1.
1Pivotal Confidential–Internal Use Only 1
Hadoop 2.x Configuration &
Map/Reduce Performance Tuning
Suhas Gogate, Architect Hadoop Engg
CF-Meetup, SFO (20th May 2014 )

2.
A NEW PLATFORM FOR A NEW ERA

3.
3Pivotal Confidential–Internal Use Only
About Me (https://www.linkedin.com/in/vgogate)
 Since 2008, active in Hadoop infrastructure and ecosystem components
with lead Hadoop technology based companies
– Yahoo, Netflix, Hortonworks, EMC-Greenplum/Pivotal
 Founder and PMC member/committer of the Apache Ambari project
 Contributed Apache “Hadoop Vaidya” – Performance diagnostics for M/R
 Prior to Hadoop,
– IBM Almaden Research (2000-2008), CS Software & Storage systems.
– In early days (1993) of my career, worked with a team that built first Indian
super computer, PARAM (Transputer based MPP system) at Center for
Development of Advance Computing (CDAC, Pune)

4.
4Pivotal Confidential–Internal Use Only
Agenda
 Introduction to Hadoop 2.0
– HDFS, YARN, Map/Reduce (M/R)
 Hadoop Cluster
– Hardware selection & Capacity Planning
 Key Hadoop Configuration Parameters
– Operating System, Local FS, HDFS, YARN
 Performance Tuning of M/R Applications
– Hadoop Vaidya demo (MAPREDUCE-3202)

5.
5Pivotal Confidential–Internal Use Only
Introduction to Hadoop

6.
6Pivotal Confidential–Internal Use Only
Hadoop 1.0 -> 2.0
Image Courtesy Arun Murthy, Hortonworks

7.
7Pivotal Confidential–Internal Use Only
HDFS Architecture

8.
8Pivotal Confidential–Internal Use Only
Hadoop Map/Reduce 1.0

9.
9Pivotal Confidential–Internal Use Only
Hadoop YARN 2.0 Architecture

10.
10Pivotal Confidential–Internal Use Only
Hardware selection & Capacity planning

11.
11Pivotal Confidential–Internal Use Only
Hadoop Cluster: Hardware selection
 Hadoop runs on cluster of commodity machines
– Does NOT mean unreliable & low-cost hardware
– 2008:
▪ Single/Dual socket, 1+ GHz, 4-8GB RAM, 2-4 Cores, 2-4 1TB SATA drives, 1GbE NIC
– 2014+:
▪ Dual socket 2+ GHz, 48-64GB RAM, 12-16 Cores, 12-16 1/3TB SATA drives, 2-4 bonded NICs
 Hadoop cluster comprises separate h/w profiles for,
– Master nodes
▪ More reliable & available configuration
▪ Low storage/memory requirements compared to worker/data nodes (except HDFS Name node)
– Worker nodes
▪ Not necessarily less reliable although not configured for high availability (e.g. JBOD not RAID)
▪ Resource requirements on storage, memory, CPU & network b/w are based on workload profile
See Appliance/Reference architectures from EMC/IBM/Cisco/HP/Dell etc

12.
12Pivotal Confidential–Internal Use Only
Cluster capacity planning
 Initial cluster capacity is commonly based on HDFS data size & growth projection
– Keep data compression in mind
 Cluster size
– HDFS space per node = (Raw disk space per node – 20/25% non-DFS local storage) / 3 (RF)
– Cluster nodes = Total HDFS space / HDFS space per node
 Start with balanced individual node configuration in terms of CPU/Memory/Number of disks
– Keep provision for growth as you learn more about the workload
– Guidelines for individual worker node configuration
▪ Latest generation processor(s) with 12/16 cores total, is a reasonable start
▪ 4 to 6 GB memory per core
▪ 1/1.5 disks per core
▪ 1 to 3 TB SATA disks per core
▪ 1GbE NIC
 Derive resource requirements service roles (typically Name node)
– NN -> 4-6 cores, default 2GB + 1 GB roughly every 100TB of raw disk space, 1M Objects
– RM/NN/DN -> 2GB RAM, 1 core (thumb rule)

