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• Should Developers Perform All Tasks or Should They Specialize?

  - by Bob Horn

  Disclaimer: The intent of this question isn't to discern what is better for the individual developer, but for the system as a whole. I've worked in environments where small teams managed certain areas. For example, there would be a small team for every one of these functions: UI Framework code Business/application logic Database I've also worked on teams where the developers were responsible for all of these areas and more (QA, analsyt, etc...). My current environment promotes agile development (specifically scrum) and everyone has their hands in every area mentioned above. While there are pros and cons to each approach, I'd be curious to know if there are more pros and cons than I list below, and also what the generally feeling is about which approach is better. Devs Do It All Pros 1. Developers may be more well-rounded 2. Developers know more of the system Cons 1. Everyone has their hands in all areas, increasing the probability of creating less-than-optimal results in that area 2. It can take longer to do something with which you are unfamiliar (jack of all trades, master of none) Devs Specialize Pros 1. Developers can create policies and procedures for their area of expertise and more easily enforce them 2. Developers have more of a chance to become deeply knowledgeable about their specific area and make it the best it can be 3. Other developers don't cross boundaries and degrade another area Cons 1. As one colleague put it: "Why would you want to pigeon-hole yourself like that?" (Meaning some developers won't get a chance to work in certain areas.) It's easy to say how wonderful agile is, and that we should do it all, but I'm somewhat of a fan of having areas of expertise. Without that expertise, I've seen code degrade, database schemas become difficult to manage, hack UI code, etc... Let's face it, some people make careers out of doing just UI work, or just database work. It's not that easy to just fill in and do as good of a job as an expert in that area.

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• What is the underlying reason for not being able to put arrays of pointers in unsafe structs in C#?

  - by cons

  If one could put an array of pointers to child structs inside unsafe structs in C# like one could in C, constructing complex data structures without the overhead of having one object per node would be a lot easier and less of a time sink, as well as syntactically cleaner and much more readable. Is there a deep architectural reason why fixed arrays inside unsafe structs are only allowed to be composed of "value types" and not pointers? I assume only having explicitly named pointers inside structs must be a deliberate decision to weaken the language, but I can't find any documentation about why this is so, or the reasoning for not allowing pointer arrays inside structs, since I would assume the garbage collector shouldn't care what is going on in structs marked as unsafe. Digital Mars' D handles structs and pointers elegantly in comparison, and I'm missing not being able to rapidly develop succinct data structures; by making references abstract in C# a lot of power seems to have been removed from the language, even though pointers are still there at least in a marketing sense. Maybe I'm wrong to expect languages to become more powerful at representing complex data structures efficiently over time.

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• Common lisp error: "should be lambda expression"

  - by Zachary

  I just started learning Common Lisp a few days ago, and I'm trying to build a function that inserts a number into a tree. I'm getting an error, * - SYSTEM::%EXPAND-FORM: (CONS NIL LST) should be a lambda expression From googling around, it seems like this happens when you have too many sets of parenthesis, but after looking at this for an hour or so and changing things around, I can't figure out where I could be doing this. This is the code where it's happening: (defun insert (lst probe) (cond ((null lst) (cons probe lst)) ((equal (length lst) 1) (if (<= probe (first lst)) (cons probe lst) (append lst (list probe)))) ((equal (length lst) 2) ((cons nil lst) (append lst nil) (insertat nil lst 3) (cond ((<= probe (second lst)) (insert (first lst) probe)) ((> probe (fourth lst)) (insert (fifth lst) probe)) (t (insert (third lst) probe))))))) I'm pretty sure it's occurring after the ((equal (length lst) 2), where the idea is to insert an empty list into the existing list, then append an empty list onto the end, then insert an empty list into the middle.

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• Land of Lisp example question

  - by cwallenpoole

  I've read a lot of good things about Land of Lisp so I thought that I might go through it to see what there was to see. (defun tweak-text (lst caps lit) (when lst (let ((item (car lst)) (rest (cdr lst))) (cond ; If item = space, then call recursively starting with ret ; Then, prepend the space on to the result. ((eq item #\space) (cons item (tweak-text rest caps lit))) ; if the item is an exclamation point. Make sure that the ; next non-space is capitalized. ((member item '(#\! #\? #\.)) (cons item (tweak-text rest t lit))) ; if item = " then toggle whether we are in literal mode ((eq item #\") (tweak-text rest caps (not lit))) ; if literal mode, just add the item as is and continue (lit (cons item (tweak-text rest nil lit))) ; if either caps or literal mode = true capitalize it? ((or caps lit) (cons (char-upcase item) (tweak-text rest nil lit))) ; otherwise lower-case it. (t (cons (char-downcase item) (tweak-text rest nil nil))))))) (the comments are mine) (FYI -- the method signature is (list-of-symbols bool-whether-to-caps bool-whether-to-treat-literally) but the author shortened these to (lst caps lit).) But anyway, here's the question: This has (cond... (lit ...) ((or caps lit) ...)) in it. My understanding is that this would translate to if(lit){ ... } else if(caps || lit){...} in a C style syntax. Isn't the or statement redundant then? Is there ever a condition where the (or caps lit) condition will be called if caps is nil?

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• Closures and universal quantification

  - by Apocalisp

  I've been trying to work out how to implement Church-encoded data types in Scala. It seems that it requires rank-n types since you would need a first-class const function of type forAll a. a -> (forAll b. b -> b). However, I was able to encode pairs thusly: import scalaz._ trait Compose[F[_],G[_]] { type Apply = F[G[A]] } trait Closure[F[_],G[_]] { def apply[B](f: F[B]): G[B] } def pair[A,B](a: A, b: B) = new Closure[Compose[PartialApply1Of2[Function1,A]#Apply, PartialApply1Of2[Function1,B]#Apply]#Apply, Identity] { def apply[C](f: A => B => C) = f(a)(b) } For lists, I was able to get encode cons: def cons[A](x: A) = { type T[B] = B => (A => B => B) => B new Closure[T,T] { def apply[B](xs: T[B]) = (b: B) => (f: A => B => B) => f(x)(xs(b)(f)) } } However, the empty list is more problematic and I've not been able to get the Scala compiler to unify the types. Can you define nil, so that, given the definition above, the following compiles? cons(1)(cons(2)(cons(3)(nil)))

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• What is a good platform for building a game framework targetting both web and native languages?

