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  • DNS Resolver Speed Techniques

    - by Rob Olmos
    I recently received a reply to my concerns about some DNS servers being slower than others despite all servers being anycast: In practice, most resolvers won't be impacted by the slower paths to some of the name servers in the set. Most resolvers employ various techniques to provide fast lookups, such as preferring name servers that were previously seen to be faster, sending simultaneous queries to multiple name servers, or pre-fetching queries before the TTL has expired. I was not aware that resolvers used these techniques and I was unsuccessful at searching for more info about this. Are there any names for these techniques? Which resolvers employ which of these techniques?

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  • What database strategy to choose for a large web application

    - by Snoopy
    I have to rewrite a large database application, running on 32 servers. The hardware is up to date, each machine has two quad core Xeon and 32 GByte RAM. The database is multi-tenant, each customer has his own file, around 5 to 10 GByte each. I run around 50 databases on this hardware. The app is open to the web, so I have no control on the load. There are no really complex queries, so SQL is not required if there is a better solution. The databases get updated via FTP every day at midnight. The database is read-only. C# is my favourite language and I want to use ASP.NET MVC. I thought about the following options: Use two big SQL servers running SQL Server 2012 to serve the 32 servers with data. On the 32 servers running IIS hosting providing REST services. Denormalize the database and use Redis on each webserver. Use booksleeve as a Redis client. Use a combination of SQL Server and Redis Use SQL Server 2012 together with Hadoop Use Hadoop without SQL Server What is the best way for a read-only database, to get the best performance without loosing maintainability? Does Map-Reduce make sense at all in such a scenario? The reason for the rewrite is, the old app written in C++ with ISAM technology is too slow, the interfaces are old fashioned and not nice to use from an website, especially when using ajax. The app uses a relational datamodel with many tables, but it is possible to write one accerlerator table where all queries can be performed on, and all other information from the other tables are possible by a simple key lookup.

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  • Installing Oracle11gr2 on redhat linux

    - by KItis
    I have basic question about installing applications on linux operating system. i am going to express my issue considering oracle db installation as a example. when installing oracle database , i created a user group called dba and and user in this group called ora112. so this users is allowed to install database. so my question is if ora112 uses umaks is set to 077, then no other uses will be able to configure oracle database. why do we need to follow this practice. is it a accepted procedure in application installation on Linux. please share your experience with me. thanks in advance for looking into this issue say i install java application on this way. then no other application which belongs to different user account won't be able use java running on this computer because of this access restriction.

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  • How to remove a package I compiled and installed manually?

    - by macek
    I recently compiled and installed Git on a new install of Mac OS 10.6 but it didn't install the documentation. I now realize I should've used the precompiled package offered here: http://code.google.com/p/git-osx-installer/downloads/list How do I remove all the files that I added to my system using make install with the Git source code? Edit: I've had similar problems in the past with other packages, too. For example, ./configure with the incorrect --prefix= or something. What's the general practice for removing unix packages?

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  • Handling user interface in a multi-threaded application (or being forced to have a UI-only main thre

    - by Patrick
    In my application, I have a 'logging' window, which shows all the logging, warnings, errors of the application. Last year my application was still single-threaded so this worked [quite] good. Now I am introducing multithreading. I quickly noticed that it's not a good idea to update the logging window from different threads. Reading some articles on keeping the UI in the main thread, I made a communication buffer, in which the other threads are adding their logging messages, and from which the main thread takes the messages and shows them in the logging window (this is done in the message loop). Now, in a part of my application, the memory usage increases dramatically, because the separate threads are generating lots of logging messages, and the main thread cannot empty the communication buffer quickly enough. After the while the memory decreases again (if the other threads have finished their work and the main thread gradually empties the communication buffer). I solved this problem by having a maximum size on the communication buffer, but then I run into a problem in the following situation: the main thread has to perform a complex action the main thread takes some parts of the action and let's separate threads execute this while the seperate threads are executing their logic, the main thread processes the results from the other threads and continues with its work if the other threads are finished Problem is that in this situation, if the other threads perform logging, there is no UI-message loop, and so the communication buffer is filled, but not emptied. I see two solutions in solving this problem: require the main thread to do regular polling of the communication buffer only performing user interface logic in the main thread (no other logic) I think the second solution seems the best, but this may not that easy to introduce in a big application (in my case it performs mathematical simulations). Are there any other solutions or tips? Or is one of the two proposed the best, easiest, most-pragmatic solution? Thanks, Patrick

