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  • Design patterns for Caching Images in a MVC?

    - by Onema
    Hi, I'm designing an image cache system that will be used in an MVC CMS. The main purpose of the image cacher is to modify images: scale, crop, etc and cache them in the client site. I have created an image cache Model and Mapper that interact with the Database, to keep track of the images and know what kind of actions have been applied to them (scale, crop, etc). In addition to the Model and Mapper I have created a ImageCacher Class that is used by the API to manage the Model and image creation based on arguments passed by the client site, this class creates the images and generates the links to the images for the View. A coworker argued that I need to include the functionality of this last Class inside the Model, as the bulk of the logic should go in the model. I respectfully disagree with him since I feel the model's responsibility is to deal with the information about the images cached at the database level, and the responsibility of the ImageCacher Class is to create the url/image that we will be caching (keeping the single responsibility principle). In addition to this I believe that a model should not have Presentation-related features, like creating or showing images. Does anyone have any insight on this? is there a particular design pattern that would make this division of tasks clear and and the image cacher reusable? Should I add all the logic in the Model? Thank you.

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  • Data Access Layer - static list objects and caching

    - by Truegilly
    Hello, i am devloping a site using .net MVC i have a data access layer which basically consists of static list objects that are created from data within my database. The method that rebuilds this data first clears all the list objects. Once they are empty it then add the data. Here is an example of one of the lists im using. its a method which generates all the UK postcodes. there are about 50 methods similar to this in my application that return all sorts of information, such as towns, regions, members, emails etc. public static List<PostCode> AllPostCodes = new List<PostCode>(); when the rebuild method is called it first clears the list. ListPostCodes.AllPostCodes.Clear(); next it re-bulilds the data, by calling the GetAllPostCodes() method /// <summary> /// static method that returns all the UK postcodes /// </summary> public static void GetAllPostCodes() { using (fab_dataContextDataContext db = new fab_dataContextDataContext()) { IQueryable AllPostcodeData = from data in db.PostCodeTables select data; IDbCommand cmd = db.GetCommand(AllPostcodeData); SqlDataAdapter adapter = new SqlDataAdapter(); adapter.SelectCommand = (SqlCommand)cmd; DataSet dataSet = new DataSet(); cmd.Connection.Open(); adapter.FillSchema(dataSet, SchemaType.Source); adapter.Fill(dataSet); cmd.Connection.Close(); // crete the objects foreach (DataRow row in dataSet.Tables[0].Rows) { PostCode postcode = new PostCode(); postcode.ID = Convert.ToInt32(row["PostcodeID"]); postcode.Outcode = row["OutCode"].ToString(); postcode.Latitude = Convert.ToDouble(row["Latitude"]); postcode.Longitude = Convert.ToDouble(row["Longitude"]); postcode.TownID = Convert.ToInt32(row["TownID"]); AllPostCodes.Add(postcode); postcode = null; } } } The rebuild occurs every 1 hour. this ensures that every 1 hour the site will have fresh set of cached data. the issue ive got is that occasionally if during a rebuild, the server will be hit by a request and an exception is thrown. The exception is "Index was outside the bounds of the array." it is due to when a list is being cleared. ListPostCodes.AllPostCodes.Clear(); - // throws exception - although its not always in regard to this list. Once this exception is thrown application dies, All users are affected. I have to restart the server to fix it. i have 2 questions... If i utilise caching instead of static objects would this help ? Is there any way i can say "while the rebuild is taking place, wait for it to complete until accepting requests" any help is most appricaiated ;) truegilly

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  • How to rewrite a TCP MMOG server designed to run in a single machine, in a distributed way?

    - by Dokkat
    I have a MMOG server running on C++, using winsockets. My server won't support more than 200 players. I had the idea of redesigning it so it will use multiple servers instead of one, so, maybe, for example, each server could take care of a number of players, and, if it was too laggy, it could transfer the responsability of that player to other server. I'm not sure of how to program a consistent game logic like that, though. Are there techniques for this?