  - by fuzzyTew

  I would like to develop (or find, if one is already in development) a framework with support for accelerated graphics and sound built on a system flexible enough to compile to the following: native ppc/x86/x86_64/arm binaries or a language which compiles to them javascript actionscript bytecode or a language which compiles to it (actionscript 3, haxe) optionally java I imagine, for example, creating an API where I can open windows and make OpenGL-like calls and the framework maps this in a relatively efficient manner to either WebGL with a canvas object, 3d graphics in Flash, OpenGL ES 2 with EGL, or desktop OpenGL in an X11, Windows, or Cocoa window. I have so far looked into these avenues: Building the game library in haXe Pros: Targets exist for php, javascript, actionscript bytecode, c++ High level, object oriented language Cons: No support for finally{} blocks or destructors, making resource cleanup difficult C++ target does not allow room for producing highly optimized libraries -- the foreign function interface requires all primitive types be boxed in a wrapper object, as if writing bindings for a scripting language; these feel unideal for real-time graphics and audio, especially exporting low-level functions. Doesn't seem quite yet mature Using the C preprocessor to create a translator, writing programs entirely with macros Pros: CPP is widespread and simple to use Cons: This is an arduous task and probably the wrong tool for the job CPP implementations differ widely in support for features (e.g. xcode cpp has no variadic macros despite claiming C99 compliance) There is little-to-no room for optimization in this route Using llvm's support for multiple backends to target c/c++ to web languages Pros: Can code in c/c++ LLVM is a very mature highly optimizing compiler performing e.g. global inlining Targets exist for actionscript (alchemy) and javascript (emscripten) Cons: Actionscript target is closed source, unmaintained, and buggy. Javascript targets do not use features of HTML5 for appropriate optimization (e.g. linear memory with typed arrays) and are immature An LLVM target must convert from low-level bytecode, so high-level constructs are lost and bloated unreadable code is created from translating individual instructions, which may be more difficult for an unprepared JIT to optimize. "jump" instructions cause problems for languages with no "goto" statements. Using libclang to write a translator from C/C++ to web languages Pros: A beautiful parsing library providing easy access to the code structure Can code in C/C++ Has sponsored developer effort from Apple Cons: Incomplete; current feature set targets IDEs. Basic operators are unexposed and must be manually parsed from the returned AST element to be identified. Translating code prior to compilation may forgo optimizations assumed in c/c++ such as inlining. Creating new code generators for clang to translate into web languages Pros: Can code in C/C++ as libclang Cons: There is no API; code structure is unstable A much larger job than using libclang; the innards of clang are complex Building the game library in Common Lisp Pros: Flexible, ancient, well-developed language Extensive introspection should ease writing translators Translators exist for at least javascript Cons: Unfamiliar language No standardized library functions, widely varying implementations Which of these avenues should I pursue? Do you know of any others, or any systems that might be useful? Does a general project like this exist somewhere already? Thank you for any input.

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• Help With Lisp Code for a Binary Tree

  - by iulia

  I have (setq l2 '(1 (2 b (c 1 b))(a (1 2) d))) ( defun drumuri (l3) ( cond ( (atom l3) ( cons l3 nil)) ( t ( append ( cons ( car l3 ) nil) ( drumuri ( cadr l3)) (cons (car l3)nil) ( drumuri ( caddr l3)) )))) ( drumuri l2) and it gives me: Break 2 [4]> DRUMURI Break 2 [4]> (1 2 B 2 C 1 C B 1 A 1 2 1 NIL A D) but i need: ((1 2 B)(1 2 C 1)(1 2 C B)(1 A 1 2)(1 A D))

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• In Scala, is there a way to get the currently evaluated items in a Stream?

  - by abhin4v

  In Scala, is there a way to get the currently evaluated items in a Stream? For example in the Stream val s: Stream[Int] = Stream.cons(1, Stream.cons(2, Stream.cons(3, s.map(_+1)))) the method should return only List(1,2,3).

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• What Apache/PHP configurations do you know and how good are they?

  - by FractalizeR

  Hello. I wanted to ask you about PHP/Apache configuration methods you know, their pros and cons. I will start myself: ---------------- PHP as Apache module---------------- Pros: good speed since you don't need to start exe every time especially in mpm-worker mode. You can also use various PHP accelerators in this mode like APC or eAccelerator. Cons: if you are running apache in mpm-worker mode, you may face stability issues because every glitch in any php script will lead to unstability to the whole thread pool of that apache process. Also in this mode all scripts are executed on behalf of apache user. This is bad for security. mpm-worker configuration requires PHP compiled in thread-safe mode. At least CentOS and RedHat default repositories doesn't have thread-safe PHP version so on these OSes you need to compile at least PHP yourself (there is a way to activate worker mpm on Apache). The use of thread-safe PHP binaries is considered experimental and unstable. Plus, many PHP extensions does not support thread-safe mode or were not well-tested in thread-safe mode. ---------------- PHP as CGI ---------------- This seems to be the slowest default configuration which seems to be a "con" itself ;) ---------------- PHP as CGI via mod_suphp ---------------- Pros: suphp allows you to execute php scipts on behalf of the script file owner. This way you can securely separate different sites on the same machine. Also, suphp allows to use different php.ini files per virtual host. Cons: PHP in CGI mode means less performance. In this mode you can't use php accelerators like APC because each time new process is spawned to handle script rendering the cache of previous process useless. BTW, do you know the way to apply some accelerator in this config? I heard something about using shm for php bytecode cache. Also, you cannot configure PHP via .htaccess files in this mode. You will need to install PECL htscanner for this if you need to set various per-script options via .htaccess (php_value / php_flag directives) ---------------- PHP as CGI via suexec ---------------- This configuration looks the same as with suphp, but I heard, that it's slower and less safe. Almost same pros and cons apply. ---------------- PHP as FastCGI ---------------- Pros: FastCGI standard allows single php process to handle several scripts before php process is killed. This way you gain performance since no need to spin up new php process for each script. You can also use PHP accelerators in this configuration (see cons section for comment). Also, FCGI almost like suphp also allows php processes to be executed on behalf of some user. mod_fcgid seems to have the most complete fcgi support and flexibility for apache. Cons: The use of php accelerator in fastcgi mode will lead to high memory consumption because each PHP process will have his own bytecode cache (unless there is some accelerator that can use shared memory for bytecode cache. Is there such?). FastCGI is also a little bit complex to configure. You need to create various configuration files and make some configuration modifications. It seems, that fastcgi is the most stable, secure, fast and flexible PHP configuration, however, a bit difficult to be configured. But, may be, I missed something? Comments are welcome!

