andy smith - Page 10 - Developer IT

MySQL Enterprise Monitor 2.3.12 Is Now Available!

- by Andy Bang

We are pleased to announce that MySQL Enterprise Monitor 2.3.12 is now available for download on the My Oracle Support (MOS) web site. It will also be available via the Oracle Software Delivery Cloud in approximately 1-2 weeks. This is a maintenance release that contains several new features and fixes a number of bugs. You can find more information on the contents of this release in the changelog: http://dev.mysql.com/doc/mysql-monitor/2.3/en/mem-news-2-3-12.html You will find binaries for the new release on My Oracle Support: https://support.oracle.com Choose the "Patches & Updates" tab, and then use the "Product or Family (Advanced Search)" feature. And from the Oracle Software Delivery Cloud (in about 1-2 weeks): http://edelivery.oracle.com/ Choose "MySQL Database" as the Product Pack and you will find the Enterprise Monitor along with other MySQL products. If you haven't looked at 2.3 recently, please do so now and let us know what you think. Thanks and Happy Monitoring! - The MySQL Enterprise Tools Development Team

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Security programming jobs

- by Mike Smith

I am a student, about to finish my undergraduate in Computer Science in about a year. I am very interested in computer/network security, but I also love programming. Is there a job or subfield that is a fusion of both? I have programmed everything from games to barcode readers to web bots, and I know for sure that I want to do some kind of programming, but ideally I would like to do some kind of software development involving computer security. Any advice would be appreciated.

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Python interview questions

- by Andy

I am going to interview within two weeks for an internship that would involve Python programming. Can anyone suggest what possible areas should I polish? I am looking for commonly asked stuff in interviews for Python openings. Apart from the fact that I have already been doing the language for over a year now, I fail to perceive what they can ask me. Like for a C or C++ interview, there are lots of questions ranging from reversing of strings to building linked lists, but for a Python interview, I am clueless. Personal experiences and/ or suggestions are welcomed.

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Are 'edited by' inline comments the norm in shops which use revision control?

- by Joshua Smith

The senior dev in our shop insists that whenever code is modified, the programmer responsible should add an inline comment stating what he did. These comments usually look like // YYYY-MM-DD <User ID> Added this IF block per bug 1234. We use TFS for revision control, and it seems to me that comments of this sort are much more appropriate as check-in notes rather than inline noise. TFS even allows you to associate a check-in with one or more bugs. Some of our older, often-modified class files look like they have a comment-to-LOC ratio approaching 1:1. To my eyes, these comments make the code harder to read and add zero value. Is this a standard (or at least common) practice in other shops?

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Adding IP address to OpenVZ VPS (OpenVZ Web Panel)

- by andy

I apologise if I sound at all dumb. This is my first dedicated server having used a VPS for over a year and I'm trying to setup a VPS on this new server. I purchased a subnet from my hosting provider that I believe allows me 6 usable IP addresses: 177.xx.xxx.201 - 177.xx.xxx.206 The subnet address looks like this: 177.xx.xxx.200/29. I've gone on my server and added them like it said on a wiki like so: ip addr add 177.**.***.201/29 dev eth0 I done that for all six and now when I go to them in the browser they point to my server. The problem is, I'm using OpenVZ web panel to create VMs (http://code.google.com/p/ovz-web-panel/) so I created a VM and assigned one of those IPs to it. However when SSHing to that IP it SSH's to the dedicated server and not the VM. Am I missing something?

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Exporting the frames in a Flash CS5.5 animation and possibly creating the spritesheet

- by Adam Smith

Some time ago, I asked a question here to know what would be the best way to create animations when making an Android game and I got great answers. I did what people told me there by exporting each frame from a Flash animation manually and creating the spritesheet also manually and it was very tedious. Now, I changed project and this one is going to contain a lot more animations and I feel like there has to be a better way to to export each frame individually and possibly create my spritesheets in an automated manner. My designer is using Flash CS5.5 and I was wondering if all of this was possible, as I can't find an option or code examples on how to save each frame individually. If this is not possible using Flash, please recommend me another program that can be used to create animations without having to create each frame on its own. I'd rather keep Flash as my designer knows how to use it and it's giving great results.

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The EXECUTE permission was denied on the object 'bam_Metadata_GetConfigurationXml'

