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• Enterprise Service Bus (ESB): Important architectural piece to a SOA or is it just vendor hype?

  Is an Enterprise Service Bus (ESB) an important architectural piece to a Service-Oriented Architecture (SOA), or is it just vendor hype in order to sell a particular product such as SOA-in-a-box? According to IBM.com, an ESB is a flexible connectivity infrastructure for integrating applications and services; it offers a flexible and manageable approach to service-oriented architecture implementation. With this being said, it is my personal belief that ESBs are an important architectural piece to any SOA. Additionally, generic design patterns have been created around the integration of web services in to ESB regardless of any vendor. ESB design patterns, according to Philip Hartman, can be classified in to the following categories: Interaction Patterns: Enable service interaction points to send and/or receive messages from the bus Mediation Patterns: Enable the altering of message exchanges Deployment Patterns: Support solution deployment into a federated infrastructure Examples of Interaction Patterns: One-Way Message Synchronous Interaction Asynchronous Interaction Asynchronous Interaction with Timeout Asynchronous Interaction with a Notification Timer One Request, Multiple Responses One Request, One of Two Possible Responses One Request, a Mandatory Response, and an Optional Response Partial Processing Multiple Application Interactions Benefits of the Mediation Pattern: Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently Design an intermediary to decouple many peers Promote the many-to-many relationships between interacting peers to “full object status” Examples of Interaction Patterns: Global ESB: Services share a single namespace and all service providers are visible to every service requester across an entire network Directly Connected ESB: Global service registry that enables independent ESB installations to be visible Brokered ESB: Bridges services that are reluctant to expose requesters or providers to ESBs in other domains Federated ESB: Service consumers and providers connect to the master or to a dependent ESB to access services throughout the network References: Mediator Design Pattern. (2011). Retrieved 2011, from SourceMaking.com: http://sourcemaking.com/design_patterns/mediator Hartman, P. (2006, 24 1). ESB Patterns that "Click". Retrieved 2011, from The Art and Science of Being an IT Architect: http://artsciita.blogspot.com/2006/01/esb-patterns-that-click.html IBM. (2011). WebSphere DataPower XC10 Appliance Version 2.0. Retrieved 2011, from IBM.com: http://publib.boulder.ibm.com/infocenter/wdpxc/v2r0/index.jsp?topic=%2Fcom.ibm.websphere.help.glossary.doc%2Ftopics%2Fglossary.html Oracle. (2005). 12 Interaction Patterns. Retrieved 2011, from Oracle® BPEL Process Manager Developer's Guide: http://docs.oracle.com/cd/B31017_01/integrate.1013/b28981/interact.htm#BABHHEHD

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• Playing with F#

  - by mroberts

  Project Euler is a awesome site.   When working with a new language it can be tricky to find problems that need solving, that are more complex than "Hello World" and simpler than a full blown application. Project Euler gives use just that, cool and thought provoking problems that usually don't take days to solve.  I've solved a number of questions with C# and some with Java.  BTW, I used Java because it had BigInteger support before .Net. A couple weeks ago, back when winter had a firm grip on Columbus, OH, I began playing (researching) with F#.  I began with Problem #1 from Project Euler.  I started by looking at my solution in C#. Here is my solution in C#. 1: using System; 2: using System.Collections.Generic; 3:   4: namespace Problem001 5: { 6: class Program 7: { 8: static void Main(string[] args) 9: { 10: List<int> values = new List<int>(); 11:   12: for (int i = 1; i < 1000; i++) 13: { 14: if (i % 3 == 0 || i % 5 == 0) 15: values.Add(i); 16: } 17: int total = 0; 18:   19: values.ForEach(v => total += v); 20:   21: Console.WriteLine(total); 22: Console.ReadKey(); 23: } 24: } 25: }   Now, after much tweaking and learning, here is my solution in F#.   1: open System 2:   3: let calc n = 4: [1..n] 5: |> List.map (fun x -> if (x % 3 = 0 || x % 5 = 0) then x else 0) 6: |> List.sum 7:   8: let main() = 9: calc 999 10: |> printfn "result = %d" 11: Console.ReadKey(true) |> ignore 12:   13: main() Just this little example highlights some cool things about F#. Type inference. F# infers the type of a value.  In the C# code above we declare a number of variables, the list, and a couple ints.  F# does not require this, it infers the calc (a function) accepts a int and returns a int. Great built in functionality for Lists.  List.map for example. BTW, I don’t think I’m spilling the beans by giving away the code for Problem 1.  It by far is the easiest question, IMHO, solved by 92,000+ people. Next I’ll look into writing a class library with F#.

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• What is the rationale behind snazzy Window Managers/Composers?

  - by Emanuele

  This is more of a generic question, based on trying out Window Managers like Awesome, Mate and others. To me looks like that other Window Managers like Gnome3 and/or Unity are heavy and pointless. I do understand that having all the composed UIs is more pleasant for the eye, but apart that, what are the other major benefits? To make an example, when I run the game Heroes of Newerth (using nVidia drivers) under: Unity : the FPS drops sharply Gnome3 : FPS is ok, but X and other processes use 15~20% of CPU and quite some additional memory Awesome : FPS is ok, and other processes use very little memory and CPU Below some numbers regarding what I'm saying (please note my system is 64 bit, AMD Phenom II X4, 8 GB RAM, nd nVidia 470 GTX, SSD disk). All data is sorted by mem usage (watch -d -n 10 "ps -e -o pcpu,pmem,pid,user,cmd --sort=-pmem | head -20"); again note that CPU time of ./hon-x86_64 might be different due to the fact I can't take the snapshot of the system during exactly same time. Awesome: %CPU %MEM PID USER CMD 91.8 21.6 3579 ema ./hon-x86_64 2.4 0.9 3223 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.6 0.4 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- -noshell -noinp 0.3 0.2 3602 ema gnome-terminal 0.0 0.2 2698 ema /usr/bin/python /usr/lib/desktopcouch/desktopcouch-service Gnome3: %CPU %MEM PID USER CMD 82.7 21.0 5528 ema ./hon-x86_64 17.7 1.7 5315 ema /usr/bin/gnome-shell 5.8 1.2 5062 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.0 0.4 5657 ema /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon 0.7 0.3 5331 ema nautilus -n 1.6 0.3 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- - 0.9 0.2 5451 ema gnome-terminal 0.1 0.2 5400 ema /usr/bin/python /usr/lib/desktopcouch/desktopcouch-service Unity 3D: %CPU %MEM PID USER CMD 87.2 21.1 6554 ema ./hon-x86_64 10.7 2.6 6105 ema compiz 17.8 1.1 5842 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.3 0.9 6672 root /usr/bin/python /usr/sbin/aptd 0.4 0.4 6606 ema /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon 0.5 0.3 6115 ema nautilus -n 1.5 0.3 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- -noshell -noinput -sasl errl 0.3 0.2 6180 ema /usr/lib/unity/unity-panel-service So my point is, what's the rationale behind going towards such heavy WMs/Composers?

