I think it is an OOME. Here's the debug log file, showing a clear descend from 189MB free to 52kB free memory before manually restarting the tserver 4 minutes later. Looks like I lost the .err files for now; would need to reproduce the crash to get them again.
2015-03-26 08:34:01,242 [tserver.TabletServer] DEBUG: gc ParNew=26.24(+0.01) secs ConcurrentMarkSweep=0.13(+0.00) secs* freemem=189,300,488(-330,224) *totalmem=259,522,560 2015-03-26 08:34:01,549 [tserver.TabletServer] DEBUG: ScanSess tid 127.0.0.1:55823 6r 374,161 entries in 2.98 secs, nbTimes = [1 69 3.27 375] 2015-03-26 08:34:01,842 [Audit ] INFO : operation: permitted; user: root; client: 127.0.0.1:55823; 2015-03-26 08:34:01,842 [Audit ] INFO : operation: permitted; user: root; client: 127.0.0.1:55823; 2015-03-26 08:34:01,844 [tserver.TabletServer] DEBUG: ScanSess tid 127.0.0.1:55823 !0 5 entries in 0.00 secs, nbTimes = [1 1 1.00 1] 2015-03-26 08:34:03,034 [tserver.TabletServer] DEBUG: Got getScans message from user: !SYSTEM 2015-03-26 08:34:03,091 [tserver.TabletServer] DEBUG: MultiScanSess 127.0.0.1:38998 2 entries in 0.00 secs (lookup_time:0.00 secs tablets:1 ranges:1) 2015-03-26 08:34:04,507 [tserver.TabletServer] DEBUG: gc ParNew=26.38(+0.14) secs ConcurrentMarkSweep=0.99(+0.86) secs *freemem=44,246,264(-145,384,448) *totalmem=259,522,560 2015-03-26 08:34:05,963 [tserver.TabletServer] DEBUG: ScanSess tid 127.0.0.1:55017 !0 0 entries in 0.00 secs, nbTimes = [2 2 2.00 1] 2015-03-26 08:34:05,966 [tserver.TabletServer] DEBUG: gc ParNew=26.38(+0.00) secs ConcurrentMarkSweep=2.25(+1.26) secs *freemem=6,657,016(-182,973,696) *totalmem=259,522,560 2015-03-26 08:34:07,549 [tserver.TabletServer] DEBUG: gc ParNew=26.38(+0.00) secs ConcurrentMarkSweep=3.73(+1.48) secs *freemem=439,152(-189,191,560) *totalmem=259,522,560 2015-03-26 08:34:08,284 [tserver.TabletServer] DEBUG: Got getScans message from user: !SYSTEM *2015-03-26 08:34:10,469 [tserver.TabletServer] WARN : Running low on memory* 2015-03-26 08:34:10,470 [tserver.TabletServer] DEBUG: gc ParNew=26.38(+0.00) secs ConcurrentMarkSweep=6.63(+2.90) secs *freemem=52,816(-189,577,896) *totalmem=259,522,560 2015-03-26 08:34:14,623 [tserver.TabletServer] DEBUG: Got getScans message from user: !SYSTEM 2015-03-26 08:34:17,382 [tserver.TabletServer] DEBUG: ScanSess tid 127.0.0.1:55017 !0 0 entries in 5.04 secs, nbTimes = [4,972 4,972 4,972.00 1] 2015-03-26 08:34:24,674 [tserver.TabletServer] DEBUG: Got getScans message from user: !SYSTEM 2015-03-26 08:34:35,716 [cache.LruBlockCache] DEBUG: Cache Stats: Sizes: Total=23.286858MB (24418040), Free=6.7131424MB (7039240), Max=30.0MB (31457280), Counts: Blocks=7750, Access=125628, Hit=102578, Miss=23050, Evictions=25, Evicted=15299, Ratios: Hit Ratio=81.65218234062195%, Miss Ratio=18.34782063961029%, Evicted/Run=611.9600219726562, Duplicate Reads=1 *2015-03-26 08:38:37,256 [server.Accumulo] INFO : tserver starting* On Thu, Apr 2, 2015 at 6:34 PM, Josh Elser <josh.el...@gmail.com> wrote: > That seems perfectly reasonable to me, IMO. I'm surprised to hear the > tserver crashed. > > Taking a quick glance at the code, it looks like this would be a good > place to do some optimization in the BatchScanner's impl > (TabletServerBatchReaderImpl). The BatchScanner will bin the ranges to the > tablets and the servers hosting those tablets. Normally, this would be > spread out, but, in your single server case, all 1M rows would all go to a > single TabletServer in one RPC call. > > I'm guessing a good optimization here would be to check the size of a > batch of Ranges for a single tabletserver, and when above a certain > threshold, split the batch in half and try to reprocess each half (the > recursion would naturally keep splitting until we get down to some > high-watermark). > > Point being, if your client VM constructed the Ranges without issue, the > BatchScanner impl should be smart enough to not knock over a TabletServer. > > What was the reason the tserver died? OOME? Was there anything at the end > of the log files or in the .out/.err files? > > - Josh > > > Dylan Hutchison wrote: > >> A friend of mine has a use case where he wants to scan ~1M individual >> rows, scattered across a ~15GB table. He performed the following: >> >> 1. Gather a List of Range objects, each one a singleton range spanning >> an entire row. >> 2. Create a BatchScanner with one read thread. >> 3. Set the ranges via BatchScanner.setRanges() >> 4. Start iterating through the scanner. >> >> Performing these steps crashed the TabletServer for my friend (haven't >> had time to verify it myself yet). We're using a single-node standalone >> 1.6.1 Accumulo instance. >> >> Is this a bad way to use Accumulo? I advised my friend to batch the >> reads into groups of ~10k ranges and see if that helps. I wanted to >> check with the community and see if we're doing something weird. If the >> behavior should have worked, I can try to put together a test case >> reproducing it, that creates a table with many entries and then scans >> with many ranges. >> >> Thanks, >> Dylan Hutchison >> >>
