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  • What library can I use to do simple, lightweight message passing?

    - by Mike
    I will be starting a project which requires communication between distributed nodes(the project is in C++). I need a lightweight message passing library to pass very simple messages(basically just strings of text) between nodes. The library must have the following characteristics: No external setup required. I need to be able to get everything up-and-running in my code - I don't want to require the user to install any packages or edit any configuration files(other than a list of IP addresses and ports to connect to). The underlying protocol which the library uses must be TCP(or if it is UDP, the library must guarantee the eventual receipt of the message). The library must be able to send and receive arbitrarily large strings(think up to 3GB+). The library needn't support any security mechanisms, fault tolerance, or encryption - I just need it to be fast, simple, and easy to use. I've considered MPI, but concluded it would require too much setup on the user's machine for my project. What library would you recommend for such a project? I would roll my own, but due to time constraints, I don't think that will be feasible.

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  • Transferring HashMap between client and server using Sockets (JAVA)

    - by sar
    I am working on a JAVA project in which there are multiple terminals. These terminals act as client and servers. For example if there are 3 terminals A,B and C.Then at any given point in time one of them say A, will be a client making broadcast request. The other two terminals, B and C, will reply. I am using sockets to make them communicate. Once the reply is received from all the other terminals A will check the pool of channels to see if any one of the channel is free. It takes up the free channel and making it availabilty false. The channelpool is implemented using HashMAp: HashMap channelpool = new HashMap(); channelpool = 1=true, 2=true, 3=false, 4=true, 5=true, 6=true, 7=true, 8=true, 9=true, 10=true So initially all the channels are true, any terminal can take any channel. But once the channel is taken it is set to false for the period of use and then reset to true. Now this Hashmap has to be shared among the distributed terminals. Also it should be kept up to date. I can not used a shared resource among the terminals to store the HashMap.Can someone tell me an easy way to transfer the HashMap between the terminals. I will appreciate if someone could point me to a website which discusses this.

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  • Computing pixel's screen position in a vertex shader: right or wrong?

    - by cubrman
    I am building a deferred rendering engine and I have a question. The article I took the sample code from suggested computing screen position of the pixel as follows: VertexShaderFunction() { ... output.Position = mul(worldViewProj, input.Position); output.ScreenPosition = output.Position; } PixelShaderFunction() { input.ScreenPosition.xy /= input.ScreenPosition.w; float2 TexCoord = 0.5f * (float2(input.ScreenPosition.x,-input.ScreenPosition.y) + 1); ... } The question is what if I compute the position in the vertex shader (which should optimize the performance as VSF is launched significantly less number of times than PSF) would I get the per-vertex lighting insted. Here is how I want to do this: VertexShaderFunction() { ... output.Position = mul(worldViewProj, input.Position); output.ScreenPosition.xy = output.Position / output.Position.w; } PixelShaderFunction() { float2 TexCoord = 0.5f * (float2(input.ScreenPosition.x,-input.ScreenPosition.y) + 1); ... } What exactly happens with the data I pass from VS to PS? How exactly is it interpolated? Will it give me the right per-pixel result in this case? I tried launching the game both ways and saw no visual difference. Is my assumption right? Thanks. P.S. I am optimizing the point light shader, so I actually pass a sphere geometry into the VS.

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  • Where could Distributed Version Control Systems currently be in Gartner's hype cycle?

    - by dukeofgaming
    Edit: Given the recent downvoting (+8/-6 at this point) it was made clear to me that Gartner's lifecycle is a biased metric from a programmer's perspective. This is something that is part of a paper I'm going to present to management, and management types are part of Gartner's audience. Giving DVCS exposure & enthusiasm (that "could" be deemed as hype, or at least attacked as such), think about the following question when reading this one: "how could I use Gartner's hype cycle to convince management that DVCSs are ready (or ready-enough) for us, and that it is not just hype" Just asking if DVCSs is hype wouldn't be constructive, Gartner's hype cycle is a more objective instrument than just asking that (even if this instrument is regarded as biased). If you know any other instrument please, by all means, mention it. Edit #2: I agree that Gartner's Life Cycle is not for every technology, but I consider it may have generated enough buzz to be considered hype by some, so it maybe deserves to be at least evaluated/pondered as such by using this instrument in order to prove/disprove it to whatever degree. I'm an advocate of DVCS, BTW. I'm doing research for a whitepaper I'm writing in favor of DVCS adoption at company and I stumbled upon the concept of social proof. I want to prove that the social proof of DVCS adoption is not necessarily cargo cult and doing further research I now stumbled upon Gartner's hype cycle which describes technology maturity in 5 phases. My question is: what could be an indicator of the current location of Distributed Version Control Systems (I mean git, mercurial, bazaar, etc. in general) at a particular phase in the hype cycle?... in other (less convoluted) words, would you say that currently expectations of DVCSs are a) starting, b)inflated, c)decreasing (disillusionment), d)increasing (enlightenment) or e)stabilizing (mature) and (more importantly) why? I know it is a hard question and there is subjectivity involved, but I'll grant the answer (and the traditional cookie) to the clearest argument/evidence for a particular phase.