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• JavaFX Dialogs, Anyone?

  - by HecklerMark

  A common question about JavaFX, especially for those coming from a Swing background, is "How do I do Dialogs?" The reason this is a question at all is that, currently, there is no baked-in capability to do dialog boxes within a pure JavaFX 2.x application. But come on...you wouldn't be reading about this at all if you weren't a resourceful programmer. You have ways of making things happen.  :-) I ran across a decent patch of code recently that handles many of the dialog chores for you. Pros and cons follow, but pointing your browser to this link on Github (appropriately named JavaFXDialog) will get you off to a good start. Here are some screen shots the original code author, Anton Smirnov, provided: Nothing fancy, just clean and functional. Now, about those pros and cons. From my perspective, here's the bottom line: Pros Already developed. Time required to implement is limited to downloading and decompressing the file, doing a bit of reading, and writing a few lines of code to try things out. Easy. Most of the work is done, and the interface is pretty simple. Open source. If you want to make changes - and I'm already thinking along those lines, so you may as well admit you will, too - you can do it. Cons Documentation. What you see on the Wiki page is the extent of it. Lack of activity. As of the date this article was published, the code hasn't been updated in several months...so the project is a bit stale. To be fair, the cons listed above won't cause anyone to lose sleep. After all, you don't expect constant revisions against something that works well enough for most purposes, and if your needs exceed what is there, it's easy to mod the code yourself or "roll your own" if you prefer. The lack of documentation isn't a show-stopper either due to the limited functionality and complexity of the code. Wrapping It Up If you need a quick, drop-in dialog capability for your JavaFX 2.x app, give it a try and see what you think. And if you're already using something you like, please share it as well! I'd love to hear from you, take a look at what you pass along, and maybe do a "dialog shoot-out" article in the future. So..what works for you?  :-) All the best, Mark

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• Allocating Entities within an Entity System

  - by miguel.martin

  I'm quite unsure how I should allocate/resemble my entities within my entity system. I have various options, but most of them seem to have cons associated with them. In all cases entities are resembled by an ID (integer), and possibly has a wrapper class associated with it. This wrapper class has methods to add/remove components to/from the entity. Before I mention the options, here is the basic structure of my entity system: Entity An object that describes an object within the game Component Used to store data for the entity System Contains entities with specific components Used to update entities with specific components World Contains entities and systems for the entity system Can create/destroy entites and have systems added/removed from/to it Here are my options, that I have thought of: Option 1: Do not store the Entity wrapper classes, and just store the next ID/deleted IDs. In other words, entities will be returned by value, like so: Entity entity = world.createEntity(); This is much like entityx, except I see some flaws in this design. Cons There can be duplicate entity wrapper classes (as the copy-ctor has to be implemented, and systems need to contain entities) If an Entity is destroyed, the duplicate entity wrapper classes will not have an updated value Option 2: Store the entity wrapper classes within an object pool. i.e. Entities will be return by pointer/reference, like so: Entity& e = world.createEntity(); Cons If there is duplicate entities, then when an entity is destroyed, the same entity object may be re-used to allocate another entity. Option 3: Use raw IDs, and forget about the wrapper entity classes. The downfall to this, I think, is the syntax that will be required for it. I'm thinking about doing thisas it seems the most simple & easy to implement it. I'm quite unsure about it, because of the syntax. i.e. To add a component with this design, it would look like: Entity e = world.createEntity(); world.addComponent<Position>(e, 0, 3); As apposed to this: Entity e = world.createEntity(); e.addComponent<Position>(0, 3); Cons Syntax Duplicate IDs

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• Azure Task Scheduling Options

