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• .NET vs Windows 8: Rematch!

  - by Simon Cooper

  So, although you will be able to use your existing .NET skills to develop Metro apps, it turns out Microsoft are limiting Visual Studio 2011 Express to Metro-only. From the Express website: Visual Studio 11 Express for Windows 8 provides tools for Metro style app development. To create desktop apps, you need to use Visual Studio 11 Professional, or higher. Oh dear. To develop any sort of non-Metro application, you will need to pay for at least VS Professional. I suspect Microsoft (or at least, certain groups within Microsoft) have a very explicit strategy in mind. By making VS Express Metro-only, developers who don't want to pay for Professional will be forced to make their simple one-shot or open-source application in Metro. This increases the number of applications available for Windows 8 and Windows mobile devices, which in turn make those platforms more attractive for consumers. When you use the free VS 11 Express, instead of paying Microsoft, you provide them a service by making applications for Metro, which in turn makes Microsoft's mobile offering more attractive to consumers, increasing their market share. Of course, it remains to be seen if developers forced to jump onto the Metro bandwagon will simply jump ship to Android or iOS instead. At least, that's what I think is going on. With Microsoft, who really knows?

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• ASP.NET MVC Cookbook - public review

  - by asiemer

  I have recently started writing another book.  The topic of this book is ASP.NET MVC.  This book differs from my previous book in that rather than working towards building one project from end to end - this book will demonstrate specific topics from end to end.  It is a recipe book (hence the cookbook name) and will be part of the Packt Publishing cookbook series.  An example recipe in this book might be how to consume JSON, creating a master /details page, jquery modal popups, custom ActionResults, etc.  Basically anything recipe oriented around the topic of ASP.NET MVC might be acceptable.  If you are interested in helping out with the review process you can join the "ASP.NET MVC 2 Cookbook-review" group on Google here: http://groups.google.com/group/aspnet-mvc-2-cookbook-review Currently the suggested TOC for the project is listed.  Also, chapters 1, 2, and most of 8 are posted.  Chapter 5 should be available tonight or tomorrow. In addition to reporting any errors that you might find (much appreciated), I am very interested in hearing about recipes that you want included, expanded, or removed (as being redundant or overly simple).  Any input is appreciated!  Hearing user feedback after the book is complete is a little late in my opinion (unless it is positive feedback of course). Thank you!

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• Help with ejb 3, weblogic and spring.

  - by berserkpi

  So,hi there. I've created a simple EJB3 test project, the code is simple: @Stateless @Remote( { ISumaSimple.class }) public class SumaSimpleBean implements ISumaSimple { /** * Default constructor. */ public SumaSimpleBean() { // TODO Auto-generated constructor stub } @Override public int sumar(int a, int b) { // TODO Auto-generated method stub return a + b; } } public interface ISumaSimple { public int sumar(int a, int b); } Ok, my client is a stand alone spring aplication which configuration is: <bean id="sumaSimpleServicio" class="org.springframework.jndi.JndiObjectFactoryBean"> <property name="jndiEnvironment"> <props> <prop key="java.naming.factory.initial"> org.apache.openejb.client.RemoteInitialContextFactory </prop> <prop key="java.naming.provider.url"> ejbd://localhost:4201 </prop> </props> </property> <property name="jndiName" value="SumaSimpleBeanRemote" /> </bean> <bean id="clienteService" class="qtx.cliente.simple.ClienteService"> <property name="sumaSimpleServicio" ref="sumaSimpleServicio"></property> </bean> All worked smoothly, but then I tried deploying using weblogic 10.3, I just changed these values: weblogic.jndi.WLInitialContextFactory t3://localhost:7010 In weblogic jndi tree my ejb is under: SimpleEJB3SimpleEJB_jarSumaSimple3_ISumaSimple Of course I added wlclient.jar to my spring client classpath. I think I am missing something in weblogic case, but dunno. My spring client is throwing this exception: Caused by: org.springframework.beans.TypeMismatchException: Failed to convert property value of type [qtx.ejb.simple._SumaSimple3_gwze0z_ISumaSimpleIntf_Stub] to required type [qtx.servicio.simple.ISumaSimple] for property 'sumaSimpleServicio'; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [qtx.ejb.simple._SumaSimple3_gwze0z_ISumaSimpleIntf_Stub] to required type [qtx.servicio.simple.ISumaSimple] for property 'sumaSimpleServicio': no matching editors or conversion strategy found at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:391) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1288) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1249) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) ... 14 more Caused by: java.lang.IllegalArgumentException: Cannot convert value of type [qtx.ejb.simple._SumaSimple3_gwze0z_ISumaSimpleIntf_Stub] to required type [qtx.servicio.simple.ISumaSimple] for property 'sumaSimpleServicio': no matching editors or conversion strategy found at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:219) at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:138) at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:386) ... 18 more Any help would be appreciated.

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• Inside the Concurrent Collections: ConcurrentDictionary