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  • How DBAs Can Tune Distributed IBM DB2 Applications

    Many critical business applications now execute in an environment separate from that of the enterprise database server. The database administrator often finds monitoring and performance tuning of these "distributed" applications to be especially difficult. This article looks at common performance issues of distributed applications and presents advice to assist the IBM DB2 database administrator in mitigating performance problems.

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  • ASP.NET Caching : Good As Well As Bad ! Page shows old content!

    - by Shyju
    I have an ASP.NET website where i have implemented page level caching using the OutPutCache directive.This boosted the page performance.My pages has few parts(Some buttons,links and labels) which are specific to the logged in user.If user is not logged in,they will see different links.Now Since i implemented the page level caching,Even after the user logged in,It's showing the old page content(Links and buttons meant for the Non logged in User). Caching is obviously good.But how to get rid of this problem ? Do i need to completely remove caching ?

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  • Asking browsers to cache our images (ASP.NET/IIS)

    - by Django Reinhardt
    I just ran Google's Page Speed application against our site and one of the recommendations was to Leverage browser caching. Expanding this revealed the following: The following cacheable resources have a short freshness lifetime: Specify an expiration at least one week in the future for the following resources: <a long list of images > <some javascript files > How do I go about lengthening the "freshness lifetime" of particular images? It's an ASP.NET project running on IIS7.5 Thanks for any help!

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  • has anyone produced an in-memory GIT repository?

    - by Andrew Matthews
    I would like to be able to take advantage of the benefits of GIT (and its workflows), but without the cost of disk access - I just would like to leverage the distributed revision control capabilities of GIT to produce something like a hybrid of memcached and GIT. (preferably in .NET) Is there such a beast out there?

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  • MSDTC attempts to enlist client machine in a distributed transaction

    - by Ken
    Hi there We're seeing the following intermittent warning logged by MSDTC: A caller has attempted to propagate a transaction to a remote system, but MSDTC network DTC access is currently disabled on machine 'X'. Please review the MS DTC configuration settings. However, MSDTC is disabled on machine X by design - it's a client machine, and has no business being enlisted in the transaction! Several windows service endpoints hosting WCF services over TCP Single SQL Server 2005 instance beneath Linq to Sql Remote client receives event callbacks over WCF/TCP The issue is tricky to reproduce - usually following restart of services. We suspect a callback to the client machine is occurring within the context of a transaction. Just wondering if anyone has seen similar issues?? Ken

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  • Ehcache - Distributed RMI not working

    - by Ted
    Hi, I have this strange problem with ehcache 2.0 that I hope someone can help me with. I have set up a cluster of two hosts, A and B. I can see that heartbeats are received at both ends, so I'm pretty sure the networking and multicast stuff is working. The problem is that is I put an element into the cache at host A, I can see in the logs of host B that it receives a remote put. But when I request the same element from host B, it runs off to the data base and performs a query nonetheless. What may be the cause of this? Thankful for any pointers!

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  • running a python script where dependencies are not avail: distributed computing

    - by sadhu_
    Hi, I have access to a grid (running condor) that would (potentially) allow to very substantially reduce how long by nltk based nlp tasks take. unfortunately, i dont have root access on the cluster so cannot install new packages, only run whatever is available on the linux boxes. python is of course available, but nltk isnt - i was wondering however, if there might be a way around this somehow ? is there a way i can somehow still distribute the task in a self-contained 'package' of some sort? Thanks for your hel

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  • Sphinx search distributed index tuning

    - by Andriy Bohdan
    I'm deciding how to split 3 large sphinx indexes between 3 servers. Each of the 3 indexes is searched separately. What's more effective: to host each index on separate machine Example machine1 - index1 machine2 - index2 machine3 - index3 or to split each index into 3 parts and host each part of the same index on separate machine. Example machine1 - index1_chunk1, index2_chunk1, index3_chunk1 machine2 - index1_chunk2, index2_chunk2, index3_chunk2 machine3 - index1_chunk3, index2_chunk3, index3_chunk3 ?