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  • architecture python question

    - by tom smith
    hi. creating a distributed crawling python app. it consists of a master server, and associated client apps that will run on client servers. the purpose of the client app is to run across a targeted site, to extract specific data. the clients need to go "deep" within the site, behind multiple levels of forms, so each client is specifically geared towards a given site. each client app looks something like main: parse initial url call function level1 (data1) function level1 (data) parse the url, for data1 use the required xpath to get the dom elements call the next function call level2 (data) function level2 (data2) parse the url, for data2 use the required xpath to get the dom elements call the next function call level3 function level3 (dat3) parse the url, for data3 use the required xpath to get the dom elements call the next function call level4 function level4 (data) parse the url, for data4 use the required xpath to get the dom elements at the final function.. --all the data output, and eventually returned to the server --at this point the data has elements from each function... my question: given that the number of calls that is made to the child function by the current function varies, i'm trying to figure out the best approach. each function essentialy fetches a page of content, and then parses the page using a number of different XPath expressions, combined with different regex expressions depending on the site/page. if i run a client on a single box, as a sequential process, it'll take awhile, but the load on the box is rather small. i've thought of attempting to implement the child functions as threads from the current function, but that could be a nightmare, as well as quickly bring the "box" to its knees! i've thought of breaking the app up in a manner that would allow the master to essentially pass packets to the client boxes, in a way to allow each client/function to be run directly from the master. this process requires a bit of rewrite, but it has a number of advantages. a bunch of redundancy, and speed. it would detect if a section of the process was crashing and restart from that point. but not sure if it would be any faster... i'm writing the parsing scripts in python.. so... any thoughts/comments would be appreciated... i can get into a great deal more detail, but didn't want to bore anyone!! thanks! tom

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  • DriverManager always returns my custom driver regardless of the connection URL

    - by JGB146
    I am writing a driver to act as a wrapper around two separate MySQL connections (to distributed databases). Basically, the goal is to enable interaction with my driver for all applications instead of requiring the application to sort out which database holds the desired data. Most of the code for this is in place, but I'm having a problem in that when I attempt to create connections via the MySQL Driver, the DriverManager is returning an instance of my driver instead of the MySQL Driver. I'd appreciate any tips on what could be causing this and what could be done to fix it! Below is a few relevant snippets of code. I can provide more, but there's a lot, so I'd need to know what else you want to see. First, from MyDriver.java: public MyDriver() throws SQLException { DriverManager.registerDriver(this); } public Connection connect(String url, Properties info) throws SQLException { try { return new MyConnection(info); } catch (Exception e) { return null; } } public boolean acceptsURL(String url) throws SQLException { if (url.contains("jdbc:jgb://")) { return true; } return false; } It is my understanding that this acceptsURL function will dictate whether or not the DriverManager deems my driver a suitable fit for a given URL. Hence it should only be passing connections from my driver if the URL contains "jdbc:jgb://" right? Here's code from MyConnection.java: Connection c1 = null; Connection c2 = null; /** *Constructors */ public DDBSConnection (Properties info) throws SQLException, Exception { info.list(System.out); //included for testing Class.forName("com.mysql.jdbc.Driver").newInstance(); String url1 = "jdbc:mysql://server1.com/jgb"; String url2 = "jdbc:mysql://server2.com/jgb"; this.c1 = DriverManager.getConnection( url1, info.getProperty("username"), info.getProperty("password")); this.c2 = DriverManager.getConnection( url2, info.getProperty("username"), info.getProperty("password")); } And this tells me two things. First, the info.list() call confirms that the correct user and password are being sent. Second, because we enter an infinite loop, we see that the DriverManager is providing new instances of my connection as matches for the mysql URLs instead of the desired mysql driver/connection. FWIW, I have separately tested implementations that go straight to the mysql driver using this exact syntax (al beit only one at a time), and was able to successfully interact with each database individually from a test application outside of my driver.