  - by Simon Cooper

  Using locks to implement a thread-safe collection is rather like using a sledgehammer - unsubtle, easy to understand, and tends to make any other tool redundant. Unlike the previous two collections I looked at, ConcurrentStack and ConcurrentQueue, ConcurrentDictionary uses locks quite heavily. However, it is careful to wield locks only where necessary to ensure that concurrency is maximised. This will, by necessity, be a higher-level look than my other posts in this series, as there is quite a lot of code and logic in ConcurrentDictionary. Therefore, I do recommend that you have ConcurrentDictionary open in a decompiler to have a look at all the details that I skip over. The problem with locks There's several things to bear in mind when using locks, as encapsulated by the lock keyword in C# and the System.Threading.Monitor class in .NET (if you're unsure as to what lock does in C#, I briefly covered it in my first post in the series): Locks block threads The most obvious problem is that threads waiting on a lock can't do any work at all. No preparatory work, no 'optimistic' work like in ConcurrentQueue and ConcurrentStack, nothing. It sits there, waiting to be unblocked. This is bad if you're trying to maximise concurrency. Locks are slow Whereas most of the methods on the Interlocked class can be compiled down to a single CPU instruction, ensuring atomicity at the hardware level, taking out a lock requires some heavy lifting by the CLR and the operating system. There's quite a bit of work required to take out a lock, block other threads, and wake them up again. If locks are used heavily, this impacts performance. Deadlocks When using locks there's always the possibility of a deadlock - two threads, each holding a lock, each trying to aquire the other's lock. Fortunately, this can be avoided with careful programming and structured lock-taking, as we'll see. So, it's important to minimise where locks are used to maximise the concurrency and performance of the collection. Implementation As you might expect, ConcurrentDictionary is similar in basic implementation to the non-concurrent Dictionary, which I studied in a previous post. I'll be using some concepts introduced there, so I recommend you have a quick read of it. So, if you were implementing a thread-safe dictionary, what would you do? The naive implementation is to simply have a single lock around all methods accessing the dictionary. This would work, but doesn't allow much concurrency. Fortunately, the bucketing used by Dictionary allows a simple but effective improvement to this - one lock per bucket. This allows different threads modifying different buckets to do so in parallel. Any thread making changes to the contents of a bucket takes the lock for that bucket, ensuring those changes are thread-safe. The method that maps each bucket to a lock is the GetBucketAndLockNo method: private void GetBucketAndLockNo( int hashcode, out int bucketNo, out int lockNo, int bucketCount) { // the bucket number is the hashcode (without the initial sign bit) // modulo the number of buckets bucketNo = (hashcode & 0x7fffffff) % bucketCount; // and the lock number is the bucket number modulo the number of locks lockNo = bucketNo % m_locks.Length; } However, this does require some changes to how the buckets are implemented. The 'implicit' linked list within a single backing array used by the non-concurrent Dictionary adds a dependency between separate buckets, as every bucket uses the same backing array. Instead, ConcurrentDictionary uses a strict linked list on each bucket: This ensures that each bucket is entirely separate from all other buckets; adding or removing an item from a bucket is independent to any changes to other buckets. Modifying the dictionary All the operations on the dictionary follow the same basic pattern: void AlterBucket(TKey key, ...) { int bucketNo, lockNo; 1: GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, m_buckets.Length); 2: lock (m_locks[lockNo]) { 3: Node headNode = m_buckets[bucketNo]; 4: Mutate the node linked list as appropriate } } For example, when adding another entry to the dictionary, you would iterate through the linked list to check whether the key exists already, and add the new entry as the head node. When removing items, you would find the entry to remove (if it exists), and remove the node from the linked list. Adding, updating, and removing items all follow this pattern. Performance issues There is a problem we have to address at this point. If the number of buckets in the dictionary is fixed in the constructor, then the performance will degrade from O(1) to O(n) when a large number of items are added to the dictionary. As more and more items get added to the linked lists in each bucket, the lookup operations will spend most of their time traversing a linear linked list. To fix this, the buckets array has to be resized once the number of items in each bucket has gone over a certain limit. (In ConcurrentDictionary this limit is when the size of the largest bucket is greater than the number of buckets for each lock. This check is done at the end of the TryAddInternal method.) Resizing the bucket array and re-hashing everything affects every bucket in the collection. Therefore, this operation needs to take out every lock in the collection. Taking out mutiple locks at once inevitably summons the spectre of the deadlock; two threads each hold a lock, and each trying to acquire the other lock. How can we eliminate this? Simple - ensure that threads never try to 'swap' locks in this fashion. When taking out multiple locks, always take them out in the same order, and always take out all the locks you need before starting to release them. In ConcurrentDictionary, this is controlled by the AcquireLocks, AcquireAllLocks and ReleaseLocks methods. Locks are always taken out and released in the order they are in the m_locks array, and locks are all released right at the end of the method in a finally block. At this point, it's worth pointing out that the locks array is never re-assigned, even when the buckets array is increased in size. The number of locks is fixed in the constructor by the concurrencyLevel parameter. This simplifies programming the locks; you don't have to check if the locks array has changed or been re-assigned before taking out a lock object. And you can be sure that when a thread takes out a lock, another thread isn't going to re-assign the lock array. This would create a new series of lock objects, thus allowing another thread to ignore the existing locks (and any threads controlling them), breaking thread-safety. Consequences of growing the array Just because we're using locks doesn't mean that race conditions aren't a problem. We can see this by looking at the GrowTable method. The operation of this method can be boiled down to: private void GrowTable(Node[] buckets) { try { 1: Acquire first lock in the locks array // this causes any other thread trying to take out // all the locks to block because the first lock in the array // is always the one taken out first // check if another thread has already resized the buckets array // while we were waiting to acquire the first lock 2: if (buckets != m_buckets) return; 3: Calculate the new size of the backing array 4: Node[] array = new array[size]; 5: Acquire all the remaining locks 6: Re-hash the contents of the existing buckets into array 7: m_buckets = array; } finally { 8: Release all locks } } As you can see, there's already a check for a race condition at step 2, for the case when the GrowTable method is called twice in quick succession on two separate threads. One will successfully resize the buckets array (blocking the second in the meantime), when the second thread is unblocked it'll see that the array has already been resized & exit without doing anything. There is another case we need to consider; looking back at the AlterBucket method above, consider the following situation: Thread 1 calls AlterBucket; step 1 is executed to get the bucket and lock numbers. Thread 2 calls GrowTable and executes steps 1-5; thread 1 is blocked when it tries to take out the lock in step 2. Thread 2 re-hashes everything, re-assigns the buckets array, and releases all the locks (steps 6-8). Thread 1 is unblocked and continues executing, but the calculated bucket and lock numbers are no longer valid. Between calculating the correct bucket and lock number and taking out the lock, another thread has changed where everything is. Not exactly thread-safe. Well, a similar problem was solved in ConcurrentStack and ConcurrentQueue by storing a local copy of the state, doing the necessary calculations, then checking if that state is still valid. We can use a similar idea here: void AlterBucket(TKey key, ...) { while (true) { Node[] buckets = m_buckets; int bucketNo, lockNo; GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, buckets.Length); lock (m_locks[lockNo]) { // if the state has changed, go back to the start if (buckets != m_buckets) continue; Node headNode = m_buckets[bucketNo]; Mutate the node linked list as appropriate } break; } } TryGetValue and GetEnumerator And so, finally, we get onto TryGetValue and GetEnumerator. I've left these to the end because, well, they don't actually use any locks. How can this be? Whenever you change a bucket, you need to take out the corresponding lock, yes? Indeed you do. However, it is important to note that TryGetValue and GetEnumerator don't actually change anything. Just as immutable objects are, by definition, thread-safe, read-only operations don't need to take out a lock because they don't change anything. All lockless methods can happily iterate through the buckets and linked lists without worrying about locking anything. However, this does put restrictions on how the other methods operate. Because there could be another thread in the middle of reading the dictionary at any time (even if a lock is taken out), the dictionary has to be in a valid state at all times. Every change to state has to be made visible to other threads in a single atomic operation (all relevant variables are marked volatile to help with this). This restriction ensures that whatever the reading threads are doing, they never read the dictionary in an invalid state (eg items that should be in the collection temporarily removed from the linked list, or reading a node that has had it's key & value removed before the node itself has been removed from the linked list). Fortunately, all the operations needed to change the dictionary can be done in that way. Bucket resizes are made visible when the new array is assigned back to the m_buckets variable. Any additions or modifications to a node are done by creating a new node, then splicing it into the existing list using a single variable assignment. Node removals are simply done by re-assigning the node's m_next pointer. Because the dictionary can be changed by another thread during execution of the lockless methods, the GetEnumerator method is liable to return dirty reads - changes made to the dictionary after GetEnumerator was called, but before the enumeration got to that point in the dictionary. It's worth listing at this point which methods are lockless, and which take out all the locks in the dictionary to ensure they get a consistent view of the dictionary: Lockless: TryGetValue GetEnumerator The indexer getter ContainsKey Takes out every lock (lockfull?): Count IsEmpty Keys Values CopyTo ToArray Concurrent principles That covers the overall implementation of ConcurrentDictionary. I haven't even begun to scratch the surface of this sophisticated collection. That I leave to you. However, we've looked at enough to be able to extract some useful principles for concurrent programming: Partitioning When using locks, the work is partitioned into independant chunks, each with its own lock. Each partition can then be modified concurrently to other partitions. Ordered lock-taking When a method does need to control the entire collection, locks are taken and released in a fixed order to prevent deadlocks. Lockless reads Read operations that don't care about dirty reads don't take out any lock; the rest of the collection is implemented so that any reading thread always has a consistent view of the collection. That leads us to the final collection in this little series - ConcurrentBag. Lacking a non-concurrent analogy, it is quite different to any other collection in the class libraries. Prepare your thinking hats!

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• Down Tools Week Cometh: Kissing Goodbye to CVs/Resumes and Cover Letters

