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Posted to commits@cassandra.apache.org by "Paulo Motta (Jira)" <ji...@apache.org> on 2021/03/15 21:10:00 UTC
[jira] [Comment Edited] (CASSANDRA-16513) Add nodetool command to
display or export the contents of a virtual table
[ https://issues.apache.org/jira/browse/CASSANDRA-16513?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17301985#comment-17301985 ]
Paulo Motta edited comment on CASSANDRA-16513 at 3/15/21, 9:09 PM:
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bq. I don't know that giving access to table data over JMX is the right way to be moving.
The idea is not to access this data from nodetool via JMX, but via CQL. The idea is to export virtual tables into different formats (tabular, csv, json) via a handy nodetool one-liner without having to write CQL on cqlsh. CQL access to virtual tables is still useful for custom scripts or tools, but nodetool is the standard way for admins to query operational state so we should make virtual table information available on nodetool IMO.
My vision is that this is a path towards deprecating JMX as we move information currently available through JMX to virtual tables (as CASSANDRA-14457 did with compactionstats) and easily expose them in nodetool as more virtual tables are added. Eventually we can also add setters when we start supporting writeable virtual tables.
Does this make more sense [~jjordan] ?
was (Author: paulo):
bq. I don't know that giving access to table data over JMX is the right way to be moving.
The idea is not to access this data from nodetool via JMX, but via CQL. The idea is to export virtual tables into different formats (tabular, csv, json) via a handy nodetool one-liner without having to write CQL on cqlsh. CQL access is still useful for custom scripts or tools, but nodetool is the standard way for admins to query operational state so we should make virtual table information available on nodetool IMO.
My vision is that this is a path towards deprecating JMX as we move information currently available through JMX to virtual tables (as CASSANDRA-14457 did with compactionstats) and easily expose them in nodetool as more virtual tables are added. Eventually we can also add setters when we start supporting writeable virtual tables.
Does this make more sense [~jjordan] ?
> 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
> Priority: Normal
> Labels: gsoc2021, mentor
>
> 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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