Have you ever tuned a Spark, Hive or Pig job? If yes, then you must know that it is a never ending cycle of executing the job, observing the running job, making sense out of hundreds of metrics and then re-running it with the better parameters. Imagine doing this for tens of thousands of jobs. Performance optimization at this scale manually is tedious, requires significant expertise and results into wasting a lot of resources to do the same task again and again.

As Hadoop/Spark is the natural choice for any data processing with many naive users, it becomes important to develop a tool to automatically tune Hadoop/Spark jobs. At LinkedIn we tried to solve the problem using Dr. Elephant, an open-sourced self-serve performance monitoring and tuning tool for Hadoop and Spark, used at LinkedIn and various other companies. While it has proven to be very successful, it relies on the developers’ initiative to check and apply the recommendation manually. It also expects some expertise from developers to arrive at the optimal configuration from the recommendations.

In this talk we will discuss TuneIn, an auto tuning framework developed on top of Dr. Elephant. We will describe how we are using an iterative approach of optimization to find optimal parameters. We will discuss the various optimization algorithms we tried and why we found Particle Swarm Optimization algorithm to give best results. We will talk about how we avoided using any extra execution and tuned the jobs during their regular scheduled execution. We go into detail on techniques employed to ensure faster convergence and zero failed executions while tuning. We will showcase how we achieved more than 50% gain in resource usage by tuning a small set of parameters. We will also talk about the lessons learned and the future roadmap.




1.TuneIn: How to get your jobs tuned while sleeping Manoj Kumar Arpan Agrawal Pralabh Kumar Senior Software Engineer Software Engineer Senior Software Engineer LinkedIn LinkedIn LinkedIn

2. OUR VISION Create economic opportunity for every member of the global workforce 2

3. OUR MISSION Connect the world’s professionals to make them more productive and successful 3

4.Agenda • Why TuneIn? • How does TuneIn work? • Architecture and framework features • Road ahead 4

5.Grid Scale at LinkedIn 2008 2018 1 cluster 10+ clusters 20 nodes 1000s of nodes 5 users 1000s of active users MapReduce Pig, Hive, Spark, etc. Few workflows 10000s workflows 5

6.Typical Conversations Hey, this Spark I will tune it to job is running improve the slowly. run time. Manager Developer 6

7.Typical Conversations We have found some jobs which I will ask my team are consuming to tune those jobs high resources on to reduce the the cluster. resource usage. Hadoop Admin Manager 7

8.Typical Conversations Is there a way we can get this I will try to tune daily report 30 it to reduce the minutes early? run time. Client Developer 8

9.Why Tuning? • Optimal parameter configuration: – leads to better cluster utilization and thus savings – reduces the execution time • Default configuration is not always optimal 9

10.Manual Tuning PHASE 3 PHASE 1 Come up with next Execute parameter set Manual Job Tuning Process PHASE 2 Observe the Execution Metrics 10

11.Dr. Elephant: Heuristic based tuning • Suggests tuning recommendations PHASE 3 PHASE 1 based on pre-defined heuristics Come up with next Execute parameter set Heuristics Job • No need to worry about the Based Manual hundreds of counters and Tuning parameters • Relies on user’s initiative to use the recommendations PHASE 2 • Expects some user expertise Look at the Dr. Elephant recommendations 11



14.Why Auto Tuning? • 10000s of jobs to tune • Increases developer productivity • Tunes without any extra effort • No expertise is expected • Option of which objective function to tune for – resource usage – execution time etc. 14

15.Let’s auto tune! Photo: memecreator.org 15

16.TuneIn • Framework to automatically tune recurring Hadoop and Spark jobs • Iteratively tries to reach the optimal configuration • Results : 20-35% reduction in Resource Usage 16

17.Particle Swarm Optimization (PSO) [1] • Mimics the behavior of swarm of birds searching food • Starts optimization by introducing particles at random positions in the search space Source: Wikipedia Particle Swarm Optimization by J. Kennedy et al., https://ieeexplore.ieee.org/document/488968/ 17

18.PSO (contd.) • Points of attraction: personal and global best known positions • Particles converge to the region with the minimum cost function value Source: Wikipedia 18

19.Why PSO? • Cost function is noisy – PSO is gradient free and robust against noise [3] • Spark and Hadoop are complex systems – PSO is a metaheuristic black box optimization algorithm • Fastest convergence K. E. Parsopoulos et al., “Particle Swarm Optimizer in Noisy and Continuously Changing Environments,” in Artificial Intelligence and Soft Computing 19

20.PSO Details [2] • Swarm size of 3 gives the best result – neither too small to cover the search space – nor too big to do many first iteration random searches • Good starting point is important to guide the swarm Optimizing Hadoop parameter settings with gene expression programming guided PSO by Mukhtaj Khan et al. 20

21.Cost function • Resource usage per unit input ∑"#$%&'$()* +,-./0-12 314,25 ∗ +,-./0-12 78.041 9,./: ;-8<. =0>1 • Approximately input size invariant 21

22.Search Space • Parameters being tuned constitutes Param 3 the search space • Depends on the cost function metric Param 2 Param 1 22

23.Search Space Cost function: Resource Usage Pig Spark mapreduce.map.memory.mb spark.executor.memory mapreduce.reduce.memory.mb spark.executor.cores mapreduce.task.io.sort.mb spark.memory.fraction mapreduce.task.io.sort.factor spark.yarn.executor.memoryOverhead 23

24.Search Space Reduction • Important to prevent failures • Speeds up convergence • Boundary parameter values – e.g. !"#$%. '(')*+,$. ),$'! ∈ 1, 10 • Parameter interdependent constraints – Captures the interdependence among the parameters – e.g. 1#"$'2*)'. +#!%. 3,. !,$+. 14 < 0.60 ∗ 1#"$'2*)'. 1#". 1'1,$8. 14 24

25.Search Space Reduction • Different jobs can have different optimal boundary values • Boundary values are tightened on the basis of previous job execution counters 25

26. Avoiding over optimization • Undesirable to squeeze memory so much that execution time shoots up significantly • Updated cost function: ∑"#$%&'$()* +,-./0-12 314,25 ∗ +,-./0-12 78.041 + @1-/:.5 9,./: ;-8<. =0>1 Photo: Ian Burt 26

27.Convergence • No theoretical bound on the steps to converge • Practically converges in 20 job executions • TuneIn gets turned off for the job automatically on convergence 27

28.Results Job type Metric Reduction range Spark Resource Usage 30 - 40 % per job Pig Resource Usage 20 - 35 % per job 28

29.Architecture Dr. Elephant 1. Get Parameters Rest API 2. Mapper memory: 2048 Sort Buffer: 200 3. Submit Job 4. Fetch Metrics MapReduce/Spark TuneIn Framework Fetchers 29

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