Hi Sungwoo, I tend to agree - for a new system, I would probably not go that route, as Spark on Kubernetes is getting there and can do a lot already. Issue I mentioned before can be fixed with proper node fencing - it is a typical stateful set problem Kubernetes has without fencing - node goes down, k8s refuses to relocate stateful set pod because it did not get confirmation that old pod was shut down or not, since lack of communication != shut down - it can be split brain too. Since it operates on "at most one" principle - it will not allow 2nd pod up.
But keeping the 2nd layer of resource abstraction has its pluses as well. >From k8s perspective you allocate memory/cpu as a block to the entire YARN/Spark, making the allocation easier. In the end - ability to support Spark 1.6, MR, Spark 2.4 and Spark 3.1 jobs in one system is what made it for us. It also makes it easier when you want full data locality with shortcut HDFS reads. Since as far as I know Spark on Kubernetes stopped talking about that - and in my experience data locality can speed up Spark by large factor. Sincerely, Leszek Reimus On Fri, Sep 30, 2022 at 2:25 AM Sungwoo Park <glap...@gmail.com> wrote: > Hi Leszek, > > For running YARN on Kubernetes and then running Spark on YARN, is there a > lot of overhead for maintaining YARN on Kubernetes? I thought people > usually want to move from YARN to Kubernetes because of the overhead of > maintaining Hadoop. > > Thanks, > > --- Sungwoo > > > On Fri, Sep 30, 2022 at 1:37 PM Leszek Reimus <leszek.rei...@gmail.com> > wrote: > >> Hi Everyone, >> >> To add my 2 cents here: >> >> Advantage of containers, to me, is that it leaves the host system >> pristine and clean, allowing standardized devops deployment of hardware for >> any purpose. Way back before - when using bare metal / ansible, reusing hw >> always involved full reformat of base system. This alone is worth the ~1-2% >> performance tax cgroup containers have. >> >> Advantage of kubernetes is more on the deployment side of things. Unified >> deployment scripts that can be written by devs. Same deployment yaml (or >> helm chart) can be used on local Dev Env / QA / Integration Env and finally >> Prod (with some tweaks). >> >> Depending on the networking CNI, and storage backend - Kubernetes can >> have a very close to bare metal performance. In the end it is always a >> trade-off. You gain some, you pay with extra overhead. >> >> I'm running YARN on kubernetes and mostly run Spark on top of YARN (some >> legacy MapReduce jobs too though) . Finding it much more manageable to >> allocate larger memory/cpu chunks to yarn pods and then have run >> auto-scaler to scale out YARN if needed; than to manage individual >> memory/cpu requirements on Spark on Kubernetes deployment. >> >> As far as I tested, Spark on Kubernetes is immature when reliability is >> concerned (or maybe our homegrown k8s does not do fencing/STONITH well >> yet). When a node dies / goes down, I find executors not getting >> rescheduled to other nodes - the driver just gets stuck for the executors >> to come back. This does not happen on YARN / Standalone deployment (even >> when ran on same k8s cluster) >> >> Sincerely, >> >> Leszek Reimus >> >> >> >> >> On Thu, Sep 29, 2022 at 7:06 PM Gourav Sengupta < >> gourav.sengu...@gmail.com> wrote: >> >>> Hi, >>> >>> dont containers finally run on systems, and the only advantage of >>> containers is that you can do better utilisation of system resources by >>> micro management of jobs running in it? Some say that containers have their >>> own binaries which isolates environment, but that is a lie, because in a >>> kubernetes environments that is running your SPARK jobs you will have the >>> same environment for all your kubes. >>> >>> And as you can see there are several other configurations, disk >>> mounting, security, etc issues to handle as an overhead as well. >>> >>> And the entire goal of all those added configurations is that someone in >>> your devops team feels using containers makes things more interesting >>> without any real added advantage to large volume jobs. >>> >>> But I may be wrong, and perhaps we need data, and not personal attacks >>> like the other person in the thread did. >>> >>> In case anyone does not know EMR does run on containers as well, and in >>> EMR running on EC2 nodes you can put all your binaries in containers and >>> use those for running your jobs. >>> >>> Regards, >>> Gourav Sengupta >>> >>> On Thu, Sep 29, 2022 at 7:46 PM Vladimir Prus <vladimir.p...@gmail.com> >>> wrote: >>> >>>> Igor, >>>> >>>> what exact instance types do you use? Unless you use local instance >>>> storage and have actually configured your Kubernetes and Spark to use >>>> instance storage, your 30x30 exchange can run into EBS IOPS limits. You can >>>> investigate that by going to an instance, then to volume, and see >>>> monitoring charts. >>>> >>>> Another thought is that you're essentially giving 4GB per core. That >>>> sounds pretty low, in my experience. >>>> >>>> >>>> >>>> On Thu, Sep 29, 2022 at 9:13 PM Igor Calabria <igor.calab...@gmail.com> >>>> wrote: >>>> >>>>> Hi Everyone, >>>>> >>>>> I'm running spark 3.2 on kubernetes and have a job with a decently >>>>> sized shuffle of almost 4TB. The relevant cluster config is as follows: >>>>> >>>>> - 30 Executors. 16 physical cores, configured with 32 Cores for spark >>>>> - 128 GB RAM >>>>> - shuffle.partitions is 18k which gives me tasks of around 150~180MB >>>>> >>>>> The job runs fine but I'm bothered by how underutilized the cluster >>>>> gets during the reduce phase. During the map(reading data from s3 and >>>>> writing the shuffle data) CPU usage, disk throughput and network usage is >>>>> as expected, but during the reduce phase it gets really low. It seems the >>>>> main bottleneck is reading shuffle data from other nodes, task statistics >>>>> reports values ranging from 25s to several minutes(the task sizes are >>>>> really close, they aren't skewed). I've tried increasing >>>>> "spark.reducer.maxSizeInFlight" and >>>>> "spark.shuffle.io.numConnectionsPerPeer" and it did improve performance by >>>>> a little, but not enough to saturate the cluster resources. >>>>> >>>>> Did I miss some more tuning parameters that could help? >>>>> One obvious thing would be to vertically increase the machines and use >>>>> less nodes to minimize traffic, but 30 nodes doesn't seem like much even >>>>> considering 30x30 connections. >>>>> >>>>> Thanks in advance! >>>>> >>>>> >>>> >>>> -- >>>> Vladimir Prus >>>> http://vladimirprus.com >>>> >>> >> >> -- >> -------------- >> "It is the common fate of the indolent to see their rights become a prey >> to the active. The condition upon which God hath given liberty to man is >> eternal vigilance; which condition if he break, servitude is at once the >> consequence of his crime and the punishment of his guilt." - John Philpot >> Curran: Speech upon the Right of Election, 1790. >> > -- -------------- "It is the common fate of the indolent to see their rights become a prey to the active. The condition upon which God hath given liberty to man is eternal vigilance; which condition if he break, servitude is at once the consequence of his crime and the punishment of his guilt." - John Philpot Curran: Speech upon the Right of Election, 1790.
