Apache CouchDB

1
What Is Apache CouchDB ?

• A document oriented NoSQL database
• Open sourced / Apache 2.0 license
• Written in Erlang, JavaScript, C, C
• Stores documents using JSON
• Single node or cluster
• Takes offline first approach / uses bi
  directional replication
• DB access via HTTP requests

2
How Does CouchDB Work?

• It provides ACID support (Atomic Consistent
  Isolated Durable)
• It has a crash-only design
• No shutdown, just termination
• CouchDB uses Multi-Version Concurrency Control
  (MVCC)
• OS crash or power failure
• Partially flushed updates are simply forgotten
  (or)
• Surviving copy of previous identical headers
  remains
• Ensures coherency of all previously committed
  data
• Crash friendly design

3
Cross Platform

• Available for
• Linux / Unix
• FreeBSD
• Windows
• Mac OSX
• Cloud
• Mobile ( IOS / Android Lite version )
• Install from binary or source
• Install via Docker / Snap
• Install on Kubernetes

4
CouchDB Replication

• Synchronise two copies of same database
• One source and one target database
• Can be on same or different CouchDB instances
• Can be one way or bi directional ( Master
  Master )
• Controlling documents to replicate
• Local documents never replicated
• Filter functions to select documents
• Use Selector Objects
• A query object to test document
• For replication

5
CouchDB Cluster

• CouchDB can be single node or clustered
• Cluster defined by
• Number of shards or parts of database (q)
• Number of document copies / replicas (n)
• Since V3 default is q2, n3
• Each database (and secondary index)
• Split into 2 shards, with 3 replicas per shard
• For a total of 6 shard replica files

6
CouchDB Cluster

• Replicas add failure resistance
• Some nodes can be offline
• Without everything crashing down
• n1 - All nodes must be up.
• n2 - Any 1 node can be down
• n3 - Any 2 nodes can be down
• Using default values and a single database
• q x n 2 x 3 6 nodes
• A maximum of six nodes
• Defines maximum nodes for horizontal scaling

7
CouchDB UI
8
CouchDB UI

• Fauxton CouchDB UI simplifies access
• Manage cluster or single node
• Manage CouchDB
• Databases
• Active tasks
• Configuration
• Replication
• Users
• Access documentation
• Verify CouchDB install

9
CouchDB CAP Theorum

• CAP Theorum examines
• Consistency
• All database clients see the same data, even with
  concurrent updates.
• Availability
• All database clients are able to access some
  version of the data.
• Partition tolerance
• The database can be split over multiple servers
• CouchDB provides eventual consistency by
• By balancing partition tolerance and availability

10
CouchDB CAP Theorum
11
Available Books

• See Big Data Made Easy
• Apress Jan 2015
• See Mastering Apache Spark
• Packt Oct 2015
• See Complete Guide to Open Source Big Data
  Stack
• Apress Jan 2018
• Find the author on Amazon
• www.amazon.com/Michael-Frampton/e/B00NIQDOOM/
• Connect on LinkedIn
• www.linkedin.com/in/mike-frampton-38563020

12
Connect

• Feel free to connect on LinkedIn
• www.linkedin.com/in/mike-frampton-38563020
• See my open source blog at
• open-source-systems.blogspot.com/
• I am always interested in
• New technology
• Opportunities
• Technology based issues
• Big data integration