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  • How to write PowerShell code part 2 (Using function)

    - by ybbest
    In the last post, I have showed you how to use external configuration file in your PowerShell script. In this post, I will show you how to create PowerShell function and call external PowerShell script.You can download the script here. 1. In the original script, I create the site directly using New-SPSite command. I will refactor it so that I will create a new function to create the site using New-SPSite. The PowerShell function is quite similar to a C# method. You put your function parameters in () and separate each parameter by a comma (,). Then you put your method body in {}. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } 2. The difference is you do not need semi-colon (;) at the end of each statement and when calling the method you do not need comma (,) to separate each parameter. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } #Calling the function [int] $num1=3 [int] $num2=4 $d= add $num1 $num2 Write-Host $d 3. If you like to return anything from the function, you just need to type in the object you like to return, not need to type return .e.g. $ObjectToReturn not return $ObjectToReturn

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  • How to write regex in asp.net MVC 3 razor

    - by anirudha
    here is a small trick to write regex and exceptional code in MVC3. first trick is use @@ instead of @ it’s work don’ worry output goes @ not @@. second trick is that you can use <text></text> tag in MVC to use some code who give error because viewengine does not accept them. like var pattern = new RegExp(/^(("[\w-\s]+")|([\w-]+(?:\.[\w-]+)*)|("[\w-\s]+")([\w-]+(?:\.[\w-]+)*))(@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$)|(@\[?((25[0-5]\.|2[0-4][0-9]\.|1[0-9]{2}\.|[0-9]{1,2}\.))((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\.){2}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\]?$)/i);   this regex not work because it’s use @ so replace them to @@ e var pattern = new RegExp(/^(("[\w-\s]+")|([\w-]+(?:\.[\w-]+)*)|("[\w-\s]+")([\w-]+(?:\.[\w-]+)*))(@@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$)|(@@\[?((25[0-5]\.|2[0-4][0-9]\.|1[0-9]{2}\.|[0-9]{1,2}\.))((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\.){2}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\]?$)/i); now it will work. second way is that use text tag in MVC to make them work like <text> function isValidEmailAddress(emailAddress) { var pattern = new RegExp(/^(("[\w-\s]+")|([\w-]+(?:\.[\w-]+)*)|("[\w-\s]+")([\w-]+(?:\.[\w-]+)*))(@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$)|(@\[?((25[0-5]\.|2[0-4][0-9]\.|1[0-9]{2}\.|[0-9]{1,2}\.))((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\.){2}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\]?$)/i); return pattern.test(emailAddress); } </text>

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  • How to write PowerShell code part 3 (calling external script)

    - by ybbest
    In this post, I’d like to show you how to calling external script from a PowerShell script. I’d like to use the site creation script as an example. You can download script here. 1. To call the external script, you need to first to grab the script path. You can do so by calling $scriptPath = Split-Path $myInvocation.MyCommand.Path to grab the current script path. You can then use this to build the path for your external script path. $scriptPath = Split-Path $myInvocation.MyCommand.Path $ExternalScript=$scriptPath+"\CreateSiteCollection.ps1" $configurationXmlPath=$scriptPath+"\SiteCollection.xml" [xml] $configurationXml=Get-Content $configurationXmlPath & "$ExternalScript" $configurationXml Write-Host 2.If you like to pass in any parameters , you need to define your script parameters in param () at the top of the script and separate each parameter by a comma (,) and when calling the method you do not need comma (,) to separate each parameter. #Pass in the Parameters. param ([xml] $xmlinput)

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  • Using Queries with Coherence Write-Behind Caches

    - by jpurdy
    Applications that use write-behind caching and wish to query the logical entity set have the option of querying the NamedCache itself or querying the database. In the former case, no particular restrictions exist beyond the limitations intrinsic to the Coherence query engine itself. In the latter case, queries may see partially committed transactions (e.g. with a parent-child relationship, the version of the parent may be different than the version of the child objects) and/or significant version skew (the query may see the current version of one object and a far older version of another object). This is consistent with "read committed" semantics, but the read skew may be far greater than would ever occur in a non-cached environment. As is usually the case, the application developer may choose to accept these limitations (with the hope that they are sufficiently infrequent), or they may choose to validate the reads (perhaps via a version flag on the objects). This also applies to situations where a third party application (such as a reporting tool) is querying the database. In many cases, the database may only be in a consistent state after the Coherence cluster has been halted.