  - by Bart Read

  I haven't blogged about what I'm doing in my (not so new) temporary role as Red Gate's technical recruiter, mostly because it's been routine, business as usual stuff, and because I've been trying to understand the role by doing it. I think now though the time has come to get a little more radical, so I'm going to tell you why I want to largely eliminate CVs/resumes and cover letters from the application process for some of our technical roles, and why I think that might be a good thing for candidates (and for us). I have a terrible confession to make, or at least it's a terrible confession for a recruiter: I don't really like CV sifting, or reading cover letters, and, unless I've misread the mood around here, neither does anybody else. It's dull, it's time-consuming, and it's somewhat soul destroying because, when all is said and done, you're being paid to be incredibly judgemental about people based on relatively little information. I feel like I've dirtied myself by saying that - I mean, after all, it's a core part of my job - but it sucks, it really does. (And, of course, the truth is I'm still a software engineer at heart, and I'm always looking for ways to do things better.) On the flip side, I've never met anyone who likes writing their CV. It takes hours and hours of faffing around and massaging it into shape, and the whole process is beset by a gnawing anxiety, frustration, and insecurity. All you really want is a chance to demonstrate your skills - not just talk about them - and how do you do that in a CV or cover letter? Often the best candidates will include samples of their work (a portfolio, screenshots, links to websites, product downloads, etc.), but sometimes this isn't possible, or may not be appropriate, or you just don't think you're allowed because of what your school/university careers service has told you (more commonly an issue with grads, obviously). And what are we actually trying to find out about people with all of this? I think the common criteria are actually pretty basic: Smart Gets things done (thanks for these two Joel) Not an a55hole* (sorry, have to get around Simple Talk's swear filter - and thanks to Professor Robert I. Sutton for this one) *Of course, everyone has off days, and I don't honestly think we're too worried about somebody being a bit grumpy every now and again. We can do a bit better than this in the context of the roles I'm talking about: we can be more specific about what "gets things done" means, at least in part. For software engineers and interns, the non-exhaustive meaning of "gets things done" is: Excellent coder For test engineers, the non-exhaustive meaning of "gets things done" is: Good at finding problems in software Competent coder Team player, etc., to me, are covered by "not an a55hole". I don't expect people to be the life and soul of the party, or a wild extrovert - that's not what team player means, and it's not what "not an a55hole" means. Some of our best technical staff are quiet, introverted types, but they're still pleasant to work with. My problem is that I don't think the initial sift really helps us find out whether people are smart and get things done with any great efficacy. It's better than nothing, for sure, but it's not as good as it could be. It's also contentious, and potentially unfair/inequitable - if you want to get an idea of what I mean by this, check out the background information section at the bottom. Before I go any further, let's look at the Red Gate recruitment process for technical staff* as it stands now: (LOTS of) People apply for jobs. All these applications go through a brutal process of manual sifting, which eliminates between 75 and 90% of them, depending upon the role, and the time of year**. Depending upon the role, those who pass the sift will be sent an assessment or telescreened. For the purposes of this blog post I'm only interested in those that are sent some sort of programming assessment, or bug hunt. This means software engineers, test engineers, and software interns, which are the roles for which I receive the most applications. The telescreen tends to be reserved for project or product managers. Those that pass the assessment are invited in for first interview. This interview is mostly about assessing their technical skills***, although we're obviously on the look out for cultural fit red flags as well. If the first interview goes well we'll invite candidates back for a second interview. This is where team/cultural fit is really scoped out. We also use this interview to dive more deeply into certain areas of their skillset, and explore any concerns that may have come out of the first interview (these obviously won't have been serious or obvious enough to cause a rejection at that point, but are things we do need to look into before we'd consider making an offer). We might subsequently invite them in for lunch before we make them an offer. This tends to happen when we're recruiting somebody for a specific team and we'd like them to meet all the people they'll be working with directly. It's not an interview per se, but can prove pivotal if they don't gel with the team. Anyone who's made it this far will receive an offer from us. *We have a slightly quirky definition of "technical staff" as it relates to the technical recruiter role here. It includes software engineers, test engineers, software interns, user experience specialists, technical authors, project managers, product managers, and development managers, but does not include product support or information systems roles. **For example, the quality of graduate applicants overall noticeably drops as the academic year wears on, which is not to say that by now there aren't still stars in there, just that they're fewer and further between. ***Some organisations prefer to assess for team fit first, but I think assessing technical skills is a more effective initial filter - if they're the nicest person in the world, but can't cut a line of code they're not going to work out. Now, as I suggested in the title, Red Gate's Down Tools Week is upon us once again - next week in fact - and I had proposed as a project that we refactor and automate the first stage of marking our programming assessments. Marking assessments, and in fact organising the marking of them, is a somewhat time-consuming process, and we receive many assessment solutions that just don't make the cut, for whatever reason. Whilst I don't think it's possible to fully automate marking, I do think it ought to be possible to run a suite of automated tests over each candidate's solution to see whether or not it behaves correctly and, if it does, move on to a manual stage where we examine the code for structure, decomposition, style, readability, maintainability, etc. Obviously it's possible to use tools to generate potentially helpful metrics for some of these indices as well. This would obviously reduce the marking workload, and would provide candidates with quicker feedback about whether they've been successful - though I do wonder if waiting a tactful interval before sending a (nicely written) rejection might be wise. I duly scrawled out a picture of my ideal process, which looked like this: The problem is, as soon as I'd roughed it out, I realised that fundamentally it wasn't an ideal process at all, which explained the gnawing feeling of cognitive dissonance I'd been wrestling with all week, whilst I'd been trying to find time to do this. Here's what I mean. Automated assessment marking, and the associated infrastructure around that, makes it much easier for us to deal with large numbers of assessments. This means we can be much more permissive about who we send assessments out to or, in other words, we can give more candidates the opportunity to really demonstrate their skills to us. And this leads to a question: why not give everyone the opportunity to demonstrate their skills, to show that they're smart and can get things done? (Two or three of us even discussed this in the down tools week hustings earlier this week.) And isn't this a lot simpler than the alternative we'd been considering? (FYI, this was automated CV/cover letter sifting by some form of textual analysis to ideally eliminate the worst 50% or so of applications based on an analysis of the 20,000 or so historical applications we've received since 2007 - definitely not the basic keyword analysis beloved of recruitment agencies, since this would eliminate hardly anyone who was awful, but definitely would eliminate stellar Oxbridge candidates - #fail - or some nightmarishly complex Google-like system where we profile all our currently employees, only to realise that we're never going to get representative results because we don't have a statistically significant sample size in any given role - also #fail.) No, I think the new way is better. We let people self-select. We make them the masters (or mistresses) of their own destiny. We give applicants the power - we put their fate in their hands - by giving them the chance to demonstrate their skills, which is what they really want anyway, instead of requiring that they spend hours and hours creating a CV and cover letter that I'm going to evaluate for suitability, and make a value judgement about, in approximately 1 minute (give or take). It doesn't matter what university you attended, it doesn't matter if you had a bad year when you took your A-levels - here's your chance to shine, so take it and run with it. (As a side benefit, we cut the number of applications we have to sift by something like two thirds.) WIN! OK, yeah, sounds good, but will it actually work? That's an excellent question. My gut feeling is yes, and I'll justify why below (and hopefully have gone some way towards doing that above as well), but what I'm proposing here is really that we run an experiment for a period of time - probably a couple of months or so - and measure the outcomes we see: How many people apply? (Wouldn't be surprised or alarmed to see this cut by a factor of ten.) How many of them submit a good assessment? (More/less than at present?) How much overhead is there for us in dealing with these assessments compared to now? What are the success and failure rates at each interview stage compared to now? How many people are we hiring at the end of it compared to now? I think it'll work because I hypothesize that, amongst other things: It self-selects for people who really want to work at Red Gate which, at the moment, is something I have to try and assess based on their CV and cover letter - but if you're not that bothered about working here, why would you complete the assessment? Candidates who would submit a shoddy application probably won't feel motivated to do the assessment. Candidates who would demonstrate good attention to detail in their CV/cover letter will demonstrate good attention to detail in the assessment. In general, only the better candidates will complete and submit the assessment. Marking assessments is much less work so we'll be able to deal with any increase that we see (hopefully we will see). There are obviously other questions as well: Is plagiarism going to be a problem? Is there any way we can detect/discourage potential plagiarism? How do we assess candidates' education and experience? What about their ability to communicate in writing? Do we still want them to submit a CV afterwards if they pass assessment? Do we want to offer them the opportunity to tell us a bit about why they'd like the job when they submit their assessment? How does this affect our relationship with recruitment agencies we might use to hire for these roles? So, what's the objective for next week's Down Tools Week? Pretty simple really - we want to implement this process for the Graduate Software Engineer and Software Engineer positions that you can find on our website. I will be joined by a crack team of our best developers (Kevin Boyle, and new Red-Gater, Sam Blackburn), and recruiting hostess with the mostest Laura McQuillen, and hopefully a couple of others as well - if I can successfully twist more arms before Monday.* Hopefully by next Friday our experiment will be up and running, and we may have changed the way Red Gate recruits software engineers for good! Stay tuned and we'll let you know how it goes! *I'm going to play dirty by offering them beer and chocolate during meetings. Some background information: how agonising over the initial CV/cover letter sift helped lead us to bin it off entirely The other day I was agonising about the new university/good degree grade versus poor A-level results issue, and decided to canvas for other opinions to see if there was something I could do that was fairer than my current approach, which is almost always to reject. This generated quite an involved discussion on our Yammer site: I'm sure you can glean a pretty good impression of my own educational prejudices from that discussion as well, although I'm very open to changing my opinion - hopefully you've already figured that out from reading the rest of this post. Hopefully you can also trace a logical path from agonising about sifting to, "Uh, hang on, why on earth are we doing this anyway?!?" Technorati Tags: recruitment,hr,developers,testers,red gate,cv,resume,cover letter,assessment,sea change

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• So it comes to PASS…

  - by Tony Davis

  How does your company gauge the benefit of attending a technical conference? What's the best change you made as a direct result of attendance? It's time again for the PASS Summit and I, like most people go with a set of general goals for enhancing technical knowledge; to learn more about PowerShell, to drill into SQL Server performance tuning techniques, and so on. Most will write up a brief report on the event for the rest of the team. Ideally, however, it will go a bit further than that; each conference should result in a specific improvement to one of your systems, or in the way you do your job. As co-editor of Simple-talk.com, and responsible for the majority of our SQL books, my “high level” goals don't vary much from conference to conference. I'm always on the lookout for good new authors. I target interesting new technologies and tools and try to learn more. I return with a list of actions, new articles to commission, and potential new authors. Three years ago, however, I started setting myself the goal of implementing “one new thing” after each conference. After one, I adopted Kanban for managing my workload, a technique that places strict limits on “work in progress” and makes the overall workload, and backlog, highly visible. After another I trialled a community book project. At PASS 2010, one of my general goals was to delve deeper into SQL Server transaction log mechanics, but on top of that, I set a specific goal of writing something useful on the topic. I started a Stairway series and, ultimately, it's turned into a book! If you're attending the PASS Summit this year, take some time to consider what specific improvement or change you'll implement as a result. Also, try to drop by the Red Gate booth (#101). During the Vendor event on Wednesday evening, Gail Shaw and I will be there to discuss, and hand out copies of the book. Cheers, Tony.  

