And make sure the loggers didn't fill up their disk. Sent from my phone, please pardon the typos and brevity. On Jan 28, 2013 8:54 AM, "Eric Newton" <eric.new...@gmail.com> wrote:
> What version of accumulo was this? > > So, you have evidence (such as a message in a log) that the tablet server > ran out of memory? Can you post that information? > > The ingested data should have been captured in the write-ahead log, and > recovered when the server was restarted. There should never be any data > loss. > > You should be able to ingest like this without a problem. It is a basic > test. "Hold time" is the mechanism by which ingest is pushed back so that > the tserver can get the data written to disk. You should not have to > manually back off. Also, the tserver dynamically changes the point at > which it flushes data from memory, so you should see less and less hold > time. > > The garbage collector cannot run if the METADATA table is not online, or > has an inconsistent state. > > You are probably seeing a lower number of tablets because not all the > tablets are online. They are probably offline due to failed recoveries. > > If you are running Accumulo 1.4, make sure you have stopped and restarted > all the loggers on the system. > > -Eric > > On Mon, Jan 28, 2013 at 8:28 AM, David Medinets <david.medin...@gmail.com > >wrote: > > > I had a plain Java program, single-threaded, that read an HDFS > > Sequence File with fairly small Sqoop records (probably under 200 > > bytes each). As each record was read a Mutation was created, then > > written via Batch Writer to Accumulo. This program was as simple as it > > gets. Read a record, Write a mutation. The Row Id used YYYYMMDD (a > > date) so the ingest targeted one tablet. The ingest rate was over 150 > > million entries for about 19 hours. Everything seemed fine. Over 3.5 > > Billion entries were written. Then the nodes ran out of memory and > > Accumulo nodes went dead. 90% of the server was lost. And data poofed > > out of existence. Only 800M entries are visible now. > > > > We restarted the data node processes and the cluster has been running > > garbage collection for over 2 days. > > > > I did not expect this simple approach to cause an issue. From looking > > at the logs file, I think that at least two compactions were being run > > while still ingested those 176 million entries per hour. The hold > > times started rising and eventually the system simply ran out of > > memory. I have no certainty about this explanation though. > > > > My current thinking is to re-initialize Accumulo and find some way to > > programatically monitoring the hold time. The add a delay to the > > ingest process whenever the hold time rises over 30 seconds. Does that > > sound feasible? > > > > I know there are other approaches to ingest and I might give up this > > method and use another. I was trying to get some kind of baseline for > > analysis reasons with this approach. > > >
