Async/Await functions in Ruby

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Async/Await functions in Ruby Sat, Dec. 14th, 2019 @平成Ruby会議01

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@sat0yu - Software engineer at - Building microservices with gRPC and GraphQL - Three years of

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What’s takeaway of this session 1. The basic use of Promise and Fiber 2. ★ The combination of Promise and Fiber performs like Async/Await syntax 3. ★★ The naive Async/Await syntax sadly does NOT work efficiently in ★: hard for @sat0yu to explain

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GraphQL as an integrator *Note: just a part of the whole Quipper services

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N+1 problems with GraphQL

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No content

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ref. https://github.com/rmosolgo/graphql-ruby/blob/master/guides/schema/lazy_execution.md

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How to use Graphql-batch - Build a loader so as inherit GraphQL::Batch::Loader - which need implementing perform(...)fetching data in bulk - Generate field values through the loader X.rb Y.rb ref. https://github.com/Shopify/graphql-batch

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Nested loaders ref. https://github.com/Shopify/graphql-batch

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“Promise” in Graphql-batch ref. https://github.com/Shopify/graphql-batch

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- A representation of an eventual value - The value won’t be calculated until evaluating it (lazy-evaluation) - Chain-able with other promises through .then(...) What is “Promise”? fulfill reject pending fulfilled rejected ※ .load(...) returns a promise

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Async/Await syntax with Promise and Genarator JavaScript

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Async/Await in JavaScript - Declared in ES2017(ES8); Almost all browsers have compatibility - Convenient to write async processing with a synchronized-ish syntax JavaScript

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Pause and Resume for promises - Declared in ES2017(ES8); Almost all browsers have compatibility - Convenient to write async processing with a synchronized-ish syntax sleeping... Pause Resume JavaScript

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Promise + Generator ≈ Async/Await ≈ JavaScript

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Generator pretends Pause and Resume JavaScript

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Generator pretends Pause and Resume JavaScript How can we use Pause & Resume in Ruby?

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Generator pretends Pause and Resume JavaScript Fiber (1.9~)

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What is “Fiber”? ⏸

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⏩ What is “Fiber”?

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⏩ What is “Fiber”?

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⏩ What is “Fiber”?

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⏸ What is “Fiber”?

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⏩ What is “Fiber”?

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⏩ What is “Fiber”?

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⏩ What is “Fiber”?

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⏸ What is “Fiber”?

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Async/Await syntax with Promise and Genarator Fiber

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2. Rewrite nested loaders with Fiber 1. Nested loaders implementation 3. Rewrite nested “resume”s

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1. Nested loaders implementation 2. Rewrite nested loaders with Fiber 3. Rewrite nested “resume”s

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1. Nested loaders implementation

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1. Nested loaders implementation

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1. Nested loaders implementation

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1. Nested loaders implementation

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1. Nested loaders implementation 2. Rewrite nested loaders with Fiber 3. Rewrite nested “resume”s

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2. Rewrite nested loaders with Fiber

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⏸ 2. Rewrite nested loaders with Fiber

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⏩ 2. Rewrite nested loaders with Fiber

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⏩ p1 2. Rewrite nested loaders with Fiber

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⏸ p1 next p1 2. Rewrite nested loaders with Fiber

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⏸ p1 next p1 2. Rewrite nested loaders with Fiber

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⏩ p1 next p1 2. Rewrite nested loaders with Fiber

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⏩ p1 next p1 p2 2. Rewrite nested loaders with Fiber

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⏸ p1 next p1 p2 next p2 2. Rewrite nested loaders with Fiber

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⏸ p1 next p1 p2 next p2 2. Rewrite nested loaders with Fiber

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⏩ p1 next p1 p2 next p2 2. Rewrite nested loaders with Fiber

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p1 next p1 p2 next p2 X 2. Rewrite nested loaders with Fiber

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p1 next p1 p2 next p2 X 2. Rewrite nested loaders with Fiber

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Looks working 2. Rewrite nested loaders with Fiber

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1. Nested loaders implementation 2. Rewrite nested loaders with Fiber 3. Rewrite nested “resume”s

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3. Rewrite nested “resume”s

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3. Rewrite nested “resume”s

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3. Rewrite nested “resume”s

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3. Rewrite nested “resume”s

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3. Rewrite nested “resume”s

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3. Rewrite nested “resume”s

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3. Rewrite nested “resume”s

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Looks working 3. Rewrite nested “resume”s

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Let’s apply the naive Async/Await syntax to xx

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Async/Await in

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When fetching A and B fields

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When fetching C and D fields N+1…

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What’s wrong with the naive Async/Await? The naive Async/Await impl. returns a value, not a promise as a result Graphql-batch allows fields to return a promise in place of a value

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Is it possible to fix it? - It makes me feel it’s do-able… but it does not work even if modifying it as returning a promise - The main difficulty comes from the difference in the promise life-cycle between Graphql-batch and the handcrafted Async/Await implementation

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Summary - Explained the basic usage of Promise and Fiber - Confirmed the combination of Promise and Fiber works as Async/Await syntax - Observed that the naive impl. is not enough to work along with Graphql-batch - Code available: https://github.com/sat0yu/heisei-ruby-kaigi01 Thank you for your time and attention

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appendix

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Promise + Generator = Async/Await https://hackernoon.com/async-await-generators-promises-51f1a6ceede2 JavaScript

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What is “Fiber”? https://www.slideshare.net/KoichiSasada/rubys-concurrency-management-now-and-future

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Graphql-batch gives an example with concurrent-ruby https://github.com/Shopify/graphql-batch/blob/master/examples/http_loader.rb