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• SQL SERVER – Guest Posts – Feodor Georgiev – The Context of Our Database Environment – Going Beyond the Internal SQL Server Waits – Wait Type – Day 21 of 28

  - by pinaldave

  This guest post is submitted by Feodor. Feodor Georgiev is a SQL Server database specialist with extensive experience of thinking both within and outside the box. He has wide experience of different systems and solutions in the fields of architecture, scalability, performance, etc. Feodor has experience with SQL Server 2000 and later versions, and is certified in SQL Server 2008. In this article Feodor explains the server-client-server process, and concentrated on the mutual waits between client and SQL Server. This is essential in grasping the concept of waits in a ‘global’ application plan. Recently I was asked to write a blog post about the wait statistics in SQL Server and since I had been thinking about writing it for quite some time now, here it is. It is a wide-spread idea that the wait statistics in SQL Server will tell you everything about your performance. Well, almost. Or should I say – barely. The reason for this is that SQL Server is always a part of a bigger system – there are always other players in the game: whether it is a client application, web service, any other kind of data import/export process and so on. In short, the SQL Server surroundings look like this: This means that SQL Server, aside from its internal waits, also depends on external waits and settings. As we can see in the picture above, SQL Server needs to have an interface in order to communicate with the surrounding clients over the network. For this communication, SQL Server uses protocol interfaces. I will not go into detail about which protocols are best, but you can read this article. Also, review the information about the TDS (Tabular data stream). As we all know, our system is only as fast as its slowest component. This means that when we look at our environment as a whole, the SQL Server might be a victim of external pressure, no matter how well we have tuned our database server performance. Let’s dive into an example: let’s say that we have a web server, hosting a web application which is using data from our SQL Server, hosted on another server. The network card of the web server for some reason is malfunctioning (think of a hardware failure, driver failure, or just improper setup) and does not send/receive data faster than 10Mbs. On the other end, our SQL Server will not be able to send/receive data at a faster rate either. This means that the application users will notify the support team and will say: “My data is coming very slow.” Now, let’s move on to a bit more exciting example: imagine that there is a similar setup as the example above – one web server and one database server, and the application is not using any stored procedure calls, but instead for every user request the application is sending 80kb query over the network to the SQL Server. (I really thought this does not happen in real life until I saw it one day.) So, what happens in this case? To make things worse, let’s say that the 80kb query text is submitted from the application to the SQL Server at least 100 times per minute, and as often as 300 times per minute in peak times. Here is what happens: in order for this query to reach the SQL Server, it will have to be broken into a of number network packets (according to the packet size settings) – and will travel over the network. On the other side, our SQL Server network card will receive the packets, will pass them to our network layer, the packets will get assembled, and eventually SQL Server will start processing the query – parsing, allegorizing, generating the query execution plan and so on. So far, we have already had a serious network overhead by waiting for the packets to reach our Database Engine. There will certainly be some processing overhead – until the database engine deals with the 80kb query and its 20 subqueries. The waits you see in the DMVs are actually collected from the point the query reaches the SQL Server and the packets are assembled. Let’s say that our query is processed and it finally returns 15000 rows. These rows have a certain size as well, depending on the data types returned. This means that the data will have converted to packages (depending on the network size package settings) and will have to reach the application server. There will also be waits, however, this time you will be able to see a wait type in the DMVs called ASYNC_NETWORK_IO. What this wait type indicates is that the client is not consuming the data fast enough and the network buffers are filling up. Recently Pinal Dave posted a blog on Client Statistics. What Client Statistics does is captures the physical flow characteristics of the query between the client(Management Studio, in this case) and the server and back to the client. As you see in the image, there are three categories: Query Profile Statistics, Network Statistics and Time Statistics. Number of server roundtrips–a roundtrip consists of a request sent to the server and a reply from the server to the client. For example, if your query has three select statements, and they are separated by ‘GO’ command, then there will be three different