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• Exceptional DBA Awards 2011

  - by Rebecca Amos

  From today, we’re accepting nominations for the 2011 Exceptional DBA Awards. DBAs make a vital contribution to the running of the companies they work for, and the Exceptional DBA Awards aim to acknowledge this and make this contribution more widely known. Check out our new website for all the info: www.exceptionaldba.com  Being an exceptional DBA doesn’t mean you have to sleep at the office, or know everything there is to know about SQL Server; who ever could? It means that you make an effort to make your servers secure and reliable, and to make your users’ lives easier. Maybe you’ve helped a junior colleague learn something new about server backups? Or cancelled your coffee break to get a database back online? Or contributed to a forum post on performance monitoring? All of these actions show that you might be an exceptional DBA. So have a think about the tasks you do every day that already make you exceptional – and then get started on your entry! You just need to answer a few questions on our website about your experience as a DBA, some of your biggest achievements, and any other activities you participate in within the SQL Server community. Anyone who is currently working as a SQL Server database administrator can enter, or be nominated by someone else. We’ve got four fantastic judges for the Awards, who you’ll be familiar with already: Brent Ozar, Brad McGehee, Rodney Landrum and Steve Jones. They’ll pick five finalists, and then we’ll ask the SQL Server community to vote for their winner. Not only could you win the respect and recognition of peers and colleagues, but the prizes also include full conference registration for the 2011 PASS Summit in Seattle (where the awards ceremony will take place), four nights' hotel accommodation, and $300 towards travel expenses. The winner will get a copy of Red Gate’s SQL DBA Bundle – and they’ll also be featured here, on Simple-Talk. So what are you waiting for? Chances are you’ve already made a small effort for someone today that means you might be an exceptional DBA. Visit the website now, and start writing your entry – or nominate your favourite DBA to enter: www.exceptionaldba.com

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• Fair Comments

  - by Tony Davis

  To what extent is good code self-documenting? In one of the most entertaining sessions I saw at the recent PASS summit, Jeremiah Peschka (blog | twitter) got a laugh out of a sleepy post-lunch audience with the following remark: "Some developers say good code is self-documenting; I say, get off my team" I silently applauded the sentiment. It's not that all comments are useful, but that I mistrust the basic premise that "my code is so clearly written, it doesn't need any comments". I've read many pieces describing the road to self-documenting code, and my problem with most of them is that they feed the myth that comments in code are a sign of weakness. They aren't; in fact, used correctly I'd say they are essential. Regardless of how far intelligent naming can get you in describing what the code does, or how well any accompanying unit tests can explain to your fellow developers why it works that way, it's no excuse not to document fully the public interfaces to your code. Maybe I just mixed with the wrong crowd while learning my favorite language, but when I open a stored procedure I lose the will even to read it unless I see a big Phil Factor- or Jeff Moden-style header summarizing in plain English what the code does, how it fits in to the broader application, and a usage example. This public interface describes the high-level process and should explain the role of the code, clearly, for fellow developers, language non-experts, and even any non-technical stake holders in the project. When you step into the body of the code, the low-level details, then I agree that the rules are somewhat different; especially when code is subject to frequent refactoring that can quickly render comments redundant or misleading. At their worst, here, inline comments are sticking plaster to cover up the scars caused by poor naming conventions, failure in clarity when mapping a complex domain into code, or just by not entirely understanding the problem (/ this is the clever part). If you design and refactor your code carefully so that it is as simple as possible, your functions do one thing only, you avoid having two completely different algorithms in the same piece of code, and your functions, classes and variables are intelligently named, then, yes, the need for inline comments should be minimal. And yet, even given this, I'd still argue that many languages (T-SQL certainly being one) just don't lend themselves to readability when performing even moderately-complex tasks. If the algorithm is complex, I still like to see the occasional helpful comment. Please, therefore, be as liberal as you see fit in the detail of the comments you apply to this editorial, for like code it is bound to increase its' clarity and usefulness. Cheers, Tony.

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• Introducing Glimpse – Firebug for your server

  - by Neil Davidson

  Here at Red Gate, we spend every waking hour trying to wow .NET and SQL developers with great products.  Every so often, though, we find something out in the wild which knocks our socks off by taking “ingeniously simple” to a whole new level.  That’s what a little community led by developers Nik Molnar and Anthony van der Hoorn has done with the open source tool Glimpse. Glimpse describes itself as ‘Firebug for the server.’  You drop the NuGet package into your ASP.NET project, and then — like magic* — your web pages will bare every detail of their execution.  Even by our high standards, it was trivial to get running: if you can use NuGet, you’re already there. You get all that lovely detail without changing any code. Our feelings go beyond respect for the developers who designed and wrote Glimpse; we’re thrilled that Nik and Anthony have come to work for Red Gate full-time. They’re going to stay in control of the project and keep doing open source development work on Glimpse.  In the medium term, we’re hoping to make paid-for products which plug into the free open source framework, especially in areas like performance profiling where we already have some deep technology.  First, though, Glimpse needs to get from beta to a v1. Given the breakneck pace of new development, this should only be a month or so away. Supporting an open source project is a first for Red Gate, so we’re going to be working with Nik and Anthony, with the Glimpse community and even with other vendors to figure out what ‘great’ looks like from the a user perspective.  Only one thing is certain: this technology deserves a wider audience than the 40,000 people who have already downloaded it, so please have a look and tell us what you think. You can hear more about what the Glimpse developers think on the Glimpse blog, and there are plenty more technical facts over at our product manager’s blog. If you have any questions or queries, please tweet with the #glimpse hashtag or contact the Glimpse team directly on [email protected]. [*That’s ”magic” in the Arthur C. Clarke “sufficiently advanced technology” sense, of course] Neil Davidson co-founder and Joint CEO Red Gate Software http://twitter.com/neildavidson    

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• What is Database Continuous Integration?

  - by David Atkinson

  Although not everyone is practicing continuous integration, many have at least heard of the concept. A recent poll on www.simple-talk.com indicates that 40% of respondents are employing the technique. It is widely accepted that the earlier issues are identified in the development process, the lower the cost to the development process. The worst case scenario, of course, is for the bug to be found by the customer following the product release. A number of Agile development best practices have evolved to combat this problem early in the development process, including pair programming, code inspections and unit testing. Continuous integration is one such Agile concept that tackles the problem at the point of committing a change to source control. This can alternatively be run on a regular schedule. This triggers a sequence of events that compiles the code and performs a variety of tests. Often the continuous integration process is regarded as a build validation test, and if issues were to be identified at this stage, the testers would simply not 'waste their time ' and touch the build at all. Such a ‘broken build’ will trigger an alert and the development team’s number one priority should be to resolve the issue. How application code is compiled and tested as part of continuous integration is well understood. However, this isn’t so clear for databases. Indeed, before I cover the mechanics of implementation, we need to decide what we mean by database continuous integration. For me, database continuous integration can be implemented as one or more of the following: 1)      Your application code is being compiled and tested. You therefore need a database to be maintained at the corresponding version. 2)      Just as a valid application should compile, so should the database. It should therefore be possible to build a new database from scratch. 3)     Likewise, it should be possible to generate an upgrade script to take your already deployed databases to the latest version. I will be covering these in further detail in future blogs. In the meantime, more information can be found in the whitepaper linked off www.red-gate.com/ci If you have any questions, feel free to contact me directly or post a comment to this blog post.

