Hi again, On Wed, Jan 21, 2015 at 4:53 PM, Tobias Pfeiffer <t...@preferred.jp> wrote: > > On Wed, Jan 21, 2015 at 4:46 PM, Akhil Das <ak...@sigmoidanalytics.com> > wrote: > >> How about using accumulators >> <http://spark.apache.org/docs/1.2.0/programming-guide.html#accumulators>? >> > > As far as I understand, they solve the part of the problem that I am not > worried about, namely increasing the counter. I was more worried about > getting that counter/accumulator value back to the executors. >
Uh, I may have been a bit quick here... So I had this one working: var totalNumberOfItems = 0L // update the keys of the stream data val globallyIndexedItems = inputStream.map(keyVal => (keyVal._1 + totalNumberOfItems, keyVal._2)) // increase the number of total seen items inputStream.foreachRDD(rdd => { totalNumberOfItems += rdd.count }) and used the dstream.foreachRDD(rdd => someVar += rdd.count) pattern at a number of places. Then, however, I added a dstream.transformWith(otherDStream, func) call, which somehow changed the order in which the DStreams are computed. In particular, suddenly some of my DStream values were computed before the foreachRDD calls that set the proper variables were executed, which lead to completely unpredictable behavior. So especially when looking at the existence of spark.streaming.concurrentJobs, I suddenly feel like none of DStream computations done on executors should depend on the ordering of output operations done on the driver. (And I am afraid this includes accumulator updates.) Thinking about this, I feel I don't even know how I can realize a globally (over the lifetime of my stream) increasing ID in my DStream. Do I need something like val counts: DStream[(Int, Long)] = stream.count().map((1, _)).updateStateByKey(...) with a pseudo-key just to keep a tiny bit of state from one interval to the next? Really thankful for any insights, Tobias