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• How to remap Fn key combinations (Lenovo G500)

  - by Anatoli

  I am running Kubuntu 13.10 on a Lenovo G500 laptop. My question is similar to this one: How can I remap my F keys on my HP laptop? That is to say, my F1-F12 keys are mapped to certain special functions, and only holding down the Fn key restores access to the standard F1-F12 keys. How do I remap certain keys? I would like to know if there is a way to remap Fx to Fn+Fx and vice-versa. As per the instructions of #87043 I checked my BIOS and there is no option to switch the Fx/Fn key functionality. Googling through Leonovo's support forums indicates a BIOS update enabling this is in the works, but there's no indication of when it will be complete. Using xev I was able to see what X sees when F1-F12 are pressed. Some send separate keycodes, but some are somehow mapped to key combinations or other unknown things: F1 - XF86AudioMute F2 - XF86AudioVolumeLower F3 - XF86AudioVolumeRaise F4 - Alt_L + F4 F5 - F5 F6 - Disables touchapd, cannot quite understand what xev tells me is happening, reenables if disabled (Kernel log reveals these have well-defined scancodes not assigned to any keycodes) F7 - XF86WLAN F8 - Alt_L + Ctrl_L + Tab F9 - Turns off LCD backlight, xev sees nothing F10 - Super_L + p F11 - XF86MonBrightnessLower F12 - XF86MonBrightnessRaise Following the instrusctions on this page: How do I remap certain keys? I remapped all the keys that have definite keycodes (F1, F2, F3, F5, F7, F11, F12) This still leaves the F4, F6, F8, F9, F10 keys not functioning properly. This is especially frustarting since F4, F6, F9 now kill the current window, the touchpad and screen, respectively. Any help on remapping these keys to their proper functions would be much appreciated! -Anatoli xev output for these 5 keys: F4 KeyPress event, serial 40, synthetic NO, window 0x4800001, root 0x9d, subw 0x0, time 3674037, (228,298), root:(911,321), state 0x0, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False FocusOut event, serial 40, synthetic NO, window 0x4800001, mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 40, synthetic NO, window 0x4800001, mode NotifyUngrab, detail NotifyAncestor KeymapNotify event, serial 40, synthetic NO, window 0x0, keys: 4294967197 0 0 0 0 0 0 0 65 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 KeyRelease event, serial 40, synthetic NO, window 0x4800001, root 0x9d, subw 0x0, time 3674040, (228,298), root:(911,321), state 0x8, keycode 70 (keysym 0xffc1, F4), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False KeyRelease event, serial 40, synthetic NO, window 0x4800001, root 0x9d, subw 0x0, time 3674042, (228,298), root:(911,321), state 0x8, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False ClientMessage event, serial 40, synthetic YES, window 0x4800001, message_type 0x12a (WM_PROTOCOLS), format 32, message 0x12b (WM_DELETE_WINDOW) F6 disabling touchpad MappingNotify event, serial 40, synthetic NO, window 0x0, request MappingKeyboard, first_keycode 8, count 248 FocusOut event, serial 40, synthetic NO, window 0x4600001, mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 40, synthetic NO, window 0x4600001, mode NotifyUngrab, detail NotifyAncestor KeymapNotify event, serial 40, synthetic NO, window 0x0, keys: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 MappingNotify event, serial 41, synthetic NO, window 0x0, request MappingKeyboard, first_keycode 8, count 248 F6 enabling touchpad MappingNotify event, serial 42, synthetic NO, window 0x0, request MappingKeyboard, first_keycode 8, count 248 FocusOut event, serial 42, synthetic NO, window 0x4600001, mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 42, synthetic NO, window 0x4600001, mode NotifyUngrab, detail NotifyAncestor KeymapNotify event, serial 42, synthetic NO, window 0x0, keys: 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 MappingNotify event, serial 43, synthetic NO, window 0x0, request MappingPointer, first_keycode 0, count 0 F8 doing whatever it is F8 does KeyPress event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3508985, (13,-12), root:(696,11), state 0x0, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False KeyPress event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3508986, (13,-12), root:(696,11), state 0x8, keycode 37 (keysym 0xffe3, Control_L), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False KeyPress event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3508988, (13,-12), root:(696,11), state 0xc, keycode 23 (keysym 0xff09, Tab), same_screen YES, XLookupString gives 1 bytes: (09) " " XmbLookupString gives 1 bytes: (09) " " XFilterEvent returns: False KeyRelease event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3508989, (13,-12), root:(696,11), state 0xc, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False KeyRelease event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3508991, (13,-12), root:(696,11), state 0x4, keycode 37 (keysym 0xffe3, Control_L), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False KeyRelease event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3508994, (13,-12), root:(696,11), state 0x0, keycode 23 (keysym 0xff09, Tab), same_screen YES, XLookupString gives 1 bytes: (09) " " XFilterEvent returns: False F9 gives no output to xev F10 doing whatever it is F10 does KeyRelease event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3586076, (9,-14), root:(692,9), state 0x0, keycode 10 (keysym 0x31, 1), same_screen YES, XLookupString gives 1 bytes: (31) "1" XFilterEvent returns: False KeyPress event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3586552, (9,-14), root:(692,9), state 0x0, keycode 133 (keysym 0xffeb, Super_L), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False KeyPress event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3586554, (9,-14), root:(692,9), state 0x40, keycode 33 (keysym 0x70, p), same_screen YES, XLookupString gives 1 bytes: (70) "p" XmbLookupString gives 1 bytes: (70) "p" XFilterEvent returns: False KeyRelease event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3586557, (9,-14), root:(692,9), state 0x40, keycode 33 (keysym 0x70, p), same_screen YES, XLookupString gives 1 bytes: (70) "p" XFilterEvent returns: False KeyRelease event, serial 40, synthetic NO, window 0x4600001, root 0x9d, subw 0x0, time 3586560, (9,-14), root:(692,9), state 0x40, keycode 133 (keysym 0xffeb, Super_L), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False