13.
13Pivotal Confidential–Internal Use Only
Ongoing Capacity Planning
 Workload profiling
– Make sure applications running on the cluster are well tuned to utilize cluster
resources
– Gather average CPU/IO/Mem/Disk utilization stats across worker nodes
– Identify the resource bottlenecks for your workload and provision accordingly
▪ E,g, bump up more cores per node if CPU is bottleneck compared to other resources such as storage, I/O
bandwidth
▪ E.g. If memory is a bottleneck (i.e. low utilization on CPU and I/O), then add more memory per node to let
more tasks run per node.
– HDFS storage growth rate & current capacity utilization
 Latency sensitive applications
– Do planned project on-boarding
▪ Estimate resource requirement ahead of time (Capacity Calculator)
– Use Resource Scheduler
▪ Schedule the jobs to maximize the resource utilization over the time

14.
14Pivotal Confidential–Internal Use Only
Hadoop Cluster Configuration

15.
15Pivotal Confidential–Internal Use Only
Key Hadoop Cluster Configuration – OS
 Operating System (RHEL/CentOS 6.1+)
– Mount disk volumes with NOATIME (speed up reads)
– Disable transparent Huge page compaction
▪ # echo never > /sys/kernel/mm/redhat_transparent_hugepages/defrag
– Turn off caching on disk controller
– vm.swappiness = 0
– vm.overcommit_memory = 1
– vm.overcommit_ratio = 100
– net.core.somaxconn=1024 (default socket listen queue size 128)
– Choice of Linux I/O scheduler
 Local File System
– Ext3 (reliable and recommended) vs Ext4 vs XFS
– Default max open file descriptors per user (default 1K may change to 32K)
– Reduce FS reserve blocks space (default 5% -> 0% on non-os partitions)
 BIOS
– Disable BIOS power saving options may boost node performance

16.
16Pivotal Confidential–Internal Use Only
Key Hadoop Cluster Configuration - HDFS
 Use multiple disk mount points
– dfs.datanode.data.dir (use all attached disks to data node)
– dfs.namenode.name.dir (NN metadata redundancy on disk)
 DFS Block size
– 128MB (you can override it while writing new files with different block size)
 Local file system buffer
– io.file.buffer.size = 131072 (128KB)
– Io.sort.factor = 50 to 100 (number merge streams while sorting file)
 NN/DN concurrency
– dfs.namenode.handler.count (100)
– dfs.datanode.max.transfer.threads (4096)
 Datanode Failed volumes tolerated
– dfs.datanode.failed.volumes.tolerated

17.
17Pivotal Confidential–Internal Use Only
Key Hadoop Cluster Configuration - HDFS
 Short circuit read
– dfs.client.read.shortcircuit = true
– dfs.domain.socket.path
 JVM options (hadoop-env.sh)
– export HADOOP_NAMENODE_OPTS=”
▪ -Dcom.sun.management.jmxremote -Xms${dfs.namenode.heapsize.mb}m
▪ -Xmx${dfs.namenode.heapsize.mb}m
▪ -Dhadoop.security.logger=INFO,DRFAS
▪ -Dhdfs.audit.logger=INFO,RFAAUDIT
▪ -XX:ParallelGCThreads=8
▪ -XX:+UseParNewGC -XX:+UseConcMarkSweepGC
▪ -XX:+HeapDumpOnOutOfMemoryError -XX:ErrorFile=${HADOOP_LOG_DIR}/hs_err_pid%p.log
$HADOOP_NAMENODE_OPTS”
– export HADOOP_DATANODE_OPTS=”
▪ -Dcom.sun.management.jmxremote
▪ -Xms${dfs.datanode.heapsize.mb}m
▪ -Xmx${dfs.datanode.heapsize.mb}m
▪ -Dhadoop.security.logger=ERROR,DRFAS $HADOOP_DATANODE_OPTS"

18.
18Pivotal Confidential–Internal Use Only
Key Hadoop Cluster Configuration - YARN
 Use multiple disk mount points on the worker node
– yarn.nodemanager.local-dirs
– yarn.nodemanager.log-dirs
 Memory allocated for node manager containers
– yarn.nodemanager.resource.memory-mb
▪ Total memory on worker node allocated for all the containers running in parallel
– yarn.scheduler.minimum-allocation-mb
▪ Minimum memory requested for map/reduce task container.
▪ Based on CPU cores and available memory on the node, this parameter can limit number of max containers
per node
– yarn.nodemanager.maximum-allocation-mb
▪ Default to yarn.nodemanager.resource.memory-mb
– yarn.mapreduce.map.memory.mb, yarn.mapreduce.reduce.memory.mb
▪ Default values for map/reduce task container memory. User can override them through job configuration
– yarn.nodemanager.vmem-pmem-ratio = 2.1

