Concurrency is a property of systems in which several processes are executing at the same time.

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1answer
51 views

Is there use case for implementing a callback if a future is returned?

If I have function which returns a future, is there any reason to also include a callback where the callback is simply called right before the future completes? The only advantage I can think of ...
2
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1answer
90 views

Should I use BackgroundWorker in Pipeline pattern?

I am planning the implementation of a Pipeline pattern as seen in this MSDN article. This is a WPF application for which I need to monitor progress of each stage of the pipeline in order to display it ...
2
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1answer
78 views

Possible DRY with Pausing Mechanism

Background I am currently working on the architecture for a future software design. The design is one long running task (hours-long) with thousands of sequential calls to various libraries. I ...
0
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0answers
52 views

Design of thread pool reuse with Executors.newFixedThreadPool in Java [migrated]

In my application I have a code, which should run every hour on a new items and execute some expensive operation with multi threading. Code fragment: int i = 1; //noinspection InfiniteLoopStatement ...
0
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2answers
99 views

Lock threads or not lock threads?

I have an application (full-stack) that is used millions of times concurrently. Some vital application properties are managed on the client side (at the time it seemed to be the simplest approach to ...
5
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2answers
125 views

Composable concurrency in Java or any other programming language

While I was reading a research paper on concurrency named Software and the Concurrency Revolution (html version). I came across following lines: Unfortunately, although locks work, they pose ...
0
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1answer
67 views

Synchronisation with offline system

I'm designing a system from which I will synchronise business data from mobile device that have an embedded application that generates datas and send them back to the server. Each line synchronised ...
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4answers
316 views

What is the ninja performance gap, why is it so large, and how can we overcome it?

According to this abstract: The "Ninja gap" [...] is the performance gap between naively written C/C++ code that is parallelism unaware (often serial) and best-optimized code on modern ...
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2answers
95 views

Why are the Coffman conditions necessary for a deadlock to occur?

Quoting https://en.wikipedia.org/wiki/Deadlock#Necessary_conditions : A deadlock situation can arise if all of the following conditions hold simultaneously in a system: Mutual exclusion: ...
0
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1answer
62 views

Concurrent languages and non-concurrent dependencies [closed]

We had a bug caused by ruby workers (4 processes, 1 thread each) doing batching records using a legacy mongodb as the store. The race condition was around whether the batch was full or not; with one ...
3
votes
1answer
30 views

Asynchronous socket.io for lots of concurrent messages

We have a web application which currently operates like this on a typical view/page: the front has to display 100+ "previews" (in the form of base64 images) each of this preview is built on-demand ...
4
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2answers
254 views

Understanding the Single-Writer Principle

The article on the Single-Writer Principle of the Mechanical Sympathy blog explains how bad queues are (performance-wise), because they need to be able to receive messages from multiple produers, and ...
0
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1answer
46 views

Concurrent and atomic updates to multiple properties/variable of an object

I have a class with multiple setters and want to make atomic updates to multiple properties/variables. As far as I can see there are three methods that could work: Call all setters in synchronized ...
0
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0answers
60 views

How to prevent parallel calls to model?

While there is some command running which calls methods on some model, how to prevent concurrent calls for critical places in that model? If multiple requests comes in then they should maintain their ...
4
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4answers
156 views

How to prevent user from requesting API method multiple times in parallel?

Let's say we have an app where the users gain points and can exchange them for rewards. The exchange request, in pseudo-code, could look like this: function exchangePointsForReward(userId, rewardId){ ...
2
votes
1answer
121 views

Event Sourcing + Updates to multiple aggregates

I'm trying to learn about event sourcing for potential application to a booking system I am building - I think I understand the core concepts, but I'm having trouble understanding how to handle cases ...
-1
votes
1answer
71 views

Approaches to Concurrency [closed]

I’ve been doing some research on the various approaches to concurrency, and I’ve ended up with the following taxonomy: Manual thread based concurrency with locks Asynchronous dispatch queues and ...
2
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0answers
71 views

Handling exceptions in multiple-issue CPUs

From what I read, VLIWs execute instructions in bundles, i.e. the CPU loads a bundle of instructions and dispatches them all at once. This is possible because the compiler scheduled instructions in ...
0
votes
1answer
339 views

akka and futures, which ExecutionContext should be used

Following this blog by @Tomasz Nurkiewicz we can see that 4 different approaches are available for picking the ExecutionContext, when interacting with akka actors, for scala futures to run on. import ...
3
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1answer
141 views

Java concurrency

I am working to solve interesting concurrent problem! Not sure if I understand it correctly since I am little bit confused. The system needs to process the prices, and typically they cannot be ...
0
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1answer
259 views

Ever-running timed tasks

I need to design a piece of software which is invoking some actions regularly. By regularly I mean that there is x things that need to be done at 12.00, y things at 12.30 etc,etc. The times and ...
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2answers
126 views

Don't quite understand check and set in concurrency

I don't entirely understand check and set behaviour.. here is an example: public static void main(String[] args) { List<String> list = Collections.synchronizedList(new ...
4
votes
2answers
333 views

Why is Akka good for concurrency?

I am new to Akka and actor framework - I am sure I am missing something obvious, please accept my apologies in advance. I keep reading that one of the main points to choose Akka is the way it manages ...
2
votes
3answers
139 views

Long running DB query with concurrent write at the same time [closed]

We have a big table with a lot of data and a select query which takes 3 seconds to run. However we are a highly concurrent environment and each second we get 100 new records in our database. So ...
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0answers
93 views

Terminology - Difference between thread and process and how they manage DB connections

I've been working more with concurrency in Ruby recently, and I keep seeing various articles using "threads" and "process" interchangeably. What are the actual definitions of these terms? Is a ...
1
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1answer
141 views

Does ReaderWriterLockSlim provide thread safety and speed efficiency (compared to a traditional lock) when using a List?