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• Simple collision detection in Unity 2D

  - by N1ghtshade3

  I realise other posts exist with this topic yet none have gone into enough detail for me. I am attempting to create a 2D game in Unity using C# as my scripting language. Basically I have two objects, player and bomb. Both were created simply by dragging the respective PNG to the stage. I have set up touch controls to move player left and right; gravity of any kind is not needed as I only require it to move x units when I tap either the left or right side of the screen. This movement is stored in a script called playerController.cs and works just fine. I also have a variable health = 3 for player, which is stored in healthScript.cs. I am now at a point where I am stuck. I would like it so that when player collides with bomb, health decreases by one and the bomb object is destroyed. So what I tried doing is using a new script called playerPhysics.cs, I added the following: void OnCollisionEnter2D(Collision2D coll){ if(coll.gameObject.name=="bomb") GameObject.Destroy("bomb"); healthScript.health -= 1; } While I'm fairly sure I don't know the proper way to reference a variable in another script and that's why the health didn't decrease when I collided, bomb never disappeared from the stage so I'm thinking there's also a problem with my collision. Initially, I had simply attached playerPhysics.cs to player. After searching around though, it appeared as though player also needed a rigidBody attached to it, so I did that. Still no luck. I tried using a circleCollider (player is a circle), using a rigidBody2D, and using all manner of colliders on one and/or both of the objects. If you could please explain what colliders (if any) should be attached to which objects and whether I need to change my script(s), that would be much more helpful than pointing me to one of the generic documentation examples I've already read. Also, if it would be simple to fix the health thing not working that would be an added bonus but not exactly the focus of this question. Bear in mind that this game is 2D; I'm not sure if that changes anything. Thanks!

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• JGridView (Part 2)

  - by Geertjan

  The second sample in the JGrid download is a picture viewer that needs to be seen to be believed. Here it is, integrated into a NetBeans Platform application (click to enlarge it): When you mouse over the images, they change, showing several different images instantaneously. Here's the explorer view above, mainly making use of code from the sample: public class JGridView extends JScrollPane { @Override public void addNotify() { super.addNotify(); final ExplorerManager em = ExplorerManager.find(this); if (em != null) { final JGrid grid = new JGrid(); Node root = em.getRootContext(); final Node[] nodes = root.getChildren().getNodes(); final PicViewerObject[] pics = new PicViewerObject[nodes.length]; for (int i = 0; i < nodes.length; i++) { Node node = nodes[i]; pics[i] = node.getLookup().lookup(PicViewerObject.class); } grid.getCellRendererManager().setDefaultRenderer(new PicViewerRenderer()); grid.setModel(new DefaultListModel() { @Override public int getSize() { return pics.length; } @Override public Object getElementAt(int i) { return pics[i]; } }); grid.setFixedCellDimension(160); grid.addMouseMotionListener(new MouseAdapter() { int lastIndex = -1; @Override public void mouseMoved(MouseEvent e) { if (lastIndex >= 0) { Object o = grid.getModel().getElementAt(lastIndex); if (o instanceof PicViewerObject) { Rectangle r = grid.getCellBounds(lastIndex); if (r != null && !r.contains(e.getPoint())) { ((PicViewerObject) o).setMarker(false); grid.repaint(r); } } } int index = grid.getCellAt(e.getPoint()); if (index >= 0) { Object o = grid.getModel().getElementAt(index); if (o instanceof PicViewerObject) { Rectangle r = grid.getCellBounds(index); if (r != null) { ((PicViewerObject) o).setFraction(((float) e.getPoint().x - (float) r.x) / (float) r.width); ((PicViewerObject) o).setMarker(true); lastIndex = index; grid.repaint(r); } } } } }); grid.getSelectionModel().addListSelectionListener(new ListSelectionListener() { @Override public void valueChanged(ListSelectionEvent e) { //Somehow compare the selected item //with the list of books and find a matching book: int selectedIndex = grid.getSelectedIndex(); for (int i = 0; i < nodes.length; i++) { int picId = pics[i].getId(); if (selectedIndex == picId) { try { em.setSelectedNodes(new Node[]{nodes[i]}); } catch (PropertyVetoException ex) { Exceptions.printStackTrace(ex); } } } } }); setViewportView(grid); } } } The next step is to create a generic JGridView that will handle any kind of object automatically.

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• Ubuntu hangs on booting up after a update

  - by alFReD NSH

  I've made a clean install yesterday, for the first time restarted, everything went good and then after I updated packages and copied my old home directory to replace the new one, when I restarted it hung when it was booting. I tried reinstalling again and doing the same thing, but again same thing happened. Here's what I see, before when the Ubuntu logo with the five dots is shown: Then after that, 3 or 4 of the dots will load and hangs there. If I press arrow up before that, this will be shown I started my laptop again today(the pictures are for the day before) and after that, boot up with live CD and got the logs. dmesg: http://pastebin.com/aVxV7BQF syslog: http://pastebin.com/4E2BrRUK And some info: alfred@alFitop:~$ uname -a Linux alFitop 3.2.0-24-generic #39-Ubuntu SMP Mon May 21 16:52:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux lshw: http://pastebin.com/AZbKJmsT sources.list : http://pastebin.com/2HazmuyV My problem is a bit similar to here: http://ubuntuforums.org/showthread.php?t=1918271 Though I didn't change my x.org config. Only changed home directory and updated packages. I've tried memtest and fschk, both passed. In the recovery mode boot option, I've also realized that same things happen in failsafe graphical mode. But when I go into the network mode, I can boot up my system, but of course same the graphics are just basic. Adding blacklist intel_ips to /etc/modprobe.d/blacklist.conf solves the first message, but still I get the broken pipe and CPU stack traces. The current kernel version is 3.2.0-25, I've tried booting up in the 3.2.0-23(the one the installer came with, but same results.) Also uninstalled apparmor, didn't help. I've installed Ubuntu again, this time without copying the home directory, also same result. --- UPDATE --- This problem was solved before with removing backports, but its back again! I've updated my laptop last night and the problem came back. It's definitely one of these packages. My /var/log/apt/term.log and /var/log/apt/history.log. I'm almost having the same situation. --- UPDATE --- I realized this also have happened on times that I have updated(haven't restarted after it) and my computer power has been cut off and its shutdown due to lack of power. And I realized if I just do as I answered but not in somewhere without GUI(networking mode has the GUI) it wouldn't work.

