Asynchronous Programming in Node with Streamline.js: how to make control flow and error handling in Node much more sane

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Digital Marketing Analytics with a Competitive Edge
Seth Pollack
Async Node Programming with
Streamline.js
February 17, 2015

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 if you use Node, you’d be nuts not to evaluate Streamline
 codebase ~1/3 smaller
 significant overall productivity gain (1.5x?)
 more fun!
My Pitch: Node + Streamline

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 Why do you love Node?
Ask Yourselves

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 Why do you love Node?
 What don’t you like about Node?
Ask Yourselves

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 Key decision point for me is productivity
 Node’s simple concurrency model is a win
 JavaScript (expressiveness; one language everywhere) is a win
My “Why Node?”

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 Control flow with callbacks is clunky
 Error handling is complex
 Correct callback behavior is easy to get wrong
Node-body’s Perfect

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My Path to Enlightenment
Node Rocks!
Control flow, ouch
Async lib!
Still painful…
Streamline!
Great Success!!!
Sadness….

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Imagine If…

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 Streamline lets you use standard control flow primitives for async
work
 You write your control flow as if async functions were sync, and pass
a special token (“_”) as the callback parameter
 Success results are presented as the return value of the function;
error response or exceptions are presented as a thrown exception
What is Streamline?

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 Example 1: user login
 [over to the IDE]
Code example 1

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 Simple control flow
 Unified error handling
 No need for manual callback invocation
 PLUS…
 JS tools work great
 Better debugging
 Logical stack trace
 No wrappers
 Transparent inter-op
Streamline FTW

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 Example 2: processing data
 [over to the IDE]
Code example 2

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 Streamline is its own language, extremely similar to JavaScript
 Streamline source JIT-ed into native JavaScript
 Can target various back-ends (callbacks, fibers, generators)
 Streamline yields and resumes on your behalf
 Under the covers, the Node event loop continues to run; no blocking
or busy-waiting occurs
Under the Hood

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 Be sure to name your files *._js
 You’ll have to use a different variable name than “_” for the
underscore library
 The magic underscore token isn’t a function, it’s a keyword
 It’s important to understand that the underscore means yield, and
when execution hits it, the event loop may run
 Fibers backend to Streamline has best combo of performance and
developer experience
 Many more goodies exist in Streamline that I haven’t covered here
Tips & Tricks

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 Some runtime overhead (very small slowdown, a bit more memory
usage)
• Extra work is only on async calls, we haven’t found it to be material
 Since Streamline needs to keep up to date with JavaScript language
enhancements (current thinking is that new ES6 language features
to be handled by integrating 6to5)
 With ES7 async/await, we may not need Streamline anymore. I can’t
wait ;-)
Streamline Drawbacks

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 Give Streamline a try!
Conclusion

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Questions

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 Streamline repo: https://github.com/Sage/streamlinejs
 Streamline FAQ:
https://github.com/Sage/streamlinejs/blob/master/FAQ.md
 Streamline mailing list:
https://groups.google.com/forum/#!forum/streamlinejs
 My blog post on Streamline: http://blog.rivaliq.com/develop-double-
time-node-plus-streamline/
 Streamline perf tests: https://gist.github.com/bjouhier/5554200
 Bruno Jouhier’s blog: https://bjouhier.wordpress.com/
References

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Digital Marketing Analytics with a Competitive Edge
Thank You