From Callback To Async Await

Transcript

1. From Callback Hell To Async Await Tamar Twena-Stern
2. Tamar Twena-Stern • Software Engineer - manager and architect • BackEnd Team Leader @XM Cyber • Was a CTO of my own startup • Passionate about Node.js ! • Twitter: @SternTwena
3. Tamar Twena-Stern • Have 3 kids • Community Leader @JavaScript Israel • Loves to play my violin
4. Traditional Approach - Blocking IO Client Server Request Request Request Thread Thread Thread
5. Problems •CPU and memory resources location for every new thread and performs context switching •On stressed – Context switching over actual work
6. Node.js Architecture - Non Blocking IO
7. Asynchronous Programming • Synchronous activities will block the event loop. • Asynchronous programming has evolved in JavaScript • Functions are first class citizens • No return values, only function calls.
8. Asynchronous Code Example
9. So, why callbacks programming is so bad ?
10. The Pyramid Of Doom
11. Easy To Miss Error Handling
12. Correct Error Handling
13. Different To Implement Control Flows • Very hard to implement control flow patterns • You want to be able to execute tasks in : • Series • Parallel • Even implementing array mapping using pure asynchronous functions very hard with plane callbacks
14. Promises
15. What Is A Promise • A proxy for a value that we don’t know yet • Register an event handler to • Success of an asynchronous operation • Failure of an asynchronous operation • Enable an asynchronous method to return value like a synchronous method
16. Promise - Explained
17. Promises Code
18. Promise Libraries • Native in ES6 • Bluebird – add a lot of extra functionality on native ES6 • Promise.mapSeries() • Promise.reduce() • Promise.map() • Promise.Some() • Promise.any() • Promise.each() • Etc …
19. Lets Measure Some Performance
20. Async Await
21. What Is An Async Function • Return an Promise • Inside an async function, we can : • Use await before a function that returns a promise • Await waits for the promise to be resolved • Handle errors with easy and popular mechanism – try / catch • Behind the scenes – asynchronous code
22. Await Keyword • Reserved word from ES7 • Can be used only inside an Async function • Await is used to wait for a promise • Await cause the execution of the function to stop • Same concept as generators • Help simplify the code to look synchronous • Behind the scenes – asynchronous code
23. Some Async Await Code
24. How The Situation Is Improved ?
25. Concise And Clean • No need to use .than • No need to write anonymous callback function for .than or for .catch • Not creating variables that we will not need • Avoid nesting • Very intuitive
26. Clear Error Handling
27. Intermediate Values
28. Parallel Execution Very Easy
29. Watch Out • The code is very concise and clean • This is miss-leading as the biggest advantages of Node.js are • Non blocking IO • Parallel IO work with the worker thread pool • You have to remember to work as much in parallel as you can!
30. Sequential IO - Example
31. How You Should Write This Code ?
32. Demo : Parallel VS Serial IO Down To Numbers
33. Implement A Promise
34. • Twitter: @SternTwena