roundtrips. TDS Packets sent from the client – TDS (tabular data stream) is the language which SQL Server speaks, and in order for applications to communicate with SQL Server, they need to pack the requests in TDS packets. TDS Packets sent from the client is the number of packets sent from the client; in case the request is large, then it may need more buffers, and eventually might even need more server roundtrips. TDS packets received from server –is the TDS packets sent by the server to the client during the query execution. Bytes sent from client – is the volume of the data set to our SQL Server, measured in bytes; i.e. how big of a query we have sent to the SQL Server. This is why it is best to use stored procedures, since the reusable code (which already exists as an object in the SQL Server) will only be called as a name of procedure + parameters, and this will minimize the network pressure. Bytes received from server – is the amount of data the SQL Server has sent to the client, measured in bytes. Depending on the number of rows and the datatypes involved, this number will vary. But still, think about the network load when you request data from SQL Server. Client processing time – is the amount of time spent in milliseconds between the first received response packet and the last received response packet by the client. Wait time on server replies – is the time in milliseconds between the last request packet which left the client and the first response packet which came back from the server to the client. Total execution time – is the sum of client processing time and wait time on server replies (the SQL Server internal processing time) Here is an illustration of the Client-server communication model which should help you understand the mutual waits in a client-server environment. Keep in mind that a query with a large ‘wait time on server replies’ means the server took a long time to produce the very first row. This is usual on queries that have operators that need the entire sub-query to evaluate before they proceed (for example, sort and top operators). However, a query with a very short ‘wait time on server replies’ means that the query was able to return the first row fast. However a long ‘client processing time’ does not necessarily imply the client spent a lot of time processing and the server was blocked waiting on the client. It can simply mean that the server continued to return rows from the result and this is how long it took until the very last row was returned. The bottom line is that developers and DBAs should work together and think carefully of the resource utilization in the client-server environment. From experience I can say that so far I have seen only cases when the application developers and the Database developers are on their own and do not ask questions about the other party’s world. I would recommend using the Client Statistics tool during new development to track the performance of the queries, and also to find a synchronous way of utilizing resources between the client – server – client. Here is another example: think about similar setup as above, but add another server to the game. Let’s say that we keep our media on a separate server, and together with the data from our SQL Server we need to display some images on the webpage requested by our user. No matter how simple or complicated the logic to get the images is, if the images are 500kb each our users will get the page slowly and they will still think that there is something wrong with our data. Anyway, I don’t mean to get carried away too far from SQL Server. Instead, what I would like to say is that DBAs should also be aware of ‘the big picture’. I wrote a blog post a while back on this topic, and if you are interested, you can read it here about the big picture. And finally, here are some guidelines for monitoring the network performance and improving it: Run a trace and outline all queries that return more than 1000 rows (in Profiler you can actually filter and sort the captured trace by number of returned rows). This is not a set number; it is more of a guideline. The general thought is that no application user can consume that many rows at once. Ask yourself and your fellow-developers: ‘why?’. Monitor your network counters in Perfmon: Network Interface:Output queue length, Redirector:Network errors/sec, TCPv4: Segments retransmitted/sec and so on. Make sure to establish a good friendship with your network administrator (buy them coffee, for example J ) and get into a conversation about the network settings. Have them explain to you how the network cards are setup – are they standalone, are they ‘teamed’, what are the settings – full duplex and so on. Find some time to read a bit about networking. In this short blog post I hope I have turned your attention to ‘the big picture’ and the fact that there are other factors affecting our SQL Server, aside from its internal workings. As a further reading I would still highly recommend the Wait Stats series on this blog, also I would recommend you have the coffee break conversation with your network admin as soon as possible. This guest post is written by Feodor Georgiev. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, Readers Contribution, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL