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• C++11 Tidbits: Decltype (Part 2, trailing return type)

  - by Paolo Carlini

  Following on from last tidbit showing how the decltype operator essentially queries the type of an expression, the second part of this overview discusses how decltype can be syntactically combined with auto (itself the subject of the March 2010 tidbit). This combination can be used to specify trailing return types, also known informally as "late specified return types". Leaving aside the technical jargon, a simple example from section 8.3.5 of the C++11 standard usefully introduces this month's topic. Let's consider a template function like: template <class T, class U> ??? foo(T t, U u) { return t + u; } The question is: what should replace the question marks? The problem is that we are dealing with a template, thus we don't know at the outset the types of T and U. Even if they were restricted to be arithmetic builtin types, non-trivial rules in C++ relate the type of the sum to the types of T and U. In the past - in the GNU C++ runtime library too - programmers used to address these situations by way of rather ugly tricks involving __typeof__ which now, with decltype, could be rewritten as: template <class T, class U> decltype((*(T*)0) + (*(U*)0)) foo(T t, U u) { return t + u; } Of course the latter is guaranteed to work only for builtin arithmetic types, eg, '0' must make sense. In short: it's a hack. On the other hand, in C++11 you can use auto: template <class T, class U> auto foo(T t, U u) -> decltype(t + u) { return t + u; } This is much better. It's generic and a construct fully supported by the language. Finally, let's see a real-life example directly taken from the C++11 runtime library as implemented in GCC: template<typename _IteratorL, typename _IteratorR> inline auto operator-(const reverse_iterator<_IteratorL>& __x, const reverse_iterator<_IteratorR>& __y) -> decltype(__y.base() - __x.base()) { return __y.base() - __x.base(); } By now it should appear be completely straightforward. The availability of trailing return types in C++11 allowed fixing a real bug in the C++98 implementation of this operator (and many similar ones). In GCC, C++98 mode, this operator is: template<typename _IteratorL, typename _IteratorR> inline typename reverse_iterator<_IteratorL>::difference_type operator-(const reverse_iterator<_IteratorL>& __x, const reverse_iterator<_IteratorR>& __y) { return __y.base() - __x.base(); } This was guaranteed to work well with heterogeneous reverse_iterator types only if difference_type was the same for both types.

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• What layer to introduce human readable error messages?

  - by MrLane

  One of the things that I have never been happy with on any project I have worked on over the years and have really not been able to resolve myself is exactly at what tier in an application should human readable error information be retrieved for display to a user. A common approach that has worked well has been to return strongly typed/concrete "result objects" from the methods on the public surface of the business tier/API. A method on the interface may be: public ClearUserAccountsResult ClearUserAccounts(ClearUserAccountsParam param); And the result class implementation: public class ClearUserAccountsResult : IResult { public readonly List<Account> ClearedAccounts{get; set;} public readonly bool Success {get; set;} // Implements IResult public readonly string Message{get; set;} // Implements IResult, human readable // Constructor implemented here to set readonly properties... } This works great when the API needs to be exposed over WCF as the result object can be serialized. Again this is only done on the public surface of the API/business tier. The error message can also be looked up from the database, which means it can be changed and localized. However, it has always been suspect to me, this idea of returning human readable information from the business tier like this, partly because what constitutes the public surface of the API may change over time...and it may be the case that the API will need to be reused by other API components in the future that do not need the human readable string messages (and looking them up from a database would be an expensive waste). I am thinking a better approach is to keep the business objects free from such result objects and keep them simple and then retrieve human readable error strings somewhere closer to the UI layer or only in the UI itself, but I have two problems here: 1) The UI may be a remote client (Winforms/WPF/Silverlight) or an ASP.NET web application hosted on another server. In these cases the UI will have to fetch the error strings from the server. 2) Often there are multiple legitimate modes of failure. If the business tier becomes so vague and generic in the way it returns errors there may not be enough information exposed publicly to tell what the error actually was: i.e: if a method has 3 modes of legitimate failure but returns a boolean to indicate failure, you cannot work out what the appropriate message to display to the user should be. I have thought about using failure enums as a substitute, they can indicate a specific error that can be tested for and coded against. This is sometimes useful within the business tier itself as a way of passing via method returns the specifics of a failure rather than just a boolean, but it is not so good for serialization scenarios. Is there a well worn pattern for this? What do people think? Thanks.

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• Push-Based Events in a Services Oriented Architecture

  - by Colin Morelli

  I have come to a point, in building a services oriented architecture (on top of Thrift), that I need to expose events and allow listeners. My initial thought was, "create an EventService" to handle publishing and subscribing to events. That EventService can use whatever implementation it desires to actually distribute the events. My client automatically round-robins service requests to available service hosts which are determined using Zookeeper-based service discovery. So, I'd probably use JMS inside of EventService mainly for the purpose of persisting messages (in the event that a service host for EventService goes down before it can distribute the message to all of the available listeners). When I started considering this, I began looking into the differences between Queues and Topics. Topics unfortunately won't work for me, because (at least for now), all listeners must receive the message (even if they were down at the time the event was pushed, or hadn't made a subscription yet because they haven't completed startup (during deployment, for example) - messages should be queued until the service is available). However, I don't want EventService to be responsible for handling all of the events. I don't think it should have the code to react to events inside of it. Each of the services should do what it needs with a given event. This would indicate that each service would need a JMS connection, which questions the value of having EventService at all (as the services could individually publish and subscribe to JMS directly). However, it also couples all of the services to JMS (when I'd rather that there be a single service that's responsible for determining how to distribute events). What I had thought was to publish an event to EventService, which pulls a configuration of listeners from some configuration source (database, flat file, irrelevant for now). It replicates the message and pushes each one back into a queue with information specific to that listener (so, if there are 3 listeners, 1 event would become 3 events in JMS). Then, another thread in EventService (which is replicated, running on multiple hots) would be pulling from the queue, attempting to make the service call to the "listener", and returning the message to the queue (if the service is down), or discarding the message (if the listener completed successfully). tl;dr If I have an EventService that is responsible for receiving events and delegating service calls to "event listeners," (which are really just endpoints on other services), how should it know how to craft the service call? Should I create a generic "Event" object that is shared among all services? Then, the EventService can just construct this object and pass it to the service call. Or is there a better answer to this problem entirely?

