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  • Good Enough Failover Strategy for DNS / MySQL / Email

    - by IMB
    I've asked and read a lot questions regarding DNS failover but the more I read the more complicated it becomes, some people say it's good enough some say it isn't. No clear answers from what I read. I was wondering if we can set it straight once and for all, at least for the requirements of most websites out there. Right now let's assume the following: We don't need really need load-balancing, what we need is a failover solution. We are running a website based on LAMP on a VPS. We need to make sure that the Web Server, MySQL, Email are always accessible if not 99%. Basically here's my idea and questions about it: Web Server: We need at least one failover server (another VPS on a separate data center). Is DNS Failover via Round Robin good, if not, what's the best? And how do you exactly implement it? How do you make the files you upload/delete on Server A is also on Server B? MySQL: I've only read a brief intro to MySQL replication and I assume that I can replicate Server A to Server B and vice versa on the fly right? So just it case Server A fails and Server B is now running, it will continue to work and replicate to Server A when it becomes available. So in essence Server B is now the primary server, and will later on failover to Server A, should a failure happen again. Email: If we are gonna use DNS Failover, using webmail or relying on emails stored on the server is probably not a good idea right? Since some emails might be on Server A while some might be on Server B? I assume a basic email forwarder to a 3rdparty is good enough (like Gmail for example) to ensure all emails are kept in one place. Here's a basic diagram for a better picture: http://i.stack.imgur.com/KWSIi.png

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  • IIS/MSSQL HA on two servers? NLB + Mirroring

    - by Igor K
    Currently have the one server doing MSSQL/IIS. Can use NLB with two servers running IIS for HA and can use database mirroring and put the failover partner in the connection string for HA. Can we use NLB + Mirroring together? So if one of the servers died (ie power plug removed), everything will continue to work (after the timeout for the mirror to become the principal)?

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  • How to do client side NFS failover in Linux?

    - by Doug
    I have a CentOS 6.3 client that needs to access NFS storage. There are two NFS servers that serve up the same content stored on a SAN with a clustered filesystem. How do I set up CentOS to failover to the backup NFS server if needed? When I Google, I keep reading that Linux does not support this, but that would be strange since there is plenty of information out there on how to set up a clustered Linux NFS server farm...

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  • 250k connections for comet with node.js

    - by Nenad
    How to implement node.js to be able to handle 250k connections as comet server (client side we use socket.io)? Would the use of nginx as proxy/loadbalancer be the right solution? Or will HA-Proxy be the better way? Has anyone real world experience with 100k+ connections and can share his setup? Would a setup like this be the right one (Quad core CPU per server - start 4 Instances of node.js per Server?): nginx (as proxy / load balancing server) / | \ / | \ / | \ / | \ node server #1 node server #2 node server #3 4 instances 4 instances 4 instances

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  • Hard disk permission after bootcamp ??

    - by Sladiki
    Hi all, I have a question concerning hard disk permission after Using boot camp, i have a macbook pro 17 i7, 500gb, yesterday i installed window 7 ultimate in 80 gb (bootcamp) ntfs offcourse. I was testing my HD permission since i found that the start up is slow in mac side. I found there's alot of changes in permissions is that normal or i should to repair all this permission problems, need to mention that from Windows side i can see my mac drive which i don't want... Any idea... Regards, Sami

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  • Can I replace a router and DHCP server without disrupting traffic?

    - by SRobertJames
    I have a device which acts as a router and DHCP server. I'm replacing it, and would like to minimize down time. If I unplug it, and plug in a different device with the same IP, will all the PCs with DHCP leases keep on working? (I have DHCP Conflict detect on, so it shouldn't reassign a DHCP address already used). What if I want to change the IP (new subnet) - is there anyway to tell all the clients (Windows PCs) to release their DHCP leases and request new ones in a minute? If before unplugging the old device, I have it release all DHCP leases, will the Windows PCs automatically ask for new DHCP addresses?