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  • How can I go about learning to write a shader

    - by Donutz
    So here's the background: I'm writing a game, just for my own amusement and education really. I've already come to the conclusion that XNA was the way to go for graphics, I've bought a couple of books, I've gotten basic game graphics going, and that's great. Now I'm starting to get a little in-depth and I'm starting to need to do stuff not covered in my (beginner) books. In particular, I need to display a sprite using a mask. Actually, what I need to do is display a generic sprite with a different color for each player. After banging around on the web, it seems the way to go is to have a color texture (one for each player) which I display using the mask, then display the generic part of the sprite. This has to be done dynamically, i.e. at runtime because there are too many sprites to keep in memory if I try to generate all the permutations at startup. So, I need to use a shader. Fine. I've downloaded a sample shader program, and managed to hit it with a hammer until it does something close enough to what I want so that I know I'm on the right track. And here, we come to my problem... I have no friggin' clue what I'm doing. While there are a lot of samples and such about shaders, no one ever actually explains what's going on. For instance, I can't find any real docs on Tex2D. I feel like the guys in Zoolander poking at the computer. So, my question (yes, I have a question) -- where is a good URL or what is a good book to take me from dumskie to reasonably competent to write a basic shader?

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  • input / output error, drives randomly refusing to read / write

    - by ILMV
    I have an issue with one of our servers running Ubuntu 10.04, it is running BackupPC and collects backups from various machines / servers around the building. On the 8th minute (12:08, 12:18, 12:28 etc) the backups are transferred to an external hard drive, we have three and rotate one drive for another everyday. The problem we are having is we are randomly experiencing input / output errors, when this happens you cannot read / write to the drive, it hasn't unmounted so I can cd to the mount point /media/backup1. The drives are not faulty as it's happening on all of them, so I'm at a loss as to what the problem could be, here is an example of the many errors we get: gzip: stdout: Input/output error /var/lib/backuppc/backuppc_offline: line 47: /media/backup1/Tue/offline.log: Input/output error ls: cannot access /media/backup1/Tue/incr_1083_host1.something.co.uk.tar.gz: Input/output error ls: cannot access /media/backup1/Tue/incr_1088_host1.something.co.uk.tar.gz: Input/output error ls: cannot access /media/backup1/Tue/incr_1089_host1.something.co.uk.tar.gz: Input/output error ls: cannot access /media/backup1/Tue/incr_1090_host1.something.co.uk.tar.gz: Input/output error /var/lib/backuppc/backuppc_offline: line 39: /media/backup1/Tue/offline.log: Input/output error /var/lib/backuppc/backuppc_offline: line 44: /media/backup1/Tue/offline.log: Input/output error /var/lib/backuppc/backuppc_offline: line 45: /media/backup1/Tue/incr_1090_host1.something.co.uk.tar.gz: Input/output error /var/lib/backuppc/backuppc_offline: line 47: /media/backup1/Tue/offline.log: Input/output error ls: cannot access /media/backup1/Tue/incr_591_tech2.something.co.uk.tar.gz: Input/output error /var/lib/backuppc/backuppc_offline: line 44: /media/backup1/Tue/offline.log: Input/output error /var/lib/backuppc/backuppc_offline: line 45: /media/backup1/Tue/incr_591_tech2.something.co.uk.tar.gz: Input/output error /var/lib/backuppc/backuppc_offline: line 47: /media/backup1/Tue/offline.log: Input/output error ls: cannot access /media/backup1/Tue/incr_592_tech3.something.co.uk.tar.gz: Input/output error ls: cannot access /media/backup1/Tue/incr_593_tech3.something.co.uk.tar.gz: Input/output error /var/lib/backuppc/backuppc_offline: line 44: /media/backup1/Tue/offline.log: Input/output error /var/lib/backuppc/backuppc_offline: line 45: /media/backup1/Tue/incr_593_tech3.something.co.uk.tar.gz: Input/output error /var/lib/backuppc/backuppc_offline: line 47: /media/backup1/Tue/offline.log: Input/output error EDIT » Resolved So it turns out Quamis was right, even though I didn't think it was possible it was actually a problem with the drive. You see we have three drives all formatted to ext2, on two of them we were getting I/O errors frequently, I cam back to Quamis' answer and discovered the fsck command, so ran it against the problems drives: fsck /dev/sdb1 This found and fixed a load of problems on the drive, most probably caused by power outages / unsafe removal of drives etc, as the drives are in the xt2 format they aren't journalled and thus aren't protected against such issues. Drives are now working beautifully, thanks all! :D

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  • Need help troubleshooting why Solr wont start (or why solr admin page wont show)