- by Andy Morrison

We were seeing this exception on two servers when we tried to access the BAM Portal... after having to reconfigure the BAM Portal and Tools for reasons unrelated to the error: --- Log Name: Application Source: Bam Web Service Date: 2/18/2011 10:24:07 AM Event ID: 1534 Task Category: None Level: Error Keywords: Classic User: N/A Computer: yyyyyyyyyyyyyyyyyyyy Description: Current User: yy\yyyyyyyy EXCEPTION: Microsoft.BizTalk.Bam.Management.BamManagerException: Encountered error while executing command on SQL Server "yyyyyyyyyyyyyyy". ---> System.Data.SqlClient.SqlException: The EXECUTE permission was denied on the object 'bam_Metadata_GetConfigurationXml', database 'BAMPrimaryImport', schema 'dbo'. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlDataReader.ConsumeMetaData() at System.Data.SqlClient.SqlDataReader.get_MetaData() at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior) at Microsoft.BizTalk.Bam.Management.SqlHelper.ExecuteQuery(String cmdText, CommandType cmdType, Transaction transaction) --- End of inner exception stack trace --- at Microsoft.BizTalk.Bam.Management.SqlHelper.ExecuteQuery(String cmdText, CommandType cmdType, Transaction transaction) at Microsoft.BizTalk.Bam.Management.BamConfigurationManager.GetConfigurationXmlFromPrimaryImportDb() at Microsoft.BizTalk.Bam.Management.BamConfigurationManager..ctor(String piServer, String piDatabase, Int32 sqlHelperCmdTimeout, Boolean validateServerNames) at Microsoft.BizTalk.Bam.Management.BamManager..ctor(String primaryImportServer, String primaryImportDatabase, Int32 sqlCmdTimeout, Boolean validateServerNames) at Microsoft.BizTalk.Bam.Management.BamManager..ctor(String primaryImportServer, String primaryImportDatabase) at Microsoft.BizTalk.Bam.WebServices.Utilities.FetchBamManager() at Microsoft.BizTalk.Bam.WebServices.Management.BamManagementService.GetViewSummaryForCurrentUser() EXCEPTION: Microsoft.BizTalk.Bam.Management.BamManagerException: Encountered error while executing command on SQL Server "yyyyyyyyyyyyyyyyyy". ---> System.Data.SqlClient.SqlException: The EXECUTE permission was denied on the object 'bam_Metadata_GetConfigurationXml', database 'BAMPrimaryImport', schema 'dbo'. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlDataReader.ConsumeMetaData() at System.Data.SqlClient.SqlDataReader.get_MetaData() at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior) at Microsoft.BizTalk.Bam.Management.SqlHelper.ExecuteQuery(String cmdText, CommandType cmdType, Transaction transaction) --- End of inner exception stack trace --- at Microsoft.BizTalk.Bam.Management.SqlHelper.ExecuteQuery(String cmdText, CommandType cmdType, Transaction transaction) at Microsoft.BizTalk.Bam.Management.BamConfigurationManager.GetConfigurationXmlFromPrimaryImportDb() at Microsoft.BizTalk.Bam.Management.BamConfigurationManager..ctor(String piServer, String piDatabase, Int32 sqlHelperCmdTimeout, Boolean validateServerNames) at Microsoft.BizTalk.Bam.Management.BamManager..ctor(String primaryImportServer, String primaryImportDatabase, Int32 sqlCmdTimeout, Boolean validateServerNames) at Microsoft.BizTalk.Bam.Management.BamManager..ctor(String primaryImportServer, String primaryImportDatabase) at Microsoft.BizTalk.Bam.WebServices.Utilities.FetchBamManager() at Microsoft.BizTalk.Bam.WebServices.Management.BamManagementService.GetViewSummaryForCurrentUser() --- We reconfigured the BAM Portal and Tools multiple times, trying to fix this issue, but kept getting the exception. The fix was to add the BizTalk Server Administrators and BizTalk Application Users to the BAM_ManagementWS role in the BAMPrimaryImport database. (Note that these two groups do not appear to be added to this role in a "clean" configuration. Thanks go to Ed at http://talentedmonkeys.wordpress.com/ for figuring out a solution.

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Project structure: where to put business logic

- by Mister Smith

First of all, I'm not asking where does business logic belong. This has been asked before and most answers I've read agree in that it belongs in the model: Where to put business logic in MVC design? How much business logic should be allowed to exist in the controller layer? How accurate is "Business logic should be in a service, not in a model"? Why put the business logic in the model? What happens when I have multiple types of storage? However people disagree in the way this logic should be distributed across classes. There seem to exist three major currents of thought: Fat model with business logic inside entity classes. Anemic model and business logic in "Service" classes. It depends. I find all of them problematic. The first option is what most Fowlerites stick to. The problem with a fat model is that sometimes a business logic funtion is not only related to a class, and instead uses a bunch of other classes. If, for example, we are developing a web store, there should be a function that calcs an order's total. We could think of putting this function inside the Order class, but what actually happens is that the logic needs to use different classes, not only data contained in the Order class, but also in the User class, the Session class, and maybe the Tax class, Country class, or Giftcard, Payment, etc. Some of these classes could be composed inside the Order class, but some others not. Sorry if the example is not very good, but I hope you understand what I mean. Putting such a function inside the Order class would break the single responsibility principle, adding unnecesary dependences. The business logic would be scattered across entity classes, making it hard to find. The second option is the one I usually follow, but after many projects I'm still in doubt about how to name the class or classes holding the business logic. In my company we usually develop apps with offline capabilities. The user is able to perform entire transactions offline, so all validation and business rules should be implemented in the client, and then there's usually a background thread that syncs with the server. So we usually have the following classes/packages in every project: Data model (DTOs) Data Access Layer (Persistence) Web Services layer (Usually one class per WS, and one method per WS method). Now for the business logic, what is the standard approach? A single class holding all the logic? Multiple classes? (if so, what criteria is used to distribute the logic across them?). And how should we name them? FooManager? FooService? (I know the last one is common, but in our case it is bad naming because the WS layer usually has classes named FooWebService). The third option is probably the right one, but it is also devoid of any useful info. To sum up: I don't like the first approach, but I accept that I might have been unable to fully understand the Zen of it. So if you advocate for fat models as the only and universal solution you are welcome to post links explaining how to do it the right way. I'd like to know what is the standard design and naming conventions for the second approach in OO languages. Class names and package structure, in particular. It would also be helpful too if you could include links to Open Source projects showing how it is done. Thanks in advance.

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How to become an expert web-developer?

- by John Smith

I am currently a Junior PHP developer and I really LOVE it, I love internet from first time I got into it, I always loved smartly-created websites, always was wondering how it all works, always admired websites with good design and rich functionality, and finally I am creating web-sites on my own and it feels really great. My goals are to become expert web-developer (aiming for creating websites for small and medium business, not enterprise-sized systems), to have a great full-time job, to do freelance and to create my own startup in future. General question: What do I do to be an expert, professional and demanded web-programmer? More concrete questions: 1). How do I choose languages and technologies needed? I know that every web-developer must know HTML+CSS+JS+AJAX+JQuery, I am doing some design aswell cause I like it and I need it for freelance also. But what about backend languages? Currently I picked PHP cause it's most demanded in my area and most of web uses it, but what would happen in future? Say, in 3 years, I am good at PHP and PHP frameworks by than, but what if some other languages get most popular? Do I switch to them? I know that good programmer is not about languages and frameworks but about ability to learn and to aim the goals, but still I think that learning frameworks for some language can take quite some time. Am I wrong? 2). In general, what are basic guidelines to be expert web-developer? What are most important things I should focus on? Thank you!

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setting globals in html or body [migrated]

- by paul smith

I have some questions regarding the following css that I found: html, body { height:100%; min-width:100%; position:absolute; } html { background: none repeat scroll 0 0 #fff; color:#fff; font-family:arial,helvetica,sans-serif; font-size:15px; } is it necessary to have height and min-width to 100% on the html and body? What's the benefit? what is the reason for using position absolute? why did they set the background/color/font on the html and not the body? Is there a difference? Or is it just preference?

