Cassandra Summit 2014: Monitor Everything!

About Me

#CassandraSummit 2014

●  Sr. Engineer at Pythian o  Lead of Cassandra Practice

●  Remote in Minnesota ●  Interests

o  Java, Clojure, Python dev o  Data science o  Information Security o  Hobbyist electronics

About Pythian

Pythian is a global data outsourcing and consulting company that specializes in optimizing and managing mission-critical data systems.

Pythian blends the world’s leading data experts with advanced, secure service delivery processes to create the industry’s best standard of care for its clients.

Since its inception, Pythian has managed some of the world’s largest, most business-critical data infrastructures.

10,000 Pythian currently manages more than 10,000 systems.

350 Pythian currently employs more than 350 people in 25 countries worldwide.

1997 Pythian was founded in 1997

About Cassandra

●  No Single Point of Failure

●  Fault Tolerant

●  Awesome properties for an operations team who does not want to get up at 3am

About Cassandra

●  Nothing should be set up and forgotten about ●  Easy to do with Cassandra though

o  Fault tolerance on properly configured setup handles single node being down or having temp performance issues

o  No back pressure on writes until there is a lot of trouble

Utilize the fault tolerance buffer

●  Need to observe and react to current issues ●  Predict future issues ●  Divide this into two approaches o  Proactive o  Reactive

Proactive

●  Daily & Weekly checkups to prevent, and predict problems o  Capacity o  Performance bottlenecks o  Data Modeling issues

Reactive

●  Something about best laid plans… o  Hardware failures o  Bugs o  Malicious or Non-Malicious users

●  Alarms, Pager Duty

Common element

●  Data is needed o  form alerts o  find anomalies o  trending o  debugging

Metrics

●  Window to the application o  Bridge the gap - Coda Hale

Cassandra Environment

OpsCenter Logs

JMX CPU, Disk, Network

Nodetool JVM, GC

SOURCES

Gathering Metrics

Metrics but of course… Without context, the data is just pretty graphs

●  Java Management Extensions ●  Complex… very engineered ●  Resources represented as objects with

attributes and operations ●  Used for monitoring or as input

●  The annoying gateway to metrics ○  Poor tooling - requires java ○  Slow, Memory Leaks ○  Historically and currently frustrating for ops (pre 2.0.8)

1024-65535

Init connection to port 7199 Reply with hostname:port for

RMI connection

Client (You)

Gets new hostname:port, drops old connection and attempts to connect

Connected!

Cassandra

●  Visual o  jconsole o  visualvm

●  Command line o  jmxterm o  jmxsh

●  MX4J ●  Jolokia

[domain]:[key]=[value],[key2]=[value2]...

[domain]:[key]=[value],[key2]=[value2]... com.pythian:site=blog,type=views,target=post1

JMX Domains

org.apache.cassandra. ●  db ●  internal ●  net ●  request

org.apache.cassandra.metrics ●  db ●  internal ●  net ●  request

JMX Beans

org.apache.cassandra.metrics :type=

●  Cache ●  Client ●  ClientRequest ●  ClientRequestMetrics ●  ColumnFamily ●  CommitLog ●  Compaction

●  DroppedMessage ●  FileCache ●  Keyspace ●  Storage ●  ThreadPools

org.apache.cassandra.metrics

type=*, scope=*, name=*,

type=ThreadPools, path=*, scope=*, name=*,

type=ColumnFamily, keyspace=*, scope=*, name=*,

type=Keyspace, keyspace=*, name=*,

Metrics

●  Toolkit called metrics for metrics o  By Coda Hale @ Yammer

●  Easy to use ●  Popular

Types of Metrics

●  Gauge o  instantaneous value

●  Counter o  number that can be incremented & decremented

●  Meter o  rate of events over time (1/5/15 min moving avg)

●  Histogram o  representation of statistical distribution

§  50, 75, 95, 98, 99, 99.9 percentile §  average, median, min, max, standard deviation

●  Timer o  rate of events (meter) o  histogram of duration

75th percentile is 683 MICROSECONDS (75% took 683us or less)

One minute rate is 13,915 calls per SECOND

●  Overwhelming at first ●  Hard to tell what they mean without the source ●  Moves around a lot ●  Fortunately there is nodetool

Nodetool

●  JMX command line wrapper ●  Many options ●  Operations and diagnostic procedures ●  For reactive analysis

o  ad hoc, spot checks

Nodetool tpstats

nodetool tpstats org.apache.cassandra.metrics:type=ThreadPools,path={internal|request|transport},scope={*},name= {ActiveTasks|PendingTasks|CompletedTasks|CurrentlyBlockedTasks|TotalBlockedTasks} Pool Name Active Pending Completed Blocked All time blocked

ReadStage 0 0 113702 0 0 RequestResponseStage 0 0 0 0 0 MutationStage 0 0 164503 0 0 ... InternalResponseStage 0 0 0 0 0 HintedHandoff 0 0 0 0 0 Message type Dropped RANGE_SLICE 0 READ_REPAIR 0 ... REQUEST_RESPONSE 0 COUNTER_MUTATION 0

Staged Event Driven Architecture

●  Decomposes complex event system ●  Set of stages (thread pools) ●  Queue between each ●  Shares a lot of pros cons as SOA

Threads

ReadStage

st RequestResponse

Threads

ReadRepairStage

Threads

Messaging Service

Node 2

Node 1 Node 1

= Task

●  Its easy to overrun the processing capabilities of a stage that is not in the requests feedback loop (i.e. ReadRepairStage).