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• 2D Platformer Collision Handling

  - by defender-zone

  Hello, everyone! I am trying to create a 2D platformer (Mario-type) game and I am some having some issues with handling collisions properly. I am writing this game in C++, using SDL for input, image loading, font loading, etcetera. I am also using OpenGL via the FreeGLUT library in conjunction with SDL to display graphics. My method of collision detection is AABB (Axis-Aligned Bounding Box), which is really all I need to start with. What I need is an easy way to both detect which side the collision occurred on and handle the collisions properly. So, basically, if the player collides with the top of the platform, reposition him to the top; if there is a collision to the sides, reposition the player back to the side of the object; if there is a collision to the bottom, reposition the player under the platform. I have tried many different ways of doing this, such as trying to find the penetration depth and repositioning the player backwards by the penetration depth. Sadly, nothing I've tried seems to work correctly. Player movement ends up being very glitchy and repositions the player when I don't want it to. Part of the reason is probably because I feel like this is something so simple but I'm over-thinking it. If anyone thinks they can help, please take a look at the code below and help me try to improve on this if you can. I would like to refrain from using a library to handle this (as I want to learn on my own) or the something like the SAT (Separating Axis Theorem) if at all possible. Thank you in advance for your help! void world1Level1CollisionDetection() { for(int i; i < blocks; i++) { if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==true) { int up = 0; int left = 0; int right = 0; int down = 0; if(ball.coords[0] < block[i].coords[0] && block[i].coords[0] < ball.coords[2] && ball.coords[2] < block[i].coords[2]) { left = 1; } if(block[i].coords[0] < ball.coords[0] && ball.coords[0] < block[i].coords[2] && block[i].coords[2] < ball.coords[2]) { right = 1; } if(ball.coords[1] < block[i].coords[1] && block[i].coords[1] < ball.coords[3] && ball.coords[3] < block[i].coords[3]) { up = 1; } if(block[i].coords[1] < ball.coords[1] && ball.coords[1] < block[i].coords[3] && block[i].coords[3] < ball.coords[3]) { down = 1; } cout << left << ", " << right << ", " << up << ", " << down << ", " << endl; if (left == 1) { ball.coords[0] = block[i].coords[0] - 16.0f; ball.coords[2] = block[i].coords[0] - 0.0f; } if (right == 1) { ball.coords[0] = block[i].coords[2] + 0.0f; ball.coords[2] = block[i].coords[2] + 16.0f; } if (down == 1) { ball.coords[1] = block[i].coords[3] + 0.0f; ball.coords[3] = block[i].coords[3] + 16.0f; } if (up == 1) { ball.yspeed = 0.0f; ball.gravity = 0.0f; ball.coords[1] = block[i].coords[1] - 16.0f; ball.coords[3] = block[i].coords[1] - 0.0f; } } if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==false) { ball.gravity = -0.5f; } } } To explain what some of this code means: The blocks variable is basically an integer that is storing the amount of blocks, or platforms. I am checking all of the blocks using a for loop, and the number that the loop is currently on is represented by integer i. The coordinate system might seem a little weird, so that's worth explaining. coords[0] represents the x position (left) of the object (where it starts on the x axis). coords[1] represents the y position (top) of the object (where it starts on the y axis). coords[2] represents the width of the object plus coords[0] (right). coords[3] represents the height of the object plus coords[1] (bottom). de2dCheckCollision performs an AABB collision detection. Up is negative y and down is positive y, as it is in most games. Hopefully I have provided enough information for someone to help me successfully. If there is something I left out that might be crucial, let me know and I'll provide the necessary information. Finally, for anyone who can help, providing code would be very helpful and much appreciated. Thank you again for your help!

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• What is the Policy for Updating grub-pc in LTS?

  - by nutznboltz

  After having attempted an SRU request for a small patch to grub-pc for 10.04 LTS that fixes an issue that has left many people with unbootable servers nothing has been done for some time. The patch went through d-i into Maverick and only modifies a small amount of a single *.c file over a year ago. I updated the ticket with a debdiff of the patch and rebuilt the current grub-pc package plus the patch in a PPA and changed the ticket description to be the SRU request format subscribed the "sru" and "sponsors" teams but then nothing happened. Is there some policy against updating grub-pc in LTS that I don't know about? Thanks.

