Concurrency is a property of systems in which several processes are executing at the same time.
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31 views
How do I handle the potential concurrency problem of making a payment to Paypal for a limited number of items?
After doing some investigation* I have learned that I could potentially have a concurrency problem.
I'm currently building a Tournament Platform in ASP.NET MVC 5 with Entity Framework 6. So far, ...
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0answers
30 views
Book of problems for c++ concurrency [closed]
Now I am reading the book "C++ Concurrency in Action" by Antony Williams, and looking for some book of problems about concurrency, to train on and consolidate knowledge.
Can anyone suggest me some ...
1
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0answers
49 views
One producer and one consumer vs inconsistent shared resource state
I was reading about implementation of producer-consumer problem with one producer and one consumer. Looking at this paragraph I see the implementation where shared resource access is not synchronized ...
4
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2answers
77 views
How to handle a one-time startup SQL script
I'm trying to figure out the best way to tackle running a one-time SQL script when a service instance starts up. Here's the scenario:
We run multiple Amazon instances of our service in parallel.
...
4
votes
4answers
136 views
Serializing mutating objects
In our system a media file can have several states: invalid, empty, uploading, ingesting, ready… Depending of the state, information about the media are accessed in different ways. For example, during ...
4
votes
0answers
77 views
possible to achieve Rust's ownership model with a generic C++ wrapper?
Looking through this article on Rust's concurrency safety:
http://blog.rust-lang.org/2015/04/10/Fearless-Concurrency.html
I was wondering how many of these ideas can be achieved in C++11 (or ...
17
votes
1answer
388 views
How does Rust diverge from the concurrency facilities of C++?
I am trying to decide whether Rust fundamentally, sufficiently improves upon the concurrency facilities of C++ that I should spend the time to learn Rust. In light of Stackexchange's format, I should ...
2
votes
1answer
128 views
What are the advantages of Observables over an iterable of futures?
I recently came across the ReactiveX pattern for asynchronous data-flows. I studied the information provided there and also watched this talk by a Netflix engineer on how they used Observables to ...
3
votes
1answer
69 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
votes
1answer
102 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
votes
1answer
80 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 ...
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2answers
122 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 ...
9
votes
4answers
294 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 ...
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1answer
104 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 ...
1
vote
4answers
326 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
...
1
vote
2answers
104 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
votes
1answer
63 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
34 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
votes
2answers
290 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 ...
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1answer
55 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
votes
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
votes
4answers
180 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
160 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
77 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
votes
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
558 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
votes
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
votes
1answer
260 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 ...
1
vote
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
366 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
162 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 ...
1
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0answers
104 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
vote
1answer
155 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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votes
0answers
46 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
votes
1answer
107 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 ...
5
votes
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 ...
4
votes
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 ...
1
vote
0answers
136 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 ...
1
vote
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
votes
4answers
523 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
vote
1answer
163 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
votes
1answer
466 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 ...
1
vote
1answer
762 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 ...
-2
votes
1answer
500 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
4k 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
vote
1answer
111 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 ...
-1
votes
1answer
85 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
vote
1answer
256 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
votes
3answers
780 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 ...
6
votes
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 ...
