Sorry if this is a duplicate - I was having mailer problems last night: > Assuming their were no further writes, running repair or using CL all should > have fixed it. > > Can you describe the inconsistency between runs?
Sure. The job output is generated by a single reducer and consists of a list of key/value pairs where the key is the row key of the original table, and the value is the total count of all columns in the row. Each run produces a file with a different size, and running a diff against various output file pairs displays rows that only appear in one file, or rows with the same key but different counts. What seems particularly hard to explain is the behavior after setting CL to ALL, where the results eventually become reproducible (making it hard to place the blame on my trivial mapper/reducer implementations) but only after about half a dozen runs. And once reaching this state, setting CL to QUORUM results in additional inconsistent results. I can say with certainty that there were no other writes. I'm the sole developer working with the CF in question. I haven't seen behavior like this before, though I don't have a tremendous amount of experience. But this is the first time I've tried to use the wide-row support, which makes me a little suspicious. The wide-row support is not very well documented, so maybe I'm doing something wrong there in ignorance. Brian > > Cheers > > ----------------- > Aaron Morton > Freelance Cassandra Developer > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > On 8/01/2013, at 2:16 AM, Brian Jeltema <brian.jelt...@digitalenvoy.net> > wrote: > >> I need some help understanding unexpected behavior I saw in some recent >> experiments with Cassandra 1.1.5 and Hadoop 1.0.3: >> >> I've written a small map/reduce job that simply counts the number of columns >> in each row of a static CF (call it Foo) >> and generates a list of every row and column count. A relatively small >> fraction of the rows have a large number >> of columns; worst case is approximately 36 million. So when I set up the >> job, I used wide-row support: >> >> ConfigHelper.setInputColumnFamily(job.getConfiguration(), "fooKS", >> "Foo", WIDE_ROWS); // where WIDE_ROWS == true >> >> When I ran this job using the default CL (1) I noticed that the results >> varied from run to run, which I attributed to inconsistent >> replicas, since Foo was generated with CL == 1 and the RF == 3. >> >> So I ran repair for that CF on every node. The cassandra log on every node >> contains lines similar to: >> >> INFO [AntiEntropyStage:1] 2013-01-05 20:38:48,605 AntiEntropyService.java >> (line 778) [repair #e4a1d7f0-579d-11e2-0000-d64e0a75e6df] Foo is fully synced >> >> However, repeated runs were still inconsistent. Then I set CL to ALL, which >> I presumed would always result in identical >> output, but repeated runs initially continued to be inconsistent. However, I >> noticed that the results seemed to >> be converging, and after several runs (somewhere between 4 and 6) I finally >> was producing identical results on every run. >> Then I set CL to QUORUM, and again generated inconsistent results. >> >> Does this behavior make sense? >> >> Brian >