  - by charlie.mott

  Currently, the Azure PaaS does not offer a distributed\resilient task scheduling service.  If you do want to host a task scheduling product\solution off-premise (and ideally use Azure), what are your options? PaaS Option 1: Worker Roles Use a worker role to schedule and execute actions at specific time periods.  There are a few frameworks available to assist with this: http://azuretoolkit.codeplex.com https://github.com/Lokad/lokad-cloud/wiki/TaskScheduler http://blog.smarx.com/posts/building-a-task-scheduler-in-windows-azure - This addresses a slightly different set of requirements. It’s a more dynamic approach for queuing up tasks, but not repeatable tasks (e.g. daily). I found the Azure Toolkit option the most simple to implement.  Step 1 : Create a domain entity implementing IJob for each job to schedule.  In this sample, I asynchronously call a WCF service method. 1: namespace Acme.WorkerRole.Jobs 2: { 3: using AzureToolkit; 4: using ScheduledTasksService; 5: 6: public class UploadEmployeesJob : IJob 7: { 8: public void Run() 9: { 10: // Call Tasks Service 11: var client = new ScheduledTasksServiceClient("BasicHttpBinding_IScheduledTasksService"); 12: client.UploadEmployees(); 13: client.Close(); 14: } 15: } 16: } Step 2 : In the worker role run method, add the jobs to the toolkit engine. 1: namespace Acme.WorkerRole 2: { 3: using AzureToolkit.Engine; 4: using Jobs; 5:   6: public class WorkerRole : WorkerRoleEntryPoint 7: { 8: public override void Run() 9: { 10: var engine = new CloudEngine(); 11:   12: // Add Scheduled Jobs (using CronJob syntax - see http://www.adminschoice.com/crontab-quick-reference). 13:   14: // 1. Upload Employee job - 8.00 PM every weekday (Mon-Fri) 15: engine.WithJobScheduler().ScheduleJob<UploadEmployeesJob>(c => { c.CronSchedule = "0 20 * * 1-5"; }); 16: // 2. Purge Data job - 10 AM every Saturday 17: engine.WithJobScheduler().ScheduleJob<PurgeDataJob>(c => { c.CronSchedule = "0 10 * * 6"; }); 18: // 3. Process Exceptions job - Every 5 minutes 19: engine.WithJobScheduler().ScheduleJob<ProcessExceptionsJob>(c => { c.CronSchedule = "*/5 * * * *"; }); 20:   21: engine.Run(); 22: base.Run(); 23: } 24: } 25: } Pros Cons Azure Toolkit option is simple to implement. For the AzureToolkit option, you are limited to a single worker role.  Otherwise, the jobs will be executed multiple times, once for each worker role instance.   Paying for a continuously running worker role, even if it just processes a single job once a week.  If you only have a few scheduled tasks to run calling asynchronous services hosted in different web roles, an extra small worker role likely to be sufficient.  However, for an extra small worker role this still costs $14.40/month (03/09/2012). Option 2: Use Scheduled Task on Azure Web Role calling a console app Setup a Windows Scheduled Task on the Azure Web Role. This calls a console application that calls the WCF service methods that run the task actions. This design is described here: http://www.ronaldwidha.net/2011/02/23/cron-job-on-azure-using-scheduled-task-on-a-web-role-to-replace-azure-worker-role-for-background-job/ http://www.voiceoftech.com/swhitley/index.php/2011/07/windows-azure-task-scheduler/ http://devlicio.us/blogs/vinull/archive/2011/10/23/moving-to-azure-worker-roles-for-nothing-and-tasks-for-free.aspx Pros Cons Fairly easy to implement. Supportability - I RDC’ed onto the Azure server and stopped the scheduled task. I then rebooted the machine and the task was re-started. I also tried deleting the task and rebooting, the same thing occurred. The only way to permanently guarantee that a task is disabled is to do a fresh deployment. I think this is a major supportability concern.   Saleability - multiple instances would trigger multiple tasks. You can only have one instance for the scheduled task web role. The guidance implements setup of the scheduled task as part of a web role instance. But if you have more than one instance in a web role, the task will be triggered multiple times for each scheduled action (once per machine). Workaround: If we wanted to use scheduled tasks for another client with a saleable WCF service, then we could include the console & tasks scripts in a separate web role (e.g. a empty WCF service with no real purpose to it). SaaS Option 3: Azure Marketplace I thought that someone might be offering this type of service via the Azure marketplace. At the point of writing this blog post, I did not find anyone doing so. https://datamarket.azure.com/ Pros Cons   Nobody currently offers this on the Azure Marketplace. Option 4: Online Job Scheduling Service Provider There are plenty of online providers that offer this type of service on a pay-as-you-go approach.  Some of these are free for small usage.   Many of these providers are listed here: http://en.wikipedia.org/wiki/Webcron Pros Cons No bespoke development for scheduler. Reliance on third party. IaaS Option 5: Setup Scheduling Software on Azure IaaS VM’s One of job scheduling software offerings could be installed and configured on Azure VM’s.  A list of software options is listed here: http://en.wikipedia.org/wiki/List_of_job_scheduler_software Pros Cons Enterprise distributed\resilient task scheduling service VM Setup and maintenance   Software Licence Costs Option 6: VM Gallery A the time of writing this blog post, I did not spot a VM in the gallery that included pre-installation of any of the above software options. Pros Cons   No current VM template. Summary For my current project that had a small handful of tasks to schedule with a limited project budget I chose option 1 (a worker role using the Azure Toolkit to schedule tasks).  If I was building an enterprise scale solution for the future, options 4 and 5 are currently worthy of consideration. Hopefully, Microsoft will include tasks scheduling in the future as part of their PaaS offerings.

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• Need to find a find a fast/multi-user database program

  - by user65961

  Our company is currently utilizing Excel and have been encountering a series of issues for starters we have multiple users sharing this application. We utilize it write our schedules for our employees and generate staffing levels. May someone give me please or inform me what are the pros and cons of this program and offer suggestions for another database that allows multiple users to share and also give the pros and cons need something that will hold massive data and allow sharing, protecting capabilities.

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• MySQL: Functional Partitioning

  This article contains common different methods of functional partitioning and common considerations for database setup and capacity. Company DBAs, database developers, engineers and architects should consider the pros and cons of any method of sharding or partitioning since compromises will have to be made given the pros and cons of a system setup.

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• MySQL: Functional Partitioning

  This article contains common different methods of functional partitioning and common considerations for database setup and capacity. Company DBAs, database developers, engineers and architects should consider the pros and cons of any method of sharding or partitioning since compromises will have to be made given the pros and cons of a system setup.