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• Why do camera's aspect ratio look good on computer but not on Android devices?

  - by Pooya Fayyaz

  I'm developing a game for Android devices and I have a script that solves the aspect-ratio problem for computer screens but not for my intended target platform. It looks perfect on computer, even when re-sizing the game screen, but not when running my game in landscape mode on mobile phones. This is my script using UnityEngine; using System.Collections; using System.Collections.Generic; public class reso : MonoBehaviour { void Update() { // set the desired aspect ratio (the values in this example are // hard-coded for 16:9, but you could make them into public // variables instead so you can set them at design time) float targetaspect = 16.0f / 9.0f; // determine the game window's current aspect ratio float windowaspect = (float)Screen.width / (float)Screen.height; // current viewport height should be scaled by this amount float scaleheight = windowaspect / targetaspect; // obtain camera component so we can modify its viewport Camera camera = GetComponent<Camera>(); // if scaled height is less than current height, add letterbox if (scaleheight < 1.0f && Screen.width <= 490 ) { Rect rect = camera.rect; rect.width = 1.0f; rect.height = scaleheight; rect.x = 0; rect.y = (1.0f - scaleheight) / 2.0f; camera.rect = rect; } else // add pillarbox { float scalewidth = 1.0f / scaleheight; Rect rect = camera.rect; rect.width = scalewidth; rect.height = 1.0f; rect.x = (1.0f - scalewidth) / 2.0f; rect.y = 0; camera.rect = rect; } } } I figured that my problem occurs in this part of the script: if (scaleheight < 1.0f) { Rect rect = camera.rect; rect.width = 1.0f; rect.height = scaleheight; rect.x = 0; rect.y = (1.0f - scaleheight) / 2.0f; camera.rect = rect; } Its look like this on my mobile phone (portrait): and on landscape mode:

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• Design pattern to handle queries using multiple models

  - by coderkane

  I am presented with a dilemma while trying to re-designing the class structure for my PHP/MySQL application to make it more elegant and conform it to the SOLID principle. The problem goes like this: Let as assume, there is an abstract class called person which has certain properties to define a generic person, such as name, age, date of birth etc. There are two classes, student, and teacher, that implements this abstract class. They add their own unique properties to it. I have designed all the three classes to include all the operational logic (details of which are not relevant in context of the question). Now, I need to create views/reports/data grids which contain details from multiple classes, for example, say, a list of all students doing projects in Chemistry mentored by a teacher whose name is the parameter to the query. This is just one example of a view, there are many different views in the application, which uses data from 3-4 tables, and each of them have multiple input parameters to generate them. Considering this particular example, I have written the relevant query using JOIN and the results are as expected and proper, now here is the dilemma: Keeping in mind the single responsibility principle, where should I keep this query? It does not belong to either Student class, or Teacher class or any other classes currently present. a) Should I create a new class, say dataView class, and design it as a MVC pattern and keep the query there? What about the other views? how do they fit in this architecture? b) Should I not keep the query in code at all, and make it DB View ? c) Am I completely wrong in the approach? If so what is the right approach? My considerations are as follows: a) should be easy to add new views later on if requirement comes, without having to copy-paste-modify code b) would like to make it as loosely coupled as possible so that if minor db structure changes happen, it does not break I did google searches on report design and OOP report generators, but all the result seem to focus on the visual design of the report rather than fetching the data. I have already taken care of the visual aspect of the report using MVC with html templates. I am sure this is a very fundamental problem with known solution, but I am somehow not able to find it (maybe searching with wrong keyword). Edit1: Modified the title to make it more relevant Edit2: The accepted answer got me thinking in the right direction and identify my design flaws, which eventually led me to find this question and the solution in Stack Overflow which gave me the detailed answer to clear the confusion.

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• Java: How to manage UDP client-server state

  - by user92947

  I am trying to write a Java application that works similar to MapReduce. There is a server and several workers. Workers may come and go as they please and the membership to the group has a soft-state. To become a part of the group, the worker must send a UDP datagram to the server, but to continue to be part of the group, the worker must send the UDP datagram to the server every 5 minutes. In order to accommodate temporary errors, a worker is allowed to miss as many as two consecutive periodic UDP datagrams. So, the server must keep track of the current set of workers as well as the last time each worker had sent a UDP datagram. I've implemented a class called WorkerListener that implements Runnable and listens to UDP datagrams on a particular UDP port. Now, to keep track of active workers, this class may maintain a HashSet (or HashMap). When a datagram is received, the server may query the HashSet to check if it is a new member. If so, it can add the new worker to the group by adding an entry into the HashSet. If not, it must reset a "timer" for the worker, noting that it has just heard from the corresponding worker. I'm using the word timer in a generic sense. It doesn't have to be a clock of sorts. Perhaps this could also be implemented using int or long variables. Also, the server must run a thread that continuously monitors the timers for the workers to see that a client that times out on two consecutive datagram intervals, it is removed from the HashSet. I don't want to do this in the WorkerListener thread because it would be blocking on the UDP datagram receive() function. If I create a separate thread to monitor the worker HashSet, it would need to be a different class, perhaps WorkerRegistrar. I must share the HashSet with that thread. Mutual exclusion must also be implemented, then. My question is, what is the best way to do this? Pointers to some sample implementation would be great. I want to use the barebones JDK implementation, and not some fancy state maintenance API that takes care of everything, because I want this to be a useful demonstration for a class that I am teaching. Thanks

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• Gettings Terms asscoiated to a Specific list item