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  • How can HAProxy improve availibility, or "how can I prevent my site from going down"? [closed]

    - by Joe Hopfgartner
    I am aware of what HAProxy does, but what if my HAproxy goes down? Or what if my DNS servers go down? Yes, dns is less the problem. However dns only solves to an IP and an IP is announced via BGP to be routed over some router. What if that router goes down? Of course if I have complicated application servers that are likely to fail HAProxy can significantly improve uptime. But my application isnt. In fact my application may very well just be delivering a small static html file via HTTP. Basically if any user anywhere types in MYDOMAIN.COM, I want the user to get SOMETHING on the screen other than a timeout or DNS resolution error. How can I do that? The point of entry is difficult. The so called "initial closure mechanism".

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  • Managed LAMP platform for maximizing availability and global reach, not scalability

    - by user66819
    Assume a Linux/Apache/MySQL/PHP application for a small base of registered users. With small userbase, there are no traffic peaks so the scalability that cloud platforms offer is not imperative. But the system is mission-critical, so availability is the primary goal. Users are also distributed across Asia, Europe, and US, so multiple server locations that minimize users' network hops would be highly desirable. The dream: a managed VPS platform where we would configure a single server (uploading PHP and other files, manipulating database, etc.), and the platform would automatically mirror the server in a handful of key places around the world (say one on each US coast, one in Europe, one in east Asia). File system synchronization and MySQL replication would happen automatically. Core operating system is managed, so we don't need to do full system administration and security, and low-level backups are also done by service provider, though we also do our own backups as well. Couple this with some sort of DNS geo-detection, so users are routed to the nearest operational server... with support for https, of course. Does such a dream exist? If not, what are some approaches to accomplish the same end with minimal time investment and minimal monthly hosting costs?

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  • How do I activate the F_LINE input in a transplanted HP chassis?

    - by admin
    I have an HP Pavilion Media Center PC chassis, vintage 2003 or so and I replaced the motherboard in it with a newer (vintage 2009) HP motherboard, M2N68-LA (Narra 5). I have scoured the internet trying to find pinouts for the motherboard to no avail. My question concerns the front panel audio, specifically Line In. The old chassis was built for AC97 but the new mobo is build for the newer HD audio standard. I figured out by comparison & experimentally how to connect the Mic & Headphone jacks to the HD audio header of the mobo by adding a manual switch to set the SENSE lines. Now all works fine for Mic & headphone. The old chassis also has a front panel Line In jack that the newer HP chassis does not have. However, the new mobo has a 4 pin white connector labeled F_LINE that I believe is a line input. Under Windows 7 I see the two Line Inputs in the mixer but I can't get one of them to become active. The 4 pin F_LINE connector uses the two middle pins for ground, and presumably the other two for left and right audio inputs. There are no pins for sensing on that connector. Can anyone tell me how to use that F_LINE input for the front panel, or how to activate it?

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  • erratic response times with Apache 2.0.52 on redhat 4.

    - by Kevin
    Under load, we've noticed response times from Apache vary greatly for the same 7k image. It can range anywhere from .01 seconds to 25 seconds or greater. Unfortunately, due to corporate policy constraints we are pretty much stuck on Apache 2.0.52. I'm at best an Apache novice so I'm in over my head with this problem. My focus recently has turned to our choice of MPM modules. We use the worker model on a dual core hyper threaded blade. It doesn't appear that swapping is an issue, and I don't see any signs of a hardware problem. I've read that worker is optimal on hardware with many CPU's where prefork it more suitable for our specific hardware profile. I can see conceptually how choosing the wrong MPM could result in this erratic behavior, but I'm not confident that it's the root cause here. Has anyone else seen this type of range in your response times for simple static content? What else should I be looking into here?

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  • Looking for a solid redirection infrastructre

    - by isoman
    We have critical servers (webservers and databases) that are fully replicated, except for the reverse proxy that we use to hide the internal stuff. This proxy is acting like a router that filters and redirects traffic to the main server and switch for failover if the main one is down. We want to find an alternative to this proxy because one single entry point is not enough. Is there any company that has a solid and redundant infrastructure that offers redirection to an IP and allows quick switching to another one?

