[CASSANDRA-18283] Enhance diagnostic nodetool tablestats output

• Type: Improvement
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 5.0-alpha1, 5.0
• Component/s: Tool/nodetool
• Change Category: Operability
• Complexity: Normal
• Platform: All

Source Control Link

https://github.com/apache/cassandra/commit/48417940280021d0012b7a7db6c9f823a98086e4

Test and Documentation Plan

ci, fixed tests

• Assignee: Stefan Miklosovic
• Reporter: Brad Schoening

Authors

Stefan Miklosovic

Reviewers

Brandon Williams

• Created: 23/Feb/23 19:00
• Updated: 12/Sep/23 13:03
• Resolved: 08/Mar/23 15:51

Description

The nodetool tablestats command lacks some available details which would be very useful to report upon.  This is especially helpful in database-as-a-service environments where servers and their disk files are not directly observable by users.

1. Currently, for LCS tablestats reports useful details about the number of sstables in each level:

          SSTable count: 6635

          SSTables in each level: [1, 9, 98, 805, 5722, 0, 0, 0, 0]

This type of additional detail about the sstables is absent from STCS and TWCS as it only reports the table count. 

1a) For STCS, tablestats should report the max sstable file size on disk. This is useful to know if compaction has failed due to disk space or if a forced compaction created a jumbo table.

1b) For TWCS, tablestats should report the min & max timestamp, and duration of the sstables representing windows.  This is useful to know if out-of-window writes or rows w/out a TTL have lead many more sstables on disk than expected by the time window configuration.

STCs example:

          SSTable count: 6635

          SSTable STCS max size: 122,000,000,000

TWCs example:

         SSTable count: 6635

          SSTables Time Window 15 DAYS, max duration : 362d 7h 16m 49s

2. While tablestats reports both memtable and disk file sstable statistics. It is useful these are in the same command, but it would clarify the output to separate mem vs disk into two sections

i.e., 

     -- File statistics

     SSTable count: 6635

     SSTables in each level: [1, 9, 98, 805, 5722, 0, 0, 0, 0] 

     -- Memtable statistics

     Bloom filter false positives: 12184123

     Bloom filter false ratio: 0.07203

     Bloom filter space used: 16874424

     Bloom filter off heap memory used: 16821344

     Index summary off heap memory used: 7525546

     Space used (live): 1324067896238

3.  Read / Write count should also be reported as a ratio, such as:

     Local read count: 202961459

     Local write count: 40554481

     Local read/write ratio: 5:1    <new>

     Local read latency: 1.957 ms

     Local write count: 40554481

     Local write latency: 0.040 ms