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37
votes
2answers
21k views

Best practice/Patterns for two way data synchronisation

Quite often in my work the idea of 2-way data synchronisation between database systems crops up. The classic example is two slightly different CRM systems (say, Raiser's Edge and Salesforce) and the ...
31
votes
5answers
4k views

No central database

I have a client that is looking to get a website/mobile apps/desktop apps built that deal with very sensitive data (more sensitive than bank/card details). Because of the sensitive nature of the data, ...
30
votes
5answers
5k views

Does immutability entirely eliminate the need for locks in multi-processor programming?

Part 1 Clearly Immutability minimizes the need for locks in multi-processor programming, but does it eliminate that need, or are there instances where immutability alone is not enough? It seems to ...
19
votes
9answers
29k views

Multithreading synchronization interview question: Find n words given m threads

I came across this question: You are given a paragraph , which contain n number of words, you are given m threads. What you need to do is , each thread should print one word and give the ...
18
votes
1answer
8k views

Redis vs Zookeeper

It seems silly to compare these two servers considering that they're meant for very different things. But if you think about it, they can do lots of similar things: store configuration data, ...
16
votes
2answers
8k views

Conflict resolution for two-way sync

How do you manage two-way synchronization between a 'main' database server and many 'secondary' servers, in particular conflict resolution, assuming a connection is not always available? For example, ...
13
votes
5answers
11k views

How best do you represent a bi-directional sync in a REST api?

Assuming a system where there's a Web Application with a resource, and a reference to a remote application with another similar resource, how do you represent a bi-directional sync action which ...
9
votes
2answers
23k views

When should I use StringBuilder or StringBuffer?

In a production web application, my fellow programmers used StringBuffer everywhere. Now I am taking care of application development and corrections. After reading StringBuilder and StringBuffer I ...
9
votes
2answers
3k views

Is it time to deprecate synchronized, wait and notify?

Is there a single scenario (other than compatibility with ancient JVMs) where using synchronized is preferable to using a Lock? Can anyone justify using wait or notify over the newer systems? Is ...
8
votes
3answers
512 views

How do most sync programs monitor file changes?

Do sync programs like Dropbox typically track file changes by doing byte by byte comparisons, or using hashes, or using diff / keeping local commit logs like version control, or what?
8
votes
1answer
1k views

HTML5 video sprites

I'm currently working on a project where there is a requirement to dynamically composite multiple synchronised video sources onto a single canvas. The initial prototype I put together loaded the video ...
7
votes
1answer
4k views

Atomic Memcache Operations in PHP

This post is a follow up to this question: PHP Atomic Memcache on StackOverflow. Considering I am using Memcache (no d at the end) on PHP 5.3.10, I implemented a custom locking system where a client ...
6
votes
1answer
2k views

Solutions for iOS collaborative sync (iCloud CoreData, CouchDB)?

I'm developing an iOS app where one of the features will be allowing users to share and collaborate on data (e.g. lists). From everything I've read and based on the way that iCloud CoreData sync works ...
6
votes
3answers
2k views

How to do data synchronisation between two applications?

Our client has a CRM application (let's call it A) and a custom built Windows application (VB.NET) (let's call it B) that directly writes to and reads from the CRM database. Application A is used ...
5
votes
1answer
4k views

How to make a method synchronized across all instances of an object

Today I was asked this interview question and could not answer. : If you have two instances of a Person Object and each of them have a setAddres method that is synchronized. Now if it was only one ...
5
votes
2answers
3k views

How to sync calendars events programmatically?

I'd like to hear some ideas how to sync calendar events. Say I have two calendars having fields (id, title, start, end, updated, location and description). I'm struggling with starting point. Its easy ...
5
votes
1answer
528 views

What's a good scheme for multi-user database synchronization?

I'm working on a system to allow multiple users to collaborate on an online project. Everything is fairly straightforward, except for keeping the users in sync. Each user has their own local copy of ...
5
votes
0answers
106 views

Explicit DAG instead of Vector Clocks for synchronisation

I've started looking at approaches to data synchronisation among a set of peers. The peers must be able to work in a disconnected way and then synchronise together to merge their local changes. Peers ...
4
votes
6answers
5k views

Is it possible to half-way synchronize javascript functions that include async calls?

I am wondering if there exists a way to half way synchronize javascript functions, where data is requested on the fly. I don't want to make it purely blocking (which I guess is impossible), I just ...
4
votes
4answers
9k views

How would you approach developing a Hotel Reservation System?

Till now, I have had the experience of developing either a desktop application or a Website. But, with this Hotel reservation system, I am interfacing a problem that needs both. The application ...
4
votes
2answers
150 views

A simple approach for data synchronisation

I want to synchronise the local database of mobile devices with the server's database. This synchronisation will happen for example when user comes online, to update the local as well as the remote ...
4
votes
2answers
1k views

Is it a bad idea to sync file system with remote server using HTTP?

I have started a project which will duplicate Dropbox or Google Drive behavior but using Amazon S3 az a backend. Idea is very simple, a Node.js server that watchs a directory for file changes and PUT ...
4
votes
2answers
251 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 ...
4
votes
2answers
1k views

caching on multiple servers

Because we need to keep response times low, we get tons of requests, and we need to basically process ALMOST the same data (which I'll refer to as X) each request (the inputs are different though, so ...
4
votes
1answer
1k views

What is a good design pattern / lib for iOS 5 to synchronize with a web service?