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• Interviews: Going Beyond the Technical Quiz

  - by Tony Davis

  All developers will be familiar with the basic format of a technical interview. After a bout of CV-trawling to gauge basic experience, strengths and weaknesses, the interview turns technical. The whiteboard takes center stage and the challenge is set to design a function or query, or solve what on the face of it might seem a disarmingly simple programming puzzle. Most developers will have experienced those few panic-stricken moments, when one’s mind goes as blank as the whiteboard, before un-popping the marker pen, and hopefully one’s mental functions, to work through the problem. It is a way to probe the candidate’s knowledge of basic programming structures and techniques and to challenge their critical thinking. However, these challenges or puzzles, often devised by some of the smartest brains in the development team, have a tendency to become unnecessarily ‘tricksy’. They often seem somewhat academic in nature. While the candidate straight out of IT school might breeze through the construction of a Markov chain, a candidate with bags of practical experience but less in the way of formal training could become nonplussed. Also, a whiteboard and a marker pen make up only a very small part of the toolkit that a programmer will use in everyday work. I remember vividly my first job interview, for a position as technical editor. It went well, but after the usual CV grilling and technical questions, I was only halfway there. Later, they sat me alongside a team of editors, in front of a computer loaded with MS Word and copy of SQL Server Query Analyzer, and my task was to edit a real chapter for a real SQL Server book that they planned to publish, including validating and testing all the code. It was a tough challenge but I came away with a sound knowledge of the sort of work I’d do, and its context. It makes perfect sense, yet my impression is that many organizations don’t do this. Indeed, it is only relatively recently that Red Gate started to move over to this model for developer interviews. Now, instead of, or perhaps in addition to, the whiteboard challenges, the candidate can expect to sit with their prospective team, in front of Visual Studio, loaded with all the useful tools in the developer’s kit (ReSharper and so on) and asked to, for example, analyze and improve a real piece of software. The same principles should apply when interviewing for a database positon. In addition to the usual questions challenging the candidate’s knowledge of such things as b-trees, object permissions, database recovery models, and so on, sit the candidate down with the other database developers or DBAs. Arm them with a copy of Management Studio, and a few other tools, then challenge them to discover the flaws in a stored procedure, and improve its performance. Or present them with a corrupt database and ask them to get the database back online, and discover the cause of the corruption.

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• Subterranean IL: Fault exception handlers

  - by Simon Cooper

  Fault event handlers are one of the two handler types that aren't available in C#. It behaves exactly like a finally, except it is only run if control flow exits the block due to an exception being thrown. As an example, take the following method: .method public static void FaultExample(bool throwException) { .try { ldstr "Entering try block" call void [mscorlib]System.Console::WriteLine(string) ldarg.0 brfalse.s NormalReturn ThrowException: ldstr "Throwing exception" call void [mscorlib]System.Console::WriteLine(string) newobj void [mscorlib]System.Exception::.ctor() throw NormalReturn: ldstr "Leaving try block" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } fault { ldstr "Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } Return: ldstr "Returning from method" call void [mscorlib]System.Console::WriteLine(string) ret } If we pass true to this method the following gets printed: Entering try block Throwing exception Fault handler and the exception gets passed up the call stack. So, the exception gets thrown, the fault handler gets run, and the exception propagates up the stack afterwards in the normal way. If we pass false, we get the following: Entering try block Leaving try block Returning from method Because we are leaving the .try using a leave.s instruction, and not throwing an exception, the fault handler does not get called. Fault handlers and C# So why were these not included in C#? It seems a pretty simple feature; one extra keyword that compiles in exactly the same way, and with the same semantics, as a finally handler. If you think about it, the same behaviour can be replicated using a normal catch block: try { throw new Exception(); } catch { // fault code goes here throw; } The catch block only gets run if an exception is thrown, and the exception gets rethrown and propagates up the call stack afterwards; exactly like a fault block. The only complications that occur is when you want to add a fault handler to a try block with existing catch handlers. Then, you either have to wrap the try in another try: try { try { // ... } catch (DirectoryNotFoundException) { // ... // leave.s as normal... } catch (IOException) { // ... throw; } } catch { // fault logic throw; } or separate out the fault logic into another method and call that from the appropriate handlers: try { // ... } catch (DirectoryNotFoundException ) { // ... } catch (IOException ioe) { // ... HandleFaultLogic(); throw; } catch (Exception e) { HandleFaultLogic(); throw; } To be fair, the number of times that I would have found a fault handler useful is minimal. Still, it's quite annoying knowing such functionality exists, but you're not able to access it from C#. Fortunately, there are some easy workarounds one can use instead. Next time: filter handlers.

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• Hype and LINQ

  - by Tony Davis

  "Tired of querying in antiquated SQL?" I blinked in astonishment when I saw this headline on the LinqPad site. Warming to its theme, the site suggests that what we need is to "kiss goodbye to SSMS", and instead use LINQ, a modern query language! Elsewhere, there is an article entitled "Why LINQ beats SQL". The designers of LINQ, along with many DBAs, would, I'm sure, cringe with embarrassment at the suggestion that LINQ and SQL are, in any sense, competitive ways of doing the same thing. In fact what LINQ really is, at last, is an efficient, declarative language for C# and VB programmers to access or manipulate data in objects, local data stores, ORMs, web services, data repositories, and, yes, even relational databases. The fact is that LINQ is essentially declarative programming in a .NET language, and so in many ways encourages developers into a "SQL-like" mindset, even though they are not directly writing SQL. In place of imperative logic and loops, it uses various expressions, operators and declarative logic to build up an "expression tree" describing only what data is required, not the operations to be performed to get it. This expression tree is then parsed by the language compiler, and the result, when used against a relational database, is a SQL string that, while perhaps not always perfect, is often correctly parameterized and certainly no less "optimal" than what is achieved when a developer applies blunt, imperative logic to the SQL language. From a developer standpoint, it is a mistake to consider LINQ simply as a substitute means of querying SQL Server. The strength of LINQ is that that can be used to access any data source, for which a LINQ provider exists. Microsoft supplies built-in providers to access not just SQL Server, but also XML documents, .NET objects, ADO.NET datasets, and Entity Framework elements. LINQ-to-Objects is particularly interesting in that it allows a declarative means to access and manipulate arrays, collections and so on. Furthermore, as Michael Sorens points out in his excellent article on LINQ, there a whole host of third-party LINQ providers, that offers a simple way to get at data in Excel, Google, Flickr and much more, without having to learn a new interface or language. Of course, the need to be generic enough to deal with a range of data sources, from something as mundane as a text file to as esoteric as a relational database, means that LINQ is a compromise and so has inherent limitations. However, it is a powerful and beautifully compact language and one that, at least in its "query syntax" guise, is accessible to developers and DBAs alike. Perhaps there is still hope that LINQ can fulfill Phil Factor's lobster-induced fantasy of a language that will allow us to "treat all data objects, whether Word files, Excel files, XML, relational databases, text files, HTML files, registry files, LDAPs, Outlook and so on, in the same logical way, as linked databases, and extract the metadata, create the entities and relationships in the same way, and use the same SQL syntax to interrogate, create, read, write and update them." Cheers, Tony.

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• Subterranean IL: Volatile

  - by Simon Cooper

  This time, we'll be having a look at the volatile. prefix instruction, and one of the differences between volatile in IL and C#. The volatile. prefix volatile is a tricky one, as there's varying levels of documentation on it. From what I can see, it has two effects: It prevents caching of the load or store value; rather than reading or writing to a cached version of the memory location (say, the processor register or cache), it forces the value to be loaded or stored at the 'actual' memory location, so it is then immediately visible to other threads. It forces a memory barrier at the prefixed instruction. This ensures instructions don't get re-ordered around the volatile instruction. This is slightly more complicated than it first seems, and only seems to matter on certain architectures. For more details, Joe Duffy has a blog post going into the details. For this post, I'll be concentrating on the first aspect of volatile. Caching field accesses To demonstrate this, I created a simple multithreaded IL program. It boils down to the following code: .class public Holder { .field public static class Holder holder .field public bool stop .method public static specialname void .cctor() { newobj instance void Holder::.ctor() stsfld class Holder Holder::holder ret }}.method private static void Main() { .entrypoint // Thread t = new Thread(new ThreadStart(DoWork)) // t.Start() // Thread.Sleep(2000) // Console.WriteLine("Stopping thread...") ldsfld class Holder Holder::holder ldc.i4.1 stfld bool Holder::stop call instance void [mscorlib]System.Threading.Thread::Join() ret}.method private static void DoWork() { ldsfld class Holder Holder::holder // while (!Holder.holder.stop) {} DoWork: dup ldfld bool Holder::stop brfalse DoWork pop ret} If you compile and run this code, you'll find that the call to Thread.Join() never returns - the DoWork spinlock is reading a cached version of Holder.stop, which is never being updated with the new value set by the Main method. Adding volatile to the ldfld fixes this: dupvolatile.ldfld bool Holder::stopbrfalse DoWork The volatile ldfld forces the field access to read direct from heap memory, which is then updated by the main thread, rather than using a cached copy. volatile in C# This highlights one of the differences between IL and C#. In IL, volatile only applies to the prefixed instruction, whereas in C#, volatile is specified on a field to indicate that all accesses to that field should be volatile (interestingly, there's no mention of the 'no caching' aspect of volatile in the C# spec; it only focuses on the memory barrier aspect). Furthermore, this information needs to be stored within the assembly somehow, as such a field might be accessed directly from outside the assembly, but there's no concept of a 'volatile field' in IL! How this information is stored with the field will be the subject of my next post.