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  • Java DriverManager Always Assigns My Driver

    - by JGB146
    I am writing a driver to act as a wrapper around two separate MySQL connections (to distributed databases). Basically, the goal is to enable interaction with my driver for all applications instead of requiring the application to sort out which database holds the desired data. Most of the code for this is in place, but I'm having a problem in that when I attempt to create connections via the MySQL Driver, the DriverManager is returning an instance of my driver instead of the MySQL Driver. I'd appreciate any tips on what could be causing this and what could be done to fix it! Below is a few relevant snippets of code. I can provide more, but there's a lot, so I'd need to know what else you want to see. First, from MyDriver.java: public MyDriver() throws SQLException { DriverManager.registerDriver(this); } public Connection connect(String url, Properties info) throws SQLException { try { return new MyConnection(info); } catch (Exception e) { return null; } } public boolean acceptsURL(String url) throws SQLException { if (url.contains("jdbc:jgb://")) { return true; } return false; } It is my understanding that this acceptsURL function will dictate whether or not the DriverManager deems my driver a suitable fit for a given URL. Hence it should only be passing connections from my driver if the URL contains "jdbc:jgb://" right? Here's code from MyConnection.java: Connection c1 = null; Connection c2 = null; /** *Constructors */ public DDBSConnection (Properties info) throws SQLException, Exception { info.list(System.out); //included for testing Class.forName("com.mysql.jdbc.Driver").newInstance(); String url1 = "jdbc:mysql://server1.com/jgb"; String url2 = "jdbc:mysql://server2.com/jgb"; this.c1 = DriverManager.getConnection( url1, info.getProperty("username"), info.getProperty("password")); this.c2 = DriverManager.getConnection( url2, info.getProperty("username"), info.getProperty("password")); } And this tells me two things. First, the info.list() call confirms that the correct user and password are being sent. Second, because we enter an infinite loop, we see that the DriverManager is providing new instances of my connection as matches for the mysql URLs instead of the desired mysql driver/connection. FWIW, I have separately tested implementations that go straight to the mysql driver using this exact syntax (al beit only one at a time), and was able to successfully interact with each database individually from a test application outside of my driver.

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  • Is make -j distcc possible to scale over 5 times?

    - by holmes
    Since distcc cannot keep states and just possible to send jobs and headers and let those servers to use only the data just sent and preprocess and compile, I think the lastest distcc has problem in scalability. In my local build environment which has appx. 10,000 c/c++ files to build, I could only make 2 times faster than not using distcc (but using make -j) when having 20 build servers. What do you think is the problem? If anyone has achieved scalability more than 10 - 20 times using make -j and distcc, please let me know. The following product claims that it is impossible to scale make -j and distcc faster than 5 times. http://www.electric-cloud.com/products/electricaccelerator.php I think this can be improved by: Letting the distccd server to maintain sessions Tied to those sessions, they will cache their own header directories Preprocess will be done demand base from the distccd server This will be done through a LD_PRELOADed library libdistcc.so which will replace stat/open syscalls and fetches the header files over network. ... Has anyone done this kind of thing?

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  • General purpose physics engine

    - by Lucas
    Is there any general purpose physics engine that allows huge simulations of rigid bodies? I'm using PhysX from Nvidia, but the focus of this engine is game development, soft bodies. I want to know if exists physics engine that runs on top of PS3 cell processors or CUDA cores allowing massive scientific physics simulations.

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  • "Unable to associated Elastic IP with cluster" in Eclipse Plugin Tutorial