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Java, two JPanel on JFrame - Settings JPanel, StartMenu JPanel [on hold]

- by Andy Tyurin

There is my first question and I welcome community! I'm making a simple game and have some problems with Start menu. I have three buttons on my JPanel StartMenu and when I click "Settings" button, new JPanel will be open, but I don't know why buttons from StartMenu JPanel appeared in my Settings JPanel. My "Settings" JPanel has one ugly button "Back" in center and ugly grey background. I made some screens to see a problem. Start Menu JPanel when game launched Settings JPanel when button clicked Settings JPanel when mouse was over settings window There is code of StartMenu class: public class StartMenu extends JPanel { private GameButton startGameButton = new GameButton("Start game"); private GameButton settingsGameButton = new GameButton("Settings"); private GameButton exitGameButton = new GameButton("Exit game"); private Image bgImage = new ImageIcon(getClass().getClassLoader().getResource("ru/andydevs/astraLaserForce/bg.png")).getImage(); private int posX; private int posY; final private int WIDTH=(int)Game.SCREEN_DIMENSION.getWidth()/3; final private int HEIGHT=(int)Game.SCREEN_DIMENSION.getHeight()/2; public StartMenu() { setLayout(new GridBagLayout()); GridBagConstraints c = new GridBagConstraints(); setSize(new Dimension(WIDTH, HEIGHT)); posX=(int)Game.SCREEN_DIMENSION.getWidth()/2-WIDTH/2; posY=(int)Game.SCREEN_DIMENSION.getHeight()/2-HEIGHT/2; setBounds(posX, posY,WIDTH,HEIGHT); c.ipadx=95; c.ipady=15; c.fill = GridBagConstraints.HORIZONTAL; c.insets = new Insets(20,0,0,0); c.gridy=0; add(startGameButton, c); c.gridy=1; c.insets = new Insets(20,0,0,0); System.out.println(settingsGameButton.getWidth()); add(settingsGameButton, c); c.gridy=2; c.insets = new Insets(20,0,0,0); add(exitGameButton, c); settingsGameButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { GameOptionsPanel gop = new GameOptionsPanel(); Game.container.add(gop); Game.container.setComponentZOrder(gop, 0); Game.container.revalidate(); Game.container.repaint(); } }); exitGameButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { Main.currentGame.stop(); } }); } public void paintComponent(Graphics g) { g.drawImage(bgImage,0,0,WIDTH,HEIGHT,null); } } There is code of Settings JPanel public class GameOptionsPanel extends GamePanel { private GameButton backButton = new GameButton("Back"); private GameOptionsPanel that; public GameOptionsPanel() { super((int) (Game.SCREEN_DIMENSION.getWidth()/3), (int) (Game.SCREEN_DIMENSION.getHeight()/2), new Color(50,50,50)); that=this; setLayout(new GridBagLayout()); GridBagConstraints gbc = new GridBagConstraints(); gbc.fill=gbc.HORIZONTAL; add(backButton); backButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { Game.container.remove(that); Game.container.revalidate(); Game.container.repaint(); } }); } } I glad to see some suggestions. Thanks.

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Information Rights Management 11g Release Highlights

- by andy.peet

Broader Enterprise Reach Built on Fusion Middleware and Java EE Broad platform certifications Standard 27 Oracle languages SSO authentication: OAM, Windows auth, Basic auth to LDAP Extensible, First-Class Security Extensible classification model for application integrations FIPS 140-2 certification Hardware Security Module for key storage Usability and Templates New Web-based management console Best practice rights model: global roles and templates For more information see the new information available on OTN, including the Developer Area and whitepaper, and of course the IRM Blog.

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256 Worker Role 3D Rendering Demo is now a Lab on my Azure Course

- by Alan Smith

Ever since I came up with the crazy idea of creating an Azure application that would spin up 256 worker roles (please vote if you like it ) to render a 3D animation created using the Kinect depth camera I have been trying to think of something useful to do with it. I have also been busy working on developing training materials for a Windows Azure course that I will be delivering through a training partner in Stockholm, and for customers wanting to learn Windows Azure. I hit on the idea of combining the render demo and a course lab and creating a lab where the students would create and deploy their own mini render farms, which would participate in a single render job, consisting of 2,000 frames. The architecture of the solution is shown below. As students would be creating and deploying their own applications, I thought it would be fun to introduce some competitiveness into the lab. In the 256 worker role demo I capture the rendering statistics for each role, so it was fairly simple to include the students name in these statistics. This allowed the process monitor application to capture the number of frames each student had rendered and display a high-score table. When I demoed the application I deployed one instance that started rendering a frame every few minutes, and the challenge for the students was to deploy and scale their applications, and then overtake my single role instance by the end of the lab time. I had the process monitor running on the projector during the lab so the class could see the progress of their deployments, and how they were performing against my implementation and their classmates. When I tested the lab for the first time in Oslo last week it was a great success, the students were keen to be the first to build and deploy their solution and then watch the frames appear. As the students mostly had MSDN suspicions they were able to scale to the full 20 worker role instances and before long we had over 100 worker roles working on the animation. There were, however, a few issues who the couple of issues caused by the competitive nature of the lab. The first student to scale the application to 20 instances would render the most frames and win; there was no way for others to catch up. Also, as they were competing against each other, there was no incentive to help others on the course get their application up and running. I have now re-written the lab to divide the student into teams that will compete to render the most frames. This means that if one developer on the team can deploy and scale quickly, the other team still has a chance to catch up. It also means that if a student finishes quickly and puts their team in the lead they will have an incentive to help the other developers on their team get up and running. As I was using “Sharks with Lasers” for a lot of my demos, and reserved the sharkswithfreakinlasers namespaces for some of the Azure services (well somebody had to do it), the students came up with some creative alternatives, like “Camels with Cannons” and “Honey Badgers with Homing Missiles”. That gave me the idea for the teams having to choose a creative name involving animals and weapons. The team rendering architecture diagram is shown below. Render Challenge Rules In order to ensure fair play a number of rules are imposed on the lab. · The class will be divided into teams, each team choses a name. · The team name must consist of a ferocious animal combined with a hazardous weapon. · Teams can allocate as many worker roles as they can muster to the render job. · Frame processing statistics and rendered frames will be vigilantly monitored; any cheating, tampering, and other foul play will result in penalties. The screenshot below shows an example of the team render farm in action, Badgers with Bombs have taken a lead over Camels with Cannons, and both are leaving the Sharks with Lasers standing. If you are interested in attending a scheduled delivery of my Windows Azure or Windows Azure Service bus courses, or would like on-site training, more details are here.