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• handling a GET error properly

  - by Andrew Heath

  I have a website that takes two primary get strings: ?type=GAME&id=SomeGameID ?type=SCENARIO&id=SomeScenarioID for reasons unknown, I have recently begun receiving requests for erroneous get strings from both Yandex and Baidu. They are always in the form of: ?type=GAME&id=SomeScenarioID None of my users are triggering these errors, so I am (sort of) confident that this is not due to an HTML template error somewhere on my part. There is also no HTTP_REFER showing up in the $_SERVER array, so I'm guessing these are direct requests from bad dbase data on their part. I see two options for dealing with these bad requests, and would like to know which is recommended... or if there are other, better options I have not thought of: simply 404 the request, since it is incorrect redirect the request to ?type=SCENARIO&id=SomeScenarioID because the scenario IDs are always valid, the breakage is due to asking for the wrong type.

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• How can I revive a dead translation team?

  - by Rohan

  I wish to translate ubuntu in Marathi language for which a translation team already exists. But the membership of the team is moderated and unfortunately no new member has been admitted in the team after 2010-Dec-12. All request of membership are pending after that date. I tried to contact administrator of the team at his personal email id but did not get any reply from him. As I am not a team member I can not upload my translated po file. Is there any way to take charge of the team and approve all pending request? It seems that no translation work is currently being carried out. I would like to do the work but I can not.

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• Cool Tools You Can Use: Validation Templates for PeopleSoft Contracts Processes

  - by Mark Rosenberg

  This is the first in a series of postings we’ll be making under the heading of Cool Tools You Can Use. Our PeopleSoft product management team identified the need for this series after reflecting on the many conversations we have each year with our PeopleSoft community members. During these conversations, we were discovering that customers and implementation partners were often not aware that solutions exist to the problems they were trying to address and that the solutions were readily available at no additional charge. Thus, the Cool Tools You Can Use series will describe the business challenge we’ve heard, the PeopleSoft solution to the challenge, and how you can learn more about the solution so that everyone can be sure to make full use of what PeopleSoft applications have to offer. The first cool tool we’ll look at is the Validation Template for PeopleSoft Contracts Process Requests, which was first released in December 2013 as part of PeopleSoft Contracts 9.2 Update Image 4. The business issue our customers highlighted to us is the need to tightly control but easily configure and manage the scope of data that any user can process when initiating a process. Control of each user’s span of impact is essential to reducing billing reconciliation issues, passing span of authority audits, and reducing (or even eliminating) the frequency of unexpected process results.  Setting Up the Validation Template for a PeopleSoft Contracts Process With the validation template, organizations can easily and quickly ensure the software restricts the scope of transactions a user can affect and gives organizations the confidence to know that business processes are being governed effectively. Additionally, this control of PeopleSoft Contracts process requests can be applied and easily maintained and adjusted from a web browser thereby enabling analysts to administer the rules without having to engage software developers to customize the software. During the field validation template setup, an analyst specifies the combinations of fields that must contain values when a user tries to setup a run control and initiate a PeopleSoft Contracts process from a process request page. For example, for the Process Limits component, an organization could require that users enter a valid combination of values for the business unit, contract, and contract type fields or a value in the contract administrator field. Until the user enters a valid combination of entries on the process request page, he cannot launch the process. With the validation template activated for process request pages, organizations can be confident that PeopleSoft Contracts users will not accidentally begin generating invoices or triggering other revenue management processes for transactions beyond their scope of authority. To learn more about the Validation Template, please review the Defining Validation Templates section of the PeopleSoft Contracts PeopleBooks. 

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• Attachment handling for web application with Jackrabbit

  - by Andrea Girardi

  I need to manage attachments on my Spring web application and I thought to use an open source repository. My app it's a job approval system using J2EE / SPRING 3 Framework and Postgress DB to allow user to tracks the job,right through every step of the approval process. It is a fully managed, collaborative system that operates from a central server and is accessed by a standard internet browser. An user should be able to add an attach to a request or an approval step, so, I though to use Jackrabbit with Postgres database persistence manager. I took a look to this post: http://onjava.com/pub/a/onjava/2006/10/04/what-is-java-content-repository.html?page=1 It's really interesting but, I've some question about this kind of solution :- I seen that Jackrabbit standalone as a Derby database embedded solution for persistence, is it enough for a professional use of the repository with more than 50 request / days (with attachment) ? Is there a reason for which I should use another database manager for persistence instead of the default one ?

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• Why does Google report a soft 404 when I redirect to the signup page?

  - by Hettomei

  In the last month, I've got an increased number of "soft 404" errors reported by Google webmaster tools which actually work well for users. Configuration (maybe useless): I have a website built with rails 3.1 Authentication is handled by the gem Devise Problem: On this page http://en.bemyboat.com/yacht-charter/9965-sailboat-beneteau-oceanis-43 Click on "Ask a Boat request" (a simple form, in GET to: http://en.bemyboat.com/boat_requests/new/9965) You are redirected with the HTTP status 302 to sign in You are then sent back to the new page if successfully sign in. Google tells me that the link on "ask a boat request" returns a soft 404. I can't make this form in "POST" (which will solve the problem) because we need to automatically redirect users back to the page after sign in. (the Gem Devise memorizes the "get" link.) To simplify, the question is: How to protect a private page with authentication, reached with a simple "GET" and not to be penalized by Google as a "soft 404".

