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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.