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Pulseaudio no sound card detected. Dummy output only

- by Zach Smith

I'm using 12.10 Quantal with Openbox and a .xinitrc script at login instead of a display manager. Its a relatively fresh install and I noticed when I opened pavucontrol the only output was a dummy one. I check around and it appears that my soundcard is physically installed but Pulseaudio isn't detecting it. I'm really unsure what I should do but any help getting my audio back would be appreciated. Edit: further info if its at all useful: dante@dante-ubuntu:~$ uname -a && aplay -l && cat /proc/asound/version && head -n 1 /proc/asound/card*/codec#* Linux dante-ubuntu 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux aplay: device_list:252: no soundcards found... Advanced Linux Sound Architecture Driver Version 1.0.25. == /proc/asound/card0/codec#0 <== Codec: ATI R6xx HDMI == /proc/asound/card1/codec#0 <== Codec: IDT 92HD81B1X5

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Apache (XAMPP 1.8.0) access.log/Intrusion Detection Concern

- by Andy Holaday

[I originally posted on SO but it earned me a Tumbleweed badge. This looks like a better venue for the question.] I have Apache (XAMPP 1.8.0) running on Vista Pro x64. A couple times now I have seen a pattern like the example below in access.log. Concerning is the "attack" seems to somehow shift from a public IP to a valid private IP on my network (happens to be the WAN address of one of my routers). Two questions: How is this possible, and what happens if the "attacker" stumbles on a valid request? I've googled this to no avail. 177.0.X.X - - [03/Jun/2012:08:19:34 -0400] "GET /phpMyAdmin-2.5.4/index.php HTTP/1.1" 403 177.0.X.X - - [03/Jun/2012:08:19:34 -0400] "GET /phpMyAdmin-2.5.5-rc1/index.php HTTP/1.1" 403 177.0.X.X - - [03/Jun/2012:08:19:34 -0400] "GET /phpMyAdmin-2.2.6/index.php HTTP/1.1" 403 177.0.X.X - - [03/Jun/2012:08:19:34 -0400] "GET /phpMyAdmin-2.5.5-rc2/index.php HTTP/1.1" 403 192.168.15.3 - - [03/Jun/2012:08:19:56 -0400] "GET /phpMyAdmin-2.5.6-rc2/index.php HTTP/1.1" 403 177.0.X.X - - [03/Jun/2012:08:19:56 -0400] "GET /phpMyAdmin-2.5.6-rc1/index.php HTTP/1.1" 403 177.0.X.X - - [03/Jun/2012:08:19:56 -0400] "GET /phpMyAdmin-2.5.5-pl1/index.php HTTP/1.1" 403 192.168.15.3 - - [03/Jun/2012:08:19:59 -0400] "GET /phpMyAdmin-2.5.7/index.php HTTP/1.1" 403 192.168.15.3 - - [03/Jun/2012:08:20:01 -0400] "GET /phpMyAdmin-2.5.7-pl1/index.php HTTP/1.1" 403 192.168.15.3 - - [03/Jun/2012:08:20:02 -0400] "GET HTTP/1.1" 400 1060 "-" "-"

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Windows Azure Service Bus Scatter-Gather Implementation