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  • 1080p HD TV + what is minimum spec pc required to stream HD movie files to it?

    - by rutherford
    I want to stream hi-def (non flash-based) movies from my future minimum spec pc to my network-ready HDTV. What I want to know is a) when streaming from a computer (local wifi network), is the computer's cpu/video/ram resources used to the same extent as it would be if playing back on the computers local screen? If not what are the differences? b) So with streaming hd content what is the minimum spec processor I should go for, if i) only one TV is acting as client ii) two TVs are simultaneous clients.

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  • Windows 8: Multiple monitors with varying DPI? [closed]

    - by Sid
    Possible Duplicate: Dual monitors on Windows - How do I set a different DPI or text size on each monitor? I'm running Windows 8 on my Macbook Pro Retina (220dpi) which has an external 24" monitor (~96 dpi). In Mac OS 10.8.2, the display settings seem ok and I can actually use both displays without usability issues. I don't know what scaling settings etc it uses but it looks fine. On Windows 8, however when I boost the DPI settings to take advantage of the retina display, it blows up the display on the external monitor - text is giant sized. How can I tell Windows 8 to use the real DPI settings of each monitor? NOTE: I'm not asking for Windows 7.

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  • How to choose NoSQL database engine?

    - by Poma
    We have a database with following specs: 30k records, 7mb in size 20 inserts/second 1000 updates/second 1000 range selects/second, by secondary index, approx 10 rows each needs at least one secondary index needs some mechanism to expire keys if they are not updated for 75 secs (can be done via programmatic garbage collector but will require additional 'last_update' index and will add some load) consistency is not required durability is not required db should be stored in memory For now we use Redis, but it does not have secondary index and it's keys index:foo:* is too slow. Membase also does not have secondary index (as far as I know). MongoDB and MySQL memory engine have table-level locks. What engine will fit our use case?

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  • What are the ways to build a failover cluster?

    - by light
    I have a task where I need to build a failover cluster in two cases: first with servers on Red Hat Enterprise 5.1 and second with SUSE Linux Enterprise 11 SP1. Both cases have SAN. I know there are many ways to build failover cluster, but I can’t find out more, so I need next: The ways to build it? I know only virtualization. Any good book or resource to broad my mind? I’ll be glad to hear any suggestion. Thanks! EDIT #1: failover of servers with bussiness application on it. EDIT #2: will be great to hear summary about solutions with SLES servers? EDIT #3: So if I understand correctly, in my cases the main ways are to use internal solutions or virtualization. So now I have additional questions: Does manufacturer of blades provide some solution? For example HP or IBM. (Without virtualization) Do I need additional server to control "heartbeat" between main and redundant servers? (Virtualization) For example I have several physical servers with VMs. Do I need additional server to control availability of VMs and to move VMs to another physical server in the case their physical server failure? Sorry for my poor English. EDIT #4: Failover of VM or OS on physical server. In both cases will be used SAN , it's not specified, but I think with file system image on it. I started to think that my question is stupid and I need to remake it.

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  • HD video is slower than audio output

    - by Star
    I have an HD video files (1920x1080 H.264 DUAL AUDIO FLAC) file type: MKV file size: 1.25 GB file length: 24 minutes the problem is the video output is not synchronized with audio output, something slow too much sometime it gets too fast I tried running it on Windows Media Player , Media Player Classic , and a few other players, but the result is the same Additional Info: for device information I'm on LG S510 labtop

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  • Why the Indian link builders or SEO companies can make so many high quality links at the same time? [closed]

    - by chiba
    There are a lot of Indian SEO companies or link builders that offer a lot of high quality link. Some of them for example offer links just from "co.uk" or "French site" with high page ranks. I have heard that even the SEO companies from other countries outsource link building to India. Do they have special connections for building links ? or Do they exchange the information between another Indian companies and have a big database of the sites where they can link?