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• Best Practices - Dynamic Reconfiguration

  - by jsavit

  This post is one of a series of "best practices" notes for Oracle VM Server for SPARC (formerly named Logical Domains) Overview of dynamic Reconfiguration Oracle VM Server for SPARC supports Dynamic Reconfiguration (DR), making it possible to add or remove resources to or from a domain (virtual machine) while it is running. This is extremely useful because resources can be shifted to or from virtual machines in response to load conditions without having to reboot or interrupt running applications. For example, if an application requires more CPU capacity, you can add CPUs to improve performance, and remove them when they are no longer needed. You can use even use Dynamic Resource Management (DRM) policies that automatically add and remove CPUs to domains based on load. How it works (in broad general terms) Dynamic Reconfiguration is done in coordination with Solaris, which recognises a hypervisor request to change its virtual machine configuration and responds appropriately. In essence, Solaris receives a message saying "you now have 16 more CPUs numbered 16 to 31" or "8GB more RAM starting at address X" or "here's a new network or disk device - have fun with it". These actions take very little time. Solaris then can start using the new resource. In the case of added CPUs, that means dispatching processes and potentially binding interrupts to the new CPUs. For memory, Solaris adds the new memory pages to its "free" list and starts using them. Comparable actions occur with network and disk devices: they are recognised by Solaris and then used. Removing is the reverse process: after receiving the DR message to free specific CPUs, Solaris unbinds interrupts assigned to the CPUs and stops dispatching process threads. That takes very little time. primary # ldm list NAME STATE FLAGS CONS VCPU MEMORY UTIL UPTIME primary active -n-cv- SP 16 4G 1.0% 6d 22h 29m ldom1 active -n---- 5000 16 8G 0.9% 6h 59m primary # ldm set-core 5 ldom1 primary # ldm list NAME STATE FLAGS CONS VCPU MEMORY UTIL UPTIME primary active -n-cv- SP 16 4G 0.2% 6d 22h 29m ldom1 active -n---- 5000 40 8G 0.1% 6h 59m primary # ldm set-core 2 ldom1 primary # ldm list NAME STATE FLAGS CONS VCPU MEMORY UTIL UPTIME primary active -n-cv- SP 16 4G 1.0% 6d 22h 29m ldom1 active -n---- 5000 16 8G 0.9% 6h 59m Memory pages are vacated by copying their contents to other memory locations and wiping them clean. Solaris may have to swap memory contents to disk if the remaining RAM isn't enough to hold all the contents. For this reason, deallocating memory can take longer on a loaded system. Even on a lightly loaded system it took several 7 or 8 seconds to switch the domain below between 8GB and 24GB of RAM. primary # ldm set-mem 24g ldom1 primary # ldm list NAME STATE FLAGS CONS VCPU MEMORY UTIL UPTIME primary active -n-cv- SP 16 4G 0.1% 6d 22h 36m ldom1 active -n---- 5000 16 24G 0.2% 7h 6m primary # ldm set-mem 8g ldom1 primary # ldm list NAME STATE FLAGS CONS VCPU MEMORY UTIL UPTIME primary active -n-cv- SP 16 4G 0.7% 6d 22h 37m ldom1 active -n---- 5000 16 8G 0.3% 7h 7m What if the device is in use? (this is the anecdote that inspired this blog post) If CPU or memory is being removed, releasing it pretty straightforward, using the method described above. The resources are released, and Solaris continues with less capacity. It's not as simple with a network or I/O device: you don't want to yank a device out from underneath an application that might be using it. In the following example, I've added a virtual network device to ldom1 and want to take it away, even though it's been plumbed. primary # ldm rm-vnet vnet19 ldom1 Guest LDom returned the following reason for failing the operation: Resource Information ---------------------------------------------------------- ----------------------- /devices/virtual-devices@100/channel-devices@200/network@1 Network interface net1 VIO operation failed because device is being used in LDom ldom1 Failed to remove VNET instance That's what I call a helpful error message - telling me exactly what was wrong. In this case the problem is easily solved. I know this NIC is seen in the guest as net1 so: ldom1 # ifconfig net1 down unplumb Now I can dispose of it, and even the virtual switch I had created for it: primary # ldm rm-vnet vnet19 ldom1 primary # ldm rm-vsw primary-vsw9 If I had to take away the device disruptively, I could have used ldm rm-vnet -f but that could disrupt whoever was using it. It's better if that can be avoided. Summary Oracle VM Server for SPARC provides dynamic reconfiguration, which lets you modify a guest domain's CPU, memory and I/O configuration on the fly without reboot. You can add and remove resources as needed, and even automate this for CPUs by setting up resource policies. Taking things away can be more complicated than giving, especially for devices like disks and networks that may contain application and system state or be involved in a transaction. LDoms and Solaris cooperative work together to coordinate resource allocation and de-allocation in a safe and effective way. For best practices, use dynamic reconfiguration to make the best use of your system's resources.

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• Cloud to On-Premise Connectivity Patterns