19.
19Pivotal Confidential–Internal Use Only
Key Hadoop Cluster Configuration - YARN
 Use Yarn log aggregation
– yarn.log-aggregation-enable
 RM/NM JVM options (yarn-env.sh)
– export YARN_RESOURCEMANAGER_HEAPSIZE=2GB
– export YARN_NODEMANAGER_HEAPSIZE=2GB
– YARN_OPTS="$YARN_OPTS -server
– -Djava.net.preferIPv4Stack=true
– -XX:+UseParNewGC -XX:+UseConcMarkSweepGC
– -XX:+HeapDumpOnOutOfMemoryError
– -XX:ErrorFile=${YARN_LOG_DIR}/hs_err_pid%p.log"

20.
20Pivotal Confidential–Internal Use Only
Hadoop Configuration Advisor - Tool
 Given
– Data size, Growth rate, Workload profile, Latency/QoS requirements
 Suggests
– Capacity requirement for Hadoop cluster (reasonable starting point)
▪ Resource requirements for various services roles
▪ Hardware profiles for master/worker nodes (No specific h/w vendor )
– Cluster services topology i.e. placement of service roles to nodes
– Optimal services configuration for given hardware specs

21.
21Pivotal Confidential–Internal Use Only
Performance Tuning of M/R applications

22.
22Pivotal Confidential–Internal Use Only
Hadoop Map/Reduce - WordCount

23.
23Pivotal Confidential–Internal Use Only
Optimizing M/R applications – key features
 Speculative Execution
 Use of Combiner
 Data Compression
– Intermediate: LZO(native)/Snappy, Output: BZip2, Gzip
 Avoid map side disk spills
– io.sort.mb
 Increased replication factor for out-of-band Hdfs access
 Distributed cache
 Map output partitioner
 Appropriate granularity for M/R tasks
– Mapreduce.map.minsplitsize
– Mapreduce.map.maxsplitsize
– Optimal number of reducers

24.
24Pivotal Confidential–Internal Use Only
Performance Benchmark – Teragen
 Running teragen out-of-box will not utilize the cluster hardware
resources
 Determine number of map tasks to run on each node to exploit
max I/O bandwidth
– Depends on number of disks on each node
 Example
– 10 nodes, 5 disks/node, per node memory for m/r tasks 50GB
– Hadoop jar hadoop-mapreduce-examples-2.x.x.jar teragen
– -Dmapred.map.tasks=50 -Dmapreduce.map.memory.mb=10GB
– 10000000000 /teragenoutput

25.
25Pivotal Confidential–Internal Use Only
Hadoop M/R Benchmark – Terasort
 Terasort Example
hadoop jar hadoop-mapreduce/hadoop-mapreduce-examples-2.x.x.jar terasort
– -Ddfs.replication=1 -Dmapreduce.task.io.sort.mb=500
– -Dmapreduce.map.sort.spill.percent=0.9
– -Dmapreduce.reduce.shuffle.parallelcopies=10
– -Dmapreduce.reduce.shuffle.memory.limit.percent=0.1
– -Dmapreduce.reduce.shuffle.input.buffer.percent=0.95
– -Dmapreduce.reduce.input.buffer.percent=0.95
– -Dmapreduce.reduce.shuffle.merge.percent=0.95
– -Dmapreduce.reduce.merge.inmem.threshold=0
– -Dmapreduce.job.speculative.speculativecap=0.05
– -Dmapreduce.map.speculative=false
– -Dmapreduce.reduce.speculative=false -Dmapreduce.job.jvm.numtasks=-1