- by Alan Smith

One of the more challenging enterprise integration patterns that developers may wish to implement is the Scatter-Gather pattern. In this article I will show the basic implementation of a scatter-gather pattern using the topic-subscription model of the windows azure service bus. I’ll be using the implementation in demos, and also as a lab in my training courses, and the pattern will also be included in the next release of my free e-book the “Windows Azure Service Bus Developer Guide”. The Scatter-Gather pattern answers the following scenario. How do you maintain the overall message flow when a message needs to be sent to multiple recipients, each of which may send a reply? Use a Scatter-Gather that broadcasts a message to multiple recipients and re-aggregates the responses back into a single message. The Enterprise Integration Patterns website provides a description of the Scatter-Gather pattern here. The scatter-gather pattern uses a composite of the publish-subscribe channel pattern and the aggregator pattern. The publish-subscribe channel is used to broadcast messages to a number of receivers, and the aggregator is used to gather the response messages and aggregate them together to form a single message. Scatter-Gather Scenario The scenario for this scatter-gather implementation is an application that allows users to answer questions in a poll based voting scenario. A poll manager application will be used to broadcast questions to users, the users will use a voting application that will receive and display the questions and send the votes back to the poll manager. The poll manager application will receive the users’ votes and aggregate them together to display the results. The scenario should be able to scale to support a large number of users. Scatter-Gather Implementation The diagram below shows the overall architecture for the scatter-gather implementation. Messaging Entities Looking at the scatter-gather pattern diagram it can be seen that the topic-subscription architecture is well suited for broadcasting a message to a number of subscribers. The poll manager application can send the question messages to a topic, and each voting application can receive the question message on its own subscription. The static limit of 2,000 subscriptions per topic in the current release means that 2,000 voting applications can receive question messages and take part in voting. The vote messages can then be sent to the poll manager application using a queue. The voting applications will send their vote messages to the queue, and the poll manager will receive and process the vote messages. The questions topic and answer queue are created using the Windows Azure Developer Portal. Each instance of the voting application will create its own subscription in the questions topic when it starts, allowing the question messages to be broadcast to all subscribing voting applications. Data Contracts Two simple data contracts will be used to serialize the questions and votes as brokered messages. The code for these is shown below. [DataContract] public class Question { [DataMember] public string QuestionText { get; set; } } To keep the implementation of the voting functionality simple and focus on the pattern implementation, the users can only vote yes or no to the questions. [DataContract] public class Vote { [DataMember] public string QuestionText { get; set; } [DataMember] public bool IsYes { get; set; } } Poll Manager Application The poll manager application has been implemented as a simple WPF application; the user interface is shown below. A question can be entered in the text box, and sent to the topic by clicking the Add button. The topic and subscriptions used for broadcasting the messages are shown in a TreeView control. The questions that have been broadcast and the resulting votes are shown in a ListView control. When the application is started any existing subscriptions are cleared form the topic, clients are then created for the questions topic and votes queue, along with background workers for receiving and processing the vote messages, and updating the display of subscriptions. public MainWindow() { InitializeComponent(); // Create a new results list and data bind it. Results = new ObservableCollection<Result>(); lsvResults.ItemsSource = Results; // Create a token provider with the relevant credentials. TokenProvider credentials = TokenProvider.CreateSharedSecretTokenProvider (AccountDetails.Name, AccountDetails.Key); // Create a URI for the serivce bus. Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri ("sb", AccountDetails.Namespace, string.Empty); // Clear out any old subscriptions. NamespaceManager = new NamespaceManager(serviceBusUri, credentials); IEnumerable<SubscriptionDescription> subs = NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic); foreach (SubscriptionDescription sub in subs) { NamespaceManager.DeleteSubscription(sub.TopicPath, sub.Name); } // Create the MessagingFactory MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials); // Create the topic and queue clients. ScatterGatherTopicClient = factory.CreateTopicClient(AccountDetails.ScatterGatherTopic); ScatterGatherQueueClient = factory.CreateQueueClient(AccountDetails.ScatterGatherQueue); // Start the background worker threads. VotesBackgroundWorker = new BackgroundWorker(); VotesBackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages); VotesBackgroundWorker.RunWorkerAsync(); SubscriptionsBackgroundWorker = new BackgroundWorker(); SubscriptionsBackgroundWorker.DoWork += new DoWorkEventHandler(UpdateSubscriptions); SubscriptionsBackgroundWorker.RunWorkerAsync(); } When the poll manager user nters a question in the text box and clicks the Add button a question message is created and sent to the topic. This message will be broadcast to all the subscribing voting applications. An instance of the Result class is also created to keep track of the votes cast, this is then added to an observable collection named Results, which is data-bound to the ListView control. private void btnAddQuestion_Click(object sender, RoutedEventArgs e) { // Create a new result for recording votes. Result result = new Result() { Question = txtQuestion.Text }; Results.Add(result); // Send the question to the topic Question question = new Question() { QuestionText = result.Question }; BrokeredMessage msg = new BrokeredMessage(question); ScatterGatherTopicClient.Send(msg); txtQuestion.Text = ""; } The Results class is implemented as follows. public class Result : INotifyPropertyChanged { public string Question { get; set; } private int m_YesVotes; private int m_NoVotes; public event PropertyChangedEventHandler PropertyChanged; public int YesVotes { get { return m_YesVotes; } set { m_YesVotes = value; NotifyPropertyChanged("YesVotes"); } } public int NoVotes { get { return m_NoVotes; } set { m_NoVotes = value; NotifyPropertyChanged("NoVotes"); } } private void NotifyPropertyChanged(string prop) { if(PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(prop)); } } } The INotifyPropertyChanged interface is implemented so that changes to the number of yes and no votes will be updated in the ListView control. Receiving the vote messages from the voting applications is done asynchronously, using a background worker thread. // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) { while (true) { // Receive a vote message from the queue BrokeredMessage msg = ScatterGatherQueueClient.Receive(); if (msg != null) { // Deserialize the message. Vote vote = msg.GetBody<Vote>(); // Update the results. foreach (Result result in Results) { if (result.Question.Equals(vote.QuestionText)) { if (vote.IsYes) { result.YesVotes++; } else { result.NoVotes++; } break; } } // Mark the message as complete. msg.Complete(); } } } When a vote message is received, the result that matches the vote question is updated with the vote from the user. The message is then marked as complete. A second background thread is used to update the display of subscriptions in the TreeView, with a dispatcher used to update the user interface. // This runs on a background worker. private void UpdateSubscriptions(object sender, DoWorkEventArgs e) { while (true) { // Get a list of subscriptions. IEnumerable<SubscriptionDescription> subscriptions = NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic); // Update the user interface. SimpleDelegate setQuestion = delegate() { trvSubscriptions.Items.Clear(); TreeViewItem topicItem = new TreeViewItem() { Header = AccountDetails.ScatterGatherTopic }; foreach (SubscriptionDescription subscription in subscriptions) { TreeViewItem subscriptionItem = new TreeViewItem() { Header = subscription.Name }; topicItem.Items.Add(subscriptionItem); } trvSubscriptions.Items.Add(topicItem); topicItem.ExpandSubtree(); }; this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion); Thread.Sleep(3000); } } Voting Application The voting application is implemented as another WPF application. This one is more basic, and allows the user to vote “Yes” or “No” for the questions sent by the poll manager application. The user interface for that application is shown below. When an instance of the voting application is created it will create a subscription in the questions topic using a GUID as the subscription name. The application can then receive copies of every question message that is sent to the topic. Clients for the new subscription and the votes queue are created, along with a background worker to receive the question messages. The voting application is set to receiving mode, meaning it is ready to receive a question message from the subscription. public MainWindow() { InitializeComponent(); // Set the mode to receiving. IsReceiving = true; // Create a token provider with the relevant credentials. TokenProvider credentials = TokenProvider.CreateSharedSecretTokenProvider (AccountDetails.Name, AccountDetails.Key); // Create a URI for the serivce bus. Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri ("sb", AccountDetails.Namespace, string.Empty); // Create the MessagingFactory MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials); // Create a subcription for this instance NamespaceManager mgr = new NamespaceManager(serviceBusUri, credentials); string subscriptionName = Guid.NewGuid().ToString(); mgr.CreateSubscription(AccountDetails.ScatterGatherTopic, subscriptionName); // Create the subscription and queue clients. ScatterGatherSubscriptionClient = factory.CreateSubscriptionClient (AccountDetails.ScatterGatherTopic, subscriptionName); ScatterGatherQueueClient = factory.CreateQueueClient(AccountDetails.ScatterGatherQueue); // Start the background worker thread. BackgroundWorker = new BackgroundWorker(); BackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages); BackgroundWorker.RunWorkerAsync(); } I took the inspiration for creating the subscriptions in the voting application from the chat application that uses topics and subscriptions blogged by Ovais Akhter here. The method that receives the question messages runs on a background thread. If the application is in receive mode, a question message will be received from the subscription, the question will be displayed in the user interface, the voting buttons enabled, and IsReceiving set to false to prevent more questing from being received before the current one is answered. // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) { while (true) { if (IsReceiving) { // Receive a question message from the topic. BrokeredMessage msg = ScatterGatherSubscriptionClient.Receive(); if (msg != null) { // Deserialize the message. Question question = msg.GetBody<Question>(); // Update the user interface. SimpleDelegate setQuestion = delegate() { lblQuestion.Content = question.QuestionText; btnYes.IsEnabled = true; btnNo.IsEnabled = true; }; this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion); IsReceiving = false; // Mark the message as complete. msg.Complete(); } } else { Thread.Sleep(1000); } } } When the user clicks on the Yes or No button, the btnVote_Click method is called. This will create a new Vote data contract with the appropriate question and answer and send the message to the poll manager application using the votes queue. The user voting buttons are then disabled, the question text cleared, and the IsReceiving flag set to true to allow a new message to be received. private void btnVote_Click(object sender, RoutedEventArgs e) { // Create a new vote. Vote vote = new Vote() { QuestionText = (string)lblQuestion.Content, IsYes = ((sender as Button).Content as string).Equals("Yes") }; // Send the vote message. BrokeredMessage msg = new BrokeredMessage(vote); ScatterGatherQueueClient.Send(msg); // Update the user interface. lblQuestion.Content = ""; btnYes.IsEnabled = false; btnNo.IsEnabled = false; IsReceiving = true; } Testing the Application In order to test the application, an instance of the poll manager application is started; the user interface is shown below. As no instances of the voting application have been created there are no subscriptions present in the topic. When an instance of the voting application is created the subscription will be displayed in the poll manager. Now that a voting application is subscribing, a questing can be sent from the poll manager application. When the message is sent to the topic, the voting application will receive the message and display the question. The voter can then answer the question by clicking on the appropriate button. The results of the vote are updated in the poll manager application. When two more instances of the voting application are created, the poll manager will display the new subscriptions. More questions can then be broadcast to the voting applications. As the question messages are queued up in the subscription for each voting application, the users can answer the questions in their own time. The vote messages will be received by the poll manager application and aggregated to display the results. The screenshots of the applications part way through voting are shown below. The messages for each voting application are queued up in sequence on the voting application subscriptions, allowing the questions to be answered at different speeds by the voters.

