cassandra day sv 2014: building a flexible, real-time big data applications platform on apache...

Building a Flexible, Real-time Big Data Applications Platform

on Cassandra with Kiji

Cassandra Day Silicon Valley07 April 2014

Clint KellyMember of Technical StaffWibiData

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Overview

• The Kiji Project• The Kiji data model and KijiSchema• Mapping Kiji to Cassandra• Status and future work• Try it now!

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Should there be any intro page that talks about WibiData anywhere?

The Kiji Project

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Want to build this...

Have this...

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Have this...

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Want to build this...

Open source components

• Batch processing– Extract, transform, load– Train machine learning models

• Scalable storage– Time-series data

• Serialization– Complex data types

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Hadoop, C*, HBase, Avro

KijiSchema

KijiMR KijiREST

KijiHive KijiScoring

KijiExpress

KijiSchema

• Schemas and data serialization• Complex, atomic data types

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Hadoop, C*, HBase, Avro

KijiSchema

KijiMR KijiREST

KijiHive KijiScoring

KijiExpress

record UserLog { long timestamp; int user_id; string url; long session_id;}

• Schema evolution• Table metadata

Kiji batch components

• Scala DSL ➔ describe MapReduce computations

• Machine learning library• Hive adapter

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Hadoop, C*, HBase, Avro

KijiSchema

KijiMR KijiREST

KijiHive KijiScoring

KijiExpress

Kiji real-time components

• REST server• Scoring server

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Hadoop, C*, HBase, Avro

KijiSchema

KijiMR KijiREST

KijiHive KijiScoring

KijiExpress

Kiji Summary

• Bridge between open-source technologies and real-time, big data applications

• Users are building real systems with Kiji now!– Personalized recommendation systems for retail– Energy usage and analytics reporting

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The Kiji data model and KijiSchema

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row

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Table are composed of rows.

entity ID data

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We call row keys “entity IDs.”

data0xfa “bob”

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We support composite entity IDs (with hashed and unhashed components).

info0xfa “bob” songs

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Data in rows is organized into “column families.”

songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment

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Column families contain columns, named as “family:qualifier.”

songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123

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Individual columns can have many different timestamped versions.

songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123

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Data values can be complex records

record SongPlay { long song_id; int user_rating; long session_id; device_type device;}

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Locality groups

Separate logical organization of data (column families) from physical attributes (caching, compression, etc.)

info songs_todayentity ID songs_prev_year

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Locality groups

Separate logical organization of data (column families) from physical attributes (caching, compression, etc.)

Need this data ASAP for real-time scoring. Use this data only for

batch jobs.

info songs_todayentity ID songs_prev_year

info songs_todayentity ID songs_prev_year

“real_time” (in-memory, uncompressed, TTL = 1 day)

“batch” (compressed, TTL = 12mo)

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Locality groups

Always refer to columns by logical name (“family:qualifier”).

Need this data ASAP for real-time scoring. Use this data only for

batch jobs.

KijiSchema summary

• Data model similar to Cassandra, HBase, BigTable

• Contains time dimension (not present in C*)• Logical and physical organization separate• Complex schemas with Avro

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Mapping Kiji to Cassandra

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Implementation notes

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• Built for Cassandra 2.0.6+• Native protocol / Java driver (no Thrift)• Asynchronous API• Assume users have Hadoop, ZooKeeper

Mapping a Kiji table ➔ Cassandra

• Locality group ➔ Table• Entity ID ➔ Primary key

– Hashed components ➔ partition key– Unhashed components ➔ clustering columns

• Family, qualifier, timestamp ➔ clustering columns• Cell values ➔ blobs

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songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123

CQL for Kiji locality groupCREATE TABLE users_locality_group_fast ( userid bigint, user text, family text, qualifier text, timestamp bigint, value blob, PRIMARY KEY (userid, username, family, qualifier, timestamp)) WITH CLUSTERING ORDER BY ( username ASC, family ASC, qualifier ASC, timestamp DESC);

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TODO: Show row diagram, arrows pointing to components?