●  No write back pressure

Nodetool tpstats

RequestResponse

Threads

Nodetool tpstats

RequestResponse

Threads

Nodetool tpstats

nodetool tpstats org.apache.cassandra.metrics:type=ThreadPools,path={internal|request|transport},scope={*},name= {ActiveTasks|PendingTasks|CompletedTasks|CurrentlyBlockedTasks|TotalBlockedTasks}

More at: http://www.evidencebasedit.com/guide-to-cassandra-thread-pools

Nodetool cfhistograms

nodetool cfhistograms {keyspace} {table} org.apache.cassandra.metrics:type=ColumnFamily,keyspace={keyspace},scope={table}

SSTables per Read 1 sstables: 98554 2 sstables: 4534 Write Latency (microseconds) No Data Read Latency (microseconds) 10 us: 2 12 us: 17 14 us: 96 17 us: 208 20 us: 677 24 us: 3081 29 us: 4552 35 us: 3559

Read Write Path mile high overview

Memtable SSTable

Writes Reads

Memtable SSTable

Writes Reads

Memtable SSTable

Writes Reads

Memtable SSTable

Writes Reads

Memtable SSTable

Writes Reads

SSTables per Read 1 sstables: 98554 2 sstables: 4534 Write Latency (microseconds) No Data Read Latency (microseconds) 10 us: 2 12 us: 17 14 us: 96 17 us: 208 20 us: 677 24 us: 3081 29 us: 4552 35 us: 3559

Nodetool cfhistograms 1.1

Offset SSTables Write Latency Read Latency Row Size Column Count 1 3579 0 0 0 0 2 0 0 0 0 0 . . . 35 0 0 0 0 0 42 0 0 27 0 0 50 0 0 187 0 0 60 0 10 460 0 0 72 0 200 689 0 0 86 0 663 552 0 0 103 0 796 367 0 0 124 0 297 736 0 0 149 0 265 243 0 0 179 0 460 263 0 0 . . . 25109160 0 0 0 0 0

https://gist.github.com/clohfink/6068003

Nodetool cfhistograms 2.1

Keyspace/Table histograms Percentile SSTables Write Latency Read Latency Partition Size Cell Count (micros) (micros) (bytes) 50% 1.00 10.00 524.00 310 5 75% 1.00 11.75 888.00 310 5 95% 1.00 15.00 4843.75 310 5 98% 1.00 17.00 9658.90 310 5 99% 1.00 19.00 12306.47 310 5 Min 0.00 0.00 68.00 30 0 Max 2.00 1219386.00 45383.00 310 5

Nodetool cfstats

nodetool cfstats {-i} {keyspace}.{table} org.apache.cassandra.metrics:type=ColumnFamily,keyspace={keyspace},scope={table}

Keyspace: Keyspace1 Read Count: 11207 Read Latency: 0.047931114482020164 ms. Write Count: 17598 Write Latency: 0.053502954881236506 ms. Pending Tasks: 0 Table: Standard1 SSTable count: 3 Space used (live), bytes: 9088955 Space used (total), bytes: 9088955 Space used by snapshots (total), bytes: 0 SSTable Compression Ratio: 0.3672150946 Memtable cell count: 0 Memtable data size, bytes: 0 Memtable switch count: 3

Local read count: 11207 Local read latency: 0.048 ms Local write count: 17598 Local write latency: 0.054 ms Pending tasks: 0 Bloom filter false positives: 0 Bloom filter false ratio: 0.00000 Bloom filter space used, bytes: 11688 Compacted partition minimum bytes: 1110 Compacted partition maximum bytes: 126934 Compacted partition mean bytes: 2730 Average live cells per slice: 0.0 Average tombstones per slice: 0.0

Nodetool cfstats

Keyspace: Keyspace1 Read Count: 11207 Read Latency: 0.047931114482020164 ms. Write Count: 17598 Write Latency: 0.053502954881236506 ms. Pending Tasks: 0 Table: Standard1 SSTable count: 3 SSTables in each level: [14/4, 1, 0, …, 0] Space used (live), bytes: 9088955 Space used (total), bytes: 9088955 Space used by snapshots (total), bytes: 0 SSTable Compression Ratio: 0.3672150946 Memtable cell count: 0 Memtable data size, bytes: 0 Memtable switch count: 3

