[jira] [Updated] (KUDU-2701) Compaction loop resulting from small rowset compaction policy (KUDU-1400)

["Adar Dembo (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KUDU-2701?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Adar Dembo updated KUDU-2701:
-----------------------------
    Priority: Blocker  (was: Major)

> Compaction loop resulting from small rowset compaction policy (KUDU-1400)
> -------------------------------------------------------------------------
>
>                 Key: KUDU-2701
>                 URL: https://issues.apache.org/jira/browse/KUDU-2701
>             Project: Kudu
>          Issue Type: Bug
>    Affects Versions: 1.9.0
>            Reporter: Will Berkeley
>            Assignee: Will Berkeley
>            Priority: Blocker
>
> I saw an instance of rowset compaction looping, accomplishing nothing but wearing out the disk. The offending compaction's logging is
> {noformat}
> I0213 14:23:51.062127  9268 maintenance_manager.cc:306] P 09d6bf7a02124145b43f43cb7a667b3d: Scheduling CompactRowSetsOp(39aba63834b441e0b26d7aa5949f92ae): perf score=0.025948
> I0213 14:23:55.630163  8904 maintenance_manager.cc:501] P 09d6bf7a02124145b43f43cb7a667b3d: CompactRowSetsOp(39aba63834b441e0b26d7aa5949f92ae) complete. Timing: real 12.968s   user 10.285s    sys 0.578s Metrics: {"bytes_written":235680573,"cfile_cache_hit":32,"cfile_cache_hit_bytes":44035,"cfile_cache_miss":5750,"cfile_cache_miss_bytes":246197139,"cfile_init":24,"data dirs.queue_time_us":162819,"data dirs.run_cpu_time_us":1864,"data dirs.run_wall_time_us":1461840,"drs_written":8,"fdatasync":25,"fdatasync_us":1217638,"lbm_read_time_us":79002,"lbm_reads_lt_1ms":5846,"lbm_write_time_us":1043597,"lbm_writes_1-10_ms":2,"lbm_writes_10-100_ms":10,"lbm_writes_gt_100_ms":1,"lbm_writes_lt_1ms":30276,"mutex_wait_us":1,"num_input_rowsets":8,"rows_written":46640210,"spinlock_wait_cycles":1664,"thread_start_us":453,"threads_started":14,"wal-append.queue_time_us":49}
> {noformat}
> The situation is that about 8 16MB rowsets are calculated to compact to 4 32MB rowsets, but get written out as 8 16MB rowsets. The trick is that the rowsets *aren't* 16MB...they are really 32MB-- 16MB is the size of the base data and redos, which is what we use as the "size" for compaction purposes.
> Probably, we should use "everything" ({{Rowset::OnDiskSize()}}) for the KUDU-1400 calculations.



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