    - by Camran
    I can't get Solr working. I have Jetty, and my server OS is Ubuntu 9.10. It is a VPS server. So, when I execute the java -jar start.jar everything seems fine. I even do a netstat to check if there are any listeners on the port before the start and after the start, and it seems solr is starting. However, I cant access the admin page. I have even turned off the firewall. Here is some info about my server: I have changed DocumentRoot to var/www/SV/ I have Apache2, PHP5, MySql installed I have "disabled" iptables firewall I have removed the htaccess files (I used them to passw protect my site under develop) I have installed JRE (NOT JDK) on my server. I use the "example" which comes with Solr, so I use Jetty as container on my Server. My Server has 768MB RAM Doing a java -version command shows this: java version "1.6.0_15" Java(TM) SE Runtime Environment (build 1.6.0_15-b03) Java HotSpot(TM) Client VM (build 14.1-b02, mixed mode) And in the terminal the last lines when executing start.jar is: May 29, 2010 1:30:03 PM org.apache.solr.core.SolrCore registerSearcher INFO: [] Registered new searcher Searcher@1dc64a5 main NOTE: Also before this last line, there is a line which makes me suspicious: Started SocketConnector @ 0.0.0.0:8983 // Should this be with leading zeros? Is there any ways you know to troubleshoot this? Memory issue maybe? Thanks

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  • Why and why not Coldfusion (CFML) ?

    - by zarko.susnjar
    When you speak to your colleagues or you want to convince your client to use Coldfusion for some new project and not some other technology or language they heard of before, which arguments do you use? I'm asking because I'd like to make presentation to put in my company's portfolio and seems that I can't find any real life, non development kind of arguments. Yes, cfquery and cffunction access="remote" make our lives easier, but client doesn't care too much about us, right?

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  • Is Stream.Write thread-safe?

    - by Mike Spross
    I'm working on a client/server library for a legacy RPC implementation and was running into issues where the client would sometimes hang when waiting to a receive a response message to an RPC request message. It turns out the real problem was in my message framing code (I wasn't handling message boundaries correctly when reading data off the underlying NetworkStream), but it also made me suspicious of the code I was using to send data across the network, specifically in the case where the RPC server sends a large amount of data to a client as the result of a client RPC request. My send code uses a BinaryWriter to write a complete "message" to the underlying NetworkStream. The RPC protocol also implements a heartbeat algorithm, where the RPC server sends out PING messages every 15 seconds. The pings are sent out by a separate thread, so, at least in theory, a ping can be sent while the server is in the middle of streaming a large response back to a client. Suppose I have a Send method as follows, where stream is a NetworkStream: public void Send(Message message) { //Write the message to a temporary stream so we can send it all-at-once MemoryStream tempStream = new MemoryStream(); message.WriteToStream(tempStream); //Write the serialized message to the stream. //The BinaryWriter is a little redundant in this //simplified example, but here because //the production code uses it. byte[] data = tempStream.ToArray(); BinaryWriter bw = new BinaryWriter(stream); bw.Write(data, 0, data.Length); bw.Flush(); } So the question I have is, is the call to bw.Write (and by implication the call to the underlying Stream's Write method) atomic? That is, if a lengthy Write is still in progress on the sending thread, and the heartbeat thread kicks in and sends a PING message, will that thread block until the original Write call finishes, or do I have to add explicit synchronization to the Send method to prevent the two Send calls from clobbering the stream?

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  • C system calls open / read / write / close problem.

    - by Andrei Ciobanu
    Hello, given the following code (it's supposed to write "hellowolrd" in a "helloworld" file, and then read the text): #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #define FNAME "helloworld" int main(){ int filedes, nbytes; char buf[128]; /* Creates a file */ if((filedes=open(FNAME, O_CREAT | O_EXCL | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR)) == -1){ write(2, "Error1\n", 7); } /* Writes hellow world to file */ if(write(filedes, FNAME, 10) != 10) write(2, "Error2\n", 7); /* Close file */ close(filedes); if((filedes = open(FNAME, O_RDONLY))==-1) write(2, "Error3\n", 7); /* Prints file contents on screen */ if((nbytes=read(filedes, buf, 128)) == -1) write(2, "Error4\n", 7); if(write(1, buf, nbytes) != nbytes) write(2, "Error5\n", 7); /* Close rile afte read */ close(filedes); return (0); } The first time i run the program, the output is: helloworld After that every time I to run the program, the output is: Error1 Error2 helloworld I don't understand why the text isn't appended, as I've specified the O_APPEND file. Is it because I've included O_CREAT ? It the file is already created, shouldn't O_CREAT be ignored ?

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  • Edit write-protected files by breaking hard links

    - by Taymon
    A directory which I own and can write to contains hard links to files that I don't own and don't have write permission for. I want to open and edit these files in Emacs. When I save my changes, Emacs should rename the existing hard link by appending ~, then write my new version of the file as a new file owned by me. I was under the impression that Emacs could just do this (because of the way it does backups), but it's not working; when I save, it attempts to change the file's permissions in order to write to it (and fails because I don't own the file). How do I make this happen?