26.
26Pivotal Confidential–Internal Use Only
Hadoop M/R Benchmark – Terasort
– -Dmapreduce.job.reduces=84 -Dmapreduce.task.io.sort.factor=100
– -Dmapreduce.map.output.compress=true
– -Dmapreduce.map.output.compress.codec=
▪ org.apache.hadoop.io.compress.SnappyCodec
– -Dmapreduce.job.reduce.slowstart.completedmaps=0.4
– -Dmapreduce.reduce.merge.memtomem.enabled=false
– -Dmapreduce.reduce.memory.totalbytes=12348030976
– -Dmapreduce.reduce.memory.mb=12288
– -Dmapreduce.reduce.java.opts=
▪ "-Xms11776m -Xmx11776m -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -
XX:+CMSIncrementalPacing -XX:ParallelGCThreads=4"
– -Dmapreduce.map.memory.mb=4096
– -Dmapreduce.map.java.opts="-Xmx1356m"
– /terasort-input /terasort-output

27.
27Pivotal Confidential–Internal Use Only
Hadoop Vaidya: Performance diagnostic tool

28.
28Pivotal Confidential–Internal Use Only
Hadoop Vaidya: Rule based performance diagnostic tool
• Rule based performance diagnosis of M/R jobs
– Set of pre-defined diagnostic rules
– Diagnostic rules execution against job config &
Job History logs
– Targeted advice for discovered problems
• Extensible framework
– You can add your own rules,
• Based on a rule template and published
job counters
– Write complex rules using existing simpler
rules
Vaidya: An expert (versed in his own
profession , esp. in medical science) ,
skilled in the art of healing , a physician

29.
29Pivotal Confidential–Internal Use Only
Hadoop Vaidya: Diagnostic Test Rule
<DiagnosticTest>
<Title>Balanaced Reduce Partitioning</Title>
<ClassName>
org.apache.hadoop.vaidya.postexdiagnosis.tests.BalancedReducePartitioning
</ClassName>
<Description>
This rule tests as to how well the input to reduce tasks is balanced
</Description>
<Importance>High</Importance>
<SuccessThreshold>0.40</SuccessThreshold>
<Prescription>advice</Prescription>
<InputElement>
<PercentReduceRecords>0.85</PercentReduceRecords>
</InputElement>
</DiagnosticTest>

30.
30Pivotal Confidential–Internal Use Only
Hadoop Vaidya: Report Element
<TestReportElement>
<TestTitle>Balanaced Reduce Partitioning</TestTitle>
<TestDescription>
This rule tests as to how well the input to reduce tasks is balanced
</TestDescription>
<TestImportance>HIGH</TestImportance>
<TestResult>POSITIVE(FAILED)</TestResult>
<TestSeverity>0.69</TestSeverity>
<ReferenceDetails>
* TotalReduceTasks: 4096
* BusyReduceTasks processing 0.85% of total records: 3373
* Impact: 0.70
</ReferenceDetails>
<TestPrescription>
* Use the appropriate partitioning function
* For streaming job consider following partitioner and hadoop config parameters
* org.apache.hadoop.mapred.lib.KeyFieldBasedPartitioner
* -jobconf stream.map.output.field.separator, -jobconf stream.num.map.output.key.fields
</TestPrescription>
</TestReportElement>

31.
31Pivotal Confidential–Internal Use Only
Hadoop Vaidya: Example Rules
 Balanced Reduce Partitioning
– Check if intermediate data is well partitioned among reducers.
 Map/Reduce tasks reading HDFS files as side effect
– Checks if HDFS files are being read as side effect and causing the access bottleneck across
map/reduce tasks
 Percent Re-execution of Map/Reduce tasks
 Granularity of Map/Reduce task execution
 Map tasks data locality
– This rule detects % data locality for Map tasks
 Use of Combiner & Combiner efficiency
– Checks if there is a potential in using combiner after map stage
 Intermediate data compression
– Checks if intermediate data is compressed to lower the shuffle time

32.
32Pivotal Confidential–Internal Use Only
Hadoop Vaidya: Demo
Thank you!
• For Hadoop Vaidya demo
• Download Pivotal HD single node VM
(https://network.gopivotal.com/products/pivotal-hd)
• Run M/R job
• After job completed, go Resource Manager UI
• Select Job History
• To look at the diagnostic report click on “Vaidya Report” link in left
menu
• Vaidya Patch submitted to Apache Hadoop
• https://issues.apache.org/jira/browse/MAPREDUCE-3202

33.
A NEW PLATFORM FOR A NEW ERA