C* Summit EU 2013: Practice Makes Perfect: Extreme Cassandra Optimization

PRACTICE MAKES PERFECT: EXTREME CASSANDRA OPTIMIZATION

@AlTobey Open Source Mechanic

Datastax

#CASSANDRAEU

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⁍ About me⁍ How not to manage your Cassandra clusters⁍ Make it better⁍ How to be a heuristician⁍ Tools of the trade⁍ More Settings⁍ Show & Tell

#CASSANDRAEU

Outline

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⁍ Tech Lead, Compute and Data Services at Ooyala, Inc.⁍ C&D team is #devops: 3 ops, 3 eng, me⁍ C&D team is #bdaas: Big Data as a Service⁍ ~200 Cassandra nodes, expanding quickly

#CASSANDRAEU

Previously: @AlTobey / Ooyala

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⁍ Founded in 2007⁍ 230+ employees globally⁍ 200M unique users,110+ countries⁍ Over 1 billion videos played per month⁍ Over 2 billion analytic events per day

#CASSANDRAEU

Ooyala

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Ooyala has been using Cassandra since v0.4Use cases: ⁍ Analytics data (real-time and batch) ⁍ Highly available K/V store ⁍ Time series data ⁍ Play head tracking (cross-device resume) ⁍ Machine Learning Data

#CASSANDRAEU

Ooyala & Cassandra

Ooyala: Legacy Platform

cassandracassandracassandracassandra

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S3

hadoophadoophadoophadoophadoop

cassandra

ABE Service

APIloggersplayer

START HERE

#CASSANDRAEU

read-modify-write

memTable

Avoiding read-modify-write

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Albert 6 Wednesday 0

Evan Tuesday 0 Wednesday 0

Frank Tuesday 3 Wednesday 3

Kelvin Tuesday 0 Wednesday 0

cassandra13_drinks column family

Krzysztof Tuesday 0 Wednesday 0

Phillip Tuesday 12 Wednesday 0

Tuesday

memTable

Avoiding read-modify-write

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Al Tuesday 2 Wednesday 0

Phillip Tuesday 0 Wednesday 1

cassandra13_drinks column family

ssTable

Albert 6 Wednesday 0

Evan Tuesday 0 Wednesday 0

Frank Tuesday 3 Wednesday 3

Kelvin Tuesday 0 Wednesday 0

Krzysztof Tuesday 0 Wednesday 0

Phillip Tuesday 12 Wednesday 0

Tuesday

memTable

Avoiding read-modify-write

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Albert Tuesday 22 Wednesday 0

cassandra13_drinks column family

ssTableAlbert Tuesday 2 Wednesday 0

Phillip Tuesday 0 Wednesday 1

ssTable

Albert 6 Wednesday 0

Evan Tuesday 0 Wednesday 0

Frank Tuesday 3 Wednesday 3

Kelvin Tuesday 0 Wednesday 0

Krzysztof Tuesday 0 Wednesday 0

Phillip Tuesday 12 Wednesday 0

Tuesday

Avoiding read-modify-write

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cassandra13_drinks column family

ssTable

Albert Tuesday 22 Wednesday 0

Evan Tuesday 0 Wednesday 0

Frank Tuesday 3 Wednesday 3

Kelvin Tuesday 0 Wednesday 0

Krzysztof Tuesday 0 Wednesday 0

Phillip Tuesday 0 Wednesday 1

2011: 0.6 ➜ 0.8

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⁍ Migration is still a largely unsolved problem⁍ Wrote a tool in Scala to scrub data and write via Thrift⁍ Rebuilt indexes - faster than copying

hadoopcassandra

GlusterFS P2Pcassandra

Thrift

#CASSANDRAEU

Scala Map/Reduce

Changes: 0.6 ➜ 0.8

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⁍ Cassandra 0.8⁍ 24GiB heap⁍ Sun Java 1.6 update⁍ Linux 2.6.36⁍ XFS on MD RAID5⁍ Disabled swap or at least vm.swappiness=1

#CASSANDRAEU

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⁍ 18 nodes ➜ 36 nodes⁍ DSE 3.0⁍ Stale tombstones again!⁍ No downtime!