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• Encrypting your SQL Server Passwords in Powershell

  - by laerte

  A couple of months ago, a friend of mine who is now bewitched by the seemingly supernatural abilities of Powershell (+1 for the team) asked me what, initially, appeared to be a trivial question: "Laerte, I do not have the luxury of being able to work with my SQL servers through Windows Authentication, and I need a way to automatically pass my username and password. How would you suggest I do this?" Given that I knew he, like me, was using the SQLPSX modules (an open source project created by Chad Miller; a fantastic library of reusable functions and PowerShell scripts), I merrily replied, "Simply pass the Username and Password in SQLPSX functions". He rather pointed responded: "My friend, I might as well pass: Username-'Me'-password 'NowEverybodyKnowsMyPassword'" As I do have the pleasure of working with Windows Authentication, I had not really thought this situation though yet (and thank goodness I only revealed my temporary ignorance to a friend, and the embarrassment was minimized). After discussing this puzzle with Chad Miller, he showed me some code for saving passwords on SQL Server Tables, which he had demo'd in his Powershell ETL session at Tampa SQL Saturday (and you can download the scripts from here). The solution seemed to be pretty much ready to go, so I showed it to my Authentication-impoverished friend, only to discover that we were only half-way there: "That's almost what I want, but the details need to be stored in my local txt file, together with the names of the servers that I'll actually use the Powershell scripts on. Something like: Server1,UserName,Password Server2,UserName,Password" I thought about it for just a few milliseconds (Ha! Of course I'm not telling you how long it actually took me, I have to do my own marketing, after all) and the solution was finally ready. First , we have to download Library-StringCripto (with many thanks to Steven Hystad), which is composed of two functions: One for encryption and other for decryption, both of which are used to manage the password. If you want to know more about the library, you can see more details in the help functions. Next, we have to create a txt file with your encrypted passwords:$ServerName = "Server1" $UserName = "Login1" $Password = "Senha1" $PasswordToEncrypt = "YourPassword" $UserNameEncrypt = Write-EncryptedString -inputstring $UserName -Password $PasswordToEncrypt $PasswordEncrypt = Write-EncryptedString -inputstring $Password -Password $PasswordToEncrypt "$($Servername),$($UserNameEncrypt),$($PasswordEncrypt)" | Out-File c:\temp\ServersSecurePassword.txt -Append $ServerName = "Server2" $UserName = "Login2" $Password = "senha2" $PasswordToEncrypt = "YourPassword" $UserNameEncrypt = Write-EncryptedString -inputstring $UserName -Password $PasswordToEncrypt $PasswordEncrypt = Write-EncryptedString -inputstring $Password -Password $PasswordToEncrypt "$($Servername),$($UserNameEncrypt),$($PasswordEncrypt)" | Out-File c:\temp\ ServersSecurePassword.txt -Append .And in the c:\temp\ServersSecurePassword.txt file which we've just created, you will find your Username and Password, all neatly encrypted. Let's take a look at what the txt looks like: .and in case you're wondering, Server names, Usernames and Passwords are all separated by commas. Decryption is actually much more simple:Read-EncryptedString -InputString $EncryptString -password "YourPassword" (Just remember that the Password you're trying to decrypt must be exactly the same as the encrypted phrase.) Finally, just to show you how smooth this solution is, let's say I want to use the Invoke-DBMaint function from SQLPSX to perform a checkdb on a system database: it's just a case of split, decrypt and be happy!Get-Content c:\temp\ServerSecurePassword.txt | foreach { [array] $Split = ($_).split(",") Invoke-DBMaint -server $($Split[0]) -UserName (Read-EncryptedString -InputString $Split[1] -password "YourPassword" ) -Password (Read-EncryptedString -InputString $Split[2] -password "YourPassword" ) -Databases "SYSTEM" -Action "CHECK_DB" -ReportOn c:\Temp } This is why I love Powershell.

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• Database Mirroring – deprecated

  - by fatherjack

  Do you use mirroring on any of your databases? Do you use mirroring on SQL Server Standard Edition? I do, as a way of having a stand-by server ready to take over if there is a problem with the live server so that business can continue despite whatever disaster may strike at our primary server location. In my experience it has been a great solution for us as it is simple to implement, reliable and predictable. Mirroring has been around since SQL Server 2005 sp1 but with the release of SQL Server 2012 mirroring has now been placed on the deprecation list. That’s right, Microsoft are removing this feature from SQL Server. SQL Server 2012 had lots of improvements and new features around this sort of technology – the High Availability, Disaster recovery and Always On features described in detail here by Brent Ozar and  Microsoft’s own Customer Service and Support SQL Server Engineers . Now the bad news, the HADRON features are pretty much all wrapped up in the Enterprise Edition of SQL Server 2012. This is going to be a big issue for people, like me, who are only on Standard Edition of earlier versions mostly due to our requirements and the budget (or lack thereof) required for Enterprise Edition licenses. No mirroring in Standard Edition means no upgrade. Don’t Panic. There are two stages of deprecation and they dont happen fast. The first stage – Deprecation Announcement- means that Microsoft have decided that there is a limited future for a particular feature and this is your cue that new projects and developments should not be implemented on this technology as it will cease to exist in the future. This is where mirroring currently stands. You have time to consider your options and start work on planning how you will move away from using this feature. This can be 2 or 3 versions of SQL Server, possibly more. The next stage is Deprecation Final Support - this is where you are on your last chance, When you see this then the next version of SQL Server will not have this feature in it so you need to implement your plans to move to an alternative solution. While these two phases are taking place Microsoft are open to feedback on how people use their products and if enough people make the case for mirroring (or an equivalent technology) to be in the Standard Edition then they may make changes rather than lose customers or have customers cease upgrading in order to keep the functionality they need. Denny Cherry (@MrDenny) has published an article on this same topic here with more detail than me so I wont go over old ground. All I will say is that you should read his article now and then follow the link to his own site where he is collecting peoples information on how they use mirroring in Standard Edition so that our voice can be put to Microsoft.  

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• Antenna Aligner Part 5: Devil is in the detail

  - by Chris George

  "The first 90% of a project takes 90% of the time and the last 10% takes the another 200%"  (excerpt from onista) Now that I have a working app (more or less), it's time to make it pretty and slick. I can't stress enough how useful it is to get other people using your software, and my simple app is no exception. I handed my iPhone to a couple of my colleagues at Red Gate and asked them to use it and give me feedback. Immediately it became apparent that the delay between the list page being shown and the list being drawn was too long, and everyone who tried the app clicked on the "Recalculate" button before it had finished. Similarly, selecting a transmitter heralded a delay before the compass page appeared with similar consequences. All users expected there to be some sort of feedback/spinny etc. to show them it is actually doing something. In a similar vein although for opposite reasons, clicking the Recalculate button did indeed recalculate the available transmitters and redraw them, but it did this too fast! One or two users commented that they didn't know if it had done anything. All of these issues resulted in similar solutions; implement a waiting spinny. Thankfully, jquery mobile has one built in, primarily used for ajax operations. Not wishing to bore you with the many many iterations I went through trying to get this to work, I'll just give you my solution! (Seriously, I was working on this most evenings for at least a week!) The final solution for the recalculate problem came in the form of the code below. $(document).on("click", ".show-page-loading-msg", function () {            var $this = $(this),                theme = $this.jqmData("theme") ||                        $.mobile.loadingMessageTheme;            $.mobile.showPageLoadingMsg(theme, "recalculating", false);            setTimeout(function ()                           { $.mobile.hidePageLoadingMsg(); }, 2000);            getLocationData();        })        .on("click", ".hide-page-loading-msg", function () {              $.mobile.hidePageLoadingMsg();        }); The spinny is activated by setting the class of a button (for example) to the 'show-page-loading-msg' class. Recalculate This means the code above is fired, calling the showPageLoadingMsg on the document.mobile object. Then, after a 2 second timeout, it calls the hidePageLoadingMsg() function. Supposedly, it should show "recalculating" underneath the spinny, but I've not got that to work. I'm wondering if there is a problem with the jquery mobile implementation. Anyway, it doesn't really matter, it's the principle I'm after, and I now have spinnys!