    - by Jeffrey Chee
    Hi all, I am currently trying to evaluate AWS for my company and was trying to follow the tutorials on the web. http://developer.amazonwebservices.com/connect/entry.jspa?externalID=2241 However I get the below error during startup of the server instance: Unable to associated Elastic IP with cluster: Unable to detect that the Elastic IP was orrectly associated. java.lang.Exception: Unable to detect that the Elastic IP was correctly associated at com.amazonaws.ec2.cluster.Cluster.associateElasticIp(Cluster.java:802) at com.amazonaws.ec2.cluster.Cluster.start(Cluster.java:311) at com.amazonaws.eclipse.wtp.ElasticClusterBehavior.launch(ElasticClusterBehavior.java:611) at com.amazonaws.eclipse.wtp.Ec2LaunchConfigurationDelegate.launch(Ec2LaunchConfigurationDelegate.java:47) at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:853) at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:703) at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:696) at org.eclipse.wst.server.core.internal.Server.startImpl2(Server.java:3051) at org.eclipse.wst.server.core.internal.Server.startImpl(Server.java:3001) at org.eclipse.wst.server.core.internal.Server$StartJob.run(Server.java:300) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Then after a while, another error occur: Unable to publish server configuration files: Unable to copy remote file after trying 4 timeslocal file: 'XXXXXXXX/XXX.zip' Results from first attempt: Unexpected exception: java.net.ConnectException: Connection timed out: connect root cause: java.net.ConnectException: Connection timed out: connect at com.amazonaws.eclipse.ec2.RemoteCommandUtils.copyRemoteFile(RemoteCommandUtils.java:128) at com.amazonaws.eclipse.wtp.tomcat.Ec2TomcatServer.publishServerConfiguration(Ec2TomcatServer.java:172) at com.amazonaws.ec2.cluster.Cluster.publishServerConfiguration(Cluster.java:369) at com.amazonaws.eclipse.wtp.ElasticClusterBehavior.publishServer(ElasticClusterBehavior.java:538) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:866) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:708) at org.eclipse.wst.server.core.internal.Server.publishImpl(Server.java:2731) at org.eclipse.wst.server.core.internal.Server$PublishJob.run(Server.java:278) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Can anyone point me to what I'm doing wrong? I followed the tutorials and the video tutorials on youtube exactly. Best Regards ~Jeffrey

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  • Hadoop safemode recovery - taking lot of time

    - by Algorist
    Hi, We are running our cluster on Amazon EC2. we are using cloudera scripts to setup hadoop. On the master node, we start below services. 609 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start namenode' 610 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start secondarynamenode' 611 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start jobtracker' 612 613 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop dfsadmin -safemode wait' On the slave machine, we run the below services. 625 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start datanode' 626 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start tasktracker' The main problem we are facing is, hdfs safemode recovery is taking more than an hour and this is causing delays in our job completion. Below are the main log messages. 1. domU-12-31-39-0A-34-61.compute-1.internal 10/05/05 20:44:19 INFO ipc.Client: Retrying connect to server: ec2-184-73-64-64.compute-1.amazonaws.com/10.192.11.240:8020. Already tried 21 time(s). 2. The reported blocks 283634 needs additional 322258 blocks to reach the threshold 0.9990 of total blocks 606499. Safe mode will be turned off automatically. The first message is thrown in task trackers log because, job tracker is not started. job tracker didn't start because of hdfs safemode recovery. The second message is thrown during the recovery process. Is there something I am doing wrong? How much time does normal hdfs safemode recovery takes? Will there be any speedup, by not starting task trackers till job tracker is started? Are there any known hadoop problems on amazon cluster? Thanks for your help. Regards Bala Mudiam

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  • Memcached with Windows and .NET

    - by Funky81
    Is there anyone already implement memcached for production use in Windows environment? Because many blogs that I've read, it's not recommended to run memcached in Windows especially for production use, for example running memcached on windows. And one more thing, which memcached client that is good to use with c# and .net 3.5 ? I've found many alternate such as Memcached Providers @ Codeplex, Beitmemcached, and memcached provider @ Sourceforge

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  • Hadoop streaming job : stuck

    - by Algorist
    Hi, I am running a hadoop streaming job. It got stuck due to no reason. I am not sure how to cancel the task, so that hadoop schedules another task for the same job. I tried killing the job, but it still doesn't work. Anyone know, how to do this? Thank you Bala

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  • Best method of achieving bi-directional communication between Apple iPad "clients" and a Windows Ser

    - by user361910
    We are currently starting to build a client-server system which will see 10 or more Apple iPad client devices communicating to a central Windows server over a wireless LAN. We wanted to some existing plumbing (.NET remoting/WCF/web services/etc) that would allow us to implement a reliable, secure solution without having to start at a low level (e.g. sockets) and recreate the wheel. One of the major requirements that complicates this scenario is that unlike a traditional web service, the windows server needs to be able to arbitrarily notify the clients whenever certain events occur -- so it is not a simple request/response scenario like the web. Initially, we were going to use Windows clients, so our plan was to use the full-duplex mode of .NET WCF over HTTP|TCP. But now using the iPad, we don't have any of the WCF infrastructure. So my question is: what is the best way to allow an iPad and a Windows server to (securely) communicate over a LAN, with each device able to initiate communication to the other? Am I stuck writing low-level socket code? Thanks!

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  • Open source alternative to MATLAB's fmincon function?

    - by dF
    Is there an open-source alternative to MATLAB's fmincon function for constrained linear optimization? I'm rewriting a MATLAB program to use Python / NumPy / SciPy and this is the only function I haven't found an equivalent to. A NumPy-based solution would be ideal, but any language will do.