cassandraGlusterFS P2P

DSE 3.0

Thrift

#CASSANDRAEU

Scala Map/Reduce

2012: Capacity Increase

System Changes: Apache 1.0 ➜ DSE 3.0

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⁍ DSE 3.0 installed via apt packages⁍ Unchanged: heap, distro⁍ Ran much faster this time!⁍ Mistake: Moved to MD RAID 0 Fix: RAID10 or RAID5, MD, ZFS⁍ Mistake: Running on Ubuntu Lucid Fix: Ubuntu Precise

#CASSANDRAEU

Config Changes: Apache 1.0 ➜ DSE 3.0

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⁍ Schema: compaction_strategy = LCS⁍ Schema: bloom_filter_fp_chance = 0.1⁍ Schema: sstable_size_in_mb = 256⁍ Schema: compression_options = Snappy⁍ YAML: compaction_throughput_mb_per_sec: 0

#CASSANDRAEU

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⁍ 36 nodes ➜ lots more nodes⁍ As usual, no downtime!

#CASSANDRAEU

DSE 3.1DSE 3.1

replication

2013: Datacenter Move

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Upcoming use cases: ⁍ Store every event from the players at full resolution ⁍ Cache code for the Spark job server ⁍ AMPLab Tachyon backend?

#CASSANDRAEU

Coming Soon for Cassandra at Ooyala

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spark

APIloggersplayer kafka

ingest

job server

#CASSANDRAEU

DSE 3.1

Next Generation Architecture: Ooyala Event Store

Tachyon?

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⁍ Security⁍ Cost of Goods Sold⁍ Operations / support⁍ Developer happiness⁍ Physical capacity (cpu/memory/network/disk)⁍ Reliability / Resilience⁍ Compromise

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There’s more to tuning than performance:

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⁍ I’d love to be more scientific, but good science takes time⁍ Sometimes you have to make educated guesses⁍ It’s not as difficult as it’s made out to be⁍ Your brain is great at heuristics. Trust it.⁍ Concentrate on bottlenecks⁍ Make incremental changes⁍ Read Malcom Gladwell’s “Blink”

#CASSANDRAEU

I am not a scientist ... heuristician?

Testing Shiny Things

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⁍ Like kernels⁍ And Linux distributions⁍ And ZFS⁍ And btrfs⁍ And JVM’s & parameters⁍ Test them in production (if you must)

#CASSANDRAEU

ext4

ext4

ext4

ZFS

ext4

kernel upgrade

ext4

btrfs

Testing Shiny Things: In Production

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Brendan Gregg’s Tool Chart

http://joyent.com/blog/linux-performance-analysis-and-tools-brendan-gregg-s-talk-at-scale-11x

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dstat -lrvn 10

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cl-netstat.pl

https://github.com/tobert/perl-ssh-tools

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iostat -x 1

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htop

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jconsole

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opscenter

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nodetool ring

10.10.10.10 Analytics rack1 Up Normal 47.73 MB 1.72% 101204669472175663702469172037896580098 10.10.10.10 Analytics rack1 Up Normal 63.94 MB 0.86% 102671403812352122596707855690619718940 10.10.10.10 Analytics rack1 Up Normal 85.73 MB 0.86% 104138138152528581490946539343342857782 10.10.10.10 Analytics rack1 Up Normal 47.87 MB 0.86% 105604872492705040385185222996065996624 10.10.10.10 Analytics rack1 Up Normal 39.73 MB 0.86% 107071606832881499279423906648789135466 10.10.10.10 Analytics rack1 Up Normal 40.74 MB 1.75% 110042394566257506011458285920000334950 10.10.10.10 Analytics rack1 Up Normal 40.08 MB 2.20% 113781420866907675791616368030579466301 10.10.10.10 Analytics rack1 Up Normal 56.19 MB 3.45% 119650151395618797017962053073524524487

10.10.10.10 Analytics rack1 Up Normal 214.88 MB 11.62% 139424886777089715561324792149872061049 10.10.10.10 Analytics rack1 Up Normal 214.29 MB 2.45% 143588210871399618110700028431440799305 10.10.10.10 Analytics rack1 Up Normal 158.49 MB 1.76% 146577368624928021690175250344904436129 10.10.10.10 Analytics rack1 Up Normal 40.3 MB 0.92% 148140168357822348318107048925037023042