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• Why enumerator structs are a really bad idea (redux)

  - by Simon Cooper

  My previous blog post went into some detail as to why calling MoveNext on a BCL generic collection enumerator didn't quite do what you thought it would. This post covers the Reset method. To recap, here's the simple wrapper around a linked list enumerator struct from my previous post (minus the readonly on the enumerator variable): sealed class EnumeratorWrapper : IEnumerator<int> { private LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } If you have a look at the Reset method, you'll notice I'm having to cast to IEnumerator to be able to call Reset on m_Enumerator. This is because the implementation of LinkedList<int>.Enumerator.Reset, and indeed of all the other Reset methods on the BCL generic collection enumerators, is an explicit interface implementation. However, IEnumerator is a reference type. LinkedList<int>.Enumerator is a value type. That means, in order to call the reset method at all, the enumerator has to be boxed. And the IL confirms this: .method public hidebysig newslot virtual final instance void Reset() cil managed { .maxstack 8 L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> EnumeratorWrapper::m_Enumerator L_0007: box [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> L_000c: callvirt instance void [mscorlib]System.Collections.IEnumerator::Reset() L_0011: nop L_0012: ret } On line 0007, we're doing a box operation, which copies the enumerator to a reference object on the heap, then on line 000c calling Reset on this boxed object. So m_Enumerator in the wrapper class is not modified by the call the Reset. And this is the only way to call the Reset method on this variable (without using reflection). Therefore, the only way that the collection enumerator struct can be used safely is to store them as a boxed IEnumerator<T>, and not use them as value types at all.

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• Hadoop, NOSQL, and the Relational Model

  - by Phil Factor

  (Guest Editorial for the IT Pro/SysAdmin Newsletter)Whereas Relational Databases fit the world of commerce like a glove, it is useless to pretend that they are a perfect fit for all human endeavours. Although, with SQL Server, we’ve made great strides with indexing text, in processing spatial data and processing markup, there is still a problem in dealing efficiently with large volumes of ephemeral semi-structured data. Key-value stores such as Cassandra, Project Voldemort, and Riak are of great value for ephemeral data, and seem of equal value as a data-feed that provides aggregations to an RDBMS. However, the Document databases such as MongoDB and CouchDB are ideal for semi-structured data for which no fixed schema exists; analytics and logging are obvious examples. NoSQL products, such as MongoDB, tackle the semi-structured data problem with panache. MongoDB is designed with a simple document-oriented data model that scales horizontally across multiple servers. It doesn’t impose a schema, and relies on the application to enforce the data structure. This is another take on the old ‘EAV’ problem (where you don’t know in advance all the attributes of a particular entity) It uses a clever replica set design that allows automatic failover, and uses journaling for data durability. It allows indexing and ad-hoc querying. However, for SQL Server users, the obvious choice for handling semi-structured data is Apache Hadoop. There will soon be an ODBC Driver for Apache Hive .and an Add-in for Excel. Additionally, there are now two Hadoop-based connectors for SQL Server; the Apache Hadoop connector for SQL Server 2008 R2, and the SQL Server Parallel Data Warehouse (PDW) connector. We can connect to Hadoop process the semi-structured data and then store it in SQL Server. For one steeped in the culture of Relational SQL Databases, I might be expected to throw up my hands in the air in a gesture of contempt for a technology that was, judging by the overblown journalism on the subject, about to make my own profession as archaic as the Saggar makers bottom knocker (a potter’s assistant who helped the saggar maker to make the bottom of the saggar by placing clay in a metal hoop and bashing it). However, on the contrary, I find that I'm delighted with the advances made by the NoSQL databases in the past few years. Having the flow of ideas from the NoSQL providers will knock any trace of complacency out of the providers of Relational Databases and inspire them into back-fitting some features, such as horizontal scaling, with sharding and automatic failover into SQL-based RDBMSs. It will do the breed a power of good to benefit from all this lateral thinking.

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• The Birth of SSAS Compare

  - by Red Gate Software BI Tools Team

  Noemi Moreno, Red Gate Business Intelligence Specialist Software vendors – even Microsoft – tend to forget about the needs of business intelligence developers. We are a rare and rather invisible species. For example, BIDS remained in VS 2008 until SQL Server 2012. It took until this release before we got something as simple as an “undo” function. Before I joined Red Gate as a BI specialist, I worked on SQL Development. I’ll never forget the time I discovered Red Gate’s SQL Compare tool and how it reduced the task of preparing a database release from a couple of days to ten minutes. When I moved to SSAS, MDX and cubes, I became frustrated with the deployment process because I couldn’t find a tool that made Cube releases as easy as they are with SQL Compare. This became my quest. I pitched the idea to a few people in Red Gate’s regular Down Tools Week, when everyone puts down their day-to-day tasks and works on their own projects. My task was to reason with a roomful of cynical developers, hardened to the blandishments of project managers, for help to develop a tool that would compare two different SSAS databases and create the script to process only the objects that needed processing, thereby reducing release time to only a few minutes. I walked to the podium and gave them the full story of the distressed BI specialists, doomed to spend tedious hours preparing deployment scripts. A few developers recovered from their torpor to cast a languid eye at my presentation. It wasn’t enough. In a sudden impulse, I blurted out a promise to perform a flamenco dance for just the team if the tool was able to successfully compare two SSAS databases and generate a script by the end of the week. I was lucky enough that some of them believed me and jumped in: David Pond (Dev), Matt Burton (Dev), Tilman Bregler (Dev), Shobana Sekar (Test), Ruchija Raj (Test), Nick Sutherland (Product Manager) and Irma Tanovic (BI). They didn’t know that Irma and I would be away on a conference in Amsterdam and would leave them without our support. But to my surprise, they had a working tool by the time we came back – basic, and with a few bugs, but a working tool nonetheless! Seeing it compare a very basic SSAS database, detect the changes and generate the scripts was amazing! Something that normally takes half a day was done in under a minute. Since then, a few months have passed and a BI Tools team has been created at Red Gate to work full time on BI tools for BI developers, starting with SSAS Compare. How cool is that? So download the free beta and give us your feedback. And the flamenco? I still need to deliver that. Tilman reminds me every day! I need to get the full flamenco costume.

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• Some Problems Can't Be Outsourced

  - by mikef

  More and more companies are becoming attracted to the idea of Infrastructure as a Service (or IaaS). It would seem that you can outsource the provisioning and management of your services, encompassing everything from Email, through to your servers, workstations and software, all the way down to your LAN and internet services. This type of outsourcing can be a very attractive option for companies who have tight budgets who are short of technical skills or don't have the means to provide long-term IT support. Essentially, they can outsource your services at low short-term costs that are knowable and controllable, are quickly and easily scalable, and generate a minimum of hassle for your internal staff. If you want to get a sophisticated IT infrastructure set up in a hurry without the usual high buy-in costs, or the task of finding and hiring the right specialists. It would seem the way to go, particularly when their salesmen are hypnotizing you with oleaginous phrases such as "we are closely aligned with our client organization's core business requirements, providing agile services". It sounds too good to be true, and so it is. Whereas the costs will have initially been calculated on the annual renewal fees and service fees for ongoing support, there are other charges too which aren't so obvious. It can end up costing far more than the conventional solution once you take into account the extra costs, the fees for customization and upgrades. The Total Cost of Ownership (TCO) only becomes apparent when it is too late to extract the company easily from the arrangement. After a few years, these annual fees can add up to more than the initial cost of implementing a traditional in-house system. Worse than that is that you can then lose your power to determine your priorities: When you become reliant on this company, with its own schedule of priorities, to implement every change, however simple, you have effectively lost control of your technical infrastructure. This will make senior management very nervous. There is definitely a requirement for this sort of service. If you urgently need an exceptionally high class of service or more expertise than you currently possess, then outsourcing is probably for you. You and your IT colleagues will always have something to do, be it user assistance, smoothing out integrations with an external provider, or working on something entirely new. Heck, if you outsource to IBM, the SysAdmins can go along for the ride and polish their expertise. What you need to figure out is how much your time is worth, because time is ultimately all that outsourcing will buy you and your organization. Now you just need to convince your nervous CEO. Cheers, Michael

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• Antenna Aligner Part 5: Devil is in the detail