  - by Rajesh Raheja

  Do you have a requirement to convert an Opportunity in Salesforce.com to an Order/Quote in Oracle E-Business Suite? Or maybe you want the creation of an Oracle RightNow Incident to trigger an on-premise Oracle E-Business Suite Service Request creation for RMA and Field Scheduling? If so, read on. In a previous blog post, I discussed integrating TO cloud applications, however the use cases above are the reverse i.e. receiving data FROM cloud applications (SaaS) TO on-premise applications/databases that sit behind a firewall. Oracle SOA Suite is assumed to be on-premise with with Oracle Service Bus as the mediation and virtualization layer. The main considerations for the patterns are are security i.e. shielding enterprise resources; and scalability i.e. minimizing firewall latency. Let me use an analogy to help visualize the patterns: the on-premise system is your home - with your most valuable possessions - and the SaaS app is your favorite on-line store which regularly ships (inbound calls) various types of parcels/items (message types/service operations). You need the items at home (on-premise) but want to safe guard against misguided elements of society (internet threats) who may masquerade as postal workers and vandalize property (denial of service?). Let's look at the patterns. Pattern: Pull from Cloud The on-premise system polls from the SaaS apps and picks up the message instead of having it delivered. This may be done using Oracle RightNow Object Query Language or SOAP APIs. This is particularly suited for certain integration approaches wherein messages are trickling in, can be centralized and batched e.g. retrieving event notifications on an hourly schedule from the Oracle Messaging Service. To compare this pattern with the home analogy, you are avoiding any deliveries to your home and instead go to the post office/UPS/Fedex store to pick up your parcel. Every time. Pros: On-premise assets not exposed to the Internet, firewall issues avoided by only initiating outbound connections Cons: Polling mechanisms may affect performance, may not satisfy near real-time requirements Pattern: Open Firewall Ports The on-premise system exposes the web services that needs to be invoked by the cloud application. This requires opening up firewall ports, routing calls to the appropriate internal services behind the firewall. Fusion Applications uses this pattern, and auto-provisions the services on the various virtual hosts to secure the topology. This works well for service integration, but may not suffice for large volume data integration. Using the home analogy, you have now decided to receive parcels instead of going to the post office every time. A door mail slot cut out allows the postman can drop small parcels, but there is still concern about cutting new holes for larger packages. Pros: optimal pattern for near real-time needs, simpler administration once the service is provisioned Cons: Needs firewall ports to be opened up for new services, may not suffice for batch integration requiring direct database access Pattern: Virtual Private Networking The on-premise network is "extended" to the cloud (or an intermediary on-demand / managed service offering) using Virtual Private Networking (VPN) so that messages are delivered to the on-premise system in a trusted channel. Using the home analogy, you entrust a set of keys with a neighbor or property manager who receives the packages, and then drops it inside your home. Pros: Individual firewall ports don't need to be opened, more suited for high scalability needs, can support large volume data integration, easier management of one connection vs a multitude of open ports Cons: VPN setup, specific hardware support, requires cloud provider to support virtual private computing Pattern: Reverse Proxy / API Gateway The on-premise system uses a reverse proxy "API gateway" software on the DMZ to receive messages. The reverse proxy can be implemented using various mechanisms e.g. Oracle API Gateway provides firewall and proxy services along with comprehensive security, auditing, throttling benefits. If a firewall already exists, then Oracle Service Bus or Oracle HTTP Server virtual hosts can provide reverse proxy implementations on the DMZ. Custom built implementations are also possible if specific functionality (such as message store-n-forward) is needed. In the home analogy, this pattern sits in between cutting mail slots and handing over keys. Instead, you install (and maintain) a mailbox in your home premises outside your door. The post office delivers the parcels in your mailbox, from where you can securely retrieve it. Pros: Very secure, very flexible Cons: Introduces a new software component, needs DMZ deployment and management Pattern: On-Premise Agent (Tunneling) A light weight "agent" software sits behind the firewall and initiates the communication with the cloud, thereby avoiding firewall issues. It then maintains a bi-directional connection either with pull or push based approaches using (or abusing, depending on your viewpoint) the HTTP protocol. Programming protocols such as Comet, WebSockets, HTTP CONNECT, HTTP SSH Tunneling etc. are possible implementation options. In the home analogy, a resident receives the parcel from the postal worker by opening the door, however you still take precautions with chain locks and package inspections. Pros: Light weight software, IT doesn't need to setup anything Cons: May bypass critical firewall checks e.g. virus scans, separate software download, proliferation of non-IT managed software Conclusion The patterns above are some of the most commonly encountered ones for cloud to on-premise integration. Selecting the right pattern for your project involves looking at your scalability needs, security restrictions, sync vs asynchronous implementation, near real-time vs batch expectations, cloud provider capabilities, budget, and more. In some cases, the basic "Pull from Cloud" may be acceptable, whereas in others, an extensive VPN topology may be well justified. For more details on the Oracle cloud integration strategy, download this white paper.

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• Cloud to On-Premise Connectivity Patterns