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nodetool cfstatsKeyspace: gostress Read Count: 0 Read Latency: NaN ms. Write Count: 0 Write Latency: NaN ms. Pending Tasks: 0 Column Family: stressful SSTable count: 1 Space used (live): 32981239 Space used (total): 32981239 Number of Keys (estimate): 128 Memtable Columns Count: 0 Memtable Data Size: 0 Memtable Switch Count: 0 Read Count: 0 Read Latency: NaN ms. Write Count: 0 Write Latency: NaN ms. Pending Tasks: 0 Bloom Filter False Positives: 0 Bloom Filter False Ratio: 0.00000 Bloom Filter Space Used: 336 Compacted row minimum size: 7007507 Compacted row maximum size: 8409007 Compacted row mean size: 8409007

Could be using a lot of heap

Controllable by sstable_size_in_mb

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nodetool proxyhistograms

Offset Read Latency Write Latency Range Latency 35 0 20 0 42 0 61 0 50 0 82 0 60 0 440 0 72 0 3416 0 86 0 17910 0 103 0 48675 0 124 1 97423 0 149 0 153109 0 179 2 186205 0 215 5 139022 0 258 134 44058 0 310 2656 60660 0 372 34698 742684 0 446 469515 7359351 0 535 3920391 31030588 0 642 9852708 33070248 0 770 4487796 9719615 0 924 651959 984889 0

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nodetool compactionstats

al@node ~ $ nodetool compactionstats pending tasks: 3 compaction type keyspace column family bytes compacted bytes total progress Compaction hastur gauge_archive 9819749801 16922291634 58.03% Compaction hastur counter_archive 12141850720 16147440484 75.19% Compaction hastur mark_archive 647389841 1475432590 43.88% Active compaction remaining time : n/a al@node ~ $ nodetool compactionstats pending tasks: 3 compaction type keyspace column family bytes compacted bytes total progress Compaction hastur gauge_archive 10239806890 16922291634 60.51% Compaction hastur counter_archive 12544404397 16147440484 77.69% Compaction hastur mark_archive 1107897093 1475432590 75.09% Active compaction remaining time : n/a

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⁍ cassandra-stress⁍ YCSB⁍ Production⁍ Terasort (DSE)⁍ Homegrown

Stress Testing Tools

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kernel.pid_max = 999999 fs.file-max = 1048576 vm.max_map_count = 1048576 net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 net.ipv4.tcp_rmem = 4096 65536 16777216 net.ipv4.tcp_wmem = 4096 65536 16777216 vm.swappiness = 1 vm.dirty_ratio = 10 vm.dirty_background_ratio = 5

/etc/sysctl.conf

!36#echo cfq > /sys/block/sda/queue/scheduler

ra=$((2**14))# 16k ss=$(blockdev --getss /dev/sda) blockdev --setra $(($ra / $ss)) /dev/sda !

echo 256 > /sys/block/sda/queue/nr_requests #echo cfq > /sys/block/sda/queue/scheduler #echo deadline > /sys/block/sda/queue/scheduler #echo noop > /sys/block/sda/queue/scheduler !

echo 16384 > /sys/block/md7/md/stripe_cache_size

/etc/rc.local

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-Xmx8G leave it alone -Xms8G leave it alone -Xmn1200M 100MiB * nCPU -Xss180k should be fine !

-XX:+UseNUMA (test it) numactl --interleave (safe option)

JVM Args

cgroups

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Provides fine-grained control over Linux resources⁍ Makes the Linux scheduler behave⁍ Lets you manage systems under extreme load⁍ Useful on all Linux machines⁍ Can choose between determinism and flexibility

cgroups

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cat >> /etc/default/cassandra <<EOF cpucg=/sys/fs/cgroup/cpu/cassandra mkdir $cpucg cat $cpucg/../cpuset.mems >$cpucg/cpuset.mems cat $cpucg/../cpuset.cpus >$cpucg/cpuset.cpus echo 100 > $cpucg/shares echo $$ > $cpucg/tasks EOF

Successful Experiment: btrfs

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mkfs.btrfs -m raid10 -d raid0 /dev/sd[c-h]1 mkfs.btrfs -m raid10 -d raid0 /dev/sd[c-h]1 mount -o compress=lzo /dev/sdc1 /data

Successful Experiment: ZFS on Linux

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zpool create data raidz /dev/sd[c-h] zfs create data/cassandra zfs set compression=lzjb data/cassandra zfs set atime=off data/cassandra zfs set primarycache=metadata data/cassandra

Conclusions

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⁍ Tuning is multi-dimensional⁍ Production load is your most important benchmark⁍ Lean on Cassandra, experiment!⁍ No one metric tells the whole story

Questions?

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⁍ Twitter: @AlTobey⁍ Email: [email protected]