How Hailo fuels its growth using NoSQL Storage and Analytics

How Hailo fuels its growth using NoSQL Storage and Analytics

David Gardner, Architect @ Hailo

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• The world’s highest-rated taxi app – over 10,000 five-star reviews

• Over 500,000 registered passengers

• A Hailo e-hail is accepted by a driver every four seconds around the world

• Hailo operates in ten cities from Tokyo to Toronto in just over eighteen months of operation

What is Hailo?

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• Hailo is a marketplace that facilitates over $100M in run-rate transactions and is making the world a better place for passengers and drivers

• Hailo has raised over $50M in financing from the world's best investors including Union Square Ventures, Accel, the founder of Skype (via Atomico), Wellington Partners (Spotify), Sir Richard Branson, and our CEO's mother, Janice

Hailo is growing

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• Why Hailo are using NoSQL

• How we use Cassandra

• How we use Acunu Analytics

• Challenges of NoSQL

What this talk is about

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Why choose NoSQL?

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“NoSQL DBs trade off traditional features to better support new and emerging use cases”Andy Gross, Riak

http://www.slideshare.net/argv0/riak-use-cases-dissecting-the-solutions-to-hard-problems

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• More widely used, tested and documented software

• Ad-hoc querying

• Talent pool with direct experience

What are we trading off?

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• High availability

• Scalability

• Operational simplicity

What do we get back in return?

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The path to adoption at Hailo

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Hailo launched in London in November 2011

• Launched on AWS

• Two PHP/MySQL web apps plus a Java backend

• Mostly built by a team of 3 or 4 backend engineers

• MySQL multi-master for single AZ resilience

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Why Cassandra?

• A desire for greater resilience – “become a utility”Cassandra is designed for high availability

• Plans for international expansion around a single consumer appCassandra is good at global replication

• Expected growthCassandra scales linearly for both reads and writes

• Prior experienceI had experience with Cassandra and could recommend it

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The path to adoption

• Largely unilateral decision by developers – a result of a startup culture

• Replacement of key consumer app functionality, splitting up the PHP/MySQL web app into a mixture of global PHP/Java services backed by a Cassandra data store

• Launched into production in September 2012 – originally just powering North American expansion, before gradually switching over Dublin and London

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Cassandra at Hailo

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“Cassandra just works”

Dom W, Senior Engineer

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Use cases

1. Entity storage

2. Time series data

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CF = customers

126007613634425612:createdTimestamp: 1370465412email: dave@cruft.cogivenName: DavefamilyName: Gardnerlocale: en_GBphone:

+447911111111

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Considerations for entity storage

• Do not read the entire entity, update one property and then write back a mutation containing every column

• Only mutate columns that have been set

• This avoids read-before-write race conditions

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CF = comms

2013-06-01:55374fa0-ce2b-11e2-8b8b-0800200c9a66:

{“to”:”dave@c…a48bd800-ce2b-11e2-8b8b-0800200c9a66:

{“to”:”foo@ex…b0e15850-ce2b-11e2-8b8b-0800200c9a66:

{“to”:”bar@ho …bfac6c80-ce2b-11e2-8b8b-0800200c9a66:

{“to”:”baz@fo…

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CF = comms

dave@cruft.co:13b247f0-ce2c-11e2-8b8b-0800200c9a66:

{“to”:”dave@c…20f70a40-ce2c-11e2-8b8b-0800200c9a66:

{“to”:”dave@c…2b44d3b0-ce2c-11e2-8b8b-0800200c9a66:

{“to”:”dave@c…338a22f0-ce2c-11e2-8b8b-0800200c9a66:

{“to”:”dave@c…

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Considerations for time series storage

• Choose row key carefully, since this partitions the records

• Think about how many records you want in a single row

• Denormalise on write into many indexes

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Client libraries

• Astyanax (Java)

• phpcassa (PHP)

• github.com/carloscm/gossie (Go)

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2 clusters

6 machines per region

3 regions

(stats cluster pending addition of third DC) O

pera

tion

al C

luste

rS

tats

Clu

ste

r

ap-southeast-1

us-east-1 eu-west-1

us-east-1 eu-west-1

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AWS VPCs with Open VPN links

3 AZs per region

m1.large machines

Provisoned IOPS EBS

Op

era

tion

al C

luste

rS

tats

Clu

ste

r

~ 600GB/node

~ 100GB/node

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Multi DC

• Something that Cassandra makes trivial

• Would have been very difficult to accomplish active-active inter-DC replication with a team of 2 without Cassandra

• Rolling repair needed to make it safe (we use LOCAL_QUORUM)

• We schedule “narrow repairs” on different nodes in our cluster each night

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Acunu Analytics at Hailo

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Analytics

• With Cassandra we lost the ability to carry out analyticseg: COUNT, SUM, AVG, GROUP BY

• We use Acunu Analytics to give us this abilty in real time, for pre-planned query templates

• It is backed by Cassandra and therefore highly available, resilient and globally distributed

• Integration is straightforward

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NSQ Acunu C*events

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AQL

SELECT SUM(accepted), SUM(ignored), SUM(declined), SUM(withdrawn)FROM AllocationsWHERE timestamp BETWEEN '1 week ago' AND 'now’ AND driver='LON123456789’GROUP BY timestamp(day)

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Challenges

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10 Average years experience per team

member

MySQL Cassandra

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People who canattempt to queryMySQL

People who canattempt to

query Cassandra

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Lessons learned

• Have an advovate - get someone who will sell the vision internally

• Teach team members the fundamentals of how the solution works

• Don’t cause yourself a “big data” problem unnecessarily

• Explain trade-offs in choosing NoSQL to all parts of the business

• Provide solutions!

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People who canattempt to queryMySQL

People who canattempt to

query Cassandra

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Conclusion

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We like Cassandra

• Solid design

• HA characteristics

• Easy multi-DC setup

• Simplicity of operation

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The future

• We will continue to invest in Cassandra as we expand globally

• We will hire people with experience running Cassandra

• We will focus on expanding our reporting facilities

• We aspire to extend our network (1M consumer installs, wallet) beyond cabs

• We will continue to hire the best engineers in London, NYC and Asia

Thank you

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Come and work with NoSQL full time: jobs.hailocab.com