[KUDU-3406] CompactRowSetsOp can allocate much more memory than specified by the hard memory limit

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.10.0, 1.10.1, 1.11.0, 1.12.0, 1.11.1, 1.13.0, 1.14.0, 1.15.0, 1.16.0
• Fix Version/s: 1.17.0
• Component/s: master, tserver
• Labels: compaction stability
• Assignee: Ashwani Raina
• Reporter: Alexey Serbin
• Created: 13/Oct/22 04:38
• Updated: 17/Jan/23 16:12
• Resolved: 20/Dec/22 22:41

Description

In some scenarios, rowsets can accumulate a lot of data, so kudu-master and kudu-tserver processes grow far beyond the hard memory limit (controlled by the --memory_limit_hard_bytes flag) when running CompactRowSetsOp. In some cases, a Kudu server process consumes all the available memory, so that the OS might invoke the OOM killer.

At this point I'm not yet sure about the exact versions affected, and what leads to accumulating so much data in flushed rowsets, but I know that 1.13, 1.14, 1.15 and 1.16 are affected. It's also not clear whether the actual regression is in allowing the flushed rowsets growing that big.

There is a reproduction scenario for this bug with kudu-master using the real data from the fields. With that data, kudu fs list reveals a rowset with many UNDOs: see the attached fs_list.before file. When starting kudu-master with the data, the process memory usage eventually peaked with about 25GByte of RSS while running CompactRowSetsOp, and then the RSS eventually subsides down to about 200MByte once the CompactRowSetsOp is completed.

I also attached several SVG files generated by the TCMalloc's pprof from the memory profile snapshots output by kudu-master when configured to dump allocation stats every 512 MBytes. I generated the SVG reports for profiles attributed to the highest memory usage:

Dumping heap profile to /opt/tmp/master/nn1/profile.0270.heap (24573 MB currently in use)
Dumping heap profile to /opt/tmp/master/nn1/profile.0283.heap (64594 MB allocated cumulatively, 13221 MB currently in use)
Dumping heap profile to /opt/tmp/master/nn1/profile.0296.heap (77908 MB allocated cumulatively, 12110 MB currently in use)
Dumping heap profile to /opt/tmp/master/nn1/profile.0308.heap (90197 MB allocated cumulatively, 12406 MB currently in use)
Dumping heap profile to /opt/tmp/master/nn1/profile.0332.heap (114775 MB allocated cumulatively, 23884 MB currently in use)
Dumping heap profile to /opt/tmp/master/nn1/profile.0344.heap (127064 MB allocated cumulatively, 12648 MB currently in use)

The report from the compaction doesn't look like anything extraordinary (except for the duration):

I20221012 10:45:49.684247 101750 maintenance_manager.cc:603] P 68dbea0ec022440d9fc282099a8656cb: CompactRowSetsOp(00000000000000000000000000000000) complete. Timing: real 522.617s     user 471.783s   sys 46.588s Metrics: {"bytes_written":1665145,"cfile_cache_hit":846,"cfile_cache_hit_bytes":14723646,"cfile_cache_miss":1786556,"cfile_cache_miss_bytes":4065589152,"cfile_init":7,"delta_iterators_relevant":1558,"dirs.queue_time_us":220086,"dirs.run_cpu_time_us":89219,"dirs.run_wall_time_us":89163,"drs_written":1,"fdatasync":15,"fdatasync_us":150709,"lbm_read_time_us":11120726,"lbm_reads_1-10_ms":1,"lbm_reads_lt_1ms":1786583,"lbm_write_time_us":14120016,"lbm_writes_1-10_ms":3,"lbm_writes_lt_1ms":894069,"mutex_wait_us":108,"num_input_rowsets":5,"rows_written":4043,"spinlock_wait_cycles":14720,"thread_start_us":741,"threads_started":9,"wal-append.queue_time_us":307}

Issue Links

• relates to: KUDU-3407 MM: Give a chance to do other OP while server is under memory pressure