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  • Distributed Lucene.NET

    - by user72185
    Hi, I have a Terabyte of data, maybe more, which I'd like to index and search with Lucene. I'd like to be able to split the index out to different machines, similar to what Solr does (if I understand Solr correctly). Are there any existing tools to do this on the Windows platform? Thanks!

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  • Advice on designing and building distributed application to track vehicles

    - by dario-g
    I'm working on application for tracking vehicles. There will be about 10k or more vehicles. Each will be sending ~250bytes in each minute. Data contains gps location and everything from CAN Bus (every data that we can read from vehicle computer and dashboard). Data are sent by GSM/GPRS (using UDP protocol). Estimated rows with this data per day is ~2000k. I see there 3 main blocks. 1. Multithreaded Socket Server (MSS) - I have it. MSS stores received data to the queue (using NServiceBus). 2. Rule Processor Server (RPS) - this is core of this system. This block is responsible for parsing received data, storing in the database, processing rules, sending messages to Notifier Server (this will be sending e-mails/sms texts). Rule example. As I said between received bytes there will be information about current speed. When speed will be above 120 then: show alert in web application for specified users, send e-mail, send sms text. (There can be more than one instance of RPS). 3. Web application - allows reporting and defining rules by users, monitoring alerts, etc. I'm looking for advice how to design communication between RPS and Web application. Some questions: - Should Web application and RPS have separated databases or one central database will be enough? I have one domain model in web application. If there will be one central database then can I use the same model (objects) on RPS? So, how to send changed rules to RPS? I try to decouple this blocks as much as possible. I'm planning to create different instance of application for each client (each client will have separated database). One client will be have 10k vehicles, others only 100 vehicles.

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  • Distributed Message Ordering

    - by sbanwart
    I have an architectural question on handling message ordering. For purposes of this question, the transport is irrelevant, so I'm not going to specify one. Say we have three systems, a website, a CRM and an ERP. For this example, the ERP will be the "master" system in terms of data ownership. The website and the CRM can both send a new customer message to the ERP system. The ERP system then adds a customer and publishes the customer with the newly assigned account number so that the website and CRM can add the account number to their local customer records. This is a pretty straight forward process. Next we move on to placing orders. The account number is required in order for the CRM or website to place an order with the ERP system. However the CRM will permit the user to place an order even if the customer lacks an account number. (For this example assume we can't modify the CRM behavior) This creates the possibility that a user could create a new customer, and place an order before the account number gets updated in the CRM. What is the best way to handle this scenario? Would it be best to send the order message sans account number and let it go to an error queue? Would it be better to have the CRM endpoint hold the message and wait until the account number is updated in the CRM? Maybe something completely different that I haven't thought of? Thanks in advance for any help.

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  • Best Work Queue service for distributed clusters

    - by onewheelgood
    Hi there. I require a simple work queue type system for asynchronous task management. I have looked at both beanstalkd and gearman. However, both these seem to assume that the client and the queue server are on the same network, and therefore that there will always be a reliable network between them. I need one that can support the client and server being in different places in the world, and be able to manage temporary loss of network connection between clusters. Ideally, this would work in such a way where I post a job to a local proxy that attempts to send it to the main queue server. If there is no network connection, it would try again later, however it would not lose the job or delay the client. Any recommendations?

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  • JPA in distributed Java EE configuration

    - by sof
    Hello, I'm developing a JEE application to run on Glassfish: Database (javaDB, MS SQL, MySQL or Oracle) EJB layer with JPA (Toplink essentials - from Glassfish) for database access JSF/Icefaces based web UI accessing the EJB layer The application will have a lot of concurrent web client, so I want to run it on different physical servers and use a load-balancer. My problem is now how to keep the applications synchronized. I intend to set up multiple servers, each running Glassfish with my EAR app installed. Whenever on one of the servers data is added to or removed from the database (via JPA, no direct SQL queries), this change should be reflected in the JPA layer on the other servers. I've been looking around for solutions to this, but couldn't find anything I really like (the full Toplink from Oracle claims to have a solution, but don't know). Doing a refresh before every access to a JPA entity could work, but is far from efficient. Are there any patterns, libraries, ... that could help here? Thanks a lot!

