## From Eager Futures/Promises to Lazy Continuations Evolving an Actor Library Based on Lessons Learned from Large-Scale Deployments ## prologue • past life at UC Berkeley, Twitter, Mesosphere/D2iQ Nikita (@FolMing), Zakhar (@onelxj), and Artur (@ArthurBandaryk) ## chapters (1) motivating futures/promises + actors (2) libprocess (3) revisiting the problem (4) evolution of libprocess (5) eventuals eventuals (6) scheduling (7) streams (8) type erasure ## chapters (1) motivating futures/promises + actors (2) libprocess (3) revisiting the problem (4) evolution of libprocess (5) eventuals (6) scheduling

blazingly fast, prevents segfaults, and guarantees thread safety. ## Concurrency? Rust? Libraries Futures ## What's concurrency? In computer science, concurrency is a property of systems in which several Conditions • Deadlocks • Use after free Exploitable! • Double free Concurrency? Rust? Libraries Futures ## What's Rust? Rust is a systems programming language that runs blazingly fast, prevents segfaults least one is unsynchronized • at least one is a write Mutation! Concurrency? Rust? Libraries Futures ## Rust Concurrency Libs • Language only provides ownership/borrowing • Libraries implement common

78 Promise.prototype.doneとは何か? ..... 88 Promiseとメソッドチェーン ..... 94 Promiseによる逐次処理 ..... 102 Promises API Reference ..... 110 Promise#then ..... 110 Promise#catch ..... 110 Promise.resolve .. Korean: #### eBook JavaScript Promise(####)² ## はじめに ## 書籍の目的 この書籍はJavaScript標準仕様のECMAScript 6 Promisesという仕様を中心にし、JavaScriptにおけるPromiseについて学ぶことを目的とした書籍です。 この書籍を読むことで学べることとして次の3つを目標としています • Promiseに うになること • Promiseの向き不向きについて学び、何でもPromiseで解決するべきではないと知ること • ES6 Promisesを元に基本をよく学び、より発展した形を自分で形成できるようになること この書籍では、先程も述べたようにES6 Promises、つまりJavaScriptの標準仕様(ECMAScript)をベースとしたPromiseについて書かれています。 そのため、

{", f.get());}, p.get_future(); } t1.join(); t2.join(); } ## Futures and Promises • Can help communication between threads • Help build task-oriented utilities for executing executing work on different threads • Future and promise are one shoot operation ## Futures and Promises: another example int main() { std::promise prom1, prom2; auto future = prom1.get_future();

Parallel tree algorithms, divide-and-conquer, ... - Challenges: API: futures? (in Nim “Flowvar” to distinguish from IO-tasks futures) Synchronization - Scheduling overhead Thread-safe memory management data producer and the consumer(s). => Strategy used in Weave, the handle is called a Pledge (~Promises with adapted semantics) Can be implemented with broadcasting SPMC queues ## 4 ## Sources of overhead sleep ## Memory overhead ## Task parallelism might generate billions or trillions of tasks and futures Access from multiple threads: - Heap allocation Threadsafe allocation/deallocation ## Challenges

14, 17, 20C++11: thread, lambda function, TLS, asyncC++11: packaged tasks, promises, futures,C++11: locks, memory model, mutex, condition variable, atomics, static init/term,C++11: will also be in stages • C++11 atomics, async .mm • C++14 shared lock • C++17 parallel algo, futures, (still need more deep dive) unseq, • C++20 latches barriers, coroutine, atomic ref. • C++23 senders

forward declarations) C++ Tapas (typedef, virtual, pure virtual) Overload Resolution Futures & Promises Thread Safety Constexpr Static Const When Your Codebase is Old Enough to Vote Sequencing

across multiple clients. ## Asynchronous Error Handling Handling errors with future response object promises is a bit different. When using a promise, exceptions are forwarded to the $onError function provided exception. echo 'Error: ' . $error->getMessage(); } ); Please see the React/Promises project documentation for more information on how to promise resolution and rejection forwarding response is called, or the corresponding handler that created the response is destructing and there are futures that have not been resolved. Important: This option only has an effect if your handler can create

across multiple clients. ## Asynchronous Error Handling Handling errors with future response object promises is a bit different. When using a promise, exceptions are forwarded to the $onError function provided exception. echo 'Error: '. $error->getMessage(); } ); Please see the React/Promises project documentation [https://github.com/reactphp/promise] for more information on how to promise response is called, or the corresponding handler that created the response is destructing and there are futures that have not been resolved. ## I mportant This option only has an effect if your handler can create

few years, Nim has reached some important milestones: Version 1.0, which brought some stability promises, has been released. Along with the ARC and ORC memory management strategies and full destructor other code while waiting for a long-running, asynchronous task to complete, usually represented by promises or similar data structures. $ ^{[1]} $ The programming language F# (pronounced F sharp) introduced of Nim's async/await framework are provided by the modules std/async/dispatch and std/async/futures. These modules provide a dispatcher, a generic Future $$ T $$ type implementation, and the async