  - by Chris George

  "The first 90% of a project takes 90% of the time and the last 10% takes the another 200%"  (excerpt from onista) Now that I have a working app (more or less), it's time to make it pretty and slick. I can't stress enough how useful it is to get other people using your software, and my simple app is no exception. I handed my iPhone to a couple of my colleagues at Red Gate and asked them to use it and give me feedback. Immediately it became apparent that the delay between the list page being shown and the list being drawn was too long, and everyone who tried the app clicked on the "Recalculate" button before it had finished. Similarly, selecting a transmitter heralded a delay before the compass page appeared with similar consequences. All users expected there to be some sort of feedback/spinny etc. to show them it is actually doing something. In a similar vein although for opposite reasons, clicking the Recalculate button did indeed recalculate the available transmitters and redraw them, but it did this too fast! One or two users commented that they didn't know if it had done anything. All of these issues resulted in similar solutions; implement a waiting spinny. Thankfully, jquery mobile has one built in, primarily used for ajax operations. Not wishing to bore you with the many many iterations I went through trying to get this to work, I'll just give you my solution! (Seriously, I was working on this most evenings for at least a week!) The final solution for the recalculate problem came in the form of the code below. $(document).on("click", ".show-page-loading-msg", function () {            var $this = $(this),                theme = $this.jqmData("theme") ||                        $.mobile.loadingMessageTheme;            $.mobile.showPageLoadingMsg(theme, "recalculating", false);            setTimeout(function ()                           { $.mobile.hidePageLoadingMsg(); }, 2000);            getLocationData();        })        .on("click", ".hide-page-loading-msg", function () {              $.mobile.hidePageLoadingMsg();        }); The spinny is activated by setting the class of a button (for example) to the 'show-page-loading-msg' class. &lt;a data-role="button" class="show-page-loading-msg"Recalculate This means the code above is fired, calling the showPageLoadingMsg on the document.mobile object. Then, after a 2 second timeout, it calls the hidePageLoadingMsg() function. Supposedly, it should show "recalculating" underneath the spinny, but I've not got that to work. I'm wondering if there is a problem with the jquery mobile implementation. Anyway, it doesn't really matter, it's the principle I'm after, and I now have spinnys!

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• What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners!

  - by Tom Ritter

  I'm looking for the coolest thing you can do in a few lines of simple code. I'm sure you can write a Mandelbrot set in Haskell in 15 lines but it's difficult to follow. My goal is to inspire students that programming is cool. We know that programming is cool because you can create anything you imagine - it's the ultimate creative outlet. I want to inspire these beginners and get them over as many early-learning humps as I can. Now, my reasons are selfish. I'm teaching an Intro to Computing course to a group of 60 half-engineering, half business majors; all freshmen. They are the students who came from underprivileged High schools. From my past experience, the group is generally split as follows: a few rock-stars, some who try very hard and kind of get it, the few who try very hard and barely get it, and the few who don't care. I want to reach as many of these groups as effectively as I can. Here's an example of how I'd use a computer program to teach: Here's an example of what I'm looking for: a 1-line VBS script to get your computer to talk to you: CreateObject("sapi.spvoice").Speak InputBox("Enter your text","Talk it") I could use this to demonstrate order of operations. I'd show the code, let them play with it, then explain that There's a lot going on in that line, but the computer can make sense of it, because it knows the rules. Then I'd show them something like this: 4(5*5) / 10 + 9(.25 + .75) And you can see that first I need to do is (5*5). Then I can multiply for 4. And now I've created the Object. Dividing by 10 is the same as calling Speak - I can't Speak before I have an object, and I can't divide before I have 100. Then on the other side I first create an InputBox with some instructions for how to display it. When I hit enter on the input box it evaluates or "returns" whatever I entered. (Hint: 'oooooo' makes a funny sound) So when I say Speak, the right side is what to Speak. And I get that from the InputBox. So when you do several things on a line, like: x = 14 + y; You need to be aware of the order of things. First we add 14 and y. Then we put the result (what it evaluates to, or returns) into x. That's my goal, to have a bunch of these cool examples to demonstrate and teach the class while they have fun. I tried this example on my roommate and while I may not use this as the first lesson, she liked it and learned something. Some cool mathematica programs that make beautiful graphs or shapes that are easy to understand would be good ideas and I'm going to look into those. Here are some complicated actionscript examples but that's a bit too advanced and I can't teach flash. What other ideas do you have?

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• How to make software development decisions based on facts

  - by Laila

  We love to hear stories about the many and varied ways our customers use the tools that we develop, but in our earnest search for stories and feedback, we'd rather forgotten that some of our keenest users are fellow RedGaters, in the same building. It was almost by chance that we discovered how the SQL Source Control team were using SmartAssembly. As it happens, there is a separate account (here on Simple-Talk) of how SmartAssembly was used to support the Early Access program; by providing answers to specific questions about how the SQL Source Control product was used. But what really got us all grinning was how valuable the SQL Source Control team found the reports that SmartAssembly was quickly and painlessly providing. So gather round, my friends, and I'll tell you the Tale Of The Framework Upgrade . <strange mirage effect to denote a flashback. A subtle background string of music starts playing in minor key> Kevin and his team were undecided. They weren't sure whether they could move their software product from .NET 2 to .NET 3.5 , let alone to .NET 4. You see, they were faced with having to guess what version of .NET was already installed on the average user's machine, which I'm sure you'll agree is no easy task. Upgrading their code to .NET 3.5 might put a barrier to people trying the tool, which was the last thing Kevin wanted: "what if our users have to download X, Y, and Z before being able to open the application?" he asked. That fear of users having to do half an hour of downloads (.followed by at least ten minutes of installation. followed by a five minute restart) meant that Kevin's team couldn't take advantage of WCF (Windows Communication Foundation). This made them sad, because WCF would have allowed them to write their code in a much simpler way, and in hours instead of days (as was the case with .NET 2). Oh sure, they had a gut feeling that this probably wasn't the case, 3.5 had been out for so many years, but they weren't sure. <background music switches to major key> SmartAssembly Feature Usage Reporting gave Kevin and his team exactly what they needed: hard data on their users' systems, both hardware and software. I was there, I saw it happen, and that's not the sort of thing a woman quickly forgets. I'll always remember his last words (before he went to lunch): "You get lots of free information by just checking a box in SmartAssembly" is what he said. For example, they could see how many CPU cores their customers were using, and found out that they should be making use of parallelism to take advantage of available cores. But crucially, (and this is the moral of my tale, dear reader), Kevin saw that 99% of SQL Source Control's users were on .NET 3.5 or above.   So he knew that they could make the switch and that is was safe to do so. With this reassurance, they could use WCF to not only make development easier, but to also give them a really nice way to do inter-process communication between the Source Control and the SQL Compare products. To have done that on .NET 2.0 was certainly possible <knowing chuckle>, but Microsoft have made it a lot easier with WCF. <strange mirage effect to denote end of flashback> So you see, with Feature Usage Reporting, they finally got the hard evidence they needed to safely make the switch to .NET 3.5, knowing it would not inconvenience their users. And that, my friends, is just the sort of thing we like to hear.

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• What’s the use of code reuse?

  - by Tony Davis

  All great developers write reusable code, don’t they? Well, maybe, but as with all statements regarding what “great” developers do or don’t do, it’s probably an over-simplification. A novice programmer, in particular, will encounter in the literature a general assumption of the importance of code reusability. They spend time worrying about DRY (don’t repeat yourself), moving logic into specific “helper” modules that they can then reuse, agonizing about the minutiae of the class structure, inheritance and interface design that will promote easy reuse. Unfortunately, writing code specifically for reuse often leads to complicated object hierarchies and inheritance models that are anything but reusable. If, instead, one strives to write simple code units that are highly maintainable and perform a single function, in a concise, isolated fashion then the potential for reuse simply “drops out” as a natural by-product. Programmers, of course, care about these principles, about encapsulation and clean interfaces that don’t expose inner workings and allow easy pluggability. This is great when it helps with the maintenance and development of code but how often, in practice, do we actually reuse our code? Most DBAs and database developers are familiar with the practical reasons for the limited opportunities to reuse database code and its potential downsides. However, surely elsewhere in our code base, reuse happens often. After all, we can all name examples, such as date/time handling modules, which if we write with enough care we can plug in to many places. I spoke to a developer just yesterday who looked me in the eye and told me that in 30+ years as a developer (a successful one, I’d add), he’d never once reused his own code. As I sat blinking in disbelief, he explained that, of course, he always thought he would reuse it. He’d often agonized over its design, certain that he was creating code of great significance that he and other generations would reuse, with grateful tears misting their eyes. In fact, it never happened. He had in his head, most of the algorithms he needed and would simply write the code from scratch each time, refining the algorithms and tailoring the code to meet the specific requirements. It was, he said, simply quicker to do that than dig out the old code, check it, correct the mistakes, and adapt it. Is this a common experience, or just a strange anomaly? Viewed in a certain light, building code with a focus on reusability seems to hark to a past age where people built cars and music systems with the idea that someone else could and would replace and reuse the parts. Technology advances so rapidly that the next time you need the “same” code, it’s likely a new technique, or a whole new language, has emerged in the meantime, better equipped to tackle the task. Maybe we should be less fearful of the idea that we could write code well suited to the system requirements, but with little regard for reuse potential, and then rewrite a better version from scratch the next time.

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