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  • How to correctly write an installation or setup document

    - by UmNyobe
    I just joined a small start-up as a software engineer after graduation. The start-up is 4 year old, and I am working with the CEO and the COO, even if there are some people abroad. Basically they both used to do almost everything. I am currently on some kind of training phase. I have at my disposition architecture, setup and installation internal documentation. Architecture documentation is like a bible and should contain complete information. The rest are used to give directions in different processes. The issue is that these documents are more or less dated, as they just didn't have the time to change them. I will be in charge of training the next hires, and updating these documents is part of my training. In some there is a lot of hard-coded information like: Install this_module_which_still_exists cd this_dir_name_changed cp this_file_name_changed other_dir_name_changed ./config_script.sh ./execute_script.sh The issues i have faced : Either the module installation is completely different (for instance now there is an rpm, or a different OS) Either names changed, and i need to switch old names by new names Description of the purpose of the current step missing. Information about a whole topic is missing Fortunately these guys are around and I get all the information I want and all the explanations I need. I want to bring a design to the next documents so in the future people don't feel like they are completely rewriting a document each time they are updating it. Do you have suggestions? If there is a lightweight design methodology available online you can point me to it's nice too. One thing I will do for sure is set up a versioning repository for the documents alone. There is already one for the source code so I don't know why internal documents deserve a different treatment.

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  • Write TSQL, win a Kindle.

    - by Fatherjack
    So recently Red Gate launched sqlmonitormetrics.red-gate.com and showed the world how to embed your own scripts harmoniously in a third party tool to get the details that you want about your SQL Server performance. The site has a way to submit your own metrics and take a copy of the ones that other people have submitted to build a library of code to keep track of key metrics of your servers performance. There have been several submissions already but they have now launched a competition to provide an incentive for you to get creative and show us what you can do with a bit of TSQL and the SQL Monitor framework*. What’s it worth? Well, if you are one of the 3 winners then you get to choose either a Kindle Fire or $199. How do you win? Simply write the T-SQL for a SQL Monitor custom metric and the relevant description and introduction for it and submit it via  sqlmonitormetrics.red-gate.com before 14th Sept 2012 and then sit back and wait while the judges review your code and your aims in writing the metric. Who are the judges and how will they judge the metrics? There are two judges for this competition, Steve Jones (Microsoft SQL Server MVP, co-founder of SQLServerCentral.com, author, blogger etc) and Jonathan Allen (um, yeah, Steve has done all the good stuff, I’m here by good fortune). We will be looking to rate the metrics on each of 3 criteria: how the metric can help with performance tuning SQL Server. how having the metric running enables DBA’s to meet best practice. how interesting /original the idea for the metric is. Our combined decision will be final etc etc **  What happens to my metric? Any metrics submitted to the competition will be automatically entered into the site library and become available for sharing once the competition is over. You’ll get full credit for metrics you submit regardless of the competition results. You can enter as many metrics as you like. How long does it take? Honestly? Once you have the T-SQL sorted then so long as you can type your name and your email address you are done : http://sqlmonitormetrics.red-gate.com/share-a-metric/ What can I monitor? If you really really want a Kindle or $199 (and let’s face it, who doesn’t? ) and are momentarily stuck for inspiration, take a look at these example custom metrics that have been written by Stuart Ainsworth, Fabiano Amorim, TJay Belt, Louis Davidson, Grant Fritchey, Brad McGehee and me  to start the library off. There are some great pieces of TSQL in those metrics gathering important stats about how SQL Server is performing.   * – framework may not be the best word here but I was under pressure and couldnt think of a better one. If you prefer try ‘engine’, or ‘application’? I don’t know, pick something that makes sense to you. ** – for the full (legal) version of the rules check the details on sqlmonitormetrics.red-gate.com or send us an email if you want any point clarified. Disclaimer – Jonathan is a Friend of Red Gate and as such, whenever they are discussed, will have a generally positive disposition towards Red Gate tools. Other tools are often available and you should always try others before you come back and buy the Red Gate ones. All code in this blog is provided “as is” and no guarantee, warranty or accuracy is applicable or inferred, run the code on a test server and be sure to understand it before you run it on a server that means a lot to you or your manager.

