with RethinkDB Ilya Verbitskiy Ilya Verbitskiy Distributed - - PowerPoint PPT Presentation

Agile web-development with RethinkDB

Ilya Verbitskiy

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Ilya Verbitskiy

• Distributed systems, application security, fintech
• ilya@verbitskiy.co
• @ilich_x86
• https://github.com/ilich

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Demo

https://github.com/ilich/rethinkdb-101

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What is RethinkDB?

• Open-source database for building realtime web applications.
• NoSQL database that stores schemaless JSON documents.
• Distributed database that is easy to scale.
• High availability database with automatic failover and robust fault

tolerance.

• The second most popular database on GitHub

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The Good

• Changefeeds.
• Map-reduce.
• Geospatial queries.
• Collaborative web and mobile apps.
• Streaming analytics apps.
• Multiplayer games.
• Realtime marketplaces.
• Connected devices.

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The Bad

• RethinkDB is not a good choice if you need full ACID support or strong

schema enforcement.

• If you are doing deep, computationally-intensive analytics you are better
• ff using a system like Hadoop.
• In some cases RethinkDB trades off write availability in favor of data

consistency.

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RethinkDB vs. …

• MongoDB
• Firebase

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Can I use my programming language?

• JavaScript/Node.js
• Python
• Ruby
• Java
• C#/.NET
• C++
• Go
• PHP
• … and even more on

https://rethinkdb.com/docs/install- drivers/

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RethinkDB Structure

• Database → Table → Document
• Document is a schemaless JSON documents.

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Introduction to ReQL

• ReQL is the RethinkDB query language.
• ReQL key principles:
• ReQL embeds into your programming language.
• All ReQL queries are chainable.
• All queries execute on the server.
• Good starting point if you already know SQL:

https://www.rethinkdb.com/docs/sql-to-reql/javascript/

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Understanding ReQL

• Client driver translates ReQL queries RethinkDB protocol and sends to

the server for execution.

• Anonymous function must return a valid ReQL expression.
• In JavaScript you should use lt and gt commands instead of < and >
• perators.

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Supported data types

• Number
• String (UTF-8)
• Boolean
• Null
• Object
• Array (by default, up to 100,000 elements)
• Dates and times
• Binary objects
• Geometry objects and geospatial queries (indexes, GeoJSON support)

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Data modeling in RethinkDB

• Embedded arrays
• Similar to MongoDB
• Queries are simpler.
• The data is often colocated on disk. If you have a dataset that doesn’t fit into RAM,

data is loaded from disk faster.

• Any update to the main document atomically updates both the main data and the

linked data.

• Up to 100,000 elements by default.
• Deleting, adding or updating a document requires loading the entire array, modifying

it, and writing the entire document back to disk.

• Because of the previous limitation, it’s best to keep the size of the array to no more

than a few hundred documents.

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Data modeling in RethinkDB

• Multiple tables
• Similar to SQL
• Operations on parent document don’t require loading the data for every child

document for a given parent into memory.

• There is no limitation on the number of child documents, so this approach is more

suitable for large amounts of data.

• The queries linking the data tend to be more complicated.
• With this approach you cannot atomically update both the parent data and the child

data.

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Changefeeds

• Changefeeds allow clients to receive changes on a table.
• The changes command returns a cursor that receives updates.
• Each update includes the new and old value of the modified record.
• Changefeeds cannot guarantee delivery, since they are unidirectional with

no acknowledgement returned from clients.

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// Node.js r.table('users').changes().run(conn, function(err, cursor) { // Use cursor to process changes }); …. // Sample cursor {

• ld_val: null,

new_val: { { "city" : "MINNEAPOLIS", "state" : "MN", "_id" : "55311" }, } }

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Commands supporting changefeeds

• filter
• getAll
• map
• pluck
• between
• union
• min
• max
• orderBy.limit

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Sharding and replication

• RethinkDB is designed for clustering and easy scalability.
• To add a new server to the cluster, just launch it with the --join parameter.
• Configure sharding and replication per table.
• Any feature that works with a single database will work in a sharded

cluster.

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Sharding and replication

• There is a hard limit of 64 shards.
• All sharding is currently done based on the table’s primary key only.
• RethinkDB uses system statistics for the table to find the optimal set of

split points to break up the table evenly

• Sharding and replication is configured through table configurations
• Number of shards
• Number of replicas
• Replicas can be associated with servers using server tags.
• Tags are assigned to a server using --server-tag parameter
• Use rebalance command to rebalances the shards of a table.
• Use reconfigure command to setup a table’s sharding and replication.

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RethinkDB Security

• There is a little chance to have an injection attack against RethinkDB because it

embeds into your programming language.

• Make sure that you use the latest database drivers!
• Be careful with .match() function. It may cause regular expression injection

attack.

• Do not use r.js(‘…’) to execute JavaScript code on the server. It is vulnerable to

JavaScript injection attack.

• Use TLS encryption.
• By default, admin account does not have password. Always run you primary

server with --initial-password parameter.

• You cannot set password to administrator web-interface. Make sure it is behind

firewall or bound to localhost (--bind-http parameter).

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Additional Resources

• RethinkDB: https://www.rethinkdb.com/
• RethinkDB installation: https://www.rethinkdb.com/docs/install/
• Thirty-second quickstart: https://www.rethinkdb.com/docs/quickstart/
• Ten-minute guide: https://www.rethinkdb.com/docs/guide/javascript/
• Cookbook: https://www.rethinkdb.com/docs/cookbook/javascript/
• Cheat sheet: https://www.rethinkdb.com/docs/sql-to-reql/javascript/

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Questions?