  - by Gino Abraham

  I had a fancy requirement where i had to get all tags associated to a document set in a document library. The normal tag could webpart was not working when i add it to the document set home page, so planned a custom webpart. Was checking in net to find a straight forward way to achieve this, but was not lucky enough to get something. Since i didnt get any samples in net, i looked into Microsoft.Sharerpoint.Portal.Webcontrols and found a solution.The socialdataframemanager control in 14Hive/Template/layouts/SocialDataFrame.aspx directed me to the solution. You can get the dll from ISAPI folder. Following Code snippet can get all Terms associated to the List Item given that you have list name and id for the list item. using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.SharePoint; using Microsoft.Office.Server.SocialData; namespace TagChecker { class Program { static void Main(string[] args) { // Your site url string siteUrl = http://contoso; // List Name string listName = "DocumentLibrary1"; // List Item Id for which you want to get all terms int listItemId = 35; using (SPSite site = new SPSite(siteUrl)) { using(SPWeb web = site.OpenWeb()) { SPListItem listItem = web.Lists[listName].GetItemById(listItemId); string url = string.Empty; // Based on the list type the url would be formed. Code Sniffed from Micosoft dlls :) if (listItem.ParentList.BaseType == SPBaseType.DocumentLibrary) { url = listItem.Web.Url.TrimEnd(new char[] { '/' }) + "/" + listItem.Url.TrimStart(new char[] { '/' }); } else if (SPFileSystemObjectType.Folder == listItem.FileSystemObjectType) { url = listItem.Web.Url.TrimEnd(new char[] { '/' }) + "/" + listItem.Folder.Url.TrimStart(new char[] { '/' }); } else { url = listItem.Web.Url.TrimEnd(new char[] { '/' }) + "/" + listItem.ParentList.Forms[PAGETYPE.PAGE_DISPLAYFORM].Url.TrimStart(new char[] { '/' }) + "?ID=" + listItem.ID.ToString(); } SPServiceContext serviceContext = SPServiceContext.GetContext(site); Uri uri = new Uri(url); SocialTagManager mgr = new SocialTagManager(serviceContext); SocialTerm[] terms = mgr.GetTerms(uri); foreach (SocialTerm term in terms) { Console.WriteLine(term.Term.Labels[0].Value ); } } } Console.Read(); } } } Reference dlls added are Microsoft.Sharepoint , Microsoft.Sharepoint.Taxonomy, Microsoft.office.server, Microsoft.Office.Server.UserProfiles from ISAPI folder. This logic can be used to make a custom tag cloud webpart by taking code from OOB tag cloud, so taht you can have you webpart anywhere in the site and still get Tags added to a specifc libdary/List. Hope this helps some one.

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• .Net Application & Database Modularity/Reuse

  - by Martaver

  I'm looking for some guidance on how to architect an app with regards to modularity, separation of concerns and re-usability. I'm working on an application (ASP.Net, C#) that has distinctly generic chunks of functionality, that I'd love to be able to lift out, all layers, into re-usable components. This means the module handles the database schema, data access, API, everything so that the next time I want to use it I can just register the module and hook into it. Developing modules of re-usable functionality is a no-brainer, but what is really confusing me is what to do when it comes to handling a core re-usable database schema that serves the module's functionality. In an ideal world, I would register a module and it would ensure that the associated database schema exists in the DB. I would code on the assumption that the tables exist, calling the module's functionality through the DLL, agnostic of the database layer. Kind of like Enterprise Library's Caching/Logging Application Block, which can create a DB schema in the target DB to use as a data store. My Questions is: What do you think is the best way to achieve this, firstly, in terms design architecture, and secondly solution structure. What patterns/frameworks do you know that exist & support this kind of thing? My thoughts so far: I mostly use Entity Framework and SQL Server DB Projects. I thought about a 'black box' approach to modules of functionality. I could use use a code-first approach in EF4, and use the ObjectContext to create a database when the module is initialized. However this means that all of the entities that my module encapsulates would be disconnected from the rest of the application because they belonged to an abstracted ObjectContext. Further - Creating appropriate indexes and references between domain entities and the module's entities would be impossible to do practically. I've thought of adopting Enterprise Library and creating my own Application Blocks. I'm not sure how this would play nice with Entity Framework (if at all) though. I like the idea of building on proven patterns & practices to encapsulate established, reusable functionality. I thought of abandoning Entity Framework for the Module, and just creating a separate DB schema for the module with its own set of stored procedures & ADO.Net. Then deploying the script at run-time if interrogation shows that it doesn't exist. But once again, for application developing outside of the application, I would want to use Entity Framework and I would have to use the module separately, disconnected from the domain ObjectContext. Has anyone had experience developing these sorts of full-stack modules? What advice can you offer? Am I biting off more than I can chew?

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• How to handle encryption key conflicts when synchronizing data?

  - by Rafael

  Assume that there is data that gets synchronized between several devices. The data is protected with a symmetric encryption algorithm and a key. The key is stored on each device and encrypted with a password. When a user changes the password only the key gets re-encrypted. Under normal circumstances, when there is a good network connection to other peers, the current key gets synchronized and all data on the new device gets encrypted with the same key. But how to handle situations where a new device doesn’t have a network connection and e.g. creates its own new, but incompatible key? How to keep the usability as high as possible under such circumstances? The application could detect that there is no network and hence refuse to start. That’s very bad usability in my opinion, because the application isn’t functional at all in this case. I don’t consider this a solution. The application could ignore the missing network connection and create a new key. But what to do when the application gains a network connection? There will be several incompatible keys and some parts of the underlying data could only be encrypted with one key and other parts with another key. The situation would get worse if there would be more keys than just two and the application would’ve to ask every time for a password when another object that should get decrypted with another key would be needed. It is very messy and time consuming to try to re-encrypt all data that is encrypted with another key with a main key. What should be the main key at all in this case? The oldest key? The key with the most encrypted objects? What if the key got synchronized but not all objects that got encrypted with this particular key? How should the user know for which particular password the application asks and why it takes probably very long to re-encrypt the data? It’s very hard to describe encryption “issues” to users. So far I didn’t find an acceptable solution, nor some kind of generic strategy. Do you have some hints about a concrete strategy or some books / papers that describe synchronization of symmetrically encrypted data with keys that could cause conflicts?