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  • How to write simple code using TDD [migrated]

    - by adeel41
    Me and my colleagues do a small TDD-Kata practice everyday for 30 minutes. For reference this is the link for the excercise http://osherove.com/tdd-kata-1/ The objective is to write better code using TDD. This is my code which I've written public class Calculator { public int Add( string numbers ) { const string commaSeparator = ","; int result = 0; if ( !String.IsNullOrEmpty( numbers ) ) result = numbers.Contains( commaSeparator ) ? AddMultipleNumbers( GetNumbers( commaSeparator, numbers ) ) : ConvertToNumber( numbers ); return result; } private int AddMultipleNumbers( IEnumerable getNumbers ) { return getNumbers.Sum(); } private IEnumerable GetNumbers( string separator, string numbers ) { var allNumbers = numbers .Replace( "\n", separator ) .Split( new string[] { separator }, StringSplitOptions.RemoveEmptyEntries ); return allNumbers.Select( ConvertToNumber ); } private int ConvertToNumber( string number ) { return Convert.ToInt32( number ); } } and the tests for this class are [TestFixture] public class CalculatorTests { private int ArrangeAct( string numbers ) { var calculator = new Calculator(); return calculator.Add( numbers ); } [Test] public void Add_WhenEmptyString_Returns0() { Assert.AreEqual( 0, ArrangeAct( String.Empty ) ); } [Test] [Sequential] public void Add_When1Number_ReturnNumber( [Values( "1", "56" )] string number, [Values( 1, 56 )] int expected ) { Assert.AreEqual( expected, ArrangeAct( number ) ); } [Test] public void Add_When2Numbers_AddThem() { Assert.AreEqual( 3, ArrangeAct( "1,2" ) ); } [Test] public void Add_WhenMoreThan2Numbers_AddThemAll() { Assert.AreEqual( 6, ArrangeAct( "1,2,3" ) ); } [Test] public void Add_SeparatorIsNewLine_AddThem() { Assert.AreEqual( 6, ArrangeAct( @"1 2,3" ) ); } } Now I'll paste code which they have written public class StringCalculator { private const char Separator = ','; public int Add( string numbers ) { const int defaultValue = 0; if ( ShouldReturnDefaultValue( numbers ) ) return defaultValue; return ConvertNumbers( numbers ); } private int ConvertNumbers( string numbers ) { var numberParts = GetNumberParts( numbers ); return numberParts.Select( ConvertSingleNumber ).Sum(); } private string[] GetNumberParts( string numbers ) { return numbers.Split( Separator ); } private int ConvertSingleNumber( string numbers ) { return Convert.ToInt32( numbers ); } private bool ShouldReturnDefaultValue( string numbers ) { return String.IsNullOrEmpty( numbers ); } } and the tests [TestFixture] public class StringCalculatorTests { [Test] public void Add_EmptyString_Returns0() { ArrangeActAndAssert( String.Empty, 0 ); } [Test] [TestCase( "1", 1 )] [TestCase( "2", 2 )] public void Add_WithOneNumber_ReturnsThatNumber( string numberText, int expected ) { ArrangeActAndAssert( numberText, expected ); } [Test] [TestCase( "1,2", 3 )] [TestCase( "3,4", 7 )] public void Add_WithTwoNumbers_ReturnsSum( string numbers, int expected ) { ArrangeActAndAssert( numbers, expected ); } [Test] public void Add_WithThreeNumbers_ReturnsSum() { ArrangeActAndAssert( "1,2,3", 6 ); } private void ArrangeActAndAssert( string numbers, int expected ) { var calculator = new StringCalculator(); var result = calculator.Add( numbers ); Assert.AreEqual( expected, result ); } } Now the question is which one is better? My point here is that we do not need so many small methods initially because StringCalculator has no sub classes and secondly the code itself is so simple that we don't need to break it up too much that it gets confusing after having so many small methods. Their point is that code should read like english and also its better if they can break it up earlier than doing refactoring later and third when they will do refactoring it would be much easier to move these methods quite easily into separate classes. My point of view against is that we never made a decision that code is difficult to understand so why we are breaking it up so early. So I need a third person's opinion to understand which option is much better.

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  • Why are you doing this? [closed]

    - by NIcholas Lawson
    I am working on a story that I am going to be querying to several magazines in my hometown about this work that is being done by the AXR group. This is a group of people who have networked online and are working on developing a higher level syntax structure than CSS and HTML currently offer. I am covering this is as a story because I see potential in this as a human interest story in cosmopolitan society. I have been asked by the group to pose this question to you and would appreciate any and all comments you would have on the following ... To AXR: So when does the internet become finished? At what point does a computer scientist say to himself ... my job here is finished ... the internet is complete? When is the internet ready to be more about the display of content than the uploading of new websites or computer tech? You are embarking on upon a sixty year project every day you work with this internet, what drives you? Why are you spending your hard earned hours working on the code to this computer? I spend thirty hours a week online because I love the writing and I know what would make the internet better ... ease of use ... i know it is difficult to program but I see some very elegant solutions online ... in this early inception phase of your programming development for this HSS prototype ... I would like to know why I do not see you programmers asking questions such as ... What would make the end user's life the easiest when using this code? I know you can solve the problem but an evolution forward would be simple, not simple to a computer scientist but simple to use for a career janitor ... if you could solve the problem of alleviating the stress at using a the computer you could get better content out of the computer ... right now the main problem is that the best content is in the hands of the people least likely to use the computer and the more simple you make the computer to use ... the better the content collection will be in the long run ... That is not what I want to talk about though ... why are you writing code when you could be writing stories? I know the computer is worthless without content so I build content, I know the book is worthless without the combinations of words in them, i know the television is worthless without the television news anchor or the actor, what I want to know from you folks in a very journalistic sense is why are you even bothering to bother to write code for a machine that has only made our lives i would dare say less interesting. why are you feeding the beast your time when you could be writing stories or being an actor or musician or auto mechanic ... why code? why this machine? what do you love about it? what do you hate about it? what do you wonder about it? I want to know so that starting out I know how to further shape my questions with axr ... i want the full story ... i want the real answers ... and i want to know why you are doing this, it would make for great writing if you could elucidate on this point.