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  • How to extract byte-array from one xml and store it in another in Java

    - by grobartn
    So I am using DocumentBuilderFactory and DocumentBuilder to parse an xml. So it is DOM parser. But what I am trying to do is extract byte-array data (its an image encoded in base64) Store it in one object and later in code write it out to another xml encoded in base64. What is the best way to store this in btw. Store it as string? or as ByteArray? How can I extract byte array data in best way and write it out. I am not experienced with this so wanted to get opinion from the group. UPDATE: I am given XML I do not have control of incoming XML that comes in binary64 encoded < byte-array > ... base64 encoded image ... < /byte-array > Using parser I have I need to store this node and question is should that be byte or string and then writing it out to another node in new xml. again in base64 encoding. thanks

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  • Only ONE Outlook 2010 installation "Cannot connect to Exchange server" when setting up new profile.

    - by Johnny PDEX
    Exchange 2010, one-server installation (small production, I know not best practice) OWA Connectivity has been confirmed, Autodiscover is configured and working properly for EVERY other installation. Other user accounts tested on problem Outlook, none can connect. Windows Firewall is pre-configured by Group Policy, only modifications being related to remote management. Firewall has also been disabled during diagnostic period. Network discovery and file sharing is enabled on workstation as well. Windows 7 Professional, latest updates installed. Driving me nuts. Help, serverfault?

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  • format an xml string in Ruby

    - by user1476512
    given an xml string like this : <some><nested><xml>value</xml></nested></some> what's the best option(using ruby) to format it readable like : <some> <nested> <xml>value</xml> </nested> </some> I've found an answer here: what's the best way to format an xml string in ruby?, which is really helpful. But it formats xml like: <some> <nested> <xml> value </xml> </nested> </some> As my xml string is a little big in length. So it is not readable in this format. Thanks in advance!

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  • Where should an application's default folder live?

    - by HotOil
    Hi: I'm creating a little app that configures a connected device and then saves the config information in a file. The filename cannot be chosen by the user, but its location can be chosen. Where is the best place for the app's default save-to folder? I have seen examples out there where it is the "MyDocuments" location (eg Visual Studio does this). I have seen a folder created right at the top of the C:\ drive. I find that to be a little obnoxious, personally. It could be in the Program Files[Manufacturer] or Program Files[Product Name], or wherever the app was installed. I have used this location in the past; I dislike it because Windows Explorer does not allow a user to browse to there very easily ('browsability'). Going with this last notion that 'browsability' is a factor, I suppose MyDocuments is the best choice. Is this the most common, most widely accepted practice? I think historically we have chosen the install folder because that co-locates the data with the device management utilities. But I would really like to get away from that. I don't want the user to have to go pawing through system files to find his/her data, esp if that person is not too Windows-savvy. Also, I am using the .NET WinForms FolderBrowserDialog, and the "Environment.SpecialFolders" enum isn't helpful in setting up the dialog to point into the Program Files folder. Thanks for your input! Suz.

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  • Exchange 2010 Multiple accounts in one mailbox

    - by durilai
    I am looking for best practice or recommended ways of doing the following: I have a user that has 2 email addresses, he accesses them via POP 3 and OWA. He need to be able to send as each of the addresses. I do not want to create multiple AD accounts or mailboxes, but would like to be able to provide that visual separation. Is this possible, I know using Outlook I am able to add multiple POP3 accounts and he can send from whichever he choose, but how to enable this is OWA, as well as on a mobile using POP3. Thanks

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  • Extract data from PostgreSQL DB without using pg_dump