I have a list, to which I write once in every update Loop and then I spawn some tasks which create read that List and create a duplicate to manipulate that data. More or less it's List.ToList() call ...
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0answers
44 views

Is using synchronization in service layer a bad idea?

I need to implement a mailbox monitor system as a web service. I have follow classes: MailboxMonitor: Contains information such as username, password, pulling interval etc. MailboxMonitorRepository: ...
3
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1answer
99 views

How does condition_variable::notify_one() choose which thread to unblock?

notify_one() of C++ 11 thread library is used to unblock one of the waiting threads. How does it choose which thread to unblock? To begin with, I tried googling but could not find any appropriate ...
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3answers
1k views

Is REST only limited to optimistic concurrency control?

Context Due to the statelessness of the REST architectural style involving that each requests stands completely alone, leading server to never store any informations about client. Thus, pessimistic ...
3
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1answer
1k views

Difference between Consumer/Producer and Observer/Observable

I am working on the design of an application that consists of three parts: a single thread that watches for certain events happening (file creation, external requests etc.) N worker threads that ...
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0answers
127 views

Injecting locking policy into a class

I have a class that does some operations on data, and I want to have different locking schemes (no-lock, simple-lock, and read reader-writer lock) in different situations. Think this main class like ...
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3answers
2k views

Can multiple synchronized methods in same object run concurrently

As far as i know when there are multiple synchronized methods(both static and instance) in a class, java allows only one such method to run at a time. But what if a thread acquires lock on an object ...
4
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4answers
444 views

Testing concurrency/thread-safety

A program I have wrote uses multiple threads and I believe my program is thread-safe but how can I really know? I've read a number of examples online and none of them describe how to test the code is ...
1
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1answer
156 views

Generic PHP web interface for handling concurrent updates optimistically

I'm looking in to writing a new PHP based CMS which handles concurrent edits optimistically like source version control rather than pessimistic locking like Wordpress. I want to be able to write some ...
9
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1answer
451 views

When asynchronous tasks make a bad UX

I'm writing a COM add-in that's extending an IDE that desperately needs it. There are many features involved, but let's narrow it down to 2 for the sake of this post: There's a Code Explorer ...
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1answer
649 views

How to concurrently write data in Java without locking?

How to implement a multi-threaded program in which each thread needs to write/output some data (in any order of course) but without the locking overhead that is involved with files or a particular ...
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votes
1answer
457 views

Crawler - programming language choice [closed]

I'm currently developing a web crawler. The first version was developed in Node.js and runs pretty well. The issues that I encountered with Node.js are in no particular order: slow URL and ...
25
votes
3answers
3k views

How much work should I place inside a lock statement?

I am a junior developer working on writing an update for software that receives data from a third-party solution, stores it in a database, and then conditions the data for use by another third-party ...
1
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1answer
110 views

is a DoS attack a good analogy of Dining Philosophers?

Let's say that, instead philosophers, we have TCP/IP connections to a server, and instead forks we have the server's TCP/IP avaliable ports. In this scenario, we don't have a lot of connections ...
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1answer
83 views

What's the best way to implement a real time show board to show results from concurrent result producers in Java?

I'm making a load test tool that launches multiple thread to simulate load on the target server. Each thread executes a predefined set of commands in the structure of TestSuite - TestCase- TestStep ...
1
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1answer
242 views

Experiences with C++ Async/actor model Library [closed]

I am fairly experienced with async and concurrent programming in c# using event, actor, and task based patterns, but now I have a task in c++ with which I have basic familiarity and it needs some ...
2
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3answers
702 views

Accessing shared data without blocking in TPL

I am writing a class that contains data. It exposes methods that allow to query the data, while the data is also being updated from an external source (web service, for example). All the methods ...
5
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2answers
1k views

Where is the evidence for the performance of Node.js?

A lot of developers, especially ones who haven't used Node.js in production, seem to believe that Node.js is faster than other interpreted languages such as PHP, Python, and Ruby. These claims ...
1
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2answers
105 views

When, if ever, are basic concurrency optimizations generally made?

Lets say I need to preform the following computationally intensive task For i in range(100000000): doComplexCalculationWithNoSideEffects(i) Most people I talk to tell me that basically any ...
1
vote
1answer
68 views

How to model parallel processes (in a Bounded Context) with the same data store?

The situation. Let's say a background process puts stuff into data containers. It runs all the time, observes system events, and populates the data accordingly. The user may launch a control panel ...
0
votes
2answers
404 views

Scaling locks in high concurrency web apps [closed]

Our web application has a certain resource type that is shared accross multiple users, and may thus be read and written by anyone at anytime. We resorted to the usual suspects, database transactions ...
1
vote
3answers
641 views

Is there an algorithm to determine the amount of work needed to keep workers busy?

I wrote a multi-threaded program that randomly generates strings, and after generating, checks to see if the string contains a certain value. Namely, StringGenerator and StringChecker. What I'm trying ...
1
vote
1answer
57 views

Locking on data vs locking on functions

In concurrent code, what is the difference between, and the pros and cons of each: Locking on data Locking on functions My understanding is that locking on data is better, and I think I'm doing ...
1
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2answers
90 views

Lock data in DB while external API call is pending?

I have an interesting situation, and I am looking for the best way to solve it. My app runs like this: 1) The user gets a Promotion Pin from Some Company, and I have a db table with these pins also. ...
2
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1answer
117 views

Can concurrent code (threads, distributed computing, etc.) be directly ported to single-threaded/non-networked platforms?

Take an arbitrary "perfect" multi-threaded program, on an arbitrary multi-threaded platform, using an arbitrary programming language. Assuming that this "perfect" multi-threaded program: is ...