Nodetool cfstats

Nodetool proxyhistograms

nodetool proxyhistograms org.apache.cassandra.metrics:type=ClientRequest,scope={Read|Write|RangeSlice},name=Latency

$ nodetool proxyhistograms proxy histograms Read Latency (microseconds) 61214 us: 1 Write Latency (microseconds) 103 us: 22 124 us: 142 149 us: 297 179 us: 1190 215 us: 1823 258 us: 2091

Nodetool compactionstats

nodetool compactionstats org.apache.cassandra.metrics:type=Compaction

pending tasks: 1

compaction type keyspace table completed total unit Progress

Compaction Keyspace1 Standard1 6076415 29605054 bytes 20.06%

Active compaction remaining time : 0h00m03s

pending tasks: 1

Nodetool

Much more!! http://www.datastax.com/documentation/cassandra/2.0/cassandra/tools/toolsNodetool_r.html

OpsCenter

●  Provides visibility to key metrics ●  Alarming ●  Basic orchestration and config management ●  Constantly improving ●  Free* ●  Almost zero barrier to get setup ●  Very few reasons not to run it

OpsCenter

●  Homogeneous tooling with rest of stack o  Integrate metrics in with what app is using o  orchestration and config management

●  (paid version) “Good enough” o  a mature environment should have more

Reporting Interface

Default Addons Community

JMX Ganglia Cassandra StatsD NewRelic Splunk

Console Graphite Cloudwatch Kafka Riemann TempDB

Csv Munin Riak InfluxDB Sematext

Slf4j MongoDB OpenTSDB Librato … MORE

Reporting Interface

●  Configurable with yaml o  console, csv, ganglia, graphite

●  Create reporter with premain agent o  compiling new jar with manifest o  add to classpath o  add javaagent in cassandra-env.sh

Garbage Collection

●  Death, Taxes, and a stop the world GC ●  Common issue to all JVM based applications

Garbage Collection

Enable gc logging ●  Virtually no overhead ●  Can be very helpful in diagnosing

performance issues

Garbage Collection

JVM_OPTS="$JVM_OPTS -XX:+PrintGCDetails" JVM_OPTS="$JVM_OPTS -XX:+PrintGCDateStamps" JVM_OPTS="$JVM_OPTS -XX:+PrintHeapAtGC" JVM_OPTS="$JVM_OPTS -XX:+PrintTenuringDistribution" JVM_OPTS="$JVM_OPTS -XX:+PrintGCApplicationStoppedTime" JVM_OPTS="$JVM_OPTS -XX:+PrintPromotionFailure" JVM_OPTS="$JVM_OPTS -XX:PrintFLSStatistics=1" JVM_OPTS="$JVM_OPTS -Xloggc:/var/log/cassandra/gc-`date +%s`.log" JVM_OPTS="$JVM_OPTS -Xloggc:/var/log/cassandra/gc.log" JVM_OPTS="$JVM_OPTS -XX:+UseGCLogFileRotation" JVM_OPTS="$JVM_OPTS -XX:NumberOfGCLogFiles=10" JVM_OPTS="$JVM_OPTS -XX:GCLogFileSize=10M"

Garbage Collection

JVM_OPTS="$JVM_OPTS -XX:+PrintGCDetails" JVM_OPTS="$JVM_OPTS -XX:+PrintGCDateStamps" JVM_OPTS="$JVM_OPTS -XX:+PrintHeapAtGC" JVM_OPTS="$JVM_OPTS -XX:+PrintTenuringDistribution" JVM_OPTS="$JVM_OPTS -XX:+PrintGCApplicationStoppedTime" JVM_OPTS="$JVM_OPTS -XX:+PrintPromotionFailure" JVM_OPTS="$JVM_OPTS -XX:PrintFLSStatistics=1" JVM_OPTS="$JVM_OPTS -Xloggc:/var/log/cassandra/gc-`date +%s`.log" JVM_OPTS="$JVM_OPTS -Xloggc:/var/log/cassandra/gc.log" JVM_OPTS="$JVM_OPTS -XX:+UseGCLogFileRotation" JVM_OPTS="$JVM_OPTS -XX:NumberOfGCLogFiles=10" JVM_OPTS="$JVM_OPTS -XX:GCLogFileSize=10M"

Garbage Collection

Could be its own talk Honorable mentions: ●  https://github.com/chewiebug/GCViewer ●  http://jworks.idv.tw/GcWeb/ ●  Python, R, Octave

Logging

/var/log/cassandra/system.log o  provides a rolling log o  log4j

/var/log/cassandra/output.log o  captured standard error and standard out o  truncated on restart

System Logs o  syslog, dmesg, etc

OS Metrics

Shout-out: http://www.brendangregg.com/linuxperf.html

●  Heap o  GC logs o  JMX

●  Threads o  jvmtop o  Jstack (+htop) o  kill -3 o  JMX

And Everything

Questions

Cassandra Summit 2014: Monitor Everything!

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