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  • Learnings from trying to write better software: Loud errors from the very start

    - by theo.spears
    Microsoft made a very small number of backwards incompatible changes between .NET 1.1 and 2.0, because they wanted to make it as easy and safe as possible to port applications to the new runtime. (Here’s a list.) However, one thing they did change was what happens when a background thread fails with an unhanded exception - in .NET 1.1 nothing happened, the thread terminated, and the application continued oblivious. Try the same trick in .NET 2.0 and the entire application, including all threads, will rudely terminate. There are three reasons for this. Firstly if a background thread has crashed, it may have left the entire application in an inconsistent state, in a way that will affect other threads. It’s better to terminate the entire application than continue and have the application perform actions based on a broken state, for example take customer orders, or write corrupt files to disk.  Secondly, during software development, it is far better for errors to be loud and obtrusive. Even if you have unit tests and integration tests (and you should), a key part of ensuring software works properly is to actually try using it, both through systematic testing and through the casual use all software gets by its developers during use. Subtle errors are easy to miss if you are not actually doing real work using the application, loud errors are obvious. Thirdly, and most importantly, even if catching and swallowing exceptions indiscriminately doesn't cause any problems in your application, the presence of unexpected exceptions shows you do not fully understand the behavior of your code. The currently released version of your application may be absolutely correct. However, because your mental model of the behavior is wrong, any future change you make to the program could and probably will introduce critical errors.  This applies to more than just exceptions causing threads to exit, any unexpected state should make the application blow up in an un-ignorable way. The worst thing you can do is silently swallow errors and continue. And let's be clear, writing to a log file does not count as blowing up in an un-ignorable way.  This is all simple as long as the call stack only contains your code, but when your functions start to be called by third party or .NET framework code, it's surprisingly easy for exceptions to start vanishing. Let's look at two examples.   1. Windows forms drag drop events  Usually if you throw an exception from a winforms event handler it will bring up the "application has crashed" dialog with abort and continue options. This is a good default behavior - the error is big and loud, but it is possible for the user to ignore the error and hopefully save their data, if somehow this bug makes it past testing. However drag and drop are different - throw an exception from one of these and it will just be silently swallowed with no explanation.  By the way, it's not just drag and drop events. Timer events do it too.  You can research how exceptions are treated in different handlers and code appropriately, but the safest and most user friendly approach is to always catch exceptions in your event handlers and show your own error message. I'll talk about one good approach to handling these exceptions at the end of this post.   2. SSMS integration for SQL Tab Magic  A while back wrote an SSMS add-in called SQL Tab Magic (learn more about the process here). It works by listening to certain SSMS events and remembering what documents are opened and closed. I deployed it internally and it was used for a few months by a number of people without problems, so I was reasonably confident in its quality. Before releasing I made a few cleanups, including introducing error reporting. Bam. A few days later I was looking at over 1,000 error reports in my inbox. In turns out I wasn't handling table designers properly. The exceptions were there, but again SSMS was helpfully swallowing them all for me, so I was blissfully unaware. Had I made my errors loud from the start, I would have noticed these issues long before and fixed them.   Handling exceptions  Now you are systematically catching exceptions throughout your application, you need to do something with them. I've tried 3 options: log them, alert the user, and automatically send them home.  There are a few good options for logging in .NET. The most widespread is Apache log4net, which provides a very capable and configurable logging framework. There is also NLog which has a compatible interface, with a greater emphasis on fluent rather than XML configuration.  Alerting the user serves two purposes. Firstly it means they understand their action has failed to they don't just assume it worked (Silent file copy failure is a problem if you then delete the originals) or that they should keep waiting for a background task to complete. Secondly, it means the users can report the bug to your support team, and then you can fix it. This means the message you show the user should contain the information you need as a developer to identify and fix it. And the user will probably just send you a screenshot of the dialog, so it shouldn't be hidden by scroll bars.  This leads us to the third option, automatically sending error reports home. By automatic I mean with minimal effort on the part of the user, rather than doing it silently behind their backs. The advantage of this is you can send back far more detailed and precise information than you can expect a user to include in an email, and by making it easier to report errors, you make it more likely users will do so.  We do this using a great tool called SmartAssembly (full disclosure: this is a product made by Red Gate). It captures complete stack traces including the values of all local variables and then allows the user to send all this information back with a single click. We also capture log files to help understand what lead up to the error. We then use the free SmartAssembly Sync for Jira to dedupe these reports and raise them as bugs in our bug tracking system.  The combined effect of loud errors during development and then automatic error reporting once software is deployed allows us to find and fix more bugs, correct misunderstandings on how our software works, and overall is a key piece in delivering higher quality software. However it is no substitute for having motivated cunning testers in the building - and we're looking to hire more of those too.   If you found this post interesting you should follow me on twitter.  