    - by John Horton
    There is a PostgreSQL database on which I only have limited access (e.g, I can't use pg_dump). I am trying to create a local "mirror" by exporting certain tables from the database. I do not have the permissions needed to just dump a table as SQL from within psql. Right now, I just have a Python script that iterates through my table_names, selects all fields and then exports them as a CSV: for table_name, file_name in zip(table_names, file_names): cmd = """echo "\\\copy (select * from %s)" to stdout WITH CSV HEADER | psql -d remote_db | gzip > ./%s/%s.gz"""%(table_name,dir_name,file_name) os.system(cmd) I would like to not use CSV if possible, as I lose the field types and the encoding can get messed up. First best would probably be some way of getting the generating SQL code for the table using \copy. Next best would be XML, ideally with some way of preserving the field types. If that doesn't work, I think the final option might be two queries---one to get the field data types, the other to get the actual data. Any thoughts or advice would be greatly appreciated - thanks!

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  • SAN/NAS with high availability?

    - by netvope
    I have two servers that I plan to use for storage. Each of them has a few SATA disks directly attached. I want the storage to be available even if one of the storage servers is down (preferably the clients wouldn't even notice that the fail-over, although I'm not sure if this is possible). The clients may access the storage via NFS and samba, but this is not a must; I could use something else if needed. I found this guide, Installing and Configuring Openfiler with DRBD and Heartbeat, which apparently does the thing I want. It relies on three components, Openfiler, DRBD, and Heartbeat, and all three of them need to be configured separately. I'm wondering are there simpler solutions? Is using DRBD+Heartbeat the best practice for a situation like mine? I'm also interested to know if there are alternatives that don't depend on DRBD.

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  • Installing VMWare Tools in Windows Server 2008 fails system startup

    - by Hoghweed
    I recently created a vmware virtual machine with windows server 2008 enterprise as Guest. My host is Ubuntu 10.04 on my Lenovo laptop. I fall into a big trouble which makes my created VM unusable after I've installed VMWare Tools. After installing tools I'm able to run the system only in safe mode. After some event manager analysis I found the issue is with drivers installed by vnmware tools. Any one has got the same issue? Is there any good practice for doing that? The configuration of vm machine is the following CPU : 1 RAM : 1020 HD : 40GB Splitted files, SCSI CD : IDE Thanks in advance

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  • Need an Overview of Possibilities for multicolumn programming

    - by Sam
    Hi folks, From source1 and source2 i gather that IE9 will NOT support multi-column css3!! Since it is still the most popular browser (another thing i cannot understand), i am left but no other choice than to use Programming Power to make multi-columns work. Now, I use three divs that float to left, and which are manually filled with text. Please don't laugh i know its stupid! But I would wish to not to have to worry about the columns and just have a one piece of (un-interrupted) text which all goes into only 1 div, and then have a program smart enough to split it up into X equally wide columns. Question: before i start reinvent the wheel, what methods of programming power have you known that tackle this elegantly? Please suggest your best working multi-column layout sources so I can evaluate which option is the best (I will update the below table). Exploring all possibilities 2011 and further, to enable multi column text user experience: Language Author SourceCodeUsage WorksOnAllMajorBrowser? ================================================================================= html manual labour put text manually in separate left-floating divs "Y" // Upside: control! Downside: few changes necessitates to reflow 3 divs manually! CSS3 w3c css3.info/preview/multi-column-layout/ "N" // {-moz-column-count: 3; -webkit-column-count: 3; } Thats all! javascript a list apart will add url soon ? // php ? ? ? //

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  • Why do we still have to use drive letters to identify file systems?

    - by Charles E. Grant
    A friend has run into a problem where they installed Windows 7 from an external drive, and the internal boot drive is now assigned to H:. Theoretically this shouldn't cause problems because there are programming interfaces for getting the drive letter for the system drive. In practice though, there are quite a few programs that assume that C: is the only possible location for the system directories, and they refuse to run with the system directories on H:. That's not Microsoft's fault, but it's a pain none-the-less. The general consensus seems to be that a re-install, setting the internal boot drive to C:, is the only way to avoid fix these problems. UNIX-like systems display all file systems in a single unified directory tree and mostly seem to avoid problems like this. Is it possible to configure a Windows system without reference to drive letters, or does the importance of backwards compatibility mean that Windows will be working with drive letters from now until doomsday?