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• Changing Silverlight application themes at runtime

  We have received a lot of questions how can the application theme be changed at run time. The most important thing here to mark is that each time the application theme is changed all the controls should be re-drawn. Without going into too much detail, we could explain the application themes as a mechanism to replace the content of the Generic.xaml file in every loaded Telerik assembly at runtime. This does not affect the controls that already have default style applied, hence the need to create new instances. Because in the Silverlight applications the RootVisual cannot be changed at run time, we need a way to reset the application UI. The following code is in App.xaml.cs. private void Application_Startup(object sender, StartupEventArgs e)     {           // Before:           // this.RootVisual = new MainPage();            this.RootVisual = new Grid();         this.ResetRootVisual();     }        public void ResetRootVisual()     {         var rootVisual = Application.Current.RootVisual as Grid;         rootVisual.Children.Clear();         rootVisual.Children.Add(new MainPage());     }   In Application_Startup() instead of creating new MainPage UserControl instance as RootVisual, we create a new Grid panel, that will contain the MainPage UserControl. In the ResetRootVisual() method we create the instance of MainPage and add it to the RootVisual panel. Then we have to create a method in the code behind which will set StyleManager.ApplicationTheme and then will call the ResetRootVisual() method: private void ChangeApplicationTheme(Theme theme) {     StyleManager.ApplicationTheme = theme;     (Application.Current as App).ResetRootVisual(); }   Here you can find an example which illustrates the described implementation of a Silverlight theme. For more information please refer to Teleriks online demos for Silverlight, the demos for WPF and help documentation for WPF and help documentation for Silverlight. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Parallel Port Problem in 12.04

  - by Frank Oberle

  I have a “dumb” printer attached to a parallel port in my machine which works fine under the “other” resident operating system (from Redmond) on the same machine. I recently added Ubuntu 12.04 as a dual boot on the machine, but Ubuntu doesn't seem to recognize the parallel port at all. All I need to set up a printer is a really plain-vanilla fixed pitch text-only generic driver, which is present, but no parallel ports show up. (The other printers, all on USB ports, seem to work just fine). Following what appeared to me to be the most reasonable of the many conflicting pieces of advice on the web, here's what I did: I added the following lines to /etc/modules parport_pc ppdev parport Then, after rebooting, I checked to see that the lines were still present, and they were. I ran dmesg | grep par and got the following references in the output that seemed like they might have to do with the parallel port: [ 14.169511] parport_pc 0000:03:07.0: PCI INT A -> GSI 21 (level, low) -> IRQ 21 [ 14.169516] PCI parallel port detected: 9710:9805, I/O at 0xce00(0xcd00), IRQ 21 [ 14.169577] parport0: PC-style at 0xce00 (0xcd00), irq 21, using FIFO [PCSPP,TRISTATE,COMPAT,ECP] [ 14.354254] lp0: using parport0 (interrupt-driven). [ 14.571358] ppdev: user-space parallel port driver [ 16.588304] type=1400 audit(1347226670.386:5): apparmor="STATUS" operation="profile_load" name="/usr/lib/cups/backend/cups-pdf" pid=964 comm="apparmor_parser" [ 16.588756] type=1400 audit(1347226670.386:6): apparmor="STATUS" operation="profile_load" name="/usr/sbin/cupsd" pid=964 comm="apparmor_parser" [ 16.673679] type=1400 audit(1347226670.470:7): apparmor="STATUS" operation="profile_load" name="/usr/lib/lightdm/lightdm/lightdm-guest-session-wrapper" pid=1010 comm="apparmor_parser" [ 16.675252] type=1400 audit(1347226670.470:8): apparmor="STATUS" operation="profile_load" name="/usr/lib/telepathy/mission-control-5" pid=1014 comm="apparmor_parser" [ 16.675716] type=1400 audit(1347226670.470:9): apparmor="STATUS" operation="profile_load" name="/usr/lib/telepathy/telepathy-*" pid=1014 comm="apparmor_parser" [ 16.676636] type=1400 audit(1347226670.474:10): apparmor="STATUS" operation="profile_replace" name="/usr/lib/cups/backend/cups-pdf" pid=1015 comm="apparmor_parser" [ 16.677124] type=1400 audit(1347226670.474:11): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/cupsd" pid=1015 comm="apparmor_parser" [ 1545.725328] parport0: ppdev0 forgot to release port I have no idea what any of that means, but the line “parport0: ppdev0 forgot to release port ” seems unusual. I was still unable to add a printer for my old clunker, so I tried the direct approach, typing echo “Hello” > /dev/lp0 and received a Permission denied message. I then tried echo “Hello” > /dev/parport0 which didn't give me any message at all, but still didn't print anything. Running the command sudo /usr/lib/cups/backend/parallel gives the following: direct parallel:/dev/lp0 "unknown" "LPT #1" "" "" Checking the permissions for /dev/parport0, Owner, Group, and Other are all set to read and write. crw-rw---- 1 root lp 6, 0 Sep 9 16:37 /dev/lp0 crw-rw-rw- 1 root lp 99, 0 Sep 9 16:37 /dev/parport0 The output of the command lpinfo -v includes the following line: direct parallel:/dev/lp0 I've read several web postings that seem to suggest this has been a problem for several years, but the bug reports were closed because there wasn't enough information to address the issue (shades of Microsoft!). Any suggestions as to what I might be missing here?

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• Compiling for T4

  - by Darryl Gove

  I've recently had quite a few queries about compiling for T4 based systems. So it's probably a good time to review what I consider to be the best practices. Always use the latest compiler. Being in the compiler team, this is bound to be something I'd recommend But the serious points are that (a) Every release the tools get better and better, so you are going to be much more effective using the latest release (b) Every release we improve the generated code, so you will see things get better (c) Old releases cannot know about new hardware. Always use optimisation. You should use at least -O to get some amount of optimisation. -xO4 is typically even better as this will add within-file inlining. Always generate debug information, using -g. This allows the tools to attribute information to lines of source. This is particularly important when profiling an application. The default target of -xtarget=generic is often sufficient. This setting is designed to produce a binary that runs well across all supported platforms. If the binary is going to be deployed on only a subset of architectures, then it is possible to produce a binary that only uses the instructions supported on these architectures, which may lead to some performance gains. I've previously discussed which chips support which architectures, and I'd recommend that you take a look at the chart that goes with the discussion. Crossfile optimisation (-xipo) can be very useful - particularly when the hot source code is distributed across multiple source files. If you're allowed to have something as geeky as favourite compiler optimisations, then this is mine! Profile feedback (-xprofile=[collect: | use:]) will help the compiler make the best code layout decisions, and is particularly effective with crossfile optimisations. But what makes this optimisation really useful is that codes that are dominated by branch instructions don't typically improve much with "traditional" compiler optimisation, but often do respond well to being built with profile feedback. The macro flag -fast aims to provide a one-stop "give me a fast application" flag. This usually gives a best performing binary, but with a few caveats. It assumes the build platform is also the deployment platform, it enables floating point optimisations, and it makes some relatively weak assumptions about pointer aliasing. It's worth investigating. SPARC64 processor, T3, and T4 implement floating point multiply accumulate instructions. These can substantially improve floating point performance. To generate them the compiler needs the flag -fma=fused and also needs an architecture that supports the instruction (at least -xarch=sparcfmaf). The most critical advise is that anyone doing performance work should profile their application. I cannot overstate how important it is to look at where the time is going in order to determine what can be done to improve it. I also presented at Oracle OpenWorld on this topic, so it might be helpful to review those slides.