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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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• Oracle GoldenGate 11g Certified Implementation Beta Exam Available

  - by Irem Radzik

  We have great news for Oracle Data Integration partners:  Oracle GoldenGate 11g Certified Implementation Beta Exam is now available.  The Oracle GoldenGate 11g Certified Implementation Exam Essentials (1Z1-481) exam is designed for individuals who possess a strong foundation and expertise in selling and implementing Oracle Data Integration 11g solutions. This certification covers topics such as: Oracle GoldenGate 11g Overview Architecture Overview,  Configuring Oracle GoldenGate Parameters, Mapping and Transformation Overview,  Configuration Options,  Managing and Monitoring Oracle GoldenGate 11g.  This certification helps OPN members differentiate themselves in the marketplace through proven in-depth expertise and helps their partner company qualify for the Oracle Data Integration 11g Specialization Criteria. We recommend up-to-date training and field experience. OPN members earning this certification will be recognized as OPN Certified Specialists. Request a discounted beta voucher today using the OPN Beta Certified Specialist Exam  Voucher Request Form.  You can take the exam now at a near-by Pearson VUE testing center.

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• .NET Code Evolution

  - by Alois Kraus

  Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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• Software developer needs Validation for VA Chap 31 to purchase Macbook Pro vs. PC [closed]

  - by David

  I am currently attending college with a path of software development and working towards my BS thanks to VA Chap 31. My old original Macbook Pro is near dead and no longer upgradable on the software or hardware side. The VA has offered to purchase a PC laptop for me (Because my syllabi says computer required), but I do not want to go backwards. I have a lot invested in OS X software and Mac peripherals, not to mention I prefer to program in an Apple environment. PC vs. Mac costs are so drastically different that I must validate my request for a new Macbook Pro. In my request to the VA, I stated the above and some other topics but they requested more validation. Can anyone recommend issues, reasons, etc. to help me validate this purchase by the VA for school? Thanks in advance for your help, David

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• Do CDNs work with POST operations?

  - by iddqd

  I'm using a CDN (Level3) for the first time and I'm a bit confused. I'm accessing dynamic URLs such as http://cdn.mysite.com?getItem=1234 that return text data. Do CDNs work with HTTP POST operations? When i issue a HTTP POST operation, my "real" server receives this request every time, so I'm wondering if the CDN has a problem with POST operations. If i use HTTP GET it seems to work, i call the URL once (from my application), i can see my server receiving the request. If i call it a second time, the CDN delivers it directly, my server doesn't get anything. However if i open same the link manually from a second browser tab, my server is asked to deliver again, shouldn't it be cached by now? Many thanks.

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• Add Widget via Action in Toolbar

  - by Geertjan

  The question of the day comes from Vadim, who asks on the NetBeans Platform mailing list: "Looking for example showing how to add Widget to Scene, e.g. by toolbar button click." Well, the solution is very similar to this blog entry, where you see a solution provided by Jesse Glick for VisiTrend in Boston: https://blogs.oracle.com/geertjan/entry/zoom_capability Other relevant articles to read are as follows: http://netbeans.dzone.com/news/which-netbeans-platform-action http://netbeans.dzone.com/how-to-make-context-sensitive-actions Let's go through it step by step, with this result in the end, a solution involving 4 classes split (optionally, since a central feature of the NetBeans Platform is modularity) across multiple modules: The Customer object has a "name" String and the Droppable capability has a method "doDrop" which takes a Customer object: public interface Droppable {    void doDrop(Customer c);} In the TopComponent, we use "TopComponent.associateLookup" to publish an instance of "Droppable", which creates a new LabelWidget and adds it to the Scene in the TopComponent. Here's the TopComponent constructor: public CustomerCanvasTopComponent() {    initComponents();    setName(Bundle.CTL_CustomerCanvasTopComponent());    setToolTipText(Bundle.HINT_CustomerCanvasTopComponent());    final Scene scene = new Scene();    final LayerWidget layerWidget = new LayerWidget(scene);    Droppable d = new Droppable(){        @Override        public void doDrop(Customer c) {            LabelWidget customerWidget = new LabelWidget(scene, c.getTitle());            customerWidget.getActions().addAction(ActionFactory.createMoveAction());            layerWidget.addChild(customerWidget);            scene.validate();        }    };    scene.addChild(layerWidget);    jScrollPane1.setViewportView(scene.createView());    associateLookup(Lookups.singleton(d));} The Action is displayed in the toolbar and is enabled only if a Droppable is currently in the Lookup: @ActionID(        category = "Tools",        id = "org.customer.controler.AddCustomerAction")@ActionRegistration(        iconBase = "org/customer/controler/icon.png",        displayName = "#AddCustomerAction")@ActionReferences({    @ActionReference(path = "Toolbars/File", position = 300)})@NbBundle.Messages("AddCustomerAction=Add Customer")public final class AddCustomerAction implements ActionListener {    private final Droppable context;    public AddCustomerAction(Droppable droppable) {        this.context = droppable;    }    @Override    public void actionPerformed(ActionEvent ev) {        NotifyDescriptor.InputLine inputLine = new NotifyDescriptor.InputLine("Name:", "Data Entry");        Object result = DialogDisplayer.getDefault().notify(inputLine);        if (result == NotifyDescriptor.OK_OPTION) {            Customer customer = new Customer(inputLine.getInputText());            context.doDrop(customer);        }    }} Therefore, when the Properties window, for example, is selected, the Action will be disabled. (See the Zoomable example referred to in the link above for another example of this.) As you can see above, when the Action is invoked, a Droppable must be available (otherwise the Action would not have been enabled). The Droppable is obtained in the Action and a new Customer object is passed to its "doDrop" method. The above in pictures, take note of the enablement of the toolbar button with the red dot, on the extreme left of the toolbar in the screenshots below: The above shows the JButton is only enabled if the relevant TopComponent is active and, when the Action is invoked, the user can enter a name, after which a new LabelWidget is created in the Scene. The source code of the above is here: http://java.net/projects/nb-api-samples/sources/api-samples/show/versions/7.3/misc/WidgetCreationFromAction Note: Showing this as an MVC example is slightly misleading because, depending on which model object ("Customer" and "Droppable") you're looking at, the V and the C are different. From the point of view of "Customer", the TopComponent is the View, while the Action is the Controler, since it determines when the M is displayed. However, from the point of view of "Droppable", the TopComponent is the Controler, since it determines when the Action, i.e., which is in this case the View, displays the presence of the M.