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Given an XML which contains a representation of a graph, how to apply it DFS algorithm? [on hold]

- by winston smith

Given the followin XML which is a directed graph: <?xml version="1.0" encoding="iso-8859-1" ?> <!DOCTYPE graph PUBLIC "-//FC//DTD red//EN" "../dtd/graph.dtd"> <graph direct="1"> <vertex label="V0"/> <vertex label="V1"/> <vertex label="V2"/> <vertex label="V3"/> <vertex label="V4"/> <vertex label="V5"/> <edge source="V0" target="V1" weight="1"/> <edge source="V0" target="V4" weight="1"/> <edge source="V5" target="V2" weight="1"/> <edge source="V5" target="V4" weight="1"/> <edge source="V1" target="V2" weight="1"/> <edge source="V1" target="V3" weight="1"/> <edge source="V1" target="V4" weight="1"/> <edge source="V2" target="V3" weight="1"/> </graph> With this classes i parsed the graph and give it an adjacency list representation: import java.io.IOException; import java.util.HashSet; import java.util.LinkedList; import java.util.Collection; import java.util.Iterator; import java.util.logging.Level; import java.util.logging.Logger; import practica3.util.Disc; public class ParsingXML { public static void main(String[] args) { try { // TODO code application logic here Collection<Vertex> sources = new HashSet<Vertex>(); LinkedList<String> lines = Disc.readFile("xml/directed.xml"); for (String lin : lines) { int i = Disc.find(lin, "source=\""); String data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } Vertex v = new Vertex(); v.setName(data); v.setAdy(new HashSet<Vertex>()); sources.add(v); } } Iterator it = sources.iterator(); while (it.hasNext()) { Vertex ver = (Vertex) it.next(); Collection<Vertex> adyacencias = ver.getAdy(); LinkedList<String> ls = Disc.readFile("xml/graphs.xml"); for (String lin : ls) { int i = Disc.find(lin, "target=\""); String data = ""; if (lin.contains("source=\""+ver.getName())) { Vertex v = new Vertex(); if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setName(data); } i = Disc.find(lin, "weight=\""); data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setWeight(Integer.parseInt(data)); } if (v.getName() != null) { adyacencias.add(v); } } } } for (Vertex vert : sources) { System.out.println(vert); System.out.println("adyacencias: " + vert.getAdy()); } } catch (IOException ex) { Logger.getLogger(ParsingXML.class.getName()).log(Level.SEVERE, null, ex); } } } This is another class: import java.util.Collection; import java.util.Objects; public class Vertex { private String name; private int weight; private Collection ady; public Collection getAdy() { return ady; } public void setAdy(Collection adyacencias) { this.ady = adyacencias; } public String getName() { return name; } public void setName(String nombre) { this.name = nombre; } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } @Override public int hashCode() { int hash = 7; hash = 43 * hash + Objects.hashCode(this.name); hash = 43 * hash + this.weight; return hash; } @Override public boolean equals(Object obj) { if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final Vertex other = (Vertex) obj; if (!Objects.equals(this.name, other.name)) { return false; } if (this.weight != other.weight) { return false; } return true; } @Override public String toString() { return "Vertice{" + "name=" + name + ", weight=" + weight + '}'; } } And finally: /** * * @author user */ /* -*-jde-*- */ /* <Disc.java> Contains the main argument*/ import java.io.*; import java.util.LinkedList; /** * Lectura y escritura de archivos en listas de cadenas * Ideal para el uso de las clases para gráficas. * * @author Peralta Santa Anna Victor Miguel * @since Julio 2011 */ public class Disc { /** * Metodo para lectura de un archivo * * @param fileName archivo que se va a leer * @return El archivo en representacion de lista de cadenas */ public static LinkedList<String> readFile(String fileName) throws IOException { BufferedReader file = new BufferedReader(new FileReader(fileName)); LinkedList<String> textlist = new LinkedList<String>(); while (file.ready()) { textlist.add(file.readLine().trim()); } file.close(); /* for(String linea:textlist){ if(linea.contains("source")){ //String generado = linea.replaceAll("<\\w+\\s+\"", ""); //System.out.println(generado); } }*/ return textlist; }//readFile public static int find(String linea,String palabra){ int i,j; boolean found = false; for(i=0,j=0;i<linea.length();i++){ if(linea.charAt(i)==palabra.charAt(j)){ j++; if(j==palabra.length()){ found = true; return i; } }else{ continue; } } if(!found){ i= -1; } return i; } /** * Metodo para la escritura de un archivo * * @param fileName archivo que se va a escribir * @param tofile la lista de cadenas que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String fileName, LinkedList<String> tofile, boolean append) throws IOException { FileWriter file = new FileWriter(fileName, append); for (int i = 0; i < tofile.size(); i++) { file.write(tofile.get(i) + "\n"); } file.close(); }//writeFile /** * Metodo para escritura de un archivo * @param msg archivo que se va a escribir * @param tofile la cadena que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String msg, String tofile, boolean append) throws IOException { FileWriter file = new FileWriter(msg, append); file.write(tofile); file.close(); }//writeFile }// I'm stuck on what can be the best way to given an adjacency list representation of the graph how to apply it Depth-first search algorithm. Any idea of how to aproach to complete the task?