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  • Dashboard for collaborative science / data processing projects

    - by rescdsk
    Hi, Continuous Integration servers like Hudson are a pretty amazing addition to software development. I work in an academic research lab, and I'd love to apply similar principles to scientific data analysis. I want a dashboard-like view of which collections of data are fine, which ones are failing their tests (simple shell scripts, mostly), and so on. A lot like the Chromium dashboard (WARNING: page takes a long time to load). It takes work from at least 4 people, and maybe 10 or 12 hours of computer time, to bring our data (from behavioral studies) from its raw form to its final, easily-analyzed form. I've tried Hudson and buildbot, but neither is really appropriate to our workflow. We just want to run a bunch of tests on maybe fifty independent collections of subject data, and display the results nicely. SO! Does anyone have a recommendation of a way to generate this kind of report easily? Or, can you think of a good way to shoehorn this kind of workflow into a continuous integration server? Or, can you recommend a unit testing dashboard that could deal with tests that are little shell scripts rather than little functions? Thank you!

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  • Best cubicle toys for programming

    - by dlamblin
    I need some employee/co-worker Christmas gift ideas. Do you have any good cubicle toys that help you to do any of: think about programming problems solve programming problems by representing common abstractions can be directly programmed can interface with a PC based IDE to be programmed. it may present problems that can be solved, to kick start problem solving. Disallowed items are: reference material in book, pamphlet, poster or cheat-sheet form, even if it has kick ass pop-cultural references. edibles. [discuss separately] things that need their own lab-space and/or extensive tools to be worked with. So yes, Lego Mindstorms come to mind, but they aren't cubicle toys because they cost more than cubicle toys would, and they have too many losable parts. comments on the answers so far: The 20 Questions game sounds quite neat as it could get you thinking; The bean balls could be used as tokens in a problem, so I can see that working. The magnetic toys like ball of whacks or the ball-and-stick ones present hands on fun of a structural nature... now can there be a similar hands on fun toy that aids in representing a solution to a problem? The Gui Mags clearly could, but they're quite utility oriented. The AVR Butterfly is less of a toy but definitely priced attractively, cheaper and more responsive than a basic stamp. I'm not going to pick an answer; there's several great suggestions here. Thank you.

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  • Software tools for allowing end users to reprogram interfaces

    - by iceman
    What would be the examples of commercial software products (specially web-services) which allow the end user to reprogram their user-interface? I mean end users who do not know programming and they are allowed to add more functionality. One way of doing it is allowing XML gadgets like iGoogle does. What are the other approaches and also the technologies enabling them? This would be a futuristic application like collaborative software development for users.

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  • Hadooop map reduce

    - by Aina Ari
    Im very much new to map reduce and i completed hadoop wordcount example. In that example it produces unsorted file (with key value) of word counts. So is it possible to make it sorted according to the most number of word occurrences by combining another map reduce task to the earlier one. Thanks in Advance

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  • Draw on screen border in Commodore 64

    - by Stefano Borini
    Ok. I hope it does not get closed because I have this curiosity since 25 years and I would love to understand the trick. In the commodore 64 the border was not addressable by the 6569 VIC. All you could do was to draw pixels in the central area, the one where the cursor moved. The border was always uniform, although you could change its color with poke 53280,color if i remember correctly. Nevertheless I clearly remember games intros where the border was featured with graphics, like it was fully addressable. I tried to understand how it worked but never got to the point. legends say it was a clever use of sprites, which could, under some circumstances, be drawn on the border, but I don't know if it's an urban legend. edit: just read this from one of the provided links Sprites were multiplexed across vertical raster lines (over 8 sprites, sometimes up to 120 sprites). Until the Group Crest released Krestage 3 in May 2007 there was the common perception that no more than 8 sprites could appear at one raster line, but assigning new Y coordinates made it reappear further down the screen. This is evil.... you beat the raster and reposition the sprite before it gets there...

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  • 404 redirect with cloud storage

    - by Jeremy DeGroot
    I'm hoping to reach someone with some experience using a service like Amazon's S3 with this question. On my site we have a dedicated image server. And on this server, we have an automatic 404 redirect through Apapche so that, if a user tries to access an image that doesn't exist, they'll see a snazzy "Image Not Available" image. We're looking to move the hosting of these images to a cloud storage solution (S3 or Rackspace's CloudFiles), and I'm wondering if anyone's had any success replicating this behavior on a cloud storage service and if so how they did it.

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