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• Thread.Interrupt Is Evil

  - by Alois Kraus

  Recently I have found an interesting issue with Thread.Interrupt during application shutdown. Some application was crashing once a week and we had not really a clue what was the issue. Since it happened not very often it was left as is until we have got some memory dumps during the crash. A memory dump usually means WindDbg which I really like to use (I know I am one of the very few fans of it).  After a quick analysis I did find that the main thread already had exited and the thread with the crash was stuck in a Monitor.Wait. Strange Indeed. Running the application a few thousand times under the debugger would potentially not have shown me what the reason was so I decided to what I call constructive debugging. I did create a simple Console application project and try to simulate the exact circumstances when the crash did happen from the information I have via memory dump and source code reading. The thread that was  crashing was actually MS code from an old version of the Microsoft Caching Application Block. From reading the code I could conclude that the main thread did call the Dispose method on the CacheManger class which did call Thread.Interrupt on the cache scavenger thread which was just waiting for work to do. My first version of the repro looked like this   static void Main(string[] args) { Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); } static void ThreadFunc() { while (true) { object value = Dequeue(); // block until unblocked or awaken via ThreadInterruptedException } } static object WaitObject = new object(); static object Dequeue() { object lret = "got value"; try { lock (WaitObject) { } } catch (ThreadInterruptedException) { Console.WriteLine("Got ThreadInterruptException"); lret = null; } return lret; } I do start a background thread and call Thread.Interrupt on it and then directly let the application terminate. The thread in the meantime does plenty of Monitor.Enter/Leave calls to simulate work on it. This first version did not crash. So I need to dig deeper. From the memory dump I did know that the finalizer thread was doing just some critical finalizers which were closing file handles. Ok lets add some long running finalizers to the sample. class FinalizableObject : CriticalFinalizerObject { ~FinalizableObject() { Console.WriteLine("Hi we are waiting to finalize now and block the finalizer thread for 5s."); Thread.Sleep(5000); } } class Program { static void Main(string[] args) { FinalizableObject fin = new FinalizableObject(); Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); GC.KeepAlive(fin); // prevent finalizing it too early // After leaving main the other thread is woken up via Thread.Abort // while we are finalizing. This causes a stackoverflow in the CLR ThreadAbortException handling at this time. } With this changed Main method and a blocking critical finalizer I did get my crash just like the real application. The funny thing is that this is actually a CLR bug. When the main method is left the CLR does suspend all threads except the finalizer thread and declares all objects as garbage. After the normal finalizers were called the critical finalizers are executed to e.g. free OS handles (usually). Remember that I did call Thread.Interrupt as one of the last methods in the Main method. The Interrupt method is actually asynchronous and does wake a thread up and throws a ThreadInterruptedException only once unlike Thread.Abort which does rethrow the exception when an exception handling clause is left. It seems that the CLR does not expect that a frozen thread does wake up again while the critical finalizers are executed. While trying to raise a ThreadInterrupedException the CLR goes down with an stack overflow. Ups not so nice. Why has this nobody noticed for years is my next question. As it turned out this error does only happen on the CLR for .NET 4.0 (x86 and x64). It does not show up in earlier or later versions of the CLR. I have reported this issue on connect here but so far it was not confirmed as a CLR bug. But I would be surprised if my console application was to blame for a stack overflow in my test thread in a Monitor.Wait call. What is the moral of this story? Thread.Abort is evil but Thread.Interrupt is too. It is so evil that even the CLR of .NET 4.0 contains a race condition during the CLR shutdown. When the CLR gurus can get it wrong the chances are high that you get it wrong too when you use this constructs. If you do not believe me see what Patrick Smacchia does blog about Thread.Abort and List.Sort. Not only the CLR creators can get it wrong. The BCL writers do sometimes have a hard time with correct exception handling as well. If you do tell me that you use Thread.Abort frequently and never had problems with it I do suspect that you do not have looked deep enough into your application to find such sporadic errors.

