Paulo Motta created CASSANDRA-16513:
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Summary: Add nodetool command to display or export the contents of
a virtual table
Key: CASSANDRA-16513
URL: https://issues.apache.org/jira/browse/CASSANDRA-16513
Project: Cassandra
Issue Type: Improvement
Components: Observability/Metrics, Tool/nodetool
Reporter: Paulo Motta
Several virtual tables were recently added, but they're currently only
accessible via cqlsh or programmatically. While this is valuable for many use
cases, operators are accustomed with the convenience of querying system metrics
with a simple nodetool command.
In addition to that, a relatively common request is to provide nodetool output
in different formats (JSON, YAML and even XML) (CASSANDRA-5977,
CASSANDRA-12035, CASSANDRA-12486, CASSANDRA-12698, CASSANDRA-12503). However
this requires lots of manual labor as each nodetool subcommand needs to be
adapted to support new output formats.
I propose adding a new nodetool command that will consistently print to the
standard output the contents of a virtual table. By default the command will
print the output in a human-readable tabular format similar to cqlsh, but a
"--format" parameter can be specified to modify the output to some other format
like JSON or YAML.
It should be possible to add a limit to the amount of rows displayed and filter
to display only rows from a specific keyspace or table. The command should be
flexible and provide simple hooks for registration and customization of new
virtual tables.
I propose calling this command nodetool show <virtualtable> (naming
bikeshedding welcome), for example:
{noformat}
nodetool show --list
caches
clients
internode_inbound
internode_outbound
settings
sstable_tasks
system_properties
thread_pools
nodetool show clients --format yaml
...
nodetool show internode_outboud --format json
...
nodetool show sstabletasks --keyspace my_ks --table -my_table
...
{noformat}
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