We are developing an iOS application that needs to synchronize with a remote server using web services. The existing web services have an "operations" style rather than REST (implemented in WCF but ...
4
votes
2answers
2k views

Ideas for Offline & Sync Across Multiple Platforms [closed]

I'm looking for some implementation ideas to be able to have offline apps sync data to a central server. The server will be Sql Server 2008. The clients will download data from the server when ...
4
votes
3answers
862 views

Programmatically syncing with remote servers

My application generates text files that need to be synced with remote servers, which may be windows or linux. Sync has to happen without user's intervention. I tried with rsync but windows doesn't ...
3
votes
5answers
552 views

New application development - Use existing database or create a new one?

A Client has a huge Windows Application running on a Database. This client wants you to develop an "Express" version of this application, including only, let's say, 20% of its features. This Express ...
3
votes
2answers
892 views

Combining asynchronous and synchronous programming

I've got trouble wrapping my head around a certain problem: In my data-flow app (a visual editor), I have both autonomous objects which communicate though ports via unordered simultaneous messages ...
3
votes
4answers
476 views

What's the best way to synchronise an event over multiple processes?

Imagine I have two distinct OS processes (the actual OS is unimportant). Process A is responsible for playing a video file. Process B is responsible for playing the audio that accompanies the video ...
3
votes
2answers
474 views

Do I need a web-service for this case? Data-synchronization over multiple clients

I'm new in this area and a little bit confused about my current thoughts on a web-service implementation for my application. I want to synchronize all connected clients with the current data on a ...
3
votes
3answers
259 views

How to improve enterprise level application that consists of only static methods

I am new in a enterprise level application project and discovered that 99% of everything I've seen in code is static methods, static properties. The application at hand is a distributed app ...
3
votes
2answers
99 views

Best way to develop new features as well as fix any bugs for a web system on Windows [closed]

I'm a one-man band and I have a contract with a client to develop and maintain a web-based system that is relied upon. This is the first project of this size and type that I have done for anyone else ...
3
votes
1answer
1k views

How to implement await in Android

This is a general question to understand how await in C# works, and particularly I am interested in implementing it in Android. So C# await allows you to go in to waiting mode in the middle of the ...
3
votes
1answer
80 views

Synchronization of resource that has moved out of requests filter range

I have a RESTful API with corresponding clients. If a client request fetches a set of resources (Events) based on a filter, say events taking place between 2015-04-13 - 2015-04-19. If an event which ...
3
votes
1answer
388 views

Synchronization between two systems using MongoDB as changelog

We are developing two related system. One of them (A) will be installed in our customers' machines. The remaining (B) will be used by my organization. Each system has its own database (relational) ...
2
votes
1answer
355 views

Does Dropbox use a cronjob to sync up? [closed]

I was looking into lipsync on a Dropbox clone. I was looking at the diagram on how it works here. It shows that a cronjob is used to keep files in sync between client and server. Does that mean that ...
2
votes
2answers
553 views

Difference between mutex in windows and linux

Is that correct that a mutex object in Linux cannot be used for cross process synchronization as opposed to its Windows counterpart? If that is true - what was the idea to limit mutex synchronisation ...
2
votes
4answers
1k views

Best practice to sync long paths to filesystems where path length is limited?

I wrote a sync tool to synchronize folders/files from Alfresco to Windows. PROBLEM: In Alfresco, /files/can/have/very/very/very/long/filepaths/like/this.txt The Windows API prevents me from creating ...
2
votes
3answers
423 views

Offline data that will need imported later

My existing application is a .NET 3.0 winform app that talks to a WCF service which in turn updates a MS SQL Server database; I can make changes at all spots (Windows client, WCF, server). I've had an ...
2
votes
2answers
45 views

How do you address the problem of dealing with an external service that stores your data and you want to keep in sync?

I'm integrating an enterprise application with an existing pattern. The main problem is how to synchronize data between my system and an external system through RPC (HTTP API calls to be precise). ...
2
votes
2answers
64 views

Perfect time synchonization betweeen devices

I want to make two devices synchronize metronome over bluetooth/wifi. However I've got no idea how to make it perfectly synchronized. There are two possible solutions that I've found out: Naive -> ...
2
votes
1answer
26 views

Remote job execution and synchronization

I have master and nodes infrastructure. Master executes remote jobs on nodes. Each job returns success/failure message back to master. So the flow of execution is the following: master receives ...
2
votes
1answer
28 views

Mechanisms to ensure distributed systems do not sychchronize (anti-synchronize)

We have a service that based on a local timer does a GET request to our server on Azure to transmit some information to be saved on the server. At this stage we are only testing and we are finding ...
2
votes
5answers
550 views

A separate endpoint specifically for sync in a REST api

I am working on a multi client/single server app. Communication between the two happens via RESTful API. There are several resources that need to stay in sync across all clients, including images ...
2
votes
3answers
326 views

How much time should you allow for clock skew?

We are writing a B2B application that uses OAuth 2.0. Before a token expires we want to refresh it since it faster to refresh a token, than request a new one. However, we want to build in some ...
2
votes
2answers
866 views

Multithreaded UI desktop application issues

I am involved into development a rich UI project: desktop windows application. Application uses asynchronous invocations and in its turn it should be ready to process external messages (events). The ...
2
votes
1answer
52 views

performance issues when synchronizing on an interned String

I want to lock a remote file with the string "ip + filename" using java. public boolean execCmd(String ip,String filename, String command) { String file = ip + filename; String lock = ...
2
votes
1answer
177 views

Conflict resolution for two-way sync offline sync

How do you manage two-way synchronization between a 'main' database server and many 'secondary' servers, in particular conflict resolution, assuming a connection is not always available(offline ...
2
votes
0answers
259 views

Syncing structured data and files in Android App with an ORM?

I am developing an Android App which I have developed for iOS before. The app requires that structured data and files are synced across android devices. In iOS, I was using Core Data and synced to ...