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  • Preventing my postfix to send my local users spam

    - by Jack
    I have a postfix/dovecot mail server with 100 different users. When they send an email they need to be authenticated. I successfully use saslauth to achieve this. Few days ago I had a problem. One specific user, probably with a virus or a spam-bot installed in its computer, started to send out through my server thousands of emails in few hours. As result, my ip has been blocked by many isp provider (@aol, @yahoo, and others) and has been listed in many blacklist, making all my 100 users unable to send any email to anyone. What is the best practice to avoid this problem? It would be great if my server could recognize a spamming user and automatically block it. Also, have a limit of, say, 30 emails per hour could be a partial solution. Any idea how to face this problem? Thank you

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  • users connecting to remote desktop to use software

    - by Jordan
    Im an IT assistant at a CNC milling company and we use a program called made2manage. Its an ERP (enterprise resource management) software. Each license is something like 5k and instead of giving each employee there own copy of the software he has everyone that uses the program connect to a server that has a copy of m2m on it. Its slow when there are a bunch of people connected to it. But I guess they dont want to buy more licenses. Is there a better way to do something like this? How bad of a practice is this?

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  • Building static (but complicated) lookup table using templates.

    - by MarkD
    I am currently in the process of optimizing a numerical analysis code. Within the code, there is a 200x150 element lookup table (currently a static std::vector < std::vector < double ) that is constructed at the beginning of every run. The construction of the lookup table is actually quite complex- the values in the lookup table are constructed using an iterative secant method on a complicated set of equations. Currently, for a simulation, the construction of the lookup table is 20% of the run time (run times are on the order of 25 second, lookup table construction takes 5 seconds). While 5-seconds might not seem to be a lot, when running our MC simulations, where we are running 50k+ simulations, it suddenly becomes a big chunk of time. Along with some other ideas, one thing that has been floated- can we construct this lookup table using templates at compile time? The table itself never changes. Hard-coding a large array isn't a maintainable solution (the equations that go into generating the table are constantly being tweaked), but it seems that if the table can be generated at compile time, it would give us the best of both worlds (easily maintainable, no overhead during runtime). So, I propose the following (much simplified) scenario. Lets say you wanted to generate a static array (use whatever container suits you best- 2D c array, vector of vectors, etc..) at compile time. You have a function defined- double f(int row, int col); where the return value is the entry in the table, row is the lookup table row, and col is the lookup table column. Is it possible to generate this static array at compile time using templates, and how?

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  • Connect Rails model to non-rails database

    - by the_snitch
    I'm creating a new web application (Rails 3 beta), of which pieces of it will access data from a legacy mysql database that a current php application is using. I do not wish to modify the legacy db schema, I just want to be able to read/write to it, as well as the rails application having it's own database using activerecord for the newer stuff. I'm using mysql for the rails app, so I have the adapter installed. How is the best way to do this? For example, I want contacts to come from the old database. Should I create a contacts controller, and manually call sql to get the variables for the views? Or should I create a Contact model, and define attributes that match the fields in the database, and am I able to use it like Contact.mail_address to have it call "SELECT mailaddr FROM contacts WHERE id=Contact.id". Sorry, I've never done much in Rails outside of the standard stuff that is documented well. I'm not sure of what the best approach would be. Ideally, I want the contacts to be presented to my rails application as native as possible, so that I can expose them RESTfully for API access. Any suggestions and code examples would be much appreciated

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  • Java Constructor Style (Check parameters aren't null)