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• ASP.NET Multi-Select Radio Buttons

  - by Ajarn Mark Caldwell

  “HERESY!” you say, “Radio buttons are for single-select items!  If you want multi-select, use checkboxes!”  Well, I would agree, and that is why I consider this a significant bug that ASP.NET developers need to be aware of.  Here’s the situation. If you use ASP:RadioButton controls on your WebForm, then you know that in order to get them to behave properly, that is, to define a group in which only one of them can be selected by the user, you use the Group attribute and set the same value on each one.  For example: 1: <asp:RadioButton runat="server" ID="rdo1" Group="GroupName" checked="true" /> 2: <asp:RadioButton runat="server" ID="rdo2" Group="GroupName" /> With this configuration, the controls will render to the browser as HTML Input / Type=radio tags and when the user selects one, the browser will automatically deselect the other one so that only one can be selected (checked) at any time. BUT, if you user server-side code to manipulate the Checked attribute of these controls, it is possible to set them both to believe that they are checked. 1: rdo2.Checked = true; // Does NOT change the Checked attribute of rdo1 to be false. As long as you remain in server-side code, the system will believe that both radio buttons are checked (you can verify this in the debugger).  Therefore, if you later have code that looks like this 1: if (rdo1.Checked) 2: { 3: DoSomething1(); 4: } 5: else 6: { 7: DoSomethingElse(); 8: } then it will always evaluate the condition to be true and take the first action.  The good news is that if you return to the client with multiple radio buttons checked, the browser tries to clean that up for you and make only one of them really checked.  It turns out that the last one on the screen wins, so in this case, you will in fact end up with rdo2 as checked, and if you then make a trip to the server to run the code above, it will appear to be working properly.  However, if your page initializes with rdo2 checked and in code you set rdo1 to checked also, then when you go back to the client, rdo2 will remain checked, again because it is the last one and the last one checked “wins”. And this gets even uglier if you ever set these radio buttons to be disabled.  In that case, although the client browser renders the radio buttons as though only one of them is checked the system actually retains the value of both of them as checked, and your next trip to the server will really frustrate you because the browser showed rdo2 as checked, but your DoSomething1() routine keeps getting executed. The following is sample code you can put into any WebForm to test this yourself. 1: <body> 2: <form id="form1" runat="server"> 3: <h1>Radio Button Test</h1> 4: <hr /> 5: <asp:Button runat="server" ID="cmdBlankPostback" Text="Blank Postback" /> 6: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 7: <asp:Button runat="server" ID="cmdEnable" Text="Enable All" OnClick="cmdEnable_Click" /> 8: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 9: <asp:Button runat="server" ID="cmdDisable" Text="Disable All" OnClick="cmdDisable_Click" /> 10: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 11: <asp:Button runat="server" ID="cmdTest" Text="Test" OnClick="cmdTest_Click" /> 12: <br /><br /><br /> 13: <asp:RadioButton ID="rdoG1R1" GroupName="Group1" runat="server" Text="Group 1 Radio 1" Checked="true" /><br /> 14: <asp:RadioButton ID="rdoG1R2" GroupName="Group1" runat="server" Text="Group 1 Radio 2" /><br /> 15: <asp:RadioButton ID="rdoG1R3" GroupName="Group1" runat="server" Text="Group 1 Radio 3" /><br /> 16: <hr /> 17: <asp:RadioButton ID="rdoG2R1" GroupName="Group2" runat="server" Text="Group 2 Radio 1" /><br /> 18: <asp:RadioButton ID="rdoG2R2" GroupName="Group2" runat="server" Text="Group 2 Radio 2" Checked="true" /><br /> 19:  20: </form> 21: </body> 1: protected void Page_Load(object sender, EventArgs e) 2: { 3:  4: } 5:  6: protected void cmdEnable_Click(object sender, EventArgs e) 7: { 8: rdoG1R1.Enabled = true; 9: rdoG1R2.Enabled = true; 10: rdoG1R3.Enabled = true; 11: rdoG2R1.Enabled = true; 12: rdoG2R2.Enabled = true; 13: } 14:  15: protected void cmdDisable_Click(object sender, EventArgs e) 16: { 17: rdoG1R1.Enabled = false; 18: rdoG1R2.Enabled = false; 19: rdoG1R3.Enabled = false; 20: rdoG2R1.Enabled = false; 21: rdoG2R2.Enabled = false; 22: } 23:  24: protected void cmdTest_Click(object sender, EventArgs e) 25: { 26: rdoG1R2.Checked = true; 27: rdoG2R1.Checked = true; 28: } 29: 30: protected void Page_PreRender(object sender, EventArgs e) 31: { 32:  33: } After you copy the markup and page-behind code into the appropriate files.  I recommend you set a breakpoint on Page_Load as well as cmdTest_Click, and add each of the radio button controls to the Watch list so that you can walk through the code and see exactly what is happening.  Use the Blank Postback button to cause a postback to the server so you can inspect things without making any changes. The moral of the story is: if you do server-side manipulation of the Checked status of RadioButton controls, then you need to set ALL of the controls in a group whenever you want to change one.

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• Bug Tracking Etiquette - Necromancy or Duplicate?