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  • Cost of creating exception compared to cost of logging it

    - by Sebastien Lorber
    Hello, Just wonder how much cost to raise a java exception (or to call native fillInStackTrace() of Throwable) compared to what it cost to log it with log4j (in a file, with production hard drive)... Asking myself, when exceptions are raised, does it worth to often log them even if they are not necessary significant... (i work in a high load environment) Thanks

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  • Seven Worlds will collide…. High Availability BI is not such a Distant Sun.

    - by Testas
    Over the last 5 years I have observed Microsoft persevere with the notion of Self Service BI over a series of conferences as far back as SQLBits V in Newport. The release of SQL Server 2012, improvements in Excel and the integration with SharePoint 2010 is making this a reality. Business users are now empowered to create their own BI reports through a number of different technologies such as PowerPivot, PowerView and Report Builder. This opens up a whole new way of working; improving staff productivity, promoting efficient decision making and delivering timely business reports. There is, however; a serious question to answer. What happens should any of these applications become unavailable? More to the point, how would the business react should key business users be unable to fulfil reporting requests for key management meetings when they require it?  While the introduction of self-service BI will provide instant access to the creation of management information reports, it will also cause instant support calls should the access to the data become unavailable. These are questions that are often overlooked when a business evaluates the need for self-service BI. But as I have written in other blog posts, the thirst for information is unquenchable once the business users have access to the data. When they are unable to access the information, you will be the first to know about it and will be expected to have a resolution to the downtime as soon as possible. The world of self-service BI is pushing reporting and analytical databases to the tier 1 application level for some of Coeo’s customers. A level that is traditionally associated with mission critical OLTP environments. There is recognition that by making BI readily available to the business user, provisions also need to be made to ensure that the solution is highly available so that there is minimal disruption to the business. This is where High Availability BI infrastructures provide a solution. As there is a convergence of technologies to support a self-service BI culture, there is also a convergence of technologies that need to be understood in order to provide the high availability architecture required to support the self-service BI infrastructure. While you may not be the individual that implements these components, understanding the concepts behind these components will empower you to have meaningful discussions with the right people should you put this infrastructure in place. There are 7 worlds that you will have to understand to successfully implement a highly available BI infrastructure   1.       Server/Virtualised server hardware/software 2.       DNS 3.       Network Load Balancing 4.       Active Directory 5.       Kerberos 6.       SharePoint 7.       SQL Server I have found myself over the last 6 months reaching out to knowledge that I learnt years ago when I studied for the Windows 2000 and 2003 (MCSE) Microsoft Certified System Engineer. (To the point that I am resuming my studies for the Windows Server 2008 equivalent to be up to date with newer technologies) This knowledge has proved very useful in the numerous engagements I have undertaken since being at Coeo, particularly when dealing with High Availability Infrastructures. As a result of running my session at SQLBits X and SQL Saturday in Dublin, the feedback I have received has been that many individuals desire to understand more of the concepts behind the first 6 “worlds” in the list above. Over the coming weeks, a series of blog posts will be put on this site to help understand the key concepts of each area as it pertains to a High Availability BI Infrastructure. Each post will not provide exhaustive coverage of the topic. For example DNS can be a book in its own right when you consider that there are so many different configuration options with Forward Lookup, Reverse Lookups, AD Integrated Zones and DNA forwarders to name some examples. What I want to do is share the pertinent points as it pertains to the BI infrastructure that you build so that you are equipped with the knowledge to have the right discussion when planning this infrastructure. Next, we will focus on the server infrastructure that will be required to support the High Availability BI Infrastructure, from both a physical box and virtualised perspective. Thanks   Chris

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  • Initializing SD card in SPI issues