  - by Rajesh Raheja

  Do you have a requirement to convert an Opportunity in Salesforce.com to an Order/Quote in Oracle E-Business Suite? Or maybe you want the creation of an Oracle RightNow Incident to trigger an on-premise Oracle E-Business Suite Service Request creation for RMA and Field Scheduling? If so, read on. In a previous blog post, I discussed integrating TO cloud applications, however the use cases above are the reverse i.e. receiving data FROM cloud applications (SaaS) TO on-premise applications/databases that sit behind a firewall. Oracle SOA Suite is assumed to be on-premise with with Oracle Service Bus as the mediation and virtualization layer. The main considerations for the patterns are are security i.e. shielding enterprise resources; and scalability i.e. minimizing firewall latency. Let me use an analogy to help visualize the patterns: the on-premise system is your home - with your most valuable possessions - and the SaaS app is your favorite on-line store which regularly ships (inbound calls) various types of parcels/items (message types/service operations). You need the items at home (on-premise) but want to safe guard against misguided elements of society (internet threats) who may masquerade as postal workers and vandalize property (denial of service?). Let's look at the patterns. Pattern: Pull from Cloud The on-premise system polls from the SaaS apps and picks up the message instead of having it delivered. This may be done using Oracle RightNow Object Query Language or SOAP APIs. This is particularly suited for certain integration approaches wherein messages are trickling in, can be centralized and batched e.g. retrieving event notifications on an hourly schedule from the Oracle Messaging Service. To compare this pattern with the home analogy, you are avoiding any deliveries to your home and instead go to the post office/UPS/Fedex store to pick up your parcel. Every time. Pros: On-premise assets not exposed to the Internet, firewall issues avoided by only initiating outbound connections Cons: Polling mechanisms may affect performance, may not satisfy near real-time requirements Pattern: Open Firewall Ports The on-premise system exposes the web services that needs to be invoked by the cloud application. This requires opening up firewall ports, routing calls to the appropriate internal services behind the firewall. Fusion Applications uses this pattern, and auto-provisions the services on the various virtual hosts to secure the topology. This works well for service integration, but may not suffice for large volume data integration. Using the home analogy, you have now decided to receive parcels instead of going to the post office every time. A door mail slot cut out allows the postman can drop small parcels, but there is still concern about cutting new holes for larger packages. Pros: optimal pattern for near real-time needs, simpler administration once the service is provisioned Cons: Needs firewall ports to be opened up for new services, may not suffice for batch integration requiring direct database access Pattern: Virtual Private Networking The on-premise network is "extended" to the cloud (or an intermediary on-demand / managed service offering) using Virtual Private Networking (VPN) so that messages are delivered to the on-premise system in a trusted channel. Using the home analogy, you entrust a set of keys with a neighbor or property manager who receives the packages, and then drops it inside your home. Pros: Individual firewall ports don't need to be opened, more suited for high scalability needs, can support large volume data integration, easier management of one connection vs a multitude of open ports Cons: VPN setup, specific hardware support, requires cloud provider to support virtual private computing Pattern: Reverse Proxy / API Gateway The on-premise system uses a reverse proxy "API gateway" software on the DMZ to receive messages. The reverse proxy can be implemented using various mechanisms e.g. Oracle API Gateway provides firewall and proxy services along with comprehensive security, auditing, throttling benefits. If a firewall already exists, then Oracle Service Bus or Oracle HTTP Server virtual hosts can provide reverse proxy implementations on the DMZ. Custom built implementations are also possible if specific functionality (such as message store-n-forward) is needed. In the home analogy, this pattern sits in between cutting mail slots and handing over keys. Instead, you install (and maintain) a mailbox in your home premises outside your door. The post office delivers the parcels in your mailbox, from where you can securely retrieve it. Pros: Very secure, very flexible Cons: Introduces a new software component, needs DMZ deployment and management Pattern: On-Premise Agent (Tunneling) A light weight "agent" software sits behind the firewall and initiates the communication with the cloud, thereby avoiding firewall issues. It then maintains a bi-directional connection either with pull or push based approaches using (or abusing, depending on your viewpoint) the HTTP protocol. Programming protocols such as Comet, WebSockets, HTTP CONNECT, HTTP SSH Tunneling etc. are possible implementation options. In the home analogy, a resident receives the parcel from the postal worker by opening the door, however you still take precautions with chain locks and package inspections. Pros: Light weight software, IT doesn't need to setup anything Cons: May bypass critical firewall checks e.g. virus scans, separate software download, proliferation of non-IT managed software Conclusion The patterns above are some of the most commonly encountered ones for cloud to on-premise integration. Selecting the right pattern for your project involves looking at your scalability needs, security restrictions, sync vs asynchronous implementation, near real-time vs batch expectations, cloud provider capabilities, budget, and more. In some cases, the basic "Pull from Cloud" may be acceptable, whereas in others, an extensive VPN topology may be well justified. For more details on the Oracle cloud integration strategy, download this white paper.

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• Quartz 2D or OpenGL ES? Pros and cons in the long term, possibility of migration to other platforms.

  - by fspirit

  Hi all! I'm having a hard time deciding whether to go with Quartz2D or OpenGL for an iPad game. It will be 2D mostly, but effect-intense (simultaneous lighting effects for 10-30 objects, 10-20 simultaneous animations on the screen). So far, assuming i'm equally dumb in both technologies and have to learn them from the ground, i came to this list. (I've read several topics here, on SO, with names like "Quartz or OpenGL", but i'm still left with some questions) Quartz: Better time-to-market, because of ready to use absractions like UIView, UIImageView, CoreAnimation abstractions Open GL ES Closer to hardware, thus, performance is better. App, implemented with OpenGL ES can be easier migrated to Android, MeeGo, Windows Phone, etc. My questions are: How time will it take to rewrite Quartz 2d app to use OpenGL? Lets say it took me 2 man-month to write Quartz app, how much time will i need to rewrite it? (Please, just some subjective opinions, i'll try to summarize them somehow) Regarding the ease of migration to other platforms, when using OpenGL, is it really so? Or efforts when migrating Quartz app from iPhoneOS to Android will be not so much bigger, compared to OpenGL app migration? (Ease of migration is quite important criterion) Regarding OpenGL, should i go with OpenGL 1.1 or 2.0, concerning migration? (Android supports 2.0 through NDK, but dont know whether NDK's use will increase or decrease migration efforts)

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• Load-balancer options

  - by toolkit

  I am looking at a number of possible options for load-balancing. So far, I am constrained to the following options: DNS server load-balancer, balancing to a cluster of tomcat servers, with terracotta for session replication. Pros - don't have to buy new kit. Cons - DNS lb can keep directing to a broken server. Hardware load-balancer, direct to cluster of tomcat servers. Pros - could have second box for failover lb. Cons - expense. Apache server load-balancer. Pros - apache's lb polls for broken servers. Cons - apache server is single point of failure, plus need to buy another server. Are there any other options I should consider? Thanks. Update: Thanks for all the answers so far +1's all round. Not accepting an answer yet, to keep more ideas coming.

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• Drawbacks of installing linux on usb stick?

  - by Znarkus

  I am setting up a router/nas/http/whatever server based on an ION mini-ITX board. I've installed Ubuntu Server on an old 160 GB drive, but it generates a lot more heat and vibrates more than my other new drive (storage). It just doesn't fit the concept, and worse: it takes up a SATA port. As SSD's are crazy expensive I'm thinking of buying an extra 4 GB USB stick, and raid0 it. From my point of view, these are the pros/cons: Pros Low power consumption No vibrations No heat Smaller Get to buy new, larger USB stick (:D) Cons Shorter life time Slower Raid 0 More work maintaing/installing? I think the pros overweighs the cons. Shorter life time and raid 0 is countered by regular backups of the configs/settings. Slower is partially countered by raid 0, and I don't know about the last one. What do You think? Experience? Another solution?

