asynchronous

Promise.all is returning an array of undefined and resolves before being done

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Promise.all accepts an Array of Promise objects. You’re getting an Array of undefined because you’re not returning any Promise in your map callback: function addText(queries) { return Promise.all(queries.map(function(query) { // Add `return` here or the `map` returns an Array of `undefined`. return models.queries .findById(query.queryId, { raw: true, attributes: [ “query” ] }) .then(function(queryFetched) { query.text … Read more

Does an asynchronous call always create/call a new thread?

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This is an interesting question. Asynchronous programming is a paradigm of programming that is principally single threaded, i.e. “following one thread of continuous execution”. You refer to javascript, so lets discuss that language, in the environment of a web browser. A web browser runs a single thread of javascript execution in each window, it handles … Read more

Spring @Async limit number of threads

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If you are using Spring’s Java-configuration, your config class needs to implements AsyncConfigurer: @Configuration @EnableAsync public class AppConfig implements AsyncConfigurer { […] @Override public Executor getAsyncExecutor() { ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); executor.setCorePoolSize(2); executor.setMaxPoolSize(5); executor.setQueueCapacity(50); executor.setThreadNamePrefix(“MyExecutor-“); executor.initialize(); return executor; } } See @EnableAsync documentation for more details : http://docs.spring.io/spring/docs/3.1.x/javadoc-api/org/springframework/scheduling/annotation/EnableAsync.html

Calling TaskCompletionSource.SetResult in a non blocking manner

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I’ve discovered that TaskCompletionSource.SetResult(); invokes the code awaiting the task before returning. In my case that result in a deadlock. Yes, I have a blog post documenting this (AFAIK it’s not documented on MSDN). The deadlock happens because of two things: There’s a mixture of async and blocking code (i.e., an async method is calling … Read more

What is the difference between Asynchronous calls and Callbacks

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Very simply, a callback needn’t be asynchronous. http://docs.apigee.com/api-baas/asynchronous-vs-synchronous-calls Synchronous: If an API call is synchronous, it means that code execution will block (or wait) for the API call to return before continuing. This means that until a response is returned by the API, your application will not execute any further, which could be perceived by … Read more

ReaderWriterLockSlim and async\await

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ReaderWriterLockSlim is a thread-affine lock type, so it usually cannot be used with async and await. You should either use SemaphoreSlim with WaitAsync, or (if you really need a reader/writer lock), use my AsyncReaderWriterLock from AsyncEx or Stephen Toub’s AsyncReaderWriterLock.

Asynchronous constructor

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Update 2: Here is an updated example using an asynchronous factory method. N.B. this requires Node 8 or Babel if run in a browser. class Element { constructor(nucleus){ this.nucleus = nucleus; } static async createElement(){ const nucleus = await this.loadNucleus(); return new Element(nucleus); } static async loadNucleus(){ // do something async here and return it … Read more

Node.js – Using the async lib – async.foreach with object

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The final function does not get called because async.forEach requires that you call the callback function for every element. Use something like this: async.forEach(Object.keys(dataObj), function (item, callback){ console.log(item); // print the key // tell async that that particular element of the iterator is done callback(); }, function(err) { console.log(‘iterating done’); });

What is the best practice in EF Core for using parallel async calls with an Injected DbContext?

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Using any context.XyzAsync() method is only useful if you either await the called method or return control to a calling thread that’s doesn’t have context in its scope. A DbContext instance isn’t thread-safe: you should never ever use it in parallel threads. Which means, just for sure, never use it in multiple threads anyway, even … Read more

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