    - by Sembazuru
    Sorry for the length of this question, but I thought it best to show as much detail to fend of questions asking if I had done A when I had already done A... ;-) I've had a look at the "micro-SD card initialization using SPI interface" thread and didn't see any answers that matched my issue (i.e. things I haven't already tried). I have a similar issue where I'm trying to access a SD card through a micro-controller's SPI interface (specifically an HC908). I've tried following the flow charts in the Physical Layer Simplified Specification v2.00 and it seems to initialize correctly on Transcend 1GB & 2GB and an AE&C 1GB card. But I'm having problems on 3 other random cards from my stash of old cards that I've used on my camera. My code is all HC908 assembler. I scoped out the SPI clock line and during initialization it's running about 350kHz (the only speed multiplier that the HC908 supplies at my low MCU clock speed that falls within the 100-400kHz window). Here are the results of the three cards that aren't completing my initialization routine (all done consecutively w/o changing any code or timing parameters): Canon 16Meg card (labeled as SD): Set card select high Send 80 SPI clock cycles (done by writing 0xFF 10 times) Set card select low Send CMD0 [0x400000000095] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x01 (indicates idle) Send CMD8 [0x48000001AA87] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x05 (idle and illegal command) Because illegal command set local flag to indicate v1 or MMC card Send CMD58 [0x7A00000000FD] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x05 (idle and illegal command) because illegal command branch to error routine Send CMD13 [0x4D000000000D] (show status buffer) and Loop up to 8 times waiting for high bit on response to go low R1= 0x05 (idle and illegal command) Is the illegal command flag stuck? Should I be doing something after CMD8 to clear that flag? SanDisk UltraII 256Meg Set card select high Send 80 SPI clock cycles (done by writing 0xFF 10 times) Set card select low Send CMD0 [0x400000000095] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x01 (idle) Send CMD8 [0x48000001AA87] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x05 (idle and illegal command) Because illegal command set local flag to indicate v1 or MMC card Send CMD58 [0x7A00000000FD] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x01 (idle) Send 0xFF 4 times to read OCR OCR = 0xFFFFFFFF Send CMD55 [0x770000000065] (1st part of ACMD41) and Loop up to 8 times waiting for high bit on response to go low R1 = 0x01 (idle) Send CMD41 [0x6900000000E5] (2nd part of ACMD41) and Loop up to 8 times waiting for high bit on response to go low R1 = 0x05 (idle and illegal command) Because illegal command, assume card is MMC Send CMD1 [0x4100000000F9] (for MMC) and Loop up to 8 times waiting for high bit on response to go low R1 = 0x05 (idle and illegal command) Repeat the CMD1 50 times (my arbitrary number to wait until idle clears) Every R1 response is 0x05 (idle and illegal command) Why is OCR all F? Doesn't seem proper at all. Also, why does ACMD41 and CMD1 respond illegal command? Is CMD1 failing because the card is waiting for a valid ACMD after the CMD55 even with the illegal command response? SanDisk ExtremeIII 2G: Set card select high Send 80 SPI clock cycles (done by writing 0xFF 10 times) Set card select low Send CMD0 [0x400000000095] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x01 (idle) Send CMD8 [0x40000001AA87] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x7F (??? My loop shows the responses for each iteration and I got 0xFF 0xFF 0xC1 0x7F... is the card getting out of sync?) Send CMD58 [0x7A00000000FD] and Loop up to 8 times waiting for high bit on response to go low R1 = 0x01 (idle and back in sync) Send 0xFF 4 times to read OCR OCR = 0x00FF80 Send CMD55 [0x770000000065] (1st part of ACMD41) and Loop up to 8 times waiting for high bit on response to go low R1 = 0x5F (??? loop responses are 0xFF 0xFF 0xF0 0x5F... again out of sync?) Send CMD41 [0x6900000000E5] (2nd part of ACMD41) and Loop up to 8 times waiting for high bit on response to go low R1 = 0x05 (idle and illegal command, but back in sync???) Because illegal command, assume card is MMC Send CMD1 [0x4100000000F9] (for MMC) and Loop up to 8 times waiting for high bit on response to go low R1 = 0x7F (??? loop responses are 0xFF 0xFF 0xC1 0x7F... again out of sync?) Repeat CMD1 and Loop up to 8 times waiting for high bit on response to go low R1 = 0x01 (idle) Repeat CMD1 and Loop up to 8 times waiting for high bit on response to go low R1 = 0x7F (??? loop responses are 0xFF 0xFF 0xC1 0x7F... again out of sync?) Repeat CMD1 and Loop up to 8 times waiting for high bit on response to go low R1 = 0x00 (out of idle) Send CMD9 [0x4900000000AF] (get CSD) and Loop up to 8 times waiting for high bit on response to go low R1 = 0x3F (??? loop responses are 0xFF 0xFF 0xC1 0x3F... again out of sync?) Code craps out because Illegal command bit is high. WTF is wrong with that card? Sometimes in sync, other times not. (The above pattern is repeatable.) I've scoped this one out and I'm not seeing any rogue clock cycles going through between MOSI/MISO transfers. Anyone have any clues? Need any more info? Thanx in advance for spending the time to read through all of this.