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• the unity aspect ratio script looks good in computer but not in android phones

  - by Pooya Fayyaz

  I'm developing a game for android devices.and i have a script that solve the ratio problem but i have a problem in this code.and i dont know why.it looks perfect in computer even resize the game screen but in mobile phones have a problem.my game runs in landscape mode.this is the script : using UnityEngine; using System.Collections; using System.Collections.Generic; public class reso : MonoBehaviour { void Update() { // set the desired aspect ratio (the values in this example are // hard-coded for 16:9, but you could make them into public // variables instead so you can set them at design time) float targetaspect = 16.0f / 9.0f; // determine the game window's current aspect ratio float windowaspect = (float)Screen.width / (float)Screen.height; // current viewport height should be scaled by this amount float scaleheight = windowaspect / targetaspect; // obtain camera component so we can modify its viewport Camera camera = GetComponent<Camera>(); // if scaled height is less than current height, add letterbox if (scaleheight < 1.0f && Screen.width <= 490 ) { Rect rect = camera.rect; rect.width = 1.0f; rect.height = scaleheight; rect.x = 0; rect.y = (1.0f - scaleheight) / 2.0f; camera.rect = rect; } else // add pillarbox { float scalewidth = 1.0f / scaleheight; Rect rect = camera.rect; rect.width = scalewidth; rect.height = 1.0f; rect.x = (1.0f - scalewidth) / 2.0f; rect.y = 0; camera.rect = rect; } } } i figure that my problem occur in this part of the script: if (scaleheight < 1.0f) { Rect rect = camera.rect; rect.width = 1.0f; rect.height = scaleheight; rect.x = 0; rect.y = (1.0f - scaleheight) / 2.0f; camera.rect = rect; } and its look like this in my mobile phone in portrait: and in landscape mode:

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• Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

  - by Rowan Freeman

  Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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• Nvidia GT218 repository drivers don't work

  - by user1042840

  I upgraded all packages with sudo apt-get upgrade command on my Ubuntu 10.04 box and I have Ubuntu 12.04 3.2.0-29-generic-pae now. I have two monitors and the following GPU: 01:00.0 VGA compatible controller: NVIDIA Corporation GT218 [NVS 300] (rev a2) After upgrading to 12.04, I somehow lost my previous setup with one common workspace stretched across two monitors. When Ubuntu starts only one monitor is on. I can see the message on the active monitor: Not optimum mode. Recommended mode: 1680x1050 60Hz I used Nvidia proprietary drivers on 10.04 but now jockey-text --list shows: xorg:nvidia_current - NVIDIA accelerated graphics driver (Proprietary, Disabled, Not in use) xorg:nvidia_current_updates - NVIDIA accelerated graphics driver (post-release updates) (Proprietary, Enabled, Not in use) When I run sudo nvidia-settings it says You do not appear to be using the NVIDIA X driver. Please edit your X configuration file (just run `nvidia-xconfig` as root), and restart the X server.' I typed nvidia-xconfig and rebooted, but jockey-text --list says the same after the reboot: Not in use. The same with nvidia-current - Enabled but Not in use. I also tried nvidia-173 but I ended up in tty immediately at startup so I removed it. I used to have some problems with Nvidia proprietary drivers on 10.04, I had to put paths to EDID files in /etc/X11/xorg.conf explicitly, but the resolution was as recommended and both monitors were working. If I understand correctly, nouveau drivers are used now by default because the resolution is still quite high, definitely not 800x600, xrandr showed: xrandr: Failed to get size of gamma for output default Screen 0: minimum 320 x 400, current 1600 x 1200, maximum 1600 x 1200 default connected 1600x1200+0+0 0mm x 0mm 1600x1200 66.0* 1280x1024 76.0 1024x768 76.0 800x600 73.0 640x480 73.0 640x400 0.0 320x400 0.0 1680x1050_60.00 (0x4f) 146.2MHz h: width 1680 start 1784 end 1960 total 2240 skew 0 clock 65.3KHz v: height 1050 start 1053 end 1059 total 1089 clock 60.0Hz However, colors seem a bit faded and blurry with nouveau drivers. Mouse cursor is invisible if it's placed inside Firefox window, and only one monitor is working. I like open source and if it's possible I'd prefer to use nouveau drivers but a few things should be fixed. I'm curious why nvidia-current drivers from the repository don't work now. I read it has something to do with the new X11 server in Ubuntu 12.04, is it true? How can I get it back to work?

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• Accessing SQL Server data from iOS apps

  - by RobertChipperfield

  Almost all mobile apps need access to external data to be valuable. With a huge amount of existing business data residing in Microsoft SQL Server databases, and an ever-increasing drive to make more and more available to mobile users, how do you marry the rather separate worlds of Microsoft's SQL Server and Apple's iOS devices? The classic answer: write a web service layer Look at any of the questions on this topic asked in Internet discussion forums, and you'll inevitably see the answer, "just write a web service and use that!". But what does this process gain? For a well-designed database with a solid security model, and business logic in the database, writing a custom web service on top of this just to access some of the data from a different platform seems inefficient and unnecessary. Desktop applications interact with the SQL Server directly - why should mobile apps be any different? The better answer: the iSql SDK Working along the lines of "if you do something more than once, make it shared," we set about coming up with a better solution for the general case. And so the iSql SDK was born: sitting between SQL Server and your iOS apps, it provides the simple API you're used to if you've been developing desktop apps using the Microsoft SQL Native Client. It turns out a web service remained a sensible idea: HTTP is much more suited to the Big Bad Internet than SQL Server's native TDS protocol, removing the need for complex configuration, firewall configuration, and the like. However, rather than writing a web service for every app that needs data access, we made the web service generic, serving only as a proxy between the SQL Server and a client library integrated into the iPhone or iPad app. This client library handles all the network communication, and provides a clean API. OSQL in 25 lines of code As an example of how to use the API, I put together a very simple app that allowed the user to enter one or more SQL statements, and displayed the results in a rather primitively formatted text field. The total amount of Objective-C code responsible for doing the work? About 25 lines. You can see this in action in the demo video. Beta out now - your chance to give us your suggestions! We've released the iSql SDK as a beta on the MobileFoo website: you're welcome to download a copy, have a play in your own apps, and let us know what we've missed using the Feedback button on the site. Software development should be fun and rewarding: no-one wants to spend their time writing boiler-plate code over and over again, so stop writing the same web service code, and start doing exciting things in the new world of mobile data!

