Introduction to Nimrod, an experimental NodeJS project that enables you to use `require()` in MongoDB shell code.

1. Nimrod: MongoDB Shell in NodeJS
Valeri Karpov
NodeJS Engineer, MongoDB
www.thecodebarbarian.com
github.com/vkarpov15
@code_barbarian

2. *
What is this talk about?
•Why a NodeJS shell?
•Note: not an officially sponsored project
•Going off the beaten trail in JS
•NodeJS repl module
•Proxies in ECMAScript 6
•“Synchronous” I/O using fibers
•Demos

3. *
What’s the MongoDB Shell For?
•REPL for interfacing with MongoDB
•Basic find operations for debugging
•.explain() your queries

4. *
What’s the MongoDB Shell For?
•Server administration

5. *
Two Modes
•Interactive - type at a REPL
•Scripting - execute a file
•Mongo shell focuses on interactive mode
•Without I/O, scripting mode is limited

6. *
Why Write Shell in NodeJS?
•Very old V8 - no ES6
•MongoDB shell is a limited scripting environment
• No I/O
• No environment variables
• Non-standard JS environment - limited module support
•Want to do simple tasks like:
• pull credentials from config without copy/paste
• write results of a set of queries to a file
• utilize moment in the shell

7. *
NodeJS Shell Challenges
•Need a REPL
•db.collectionName.findOne() - how to make .
collectionName access query the database?
•Need synchronous I/O
•The core features for understanding nimrod’s
internals

8. *
The Core Node repl Package
•Underrated Node feature
•Can easily create repls to manage your servers

9. *
The Core Node repl Package
•Basic example

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Contexts and repl
•Contexts make repl actually useful
•Define “global” variables for the repl

11. *
ECMAScript 6 Proxies
•More generic Object.defineProperty()
•Great talk by JavaScript creator Brandon Eich

12. *
ECMAScript 6 Proxies
•More generic Object.defineProperty()
•Object.defineProperty(obj, ‘a’, { get: function() {} });
•Great talk by JavaScript creator Brandon Eich

13. *
Why Proxies?
•db.collectionName.find() ← collectionName should
really be a function call
•Difficult to sync with db on which collections exist
•Hard to get this right without proxies
•Note: proxies are only in node 0.12
•Also need --harmony --harmony_proxies flags

14. *
More About Proxies
•An 80/20 Guide to ECMAScript 6 Proxies on my blog

15. *
Coroutines for I/O
•NodeJS concurrency: great for servers, not for scripts
•Fibers: seemingly synchronous I/O

16. *
Coroutines for I/O
•Callbacks are awesome for servers
• See Callback Hell is a Myth
•But not for scripting
•Terseness and syntactic sugar are key

17. *
Why Sync-ish I/O?
•Can fake on REPL with asynchronous eval + promises
•Much harder to fake in scripting mode:

18. *
Nimrod Examples
•Now you understand nimrod’s core principles
•Time to see it in action :)

19. *
Auth From Environment

20. *
Writing Query Output to a File

21. *
Using NodeJS Packages

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•Contributors welcome! npmjs.org/package/nimrod
•More NodeJS+MongoDB content at:
• www.thecodebarbarian.com
• Twitter: @code_barbarian
Thanks for Listening!