  - by Shauna

  I came across a really old (2+ years) feature request issue in a bug tracker for an open source project that was marked as "resolved (won't fix)" due to the lack of tools required to make the requested enhancement. In the time elapsed since that determination was made, new tools have been developed that would allow it to be resolved, and I'd like to bring that to the attention of the community for that application. However, I'm not sure as to what the generally accepted etiquette is for bug tracking in cases like this. Obviously, if the system explicitly states to not duplicate and will actively mark new items as duplicates (much in the way the SE sites do), then the answer would be to follow what the system says. But what about when the system doesn't explicitly say that, or a new user can't easily find a place that says with the system's preference is? Is it generally considered better to err on the side of duplication or necromancy? Does this differ depending on whether it's a bug or a feature request?

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• Real performance of node.js

  - by uther.lightbringer

  I've got a question concerning node.js performance. There is quite lot of "benchmarks" and a lot of fuss about great performance of node.js. But how does it stand in real world? Not just process empty request at high speed. If someone could try to compare this scenario: Java (or equivalent) server running an application with complex business logic between receiving request and sending response. How would node.js deal with it? If there was need for a lot of JavaScript processing on server side, is node.js really so fast that it can execute JavaScript, and stand a chance against more heavyveight competitors?

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• several subdomains pointing to one folder. fasthosts problem

  - by David

  I have a asp.net website (e.g. www.website.com). The idea is that you will go to the url 'yourname.website.com' and my site will request the name from the sub domain, process it and change the content accordingly. So, I purchased my fasthosts hosting package and created a sub domain which points to a folder within my site. e.g. 'www.website.com/folder'. However, when i now go to the url 'yourname.website.com' it is immediately redirected to 'website.com/folder'. this means I cannot request the subdomain from the url because it has been lost. I have tried contacting these guys but they don't understand and keep going on about some sort of redirect script (although i don't see how any further redirects can solve my problem). Is there something I am missing here? Any suggests or help would be much appreciated!

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• What are the drawbacks of sending XML to browsers and let them apply XSLT?

  - by MainMa

  Context Working as a freelance developer, I often made websites completely based on XSLT. In other words, on every request, an XML file is generated, containing everything we need to know about the page content: the name of the user currently logged in, the top menu entries, if this menu is dynamic/configurable, the text to display in a specific area of the page, etc. Then XSL process (caches, etc.) it to HTML/XHTML page to send to the browser. It has a good point to make it easier to create small-scale websites, especially with PHP. It is a sort of template engine, but which I prefer to other template engines because it's much more powerful than most of template engines, and because I know it better and like it. It is also possible, when need, to give an access to raw XML data on demand for an automated access, without the need to create separate APIs. Of course, it will fail completely on any medium-scale or large-scale website, since, even with good caching techniques, XSL still degrades overall website performance and requires more CPU serverside. Question Modern browsers have the ability to take an XML file and to transform it with an associated XSL file declared in XML like <?xml-stylesheet href="demo.xslt" type="text/xsl"?>. Firefox 3 can do it. Internet Explorer 8 can do it too. It means that it is possible to migrate XSL processing from the server to the client side for 50% of users (according on browser statistics on several websites where I may want to implement this). It means that those 50% of users will receive only the XML file at each request, thus reducing their and server's bandwidth (XML file being much shorter than its processed HTML analog), and reducing server's CPU usage. What are the drawbacks of this technique? I thought about several ones, but it doesn't apply in this situation: Difficult implementation and the need to choose, based on the browser request, when to send raw XML and when to transform it to HTML instead. Obviously, the system will not be much more difficult then the actual one. The only change to make is to add XSL file link to every XML, and to add a browser check. More IO and bandwidth usage, since the XSLT file will be downloaded by the browsers, instead of being cached by the server. I don't think it will be a problem, since XSLT file will be cached by the browsers (like images, or CSS, or JavaScript files are cached actually). Possibly some problems on client side, like maybe problems when saving a page in some browsers. Difficulty to debug code: it is impossible to obtain an HTML source the browser is actually using, since the only displayed source is the downloaded XML. On the other hand, I rarely go look at HTML code on client side, and in most cases, it is unusable directly (whitespace being removed).

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• Is it bad practice to output from within a function?

  - by Nick

  For example, should I be doing something like: <?php function output_message($message,$type='success') { ?> <p class="<?php echo $type; ?>"><?php echo $message; ?></p> <?php } output_message('There were some errors processing your request','error'); ?> or <?php function output_message($message,$type='success') { ob_start(); ?> <p class="<?php echo $type; ?>"><?php echo $message; ?></p> <?php return ob_get_clean(); } echo output_message('There were some errors processing your request','error'); ?> I understand they both achieve the same end result, but are there benefits doing one way over the other? Or does it not even matter?

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• Python Multiprocessing with Queue vs ZeroMQ IPC

  - by Imraan

  I am busy writing a Python application using ZeroMQ and implementing a variation of the Majordomo pattern as described in the ZGuide. I have a broker as an intermediary between a set of workers and clients. I want to do some extensive logging for every request that comes in, but I do not want the broker to waste time doing that. The broker should pass that logging request to something else. I have thought of two ways :- Create workers that are only for logging and use the ZeroMQ IPC transport Use Multiprocessing with a Queue I am not sure which one is better or faster for that matter. The first option does allow me to use the current worker base classes that I already use for normal workers, but the second option seems quicker to implement. I would like some advice or comments on the above or possibly a different solution.

