1. TouchDB –
scaling down CouchDB
Stefan Baggström
20th Nov 2012

2. Background
• We are a research team ”Felix” in TUT/BME
developing new ICT solutions in the area of
health and wellness technology
• We have built a system prototype with
CouchDB technologies
– to iterate the product concept rapidly
– to pilot with potential customers
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3. Prototyping a wellness
application with CouchDB
• Goals for prototype:
– Can be used with any Internet devices
– Good offline functionality
• Being agile:
– Data model evolves across increments
• There is a schedule to meet:
– Consider tech learning curves and
development time
3

4. System to be built
Customer
Wellness
Professional
4

5. CouchDB http://couchdb.apache.org/
• CouchDB has some interesting features
– JSON document storage
– Distributed architecture
– Eventual consistency
– Bi-directional replication
– Serving applications directly from database
• Scaling up - see e.g. BigCouch
5

6. CouchDB – scaling down
• There is CouchDB port for iOS and Android
(Couchbase Mobile), but the project is dead
– Erlang implementation as in CouchDB
– Issues: size (~4MB) and slow startup (5-10s)
Source: http://www.funny-potato.com/
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7. Meet TouchDB
• TouchDB is a lightweight
CouchDB-compatible
database engine with
similar REST API to
CouchDB
• Replicates with CouchDB
• iOS and Android ports
implemented with
Objective-C / Java on top
of SQLite
• Native language access
via CouchCocoa / Ektorp
https://github.com/couchbaselabs/TouchDB-iOS/wiki 7

8. Personal Wellness App –
What is needed and what not?
• Good enough performance for
– Relatively small data sets (may have large
attachments)
– A few relatively simple data queries
– Good functionality when offline or with
intermittent connectivity
• Support for multi-device-ownership
– Use with any device that suits your task and
context
20.11.2012 8

9. Wellness Android app –
Abstract architecture
Application UI – HTML5 with JQuery Mobile
WebView with Java-JavaScript IF TouchDB – http listener
TouchDB -
Application Core TouchDB library
Ektorp
Android – Android –
Android – Java VM Android - SQLite
MM APIs BT API
9

10. Time for scaled down
demo?
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11. How do we use TouchDB? (1/2)
• All documents defined with ”type” property
– Database schema emerging
• Using Java Ektorp API for document CRUD
• Using HTTP API for application resources
and views
– Implemented home brewn access control
• Database provides changes feed
– Used to trigger notifications and other actions
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12. How do we use TouchDB? (2/2)
• Single responsive HTML5 application for
desktops, tablets, and smart phones
– CouchApp used for deployment to CouchDB
• Initial replication in foreground during first
time use, and then continuous replication in
background
• Data model evolves all the time
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13. TouchDB for wellness app
Pros Cons
• Offline functionality • Immature at the moment
– All transactions are always – iOS port just got v1.0 status,
fast & predictable as they Android port is behind iOS
are local transactions
– Small development community
• Replication
• Fragile security
– Data
– HTTP API is accessible by
– Applications other Android applications
– Supports filtered replication within device - better control if
• NoSQL is supports used only via Java/Ektorp
incremental development • Lack of C/TouchDB
• Meets performance professionals out there
requirements of a personal
database
• JavaScript in server and
clients
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