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  • Linux - Programmatically write to a proc file

    - by Zach
    I have found several examples online where we can create a proc file, assign read and write methods that are called every time the proc file is opened for read or written to. However, I can't seem to find any documentation on how to programatically write to a proc file. Ideally, I would like to add a timestamp with other user details every time the proc file is opened for read or for write. Again, I've found where I can add the read and write functions that are triggered when the proc file is opened, but I can't find documentation on how to actually write to a proc file programatically. This would be different from a regular IO read/write, correct?

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  • IRP_MJ_WRITE latency up to 15 seconds

    - by racitup
    We have written an application that performs small (22kB) writes to multiple files at once (one thread performing asynchronous queued writes to multiple locations on behalf of other threads) on the same local volume (RAID1). 99.9% of the writes are low-latency but occasionally (maybe every minute or two) we get one or two huge latency writes (I have seen 10 seconds and above) without any real explanation. Platform: Win2003 Server with NTFS. Monitoring: Sysinternals Process Monitor (see link below) and our own application logging. We have tried multiple things to try and solve this that have been gleaned from a few websites, e.g.: Making the first part of file names unique to aid 8.3 name generation Writing files to multiple directories Changing Intel Disk Write Caching Windows File/Printer Sharing Minimize memory used Balance Maximize data throughput for file sharing Maximize data throughput for network applications System-Advanced-Performance-Advanced NtfsDisableLastAccessUpdate - use fsutil behavior set disablelastaccess 1 disable 8.3 name generation - use "fsutil behavior set disable8dot3 1" + restart Enable a large size file system cache Disable paging of the kernel code IO Page Lock Limit Turn Off (or On) the Indexing Service But nothing seems to make much difference. There's a whole host of things we haven't tried yet but we wondered if anyone had come across the same problem, a reason and a solution (programmatic or not)? We can reproduce the problem using IOMeter and a simple setup: Start IOMeter and remove all but the first worker thread in 'Topology' using the disconnect button. Select the Worker thread and put a cross in the box next to the disk you want to use in the Disk Targets tab and put '2000000' in Maximum Disk Size (NOTE: must have at least 1GB free space; sector size is 512 bytes) Next create a new access specification and add it to the worker thread: Transfer Request Size = 22kB 100% Sequential Percent of Access Spec = 100% Percent Read/Write = 100% Write Change Results Display Update Frequency to 5 seconds, Test Setup Run Time to 20 seconds and both 'Number of Workers to Spawn Automatically' settings to zero. Select the Worker Thread in the Topology panel and hit the Duplicate Worker button 59 times to create 60 threads with identical settings. Hit the 'Go' button (green flag) and monitor the Results tab. The 'Maximum I/O Response Time (ms)' always hits at least 3500 on our machine. Our machine isn't exactly slow (Xeon 8 core rack server with 4GB and onboard RAID). I'd be interested to see what other people get. We have a feeling it might be something to do with the NTFS filesystem (ours is currently 75% full of fragmented files) and we are going to try a few things around this principle. But it is also related to disk performance since we don't see it on a RAMDisk and it's not as severe on a RAID10 array. Any help is much appreciated. Richard Right-click and select 'Open Link in New Tab': ProcMon Result

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  • Benefits of a RAID BBU in addition to a double UPS + PS system

    - by Wikser
    Today I roughly measured the benefits of enabling write-back on the RAID controller on a server at work. It got no RAID battery-backup-unit (BBU) so the write-cache is currently disabled. As the server is not used to capacity (by far), the results in most test were spectacular, e.g.: Database CRUD: before 35s, after 4s Saving a 1MB Excel file: before: 20s (!), after: 0.5s Of course having a BBU is always recommended, but what are the main benefits of installing a BBU to a system, which got redundant power supplies and is attached to UPSs? Does this depend on the type of the system (database, file, terminal)? What is a realistic fail scenario which could be prevented by a BBU? Thanks in advance!