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• Web Services Example - Part 2: Programmatic

  - by Denis T

  In this edition of the ADF Mobile blog we'll tackle part 2 of our Web Service examples.  In this posting we'll take a look at using a SOAP Web Service but calling it programmatically in code and parsing the return into a bean. Getting the sample code: Just click here to download a zip of the entire project.  You can unzip it and load it into JDeveloper and deploy it either to iOS or Android.  Please follow the previous blog posts if you need help getting JDeveloper or ADF Mobile installed.  Note: This is a different workspace than WS-Part1 Defining our Web Service: Just like our first installment, we are using the same public weather forecast web service provided free by CDYNE Corporation.  Sometimes this service goes down so please ensure you know it's up before reporting this example isn't working. We're going to concentrate on the same two web service methods, GetCityForecastByZIP and GetWeatherInformation. Defing the Application: The application setup is identical to the Weather1 version.  There are some improvements to the data that is displayed as part of this example though.  Now we are able to show the associated image along with each forecast line when using the Forecast By Zip feature.  We've also added the temperature Hi/Low values into the UI. Summary of Fundamental Changes In This Application The most fundamental change is that we're binding the UI to the Bean Data Controls instead of directly to the Web Service Data Controls.  This gives us much more flexibility to control the shape of the data and allows us to do caching of the data outside of the Web Service.  This way if your application is, say offline, your bean could still populate with data from a local cache and still show you some UI as opposed to completely failing because you don't have any connectivity. In general we promote this type of programming technique with ADF Mobile to insulate your application from any issues with network connectivity. What's different with this example? We have setup the Web Service DC the same way but now we have managed beans to process the data.  The following classes define the "Model" of our application:  CityInformation-CityForecast-Forecast, WeatherInformation-WeatherDescription.  We use WeatherBean for UI interaction to the model layer.  If you look through this example, we don't really do that much with the java code except use it to grab the image URL from the weather description.  In a more realistic example, you might be using some JDBC classes to persist the data to a local database. To have a good architecture it is always good to keep your model and UI layers separate.  This gets muddied if you start to use bindings on a page invoked from Java code and this java code starts to become your "model" layer.  Since bindings are page specific, your model layer starts to become entwined with your UI.  Not good!  To help with this, we've added some utility functions that let you invoke DC methods without having a binding and thus execute methods from your "model" layer without requiring a binding in your page definition.  We do this with the invokeDataControlMethod of the AdfmfJavaUtilities class.  An example of this method call is available in line 95 of WeatherInformation.java and line 93 of CityInformation.Java. What's a GenericType? Because Web Service Data Controls (and also URL Data Controls AKA REST) use generic name/value pairs to define their structure and don't have strongly typed objects, these are actually stored internally as GenericType objects.  The GenericType class is simply a property map of name/value pairs that can be hierarchical.  There are methods like getAttribute where you supply the index of the attribute or it's string property name.  Why is this important to know?  Because invokeDataControlMethod returns GenericType objects and developers either need to parse these GenericType objects themselves or use one of our helper functions. GenericTypeBeanSerializationHelper This class does exactly what it's name implies.  It's a helper class for developers to aid in serialization of GenericTypes to/from java objects.  This is extremely handy if you have a large GenericType object with many attributes (or you're just lazy like me!) and you just want to parse it out into a real java object you can use more easily.  Here you would use the fromGenericType method.  This method takes the class of the Java object you wish to return and the GenericType as parameters.  The method then parses through each attribute in the GenericType and uses reflection to set that same attribute in the Java class.  Then the method returns that new object of the class you specified.  This is obviously very handy to avoid a lot of shuffling code between GenericType and your own Java classes.  The reverse method, toGenericType is also available when you want to go the other way.  In this case you supply the string that represents the package location in the DataControl definition (Example: "MyDC.myParams.MyCollection") and then pass in the Java object you have that holds the data and a GenericType is returned to you.  Again, it will use reflection to calculate the attributes that match between the java class and the GenericType and call the getters/setters on those. Issues and Possible Improvements: In the next installment we'll show you how to make your web service calls asynchronously so your UI will fill dynamically when the service call returns but in the meantime you show the data you have locally in your bean fed from some local cache.  This gives your users instant delivery of some data while you fetch other data in the background.

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• Tracking Redirects Leading to your site

  - by Bill

  Is there a way in which I can find out if a user arrived at my site via a redirect? Here's an example: There are two sites, first.com & second.com. Any request to first.com will do a 302 redirect to second.com. When the request at second.com arrives, is there anyway to know it was redirected from first.com? Note that in this example you have no control over first.com. (In fact, it could be something bad, like kiddieporn.com.) Also note, because it is a redirect, it will not be in the HTTP referrer header.

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• Confused about nova-network

  - by neo0

  I'm so sorry because this question doesn't related to Ubuntu. I asked in Openstack forum but this forum is not very active. So I think if someone have experience with Openstack Nova can help me with my problem. I've read some explanations about nova-network and how to configure it like this one from wiki: http://wiki.openstack.org/UnderstandingFlatNetworking I'm confusing about a detail. If every traffic from the instances must go through nova controller node, then why we still need the public interface for nova-compute node? Is it necessary? What happen when a request from outside to an instance. For example I have a controller node and a nova-compute node. In nova-compute node I run an instance with a Wordpress website. Then someone connect to the public IP of this instance. So the request go directly from router to the nova-compute node or from router to controller node then nova-compute node? Thank you!

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