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How to prevent a hacked-server from spoofing a master server?

- by Cody Smith

I wish to setup a room-based multilayer game model where players may host matches and serve as host (IE the server with authoritative power). I wish to host a master server which tracks player's items, rank, cash, exp, etc. In such a model, how can I prevent someone that is hosting a game (with a modified server) from spoofing the master server with invalid match results, thus gaining exp, money or rankings. Thanks. -Cody

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Can unit tests verify software requirements?

- by Peter Smith

I have often heard unit tests help programmers build confidence in their software. But is it enough for verifying that software requirements are met? I am losing confidence that software is working just because the unit tests pass. We have experienced some failures in production deployment due to an untested\unverified execution path. These failures are sometimes quite large, impact business operations and often requires an immediate fix. The failure is very rarely traced back to a failing unit test. We have large unit test bodies that have reasonable line coverage but almost all of these focus on individual classes and not on their interactions. Manual testing seems to be ineffective because the software being worked on is typically large with many execution paths and many integration points with other software. It is very painful to manually test all of the functionality and it never seems to flush out all the bugs. Are we doing unit testing wrong when it seems we still are failing to verify the software correctly before deployment? Or do most shops have another layer of automated testing in addition to unit tests?

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CQRS without using others patterns

- by John Smith

I would like to explain CQRS to my team of developers. I just can't figure out how to explain it in the simplest way so they can implement the pattern rapidly without any others frameworks. I've read a lot of resources including video and articles but I don't find how to implement CQRS without using others patterns like a service Bus, event sourcing pattern, domain driven design. I know the purpose of these pattern but for the first step, I don't want them to think CQRS and theses patterns must be tied together. My first idea is to say that CQRS is about separating the read part and the write part. The read part is composed only of the UI project, and DAL project. Then the write part is composed of a typical multilayer architecture: UI/BLL/DAL. Then, does CQRS say we must also have two datastore ? What about the notion of commands which reveal the user's intention, is it also something part of CQRS or DDD ? Basically, how to implement CQRS without using others patterns. I concede it's also not that clear in my mind because I've used to work with NCQRS/DDD/Event Sourcing/ServiceBus in my personal project. Thanks

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Separate shaders from HTML file in WebGL

- by Chris Smith

I'm ramping up on WebGL and was wondering what is the best way to specify my vertex and fragment shaders. Looking at some tutorials, the shaders are embedded directly in the HTML. (And referenced via an ID.) For example: <script id="shader_1-fs" type="x-shader/x-fragment"> precision highp float; void main(void) { // ... } </script> <script id="shader_1-vs" type="x-shader/x-vertex"> attribute vec3 aVertexPosition; uniform mat4 uMVMatrix; // ... My question is, is it possible to have my shaders referenced in a separate file? (Ideally as plain text.) I presume this is straight forward in JavaScript. Is there essentially a way to do this: var shaderText = LoadRemoteFileOnSever('/shaders/shader_1.txt');

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WebCenter Content (WCC) Trace Sections