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  • writting becomes slow after few writes

    - by user1566277
    I am running an embedded Linux on arm with a SD-Card. While writing huge amounts of data I see bizarre effects. E.g, when I dd a 15 MB file few times, it writes the file (normally) in less than 2 Secs. But After lets say 3-4 times it takes sometimes 15 to 30 Seconds to write the same file. If I sync after writing the file, then this does not happen but sync takes long time too. If there is enough gap between writing two files than presumably kernel syncs itself. How can I optimize the whole performance so that write should always finish inside 2 Seconds. The File system I am using is ext3. Any pointers?

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  • pthreads: reader/writer locks, upgrading read lock to write lock

    - by ScaryAardvark
    I'm using read/write locks on Linux and I've found that trying to upgrade a read locked object to a write lock deadlocks. i.e. // acquire the read lock in thread 1. pthread_rwlock_rdlock( &lock ); // make a decision to upgrade the lock in threads 1. pthread_rwlock_wrlock( &lock ); // this deadlocks as already hold read lock. I've read the man page and it's quite specific. The calling thread may deadlock if at the time the call is made it holds the read-write lock (whether a read or write lock). What is the best way to upgrade a read lock to a write lock in these circumstances.. I don't want to introduce a race on the variable I'm protecting. Presumably I can create another mutex to encompass the releasing of the read lock and the acquiring of the write lock but then I don't really see the use of read/write locks. I might as well simply use a normal mutex. Thx

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  • pthreads: reader/writer locks, upgrading read lock to write lock

    - by ScaryAardvark
    I'm using read/write locks on Linux and I've found that trying to upgrade a read locked object to a write lock deadlocks. i.e. // acquire the read lock in thread 1. pthread_rwlock_rdlock( &lock ); // make a decision to upgrade the lock in threads 1. pthread_rwlock_wrlock( &lock ); // this deadlocks as already hold read lock. I've read the man page and it's quite specific. The calling thread may deadlock if at the time the call is made it holds the read-write lock (whether a read or write lock). What is the best way to upgrade a read lock to a write lock in these circumstances.. I don't want to introduce a race on the variable I'm protecting. Presumably I can create another mutex to encompass the releasing of the read lock and the acquiring of the write lock but then I don't really see the use of read/write locks. I might as well simply use a normal mutex. Thx

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  • How to override JS function from a firefox extension?

    - by BruceBerry
    Hello, I am trying to intercept calls to document.write for all pages. Setting up the interception inside the page by injecting a script like function overrideDocWrite() { alert("Override called"); document.write = function(w) { return function(s) { alert("special dom"); w.call(this, wrapString(s)); }; }(document.write); alert("Override finished"); } is easy and works, but i would like my extension to setup the interception for each document object from inside the extension. I couldn't find a way to do this. I tried to listen for the "load" event and set up the interception there but it also fails. How do I hook calls to doc.write from an extension?

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  • how to Retrieve the parameters of document.write to detect the creation of dynamic tags

    - by user1335906
    In my Project i am supposed to identify the dynamically created tags which can be done in scripts through document.write("<script src='jquery.js'></script>") For this i used Regular expressions and my code is as follows function find_tag_docwrite(text) { var attrib=new Object; var pat_tag=/<((\S+)\s(.*))>/g; while(t=pat_tag.exec(text) { var tag=RegExp.$1; for(i=0;i<tags.length;i++) { var pat=/(\S+)=((['"]*)(\S+)(['"]*)\3)/g; while(p=pat.exec(f)) { attr=RegExp.$1;val=RegExp.$4; attrib[attr]=val; } } } } in the above function text is parameters of document.write function. Now through this code i am getting the tag names and all the attributes of the tags. But for the below example the above code is not working var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); In such cases Regular expressions does not work so after searching some time where i found hooks on dom methods. so by using this i thought of creating hook for document.write method but i am able to understand how it is done i included the following code in my program but it is not working. function someFunction(text) { console.log(text); } document.write = someFunction; where text is the parameters of document.write. Another problem is After monitoring all the document.write methods using hooks again i have to use regex for finding tag creations. Is there Any alternative

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  • How could I insert a string into the response stream anywhere I want?

    - by DM
    There may be an easy way to do this but I can't see it... I created a simple Http Module that starts a timer on the PreRequestHandler and stops the timer on the PostRequestHandler to calculate the time it took the page to load. I then create some simple html and write my results to Response.Write. Since I'm doing this in the PostRequestHandler it's adding my results after the </html> tag. That's fine for testing but I need in a scenario where the page needs to validate. I can't seem to figure out how I could manipulate the Response object to insert my results before the </body> tag. Response.Write and Response.Output.Write don't have that flexibility and I couldn't see a way to work with the Response as a string. Am I missing something easy?

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