Thanks for this tip. I ran it in yarn-client mode with driver-memory = 4G and took a dump once the heap got close to 4G.
num #instances #bytes class name ---------------------------------------------- 1: 446169 3661137256 [J 2: 2032795 222636720 [C 3: 8992 57717200 [B 4: 2031653 48759672 java.lang.String 5: 920263 22086312 scala.collection.immutable.$colon$colon 6: 156233 20495936 [Ljava.lang.Object; So, somehow there’s 3.5G worth of Long arrays in there, each one apparently using about 8k of heap. Digging into the instances of these reveals that the vast majority of these are identical long[] of size 1024 with each element set to -1 (8,216 bytes). I’m at a bit of a loss as to what this could be. Any ideas how I can understand what’s happening? Andrew From: Ashish Rangole Date: Thursday, 27 August 2015 15:24 To: Andrew Rowson Cc: user, "ewan.le...@realitymine.com" Subject: Re: Driver running out of memory - caused by many tasks? I suggest taking a heap dump of driver process using jmap. Then open that dump in a tool like Visual VM to see which object(s) are taking up heap space. It is easy to do. We did this and found out that in our case it was the data structure that stores info about stages, jobs and tasks. There can be other reasons as well, of course. On Aug 27, 2015 4:17 AM, <andrew.row...@thomsonreuters.com> wrote: I should have mentioned: yes I am using Kryo and have registered KeyClass and ValueClass. I guess it’s not clear to me what is actually taking up space on the driver heap - I can’t see how it can be data with the code that I have. On 27/08/2015 12:09, "Ewan Leith" <ewan.le...@realitymine.com> wrote: >Are you using the Kryo serializer? If not, have a look at it, it can save a >lot of memory during shuffles > >https://spark.apache.org/docs/latest/tuning.html > >I did a similar task and had various issues with the volume of data being >parsed in one go, but that helped a lot. It looks like the main difference >from what you're doing to me is that my input classes were just a string and a >byte array, which I then processed once it was read into the RDD, maybe your classes are memory heavy? > > >Thanks, >Ewan > >-----Original Message----- >From: andrew.row...@thomsonreuters.com >[mailto:andrew.row...@thomsonreuters.com] >Sent: 27 August 2015 11:53 >To: user@spark.apache.org >Subject: Driver running out of memory - caused by many tasks? > >I have a spark v.1.4.1 on YARN job where the first stage has ~149,000 tasks >(it’s reading a few TB of data). The job itself is fairly simple - it’s just >getting a list of distinct values: > > val days = spark > .sequenceFile(inputDir, classOf[KeyClass], classOf[ValueClass]) > .sample(withReplacement = false, fraction = 0.01) > .map(row => row._1.getTimestamp.toString("yyyy-MM-dd")) > .distinct() > .collect() > >The cardinality of the ‘day’ is quite small - there’s only a handful. However, >I’m frequently running into OutOfMemory issues on the driver. I’ve had it fail >with 24GB RAM, and am currently nudging it upwards to find out where it works. >The ratio between input and shuffle write in the distinct stage is about 3TB:7MB. On a smaller dataset, it works without issue on a smaller (4GB) heap. In YARN cluster mode, I get a failure message similar to: > > Container > [pid=36844,containerID=container_e15_1438040390147_4982_01_000001] is running > beyond physical memory limits. Current usage: 27.6 GB of 27 GB physical > memory used; 29.5 GB of 56.7 GB virtual memory used. Killing container. > > >Is the driver running out of memory simply due to the number of tasks, or is >there something about the job program that’s causing it to put a lot of data >into the driver heap and go oom? If the former, is there any general guidance >about the amount of memory to give to the driver as a function of how many tasks there are? > >Andrew
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