    - by Peter
    What are the best practices if you have a class which accepts some parameters but none of them are allowed to be null? The following is obvious but the exception is a little unspecific: public class SomeClass { public SomeClass(Object one, Object two) { if (one == null || two == null) { throw new IllegalArgumentException("Parameters can't be null"); } //... } } Here the exceptions let you know which parameter is null, but the constructor is now pretty ugly: public class SomeClass { public SomeClass(Object one, Object two) { if (one == null) { throw new IllegalArgumentException("one can't be null"); } if (two == null) { throw new IllegalArgumentException("two can't be null"); } //... } Here the constructor is neater, but now the constructor code isn't really in the constructor: public class SomeClass { public SomeClass(Object one, Object two) { setOne(one); setTwo(two); } public void setOne(Object one) { if (one == null) { throw new IllegalArgumentException("one can't be null"); } //... } public void setTwo(Object two) { if (two == null) { throw new IllegalArgumentException("two can't be null"); } //... } } Which of these styles is best? Or is there an alternative which is more widely accepted? Cheers, Pete

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  • Is really good have a big (500GB/1T) Hard Disk as main one!?

    - by aSeptik
    Hi All guys! ;-) i'm building my new PC so i'm starting the usual search for a good hardware/price around the net! but this time i'm not sure i want buy a big Hard Disk! i was thinking to have a "very small" HD like 50GB as main one and external (big) for store all other stuff! Assuming i'm using classic slow softwares like adobe suite (photoshop, flash, autodesk) and some very simple soft like notepad, php and so on...! do you think this is a good practice for improve performance/speed or i'm jast saying some stupid thing!?

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  • Is really good have a big (500GB/1T) Hard Disk as main one!?

    - by aSeptik
    Hi All guys! ;-) i'm building my new PC so i'm starting the usual search for a good hardware/price around the net! but this time i'm not sure i want buy a big Hard Disk! i was thinking to have a "very small" HD like 50GB as main one and external (big) for store all other stuff! Assuming i'm using classic slow softwares like adobe suite (photoshop, flash, autodesk) and some very simple soft like notepad, php and so on...! do you think this is a good practice for improve performance/speed or i'm jast saying some stupid thing!?

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  • Google App Engine - How to implement the activity stream in a social network

    - by spidee
    I want some ideas on the best practice to implement an activity stream for a social network im building in app engine (PYTHON) I first want to keep a log for all activities of each user - so that we have a history. i.e. someone became a friend, added a picture, changed their address etc. This way we have a users history available should we need it. Also mean we can remove friendship joins, change user data but have a historical log. I also want to stream a users activity to their friends. for this only the last X activities need to be kept - that is in the scenario that messages are sent to friends when an activity occurs. Its pretty straight forward designing a history log - ie: when, what, where. The complication comes as to how we notify friends of a user as to their activity. In our app friendships are not mutual - ie they are based on the twitter following model. Some accounts could have thousands of followers. What is the best approach to model this. using a many to many join table and doing a costly query - using a feed class that fired a copy of the activity to all the subscribers - maybe into mcache? As their maybe a need to fire thousands of messages i would imagine a cron job would need to be used. Any help ideas thoughts on this Thx

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  • Prevent Java application from accessing/monitoring/altering clipboard contents

    - by mcstrother
    I'm a student using a service that provides practice questions for standardized tests. The service requires that I access the questions by downloading and running a Java application. If I try to copy anything from any window of my computer (including applications unrelated to the question bank) while the application is running, the copied item is replaced with an obnoxious message asking me to not pirate their copyrighted material. I find this obnoxious, and I also really don't like the idea that any application can slurp up any and all potentially sensitive information that I happen to copy while it's running. Is there are a way to limit the privileges of this application to stop it from doing this? Thank you!

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  • iptables: How to create a rule for a single website that does not apply to other websites?

    - by Kris
    Virtual Dedicated Server hosts 10 websites. 1 firewall made with iptables If one of those 10 websites gets hit by too many ping requests coming from one IP address, how do I limit or drop it without dropping it for the other 9 websites? Do I create a firewall for every website ? If so, how? Or is it better to change my rules? If so, how? Thank you. Original question was posted here iptables: what's best practice when there're several websites but you want to use a rule for a single website? but it was too vague. Let me know if more info is needed.

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