]
keyspace_name table_name duration
Table 1. Legend
Syntax conventions Description
UPPERCASE Literal keyword.
Lowercase Not literal.
Italics Variable value. Replace with a valid option or user-defined value.
[ ] Optional. Square brackets ( [ ] ) surround optional command arguments. Do not type the square brackets.
( ) Group. Parentheses ( ( ) ) identify a group to choose from. Do not type the parentheses.
| Or. A vertical bar ( | ) separates alternative elements. Type any one of the elements. Do not type the vertical bar.
... Repeatable. An ellipsis ( ... ) indicates that you can repeat the syntax element as often as required.
'Literal string' Single quotation ( ' ) marks must surround literal strings in CQL statements. Use single quotation marks to preserve upper case.
{ key:value } Map collection. Braces ( { } ) enclose map collections or key value pairs. A colon separates the key and the value.
<datatype1,datatype2> Set, list, map, or tuple. Angle brackets ( < > ) enclose data types in a set, list, map, or tuple. Separate the data types with a comma.
cql_statement;End CQL statement. A semicolon ( ; ) terminates all CQL statements.
[ -- ] Separate the command line options from the command arguments with two hyphens ( -- ). This syntax is useful when arguments might be mistaken for command line options.
' <schema> ... </schema> ' Search CQL only: Single quotation marks ( ' ) surround an entire XML schema declaration.
@xml_entity='xml_entity_type' Search CQL only: Identify the entity and literal value to overwrite the XML element in the schema and solrconfig files.


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

Connection options

-h, --host hostname
The hostname or IP address of a remote node or nodes. When omitted, the default is the local machine.
-p, --port jmx_port
The JMX port number.
-pw, --password jmxpassword
The JMX password for authenticating with secure JMX. If a password is not provided, you are prompted to enter one.
-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

Separates an option from an argument that could be mistaken for a option.
-a samplers, samplers2
Comma-separated list of samplers. Default is all.
Duration in milliseconds.
-k num_partitions
Number of top partitions. Default is 10.
The keyspace name.
-s size
Capacity of stream summary. A value closer to actual cardinality of partitions yields more accurate results. Default is 256.
The table name.


Sample the most active partitions for the table test.users for 1,000 milliseconds.

nodetool toppartitions test users 1000

The output of nodetool toppartitions is similar to the following:

WRITES Sampler:
                Cardinality: ~2 (256 capacity)
                Top 4 partitions:
                Partition                Count       +/-
                4b504d39354f37353131        15        14
                3738313134394d353530        15        14
                4f363735324e324e4d30        15        14
                303535324e4b4d504c30        15        14
                READS Sampler:
                Cardinality: ~3 (256 capacity)
                Top 4 partitions:
                Partition                Count       +/-
                4d4e30314f374e313730        42        41
                4f363735324e324e4d30        42        41
                303535324e4b4d504c30        42        41
                4e355030324e344d3030        41        40
For each of the samplers used (WRITES and READS in the example), toppartitions reports:
  • The cardinality of the sampled operations (that is, the number of unique operations in the sample set)
  • The n partitions in the specified table that had the most traffic in the specified time period (where n is the value of the -k argument, or ten if -k is not explicitly set in the command).

    For each Partition, toppartitions reports:

    The partition key
    The number of operations of the specified type that occurred during the specified time period.
    The margin of error for the Count statistic
    Note: To keep the toppartitions reporting from slowing performance, the database does not keep an exact count of operations, but uses sampling techniques to create an approximate number. (This example reports on a sample cluster; a production system might generate millions of reads or writes in a few seconds.) The +/- figure allows you to judge the accuracy of the toppartitions reporting.