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cqlsh:kiji_music>SELECT * FROM kiji_table_users;

userid | username | family | qualifier | timestamp | value--------+----------+--------+----------------+-----------+--------------- 0xfa | bob | info | email | 139653249 | 1243970104327 0xfa | bob | songs | abbey road | 139656012 | 0981274331032 0xfa | bob | songs | help | 139625013 | 9074132704129 0xfa | bob | songs | help | 139621359 | 1923079210370 0xfa | bob | songs | help | 139625013 | 4745018223497 0xfa | bob | songs | helter skelter | 139621324 | 7710423974234

Physical organization of data on disk

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songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

13965601230xfa:bob:info:email:t0:bob@gmail.com

0xfa:bob:info:payment:t1:AMEX1234...

0xfa:bob:songs:let it be:t5:...

0xfa:bob:songs:let it be:t4:…

0xfa:bob:songs:let it be:t2:…

0xfa:bob:songs:help:t2:…

0xfa:bob:songs:helter skelter:t1:…

Efficient queries = continuous scans!

Kiji queries ➔ CQL queries

All data in “info” column family for “bob” ➔SELECT qualifier, value FROM music WHERE userid=0xfa AND user=‘bob’ AND family=‘info’;

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songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123

Kiji queries ➔ CQL queries

Data in “info:email” and last play of “help” for “bob” ➔

SELECT value FROM music WHERE userid=0xfa AND user=‘bob’ AND family=‘info’ AND qualifier=‘email’;

SELECT value FROM music WHERE userid=0xfa AND user=‘bob’ AND family=‘songs’ AND qualifier=‘help’ LIMIT 1;

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songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123

Kiji queries ➔ CQL queries

All songs played by “bob” on April 2nd ➔SELECT qualifier, value FROM music WHERE userid=0xfa AND user=‘bob’ AND family=‘songs’ AND timestamp >= 1396396800 AND timestamp <= 1396483200 ALLOW FILTERING;😱😱

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songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123

Kiji queries ➔ CQL queries

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songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123

!Bad Request: PRIMARY KEY part timestamp cannot be restricted (preceding part qualifier is either not restricted or by a non-EQ relation)

Queries that do not map well to CQL

• Break up into multiple CQL queries– Hooray for Session#executeAsync!

• Filter on the client– Potentially very expensive, but functional– Provide warning to user

• Educate users about table layout– Layout in previous example is terrible for that query

• Most issues related to “time” dimension

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MapReduce

• Wrote new InputFormat, OutputFormat• Hadoop 2.x• Multiple C* queries per RecordReader• Does not use Thrift

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Project status and next steps

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Initial release in ~ 2 weeks

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• Cassandra as part of the Bento Box• Cassandra working in KijiSchema, KijiMR

Support in the coming months

• Cassandra integration with KijiREST, KijiScoring, KijiExpress, etc.

• Expose Cassandra-specific features to users– Variable consistency levels– Load-balancing policies– Diagnostics (e.g., route tracing)

• Kiji support in CQLSH– Decode Avro values

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Thanks to Cassandra community

• Great help on mailing lists for users, dev, java driver

• Webinars, meetups, C* Summit all available online

• Free training from DataStax• Very easy to get up-to-speed

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Try it now -- Kiji Bento Box

• Latest compatible versions of all components• Hadoop, ZooKeeper, HBase• Cassandra in ~2 weeks

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www.kiji.org/getstarted

Mention hiring?

KijiSchema

• Schemas and data serialization• Complex data types (e.g.,

nested maps)• Schema evolution• Metadata• Composite row keys• Transparent paging• Data-definition language, REPL

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Hadoop, C*, HBase, Avro

KijiSchema

KijiMR KijiREST

KijiHive KijiScoring

KijiExpress

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Schema support

Support for complex schemas with Avrorecord UserLog { long timestamp; int user_id; string url;}

KijiSchema allows schema versioning

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Column name translation

• “family:qualifier” -> “A:B”• Saves disk space• Improves performance• User-facing tools translate names• Possible to turn this off

Kiji queries ➔ CQL queries

All data in family “songs” for user “bob” ➔SELECT qualifier, value FROM music WHERE userid=0xfa AND user=‘bob’ AND family=‘songs’;

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songs:let it be

songs:help

songs:helterskelter

0xfa “bob” info:email

info:payment songs:

let it besongs:let it besongs:

let it besongs:let it be

1396560123