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  • Understanding omission failure in distributed systems

    - by karthik A
    The following text says this which I'm not able to quite agree : client C sends a request R to server S. The time taken by a communication link to transport R over the link is D. P is the maximum time needed by S to recieve , process and reply to R. If omission failure is assumed ; then if no reply to R is received within 2(D+P) , then C will never recieve a reply to R . Why is the time here 2(D+P). As I understand shouldn't it be 2D+P ?

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  • High performance distributed asynchronous RPC in java

    - by unludo
    I would like to do RPC to a list of clients with the following requirements: the server does not know the clients (implies a kind of broker?) and the cleints do not know the server there may be several clients - they share the load to treat the RPC The RPC is asynchronous very fast (round-trip < 1ms) optional : offers a fail-over mechanism. It can be done with underlying tools which are not really intended for that (Hazelcast is an example). What would you use for such requirements? Thanks!

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  • Generic DRM (Distributed resource management) wrapper

    - by Pavel Bernshtam
    I need to write a software, which launches DRM jobs in a customer environment and monitors those jobs status. It should work with various customer environments and DRMs - like LSF, Sun Grid and others. Can you recommend some 3rd party library, which hides DRM differences from me and has API like "launch job", "get list of jobs", "get job status" etc. ? Both Java and native libraries are good for me.

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  • Microsoft Enterprise Library Caching Application Block not thread safe?!

    - by AlanR
    Good aftenoon, I created a super simple console app to test out the Enterprise Library Caching Application Block, and the behavior is blaffling. I'm hoping I screwed something that's easy to fix in the setup. Have each item expire after 5 seconds for testing purposes. Basic setup -- "every second pick a number between 0 and 2. if the cache doesn't already have it, put it in there -- otherwise just grab it from the cache. Do this inside a LOCK statement to ensure thread safety. APP.CONFIG: <configuration> <configSections> <section name="cachingConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Caching.Configuration.CacheManagerSettings, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" /> </configSections> <cachingConfiguration defaultCacheManager="Cache Manager"> <cacheManagers> <add expirationPollFrequencyInSeconds="1" maximumElementsInCacheBeforeScavenging="1000" numberToRemoveWhenScavenging="10" backingStoreName="Null Storage" type="Microsoft.Practices.EnterpriseLibrary.Caching.CacheManager, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Cache Manager" /> </cacheManagers> <backingStores> <add encryptionProviderName="" type="Microsoft.Practices.EnterpriseLibrary.Caching.BackingStoreImplementations.NullBackingStore, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Null Storage" /> </backingStores> </cachingConfiguration> </configuration> C#: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.EnterpriseLibrary.Common; using Microsoft.Practices.EnterpriseLibrary.Caching; using Microsoft.Practices.EnterpriseLibrary.Caching.Expirations; namespace ConsoleApplication1 { class Program { public static ICacheManager cache = CacheFactory.GetCacheManager("Cache Manager"); static void Main(string[] args) { while (true) { System.Threading.Thread.Sleep(1000); // sleep for one second. var key = new Random().Next(3).ToString(); string value; lock (cache) { if (!cache.Contains(key)) { cache.Add(key, key, CacheItemPriority.Normal, null, new SlidingTime(TimeSpan.FromSeconds(5))); } value = (string)cache.GetData(key); } Console.WriteLine("{0} --> '{1}'", key, value); //if (null == value) throw new Exception(); } } } } OUPUT -- How can I prevent the cache to returning nulls? 2 --> '2' 1 --> '1' 2 --> '2' 0 --> '0' 2 --> '2' 0 --> '0' 1 --> '' 0 --> '0' 1 --> '1' 2 --> '' 0 --> '0' 2 --> '2' 0 --> '0' 1 --> '' 2 --> '2' 1 --> '1' Press any key to continue . . . Thanks in advance, -Alan.