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• Mutable Records in F#

  - by MarkPearl

  I’m loving my expert F# book – today I thought I would give a post on using mutable records as covered in Chapter 4 of Expert F#. So as they explain the simplest mutable data structures in F# are mutable records. The whole concept of things by default being immutable is a new one for me from my C# background. Anyhow… lets look at some C# code first. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace MutableRecords { public class DiscreteEventCounter { public int Total { get; set; } public int Positive { get; set; } public string Name { get; private set; } public DiscreteEventCounter(string name) { Name = name; } } class Program { private static void recordEvent(DiscreteEventCounter s, bool isPositive) { s.Total += 1; if (isPositive) s.Positive += 1; } private static void reportStatus (DiscreteEventCounter s) { Console.WriteLine("We have {0} {1} out of {2}", s.Positive, s.Name, s.Total); } static void Main(string[] args) { var longCounter = new DiscreteEventCounter("My Discrete Counter"); recordEvent(longCounter, true); recordEvent(longCounter, true); reportStatus(longCounter); Console.ReadLine(); } } } Quite simple, we have a class that has a few values. We instantiate an instance of the class and perform increments etc on the instance. Now lets look at an equivalent F# sample. namespace EncapsulationNS module Module1 = open System type DiscreteEventCounter = { mutable Total : int mutable Positive : int Name : string } let recordEvent (s: DiscreteEventCounter) isPositive = s.Total <- s.Total+1 if isPositive then s.Positive <- s.Positive+1 let reportStatus (s: DiscreteEventCounter) = printfn "We have %d %s out of %d" s.Positive s.Name s.Total let newCounter nm = { Total = 0; Positive = 0; Name = nm } // // Using it... // let longCounter = newCounter "My Discrete Counter" recordEvent longCounter (true) recordEvent longCounter (true) reportStatus longCounter System.Console.ReadLine() Notice in the type declaration of the DiscreteEventCounter we had to explicitly declare that the total and positive value holders were mutable. And that’s it – a very simple example of mutable types.

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• Creating a shared library that might be used with desktop applications and web projects

  - by dreza

  I have been involved in a number of MVC.NET and c# desktop projects in our company over the last year or so while also managing to kept my nose poked into other projects (in a read-only learning capacity of course). From this I've noticed that across the various projects and teams there is a-lot of functionality that has been well designed against good interfaces and abstractions. Because we tend to like our own work at times, I noticed a couple of projects had the exact same class, method copied into it as it had obviously worked on one and so was easily moved to a new project (probably by the same developer who originally wrote it) I mentioned this fact in one of our programmer meetings we have occasionally and suggested we pull some of this functionality into a core company library that we can build up over time and use across multiple projects. Everyone agreed and I started looking into this possibility. However, I've come across a stumbling block pretty early on. Our team primarily focuses on MVC at the moment and we have projects mainly in 2.0 but are starting to branch to 3.0. We also have a number of desktop applications that might benefit from some shared classes and basic helper methods. Initially when creating this DLL I included some shared classes that could be used across any project type (Web, Client etc) but then I started looking at adding some shared modules that would be useful in our MVC applications only. However this meant I had to include a reference to some Microsoft Web DLL's in order to leverage some of the classes I was creating (at this stage MVC 2.0). Now my issue is that we have a shared DLL that has references to web specific libraries that could also possibly be used in a client application. Not only that, our DLL referenced initially MVC 2.0 and we will eventually move onto MVC 3.0 for all projects. But alot of the classes in this library I expect to still be relevant to MVC 3 etc Our code within this DLL is separated into it's own namespaces such as: CompanyDLL.Primitives CompanyDLL.Web.Mvc CompanyDLL.Helpers etc etc So, my questions are: Is it OK to do a shared library like this, or if we have web specific features in it should we create a separate web DLL only targeted at a specific framework or MVC version? If it's OK, what kind of issues might we face when using the library that references MVC 2 in a MVC 3 project for example. I would be thinking that we might run into some sort of compatibility issue, or even issues where the developers using the library doesn't realize they need MVC 2.0 libraries. They might only want to use some of the generic classes etc The concept seemed like a good idea at the time, but I'm starting to think maybe it's not really a practical solution. But the number of times I've seen copied classes and methods across projects because they are proven tested code is a bit unnerving to be perfectly honest!

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• What causes Multi-Page allocations?

  - by SQLOS Team

  Writing about changes in the Denali Memory Manager In his last post Rusi mentioned: " In previous SQL versions only the 8k allocations were limited by the ‘max server memory’ configuration option.  Allocations larger than 8k weren’t constrained." In SQL Server versions before Denali single page allocations and multi-Page allocations are handled by different components, the Single Page Allocator (which is responsible for Buffer Pool allocations and governed by 'max server memory') and the Multi-Page allocator (MPA) which handles allocations of greater than an 8K page. If there are many multi-page allocations this can affect how much memory needs to be reserved outside 'max server memory' which may in turn involve setting the -g memory_to_reserve startup parameter. We'll follow up with more generic articles on the new Memory Manager structure, but in this post I want to clarify what might cause these larger allocations. So what kinds of query result in MPA activity? I was asked this question the other day after delivering an MCM webcast on Memory Manager changes in Denali. After asking around our Dev team I was connected to one of our test leads Sangeetha who had tested the plan cache, and kindly provided this example of an MPA intensive query: A workload that has stored procedures with a large # of parameters (say > 100, > 500), and then invoked via large ad hoc batches, where each SP has different parameters will result in a plan being cached for this “exec proc” batch. This plan will result in MPA.   Exec proc_name @p1, ….@p500 Exec proc_name @p1, ….@p500 . . . Exec proc_name @p1, ….@p500 Go   Another workload would be large adhoc batches of the form: Select * from t where col1 in (1, 2, 3, ….500) Select * from t where col1 in (1, 2, 3, ….500) Select * from t where col1 in (1, 2, 3, ….500) … Go  In Denali all page allocations are handled by an "Any size page allocator" and included in 'max server memory'. The buffer pool effectively becomes a client of the any size page allocator, which in turn relies on the memory manager. - Guy Originally posted at http://blogs.msdn.com/b/sqlosteam/

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