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  • SQL Server 2005 high memory usage and performance problems

    - by emzero
    Hi there guys. I have this ASP.NET/SQLServer2005 website running on a production server (Win2003, QuadCore, 4GB). The site runs smoothly normally, but after 2-3 weeks I notice a slow performance on the site (especifically in one particular page). Also I notice that the SQL Server process is using like 2GBs of RAM. So I restart the service, the site runs fast again and the process 300-400MBs. I'm looking for an explanation of why is this happening? What is SQL Server storing in RAM that takes too much space and degrades the performance? What can I do to avoid this? I'm trying to avoid restarting the SQLServer everytime this happens. Thank you!

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  • Recommendation for high performance WPF Chart

    - by Ajaxx
    We're working on a WPF-based desktop application that charts financial markets information (candlestick charts, overlayed indicator curves, volume, etc). The charts are displayed in real-time with responses to market ticks being shown in real-time (updating one to two times per second is probably a reasonable display refresh policy). We've been looking for a software package (commercial is fine by us) that has the capability of displaying these charts. Additionally, we'd like to have an approach that can render the initial amount of data in a reasonable timeframe (give or take 100-200ms from the time we hand the data over to a complete render on screen). Also we view multiple charts (5-10) simultaneously so a solution that chews up 50% of my CPU to display one chart really isn't going to work well. Has anyone had any good experiences with charting controls. We've had to hand roll the last few charts we've done and I'd prefer not to do it again. Solutions that can make use of the GPU to minimize CPU utilization would be nice as well.

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  • GetWindowPlacement/SetWindowPlacement not working in WinForms for high DPI

    - by RandomEngy
    I've got a legacy WinForms app and I want to save the window position and size across sessions. I've been using GetWindowPlacement and SetWindowPlacement during the FormClosing and Load events. The problem I'm getting is that at higher DPI settings (Such as Medium, size at 125%) the sizes keep inflating. I'll call SetWindowPlacement on it with a certain size, but when GetWindowPlacement is called, those numbers come back 25% bigger, even though the window was the same size all along. The same sort of problem exists when saving the size of a resizable element within the form. Now this works fine if I create a new WinForms project: The size stays stable even when running at the higher DPI. I'm guessing there's some legacy setting in the bowels of the project or some arcane Form setting that's messing it up, but I can't find out where. I've called IsProcessDPIAware on both projects and both are true. Does anyone know what might be causing this?

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  • How to learn high-level Java web development concepts

    - by titaniumdecoy
    I have some experience writing web applications in Java for class projects. My first project used Servlets and my second, the Stripes framework. However, I feel that I am missing the greater picture of Java web development. I don't really understand the web.xml and context.xml files. I'm not sure what constitutes a Java EE application as opposed to a generic Java web application. I can't figure out how a bean is different from an ordinary Java class (POJO?) and how that differs from an Enterprise Java Bean (EJB). These are just the first few questions I could think of, but there are many more. What is a good way to learn how Java web applications function from the top down rather than simply how to develop an application with a specific framework? (Is there a book for this sort of thing?) Ultimately, I would like to understand Java web applications well enough to write my own framework.

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