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  • Versioning millions of files with distributed SCM

    - by C. Lawrence Wenham
    I'm looking into the feasibility of using off-the-shelf distributed SCMs such as Git or Mercurial to manage millions of XML files. Each file would be a commercial transaction, such as a purchase order, that would be updated perhaps 10 times during the lifecycle of the transaction until it is "done" and changes no more. And by "manage", I mean that the SCM would be used to not just version the files, but also to replicate them to other machines for redundancy and transfer of IP. Lets suppose, for the sake of example, that a goal is to provide good performance if it was handling the volume of orders that Amazon.com claimed to have at its peak in December 2010: about 150,000 orders per minute. We're expecting the system to be distributed over many servers in order to get reasonable performance. We're also planning to use solid-state drives exclusively. There is a reason why we don't want to use an RDBMS for primary storage, but it's a bit beyond the scope of this question. Does anyone have first-hand experience with the performance of distributed SCMs under such a load, and what strategies were used? Open-source preferred, since the final product is to be FOSS, too.

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  • Standard Network Tiers in a Distributed N-Tier System

    Distributed N-Tier client/server architecture allows for segments of an application to be broken up and distributed across multiple locations on a network.  Listed below are standard tiers in a Distributed N-Tier System. End-User Client Tier The End-User Client is responsible for sending and receiving requests from web servers and other applications servers and translating the responses so that the End-User can interpret the data effectively. The primary roles for this tier are to communicate with servers and translate server responses back to the end-user to interpret. Business-Specific Functions Validate Data Display Data Send Data to Webserver Web Server Tier The Web server tier processes new requests for information coming in from the HTTP and HTTPS ports. This primarily handles the generation of user interfaces and calls the application server when needed to access Data and business logic when needed. Business-specific functions Send Data to application server Format Data for Display Validate Data Application Server Tier The application server stores and executes predefined business logic that is applied to various pieces of data as the business determines. The processed data is then returned back to the Webserver. Additionally, this server directly calls the database to obtain and store any data used by the system Business-Specific Functions Validate Data Process Data Send Data to Database Server Database Server Tier The Database Server is responsible for storing and returning all data need by the calling applications. The primary role for this this server is storage. Data is stored as needed and can be recalled at any point later in time. Business-Specific Functions Insert Data Delete Data Return Data to Application Server

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  • Preventing Flex application caching in browser (multiple modules)

    - by Simon_Weaver
    I have a Flex application with multiple modules. When I redeploy the application I was finding that modules (which are deployed as separate swf files) were being cached in the browser and the new versions weren't being loaded. So i tried the age old trick of adding ?version=xxx to all the modules when they are loaded. The value xxx is a global parameter which is actually stored in the host html page: var moduleSection:ModuleLoaderSection; moduleSection = new ModuleLoaderSection(); moduleSection.visible = false; moduleSection.moduleName = moduleName + "?version=" + MySite.masterVersion; In addition I needed to add ?version=xxx to the main .swf that was being loaded. Since this is done by HTML I had to do this by modifying my AC_OETags.js file as below : function AC_FL_RunContent(){ var ret = AC_GetArgs ( arguments, ".swf?mv=" + getMasterVersion(), "movie", "clsid:d27cdb6e-ae6d-11cf-96b8-444553540000" , "application/x-shockwave-flash" ); AC_Generateobj(ret.objAttrs, ret.params, ret.embedAttrs); } This is all fine and works great. I just have a hard time believing that Adobe doesn't already have a way to handle this. Given that Flex is being targeted to design modular applications for business I find it especially surprising. What do other people do? I need to make sure my application reloads correctly even if someone has once per session selected for their 'browser cache checking policy'.

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  • Simple Data Caching using Weak References in WCF

    - by Tawani
    Given that I have the following WCF service: class LookUpService { public List<County> GetCounties(string state) { var db = new LookUpRepository(); return db.GetCounties(state); } } class County { public string StateCode{get;set;} public string CountyName{get;set;} public int CountyCode{get;set;} } What will be the most efficient (or best) way to cache a state's counties using weak references (or any other approach) so that we don't hit the database every time we need to look up data. Note that we will not have access to the HttpRuntime (and HttpContext).

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