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• Directory "Bookmarking" in Linux

  - by Jason R. Mick

  Aside from aliasing and links, is there an easy way in Linux to tag commonly used directories and to navigate to a commonly used directory from the terminal. To be clear the disadvantages I see with alternative approaches, and why I want a bookmark/favorites like system: alias Cons: Too specific (every new favorite requires a new alias...although you could in theory make an alias that echo append your dir as a new alias, which would be sort of clever). Can't nest favorites in folders (can't think of a simple solution to this outside of heavy config scripting). links Cons: Clutter directory make ls a headache. pushd/popd Cons: Non-permanent (without shell config file scripting), can't nest favorites in directories, etc. Granted I have multiple ideas for making my own non-standard solution, but before I have at it I wanted to get some perspective on what's out there and if there is nothing, what is a recommended approach. Does anyone know of such a favorites/bookmark-like terminal solution?

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• SQL Saturday #220 - Atlanta - Pre-Conference Scholarships!

  - by Most Valuable Yak (Rob Volk)

  We Want YOU…To Learn! AtlantaMDF and Idera are teaming up to find a few good people. If you are: A student looking to work in the database or business intelligence fields A database professional who is between jobs or wants a better one A developer looking to step up to something new On a limited budget and can’t afford professional SQL Server training Able to attend training from 9 to 5 on May 17, 2013 AtlantaMDF is presenting 5 Pre-Conference Sessions (pre-cons) for SQL Saturday #220! And thanks to Idera’s sponsorship, we can offer one free ticket to each of these sessions to eligible candidates! That means one scholarship per Pre-Con! One Recipient Each will Attend: Denny Cherry: SQL Server Security http://sqlsecurity.eventbrite.com/ Adam Machanic: Surfing the Multicore Wave: Processors, Parallelism, and Performance http://surfmulticore.eventbrite.com/ Stacia Misner: Languages of BI http://languagesofbi.eventbrite.com/ Bill Pearson: Practical Self-Service BI with PowerPivot for Excel http://selfservicebi.eventbrite.com/ Eddie Wuerch: The DBA Skills Upgrade Toolkit http://dbatoolkit.eventbrite.com/ If you are interested in attending these pre-cons send an email by April 30, 2013 to [email protected] and tell us: Why you are a good candidate to receive this scholarship Which sessions you’d like to attend, and why (list multiple sessions in order of preference) What the session will teach you and how it will help you achieve your goals The emails will be evaluated by the good folks at Midlands PASS in Columbia, SC. The recipients will be notified by email and announcements made on May 6, 2013. GOOD LUCK! P.S. - Don't forget that SQLSaturday #220 offers free* training in addition to the pre-cons! You can find more information about SQL Saturday #220 at http://www.sqlsaturday.com/220/eventhome.aspx. View the scheduled sessions at http://www.sqlsaturday.com/220/schedule.aspx and register for them at http://www.sqlsaturday.com/220/register.aspx. * Registration charges a $10 fee to cover lunch expenses.

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• What is a good way to share internal helpers?

  - by toplel32

  All my projects share the same base library that I have build up over quite some time. It contains utilities and static helper classes to assist them where .NET doesn't exactly offer what I want. Originally all the helpers were written mainly to serve an internal purpose and it has to stay that way, but sometimes they prove very useful to other assemblies. Now making them public in a reliable way is more complicated than most would think, for example all methods that assume nullable types must now contain argument checking while not charging internal utilities with the price of doing so. The price might be negligible, but it is far from right. While refactoring, I have revised this case multiple times and I've come up with the following solutions so far: Have an internal and public class for each helper The internal class contains the actual code while the public class serves as an access point which does argument checking. Cons: The internal class requires a prefix to avoid ambiguity (the best presentation should be reserved for public types) It isn't possible to discriminate methods that don't need argument checking   Have one class that contains both internal and public members (as conventionally implemented in .NET framework). At first, this might sound like the best possible solution, but it has the same first unpleasant con as solution 1. Cons: Internal methods require a prefix to avoid ambiguity   Have an internal class which is implemented by the public class that overrides any members that require argument checking. Cons: Is non-static, atleast one instantiation is required. This doesn't really fit into the helper class idea, since it generally consists of independent fragments of code, it should not require instantiation. Non-static methods are also slower by a negligible degree, which doesn't really justify this option either. There is one general and unavoidable consequence, alot of maintenance is necessary because every internal member will require a public counterpart. A note on solution 1: The first consequence can be avoided by putting both classes in different namespaces, for example you can have the real helper in the root namespace and the public helper in a namespace called "Helpers".

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• NFS users getting a laggy GUI expierence

  - by elzilrac

  I am setting up a system (ubuntu 12.04) that uses ldap, pam, and autofs to load users and their home folders from a remote server. One of the options for login is sitting down at the machine and starting a GUI session. Programs such as chormium (browser) that preform many read/write operations in the ~/.cache and ~/.config files are slowing down the GUI experience as well as putting strain of the NFS server that is causing other users to have problems. Ubuntu had the handy-dandy XDG_CONFIG_HOME and XDG_CACHE_HOME variables that can be set to change the default location of .cache and .config from the home folder to somewhere else. There are several places to set them, but most of them are not optimal. /etc/environment pros: will work across all shells cons: cannot use variables like $USER so that you can't make users have different new locations for .cache and .config. Every users' new location would be the same directory. /etc/bash.bashrc pros: $USER works, so you can place them in different folders cons: only gets run for bash compatible shells ~/.pam_environment pros: works regardless of shell cons: cannot use system variables (like $USER), has it's own syntax, and has to be created for every user

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