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

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Handling or preventing conflicts in a multi-user system

I have a web application that is accessed by multiple users from different locations worldwide. Let's say I have an "edit" form for a specific document and two (or more) users are editing the document ...
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644 views

Static objects and concurrency in a web application

I'm developing small Java Web Applications on Tomcat server and I'm using MySQL as my database. Up until now I was using a connection singleton for accessing the database but I found out that this ...
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3 threads printing numbers of different range

This question was asked in an Electronic Arts interview: There are 3 threads. The first thread prints the numbers 1 to 10. The second thread prints the numbers 11 to 20. The third thread prints the ...
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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. ...
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142 views

In C++, are acquire-release memory order semantics transitive?

According to cppreference, we can use release-acquire semantics to ensure write-read precedence between two threads as follows: // Thread A 1. Write to X 2. Atomic store to Y with ...
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718 views

Java BufferedReader vs Separate Producer consumer thread

I have a very big file delimited by some sequence of characters '*L*I*N*E'. The file will be of the order of 250G. And each line comes around 600bytes to 1000 bytes. I will be performing the following ...
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569 views

How can I avoid concurrent access in PostgreSQL?

I would like to have your opinion, how I can handle the case when PDO engine and Hibernate engine "talk" to the same db? There is a PHP application as frontend, and a Java doing some job after user ...
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669 views

Model-View-Controller and client-side concurrency responsibility

In a web application that has a significant ajax component, where is the best place for the client-side concurrency responsibility to lie? We're trying to use MVC on both the server application (LAMP ...
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209 views

Descriptive Locking and Concurrency

I'm thinking about how one would go about designing a descriptive concurrency model for an OOP language that helps simplify concurrency scenarios for programmers (no easy task, concurrency is hard). ...
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162 views

Programming language and database concurrent locking primitives

I am writing an article about both programming language locking primitives (which are really wrappers for OS primitives) and database locking primitives. Are there any short wide-spread titles for ...
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108 views

Implementing distributed Semaphore for AWS workload

We have a messaging gateway in AWS (Amazon Cloud) that comprises of a number of nodes (Linux servers) responsible for receiving, routing, despatching and escalating messages (emails, SMS' and voice ...
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Cache concurrency: ensuring latest version in cache

We have a data service app working on object graphs. We place some complex graphs in a (memory) caching tier as a single data item, so as to avoid the length of time to retrieve every individual data ...
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Does Clojure borrow concurrency ideas from Haskell?

In code quarterly interview with Rich Hickey Michael Fogus hints that Clojure borrows a lot from Haskell: Fogus: As someone who only knows Haskell enough to read the papers, Clojure appears to be ...
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How do I find a good middle way to make this library safe for concurrent operations

I've made a little library called SignalR.EventAggregatorProxy Before I push it into 1.0 state I need to fix so it works safely with concurrent operations. Easiest way is lock all operations but ...
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143 views

Design question about a concurrent forking server

I'm in the early stages of designing a client/server application. The clients will be batch programs that read a file of customer contact data (name, address, email address, phone no's) and pass ...
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209 views

Requiring multithreading/concurrency for implementation of scripting language

Here's the deal: I'm looking at designing my own scripting/interpreted language for fun. I'm only in the planning stages right now; I want to make sure I have a very strong hold on exactly how I will ...
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If mutual exclusion is not implemented, how would we detect a race condition?

Suppose we are in a distributed environment, and mutual exclusion is not implemented yet. So how would we be able to detect race conditions? When I researched, use of non-blocking algorithms was ...
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How bad would it be to obtain a lock on every object?

Imagine a hypothetical programming environment that is largely like Java or .NET, i.e. object-oriented, garbage-collected, etc., but with one small change: Every time you call a method on an object, ...
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Super Fast File Storage Engine

I basically have one big gigantic table (about 1.000.000.000.000 records) in a database with these fields: id, block_id, record id is unique, block_id is not unique, it contains about 10k (max) ...
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544 views

Multiple threads and single output source

For the sake of an exercise, say you have an input file with a series of lines of text with the objective of reversing their respective character sequences. Now introduce 5 threads that will each do ...
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handling online payment for items with one quantity - design issue

I would like to implement a robust way to handle ecommerce payment for items with limited quantity, like for example exclusive paintings. Payment would ideally be accepted via PayPal and credit ...
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752 views

Examples of concurrent iterating scenarios needed

I'm trying to wrap my head around different concurrency solutions to several threads iterating over the same collection but I'm having difficulty coming up with good realistic (but preferably easy to ...
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1answer
121 views

Algorithm to create custom ConcurrentHashMap?

I tried to look into concurrent HashMap source code to look in to how it is implemented. To me it looked very difficult to understand((In no way i am saying its not required :))). I thought if i need ...
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75 views

Coordinating a complicated data migration process

A project I'm involved in has suffered a change in scope, and before I set about trying to cook up some homegrown solution, I'm wondering if there is something out there -- some framework, for example ...
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Repurpose MySQL as a mutex

My application needs to perform an operation once every 10 minutes, but that operation is triggered many times more frequently. Occasionally it is triggered three or four times a second in different ...
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Locking database records

What I have right now: A table with lot of records. About 200 users can select a record according to some rules based on the data in each record. There is a high chance that 2 or more users will ...
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330 views

Apple Dispatch Queue vs Threads

I've heard a lot about apple's famous dispatch queues and the GCD but today was the first time I decided to understand exactly what is going on, so I started reading Concurrency Programming Guide and ...
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278 views

Concurrency checking with Last Change Time

I have an app with the following three tables Email (emailNumber, Address) Recipients (reportNumber, emailNumber, lastChangeTime, status) Report (reportNumber, reportName) I have a C# application ...
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Concurrent Processes - Monitors and Reader/Writers

So this is a general question about the use of monitors in the Reader/Writers problem. I know the monitor procedures for the Readers/Writers problem are used for mutual exclusion to a critical ...
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Semaphore : one for each shared resource?

Normally semaphores are implemented as integer variables. The value of a semaphore represents initially the number of processes that are allowed to access the shared resource at the same time, which ...
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Is Resque appropriate for an evented application?

As the title says, is Resque appropriate for an evented application that requires a decent amount of speed? I'm working on a server application that emulates the default Minecraft server, and I was ...