- by Kevin Smith

Kyle has a good post on how to modify the size and number of WebCenter Content (WCC) trace files. His post reminded me I have been meaning to write a post on WCC trace sections for a while. searchcache - Tells you if you query was found in the WCC search cache. searchquery - Shows the processing of the query as it is converted form what the user submitted to the end query that will be sent to the database. Shows conversion from the universal query syntax to the syntax specific to the search solution WCC is configured to use. services (verbose) - Lists the filters that are called for each service. This will let you know what filters are available for each service and will also tell you what filters are used by WCC add-on components and any custom components you have installed. The How To Component Sample has a list of filters, but it has not been updated since 7.5, so it is a little outdated now. With each new release WCC adds more filters. If you have a filter that has no code attached to it you will see output like this: services/6 09.25 06:40:26.270 IdcServer-423 Called filter event computeDocName with no filter plugins registered When a WCC add-on or custom component uses a filter you will see trace output like this: services/6 09.25 06:40:26.275 IdcServer-423 Calling filter event postValidateCheckinData on class collections.CollectionValidateCheckinData with parameter postValidateCheckinDataservices/6 09.25 06:40:26.275 IdcServer-423 Calling filter event postValidateCheckinData on class collections.CollectionFilters with parameter postValidateCheckinData As you can see from this sample output it is possible to have multiple code points using the same filter. systemdatabase - Dumps the database call AFTER it executes. This can be somewhat troublesome if you are trying to track down some weird database problems. We had a problem where WCC was getting into a deadlock situation. We turned on the systemdatabase trace section and thought we had the problem database call, but it turned out since it printed out the database call after it was executed we were looking at the database call BEFORE the one causing the deadlock. We ended up having to turn on tracing at the database level to see the database call WCC was making that was causing the deadlock. socketrequests (verbose) - dumps the actual messages received and sent over the socket connection by WCC for a service. If you have gzip enabled you will see junk on the response coming back from WCC. For debugging disable the gzip of the WCC response.Here is an example of the dump of the request for a GET_SEARCH_RESULTS service call. socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: REMOTE_USER=sysadmin.USER-AGENT=Java;.Stel socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: lent.CIS.11g.CONTENT_TYPE=text/html.HEADER socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: _ENCODING=UTF-8.REQUEST_METHOD=POST.CONTEN socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: T_LENGTH=270.HTTP_HOST=CIS.$$$$.NoHttpHead socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: ers=0.IsJava=1.IdcService=GET_SEARCH_RESUL socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: [email protected] socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: calData.SortField=dDocName.ClientEncoding= socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: UTF-8.IdcService=GET_SEARCH_RESULTS.UserTi socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: meZone=UTC.UserDateFormat=iso8601.SortDesc socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: =ASC.QueryText=dDocType..matches..`Documen socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: t`.@end. userstorage, jps - Provides trace details for user authentication and authorization. Includes information on the determination of what roles and accounts a user has access to. In 11g a new trace section, jps, was added with the addition of the JpsUserProvider to communicate with WebLogic Server. The WCC developers decide when to use the verbose option for their trace output, so sometime you need to try verbose to see what different information you get. One of the things I would always have liked to see if the ability to turn on verbose output selectively for individual trace sections. When you turn on verbose output you get it for all trace sections you have enabled. This can quickly fill up your trace files with a lot of information if you have the socket trace section turned on.

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OS X Mavericks Won't Connect To Ubuntu Server (Netatalk, Avahi)

- by Andy Ibanez

I'm really sorry for posting this. I know it may have been asked a thousand times. I have googled like crazy and I'm on the verge of desperation here. Basically, I followed this guide: http://motionsoundfx.com/2012/05/ubuntu-vnc-afp-macosx/ To create a small personal file server. When I installed it, I was able to connect to it just fine, I connected with my Ubuntu username and password and I was able to see the home directory. But later, I had to restart the file server so I could prepare a couple of other hard drives to put in. When the server restarted, I tried to connect to it, but I got an error message on my Mac: "The version of the server you're trying to connect to is not supported. Please contact your system administrator to solve this problem." Again, I have googled like crazy for this, and everybody says it is a problem with OS X Lion and up (assuming it affects Mavericks too). I have tried all the fixes mentioned for Lion and Mountain Lion and I haven't had any luck. That's the reason I'm posting this here: I suspect the problem is with my Ubuntu server. This happened after I restarted the server. Before restarting the server, I just put in my credentials and saw my home directory. Something when I restarted the server must have been messed up. I have found some other solutions, including to use "SHX2" in the conf file, but it hasn't worked for me. I ask for your help to solve this issue. Also please understand I'm completely illiterate when it comes to Linux. This is a nice chance to me to learn the OS so please give me detailed steps to do things if you deem it necessary. Thank you! I'm using Ubuntu Server 13.10 (the latest one as of today).

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How best do you represent a bi-directional sync in a REST api?

- by Edward M Smith

Assuming a system where there's a Web Application with a resource, and a reference to a remote application with another similar resource, how do you represent a bi-directional sync action which synchronizes the 'local' resource with the 'remote' resource? Example: I have an API that represents a todo list. GET/POST/PUT/DELETE /todos/, etc. That API can reference remote TODO services. GET/POST/PUT/DELETE /todo_services/, etc. I can manipulate todos from the remote service through my API as a proxy via GET/POST/PUT/DELETE /todo_services/abc123/, etc. I want the ability to do a bi-directional sync between a local set of todos and the remote set of TODOS. In a rpc sort of way, one could do POST /todo_services/abc123/sync/ But, in the "verbs are bad" idea, is there a better way to represent this action?

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Is there any reason not to go directly from client-side Javascript to a database?

- by Chris Smith

So, let's say I'm going to build a Stack Exchange clone and I decide to use something like CouchDB as my backend store. If I use their built-in authentication and database-level authorization, is there any reason not to allow the client-side Javascript to write directly to the publicly available CouchDB server? Since this is basically a CRUD application and the business logic consists of "Only the author can edit their post" I don't see much of a need to have a layer between the client-side stuff and the database. I would simply use validation on the CouchDB side to make sure someone isn't putting in garbage data and make sure that permissions are set properly so that users can only read their own _user data. The rendering would be done client-side by something like AngularJS. In essence you could just have a CouchDB server and a bunch of "static" pages and you're good to go. You wouldn't need any kind of server-side processing, just something that could serve up the HTML pages. Opening my database up to the world seems wrong, but in this scenario I can't think of why as long as permissions are set properly. It goes against my instinct as a web developer, but I can't think of a good reason. So, why is this a bad idea? EDIT: Looks like there is a similar discussion here: Writing Web "server less" applications EDIT: Awesome discussion so far, and I appreciate everyone's feedback! I feel like I should add a few generic assumptions instead of calling out CouchDB and AngularJS specifically. So let's assume that: The database can authenticate users directly from its hidden store All database communication would happen over SSL Data validation can (but maybe shouldn't?) be handled by the database The only authorization we care about other than admin functions is someone only being allowed to edit their own post We're perfectly fine with everyone being able to read all data (EXCEPT user records which may contain password hashes) Administrative functions would be restricted by database authorization No one can add themselves to an administrator role The database is relatively easy to scale There is little to no true business logic; this is a basic CRUD app

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