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• SQLAuthority News – Job Interviewing the Right Way (and for the Right Reasons) – Guest Post by Feodor Georgiev

  - by pinaldave

  Feodor Georgiev is a SQL Server database specialist with extensive experience of thinking both within and outside the box. He has wide experience of different systems and solutions in the fields of architecture, scalability, performance, etc. Feodor has experience with SQL Server 2000 and later versions, and is certified in SQL Server 2008. Feodor has written excellent article on Job Interviewing the Right Way. Here is his article in his own language. A while back I was thinking to start a blog post series on interviewing and employing IT personnel. At that time I had just read the ‘Smart and gets things done’ book (http://www.joelonsoftware.com/items/2007/06/05.html) and I was hyped up on some debatable topics regarding finding and employing the best people in the branch. I have no problem with hiring the best of the best; it’s just the definition of ‘the best of the best’ that makes things a bit more complicated. One of the fundamental books one can read on the topic of interviewing is the one mentioned above. If you have not read it, then you must do so; not because it contains the ultimate truth, and not because it gives the answers to most questions on the subject, but because the book contains an extensive set of questions about interviewing and employing people. Of course, a big part of these questions have different answers, depending on location, culture, available funds and so on. (What works in the US may not necessarily work in the Nordic countries or India, or it may work in a different way). The only thing that is valid regardless of any external factor is this: curiosity. In my belief there are two kinds of people – curious and not-so-curious; regardless of profession. Think about it – professional success is directly proportional to the individual’s curiosity + time of active experience in the field. (I say ‘active experience’ because vacations and any distractions do not count as experience :)  ) So, curiosity is the factor which will distinguish a good employee from the not-so-good one. But let’s shift our attention to something else for now: a few tips and tricks for successful interviews. Tip and trick #1: get your priorities straight. Your status usually dictates your priorities; for example, if the person looking for a job has just relocated to a new country, they might tend to ignore some of their priorities and overload others. In other words, setting priorities straight means to define the personal criteria by which the interview process is lead. For example, similar to the following questions can help define the criteria for someone looking for a job: How badly do I need a (any) job? Is it more important to work in a clean and quiet environment or is it important to get paid well (or both, if possible)? And so on… Furthermore, before going to the interview, the candidate should have a list of priorities, sorted by the most importance: e.g. I want a quiet environment, x amount of money, great helping boss, a desk next to a window and so on. Also it is a good idea to be prepared and know which factors can be compromised and to what extent. Tip and trick #2: the interview is a two-way street. A job candidate should not forget that the interview process is not a one-way street. What I mean by this is that while the employer is interviewing the potential candidate, the job seeker should not miss the chance to interview the employer. Usually, the employer and the candidate will meet for an interview and talk about a variety of topics. In a quality interview the candidate will be presented to key members of the team and will have the opportunity to ask them questions. By asking the right questions both parties will define their opinion about each other. For example, if the candidate talks to one of the potential bosses during the interview process and they notice that the potential manager has a hard time formulating a question, then it is up to the candidate to decide whether working with such person is a red flag for them. There are as many interview processes out there as there are companies and each one is different. Some bigger companies and corporates can afford pre-selection processes, 3 or even 4 stages of interviews, small companies usually settle with one interview. Some companies even give cognitive tests on the interview. Why not? In his book Joel suggests that a good candidate should be pampered and spoiled beyond belief with a week-long vacation in New York, fancy hotels, food and who knows what. For all I can imagine, an interview might even take place at the top of the Eifel tower (right, Mr. Joel, right?) I doubt, however, that this is the optimal way to capture the attention of a good employee. The ‘curiosity’ topic What I have learned so far in my professional experience is that opinions can be subjective. Plus, opinions on technology subjects can also be subjective. According to Joel, only hiring the best of the best is worth it. If you ask me, there is no such thing as best of the best, simply because human nature (well, aside from some physical limitations, like putting your pants on through your head :) ) has no boundaries. And why would it have boundaries? I have seen many curious and interesting people, naturally good at technology, though uninterested in it as one  can possibly be; I have also seen plenty of people interested in technology, who (in an ideal world) should have stayed far from it. At any rate, all of this sums up at the end to the ‘supply and demand’ factor. The interview process big-bang boils down to this: If there is a mutual benefit for both the employer and the potential employee to work together, then it all sorts out nicely. If there is no benefit, then it is much harder to get to a common place. Tip and trick #3: word-of-mouth is worth a thousand words Here I would just mention that the best thing a job candidate can get during the interview process is access to future team members or other employees of the new company. Nowadays the world has become quite small and everyone knows everyone. Look at LinkedIn, look at other professional networks and you will realize how small the world really is. Knowing people is a good way to become more approachable and to approach them. Tip and trick #4: Be confident. It is true that for some people confidence is as natural as breathing and others have to work hard to express it. Confidence is, however, a key factor in convincing the other side (potential employer or employee) that there is a great chance for success by working together. But it cannot get you very far if it’s not backed up by talent, curiosity and knowledge. Tip and trick #5: The right reasons What really bothers me in Sweden (and I am sure that there are similar situations in other countries) is that there is a tendency to fill quotas and to filter out candidates by criteria different from their skill and knowledge. In job ads I see quite often the phrases ‘positive thinker’, ‘team player’ and many similar hints about personality features. So my guess here is that discrimination has evolved to a new level. Let me clear up the definition of discrimination: ‘unfair treatment of a person or group on the basis of prejudice’. And prejudice is the ‘partiality that prevents objective consideration of an issue or situation’. In other words, there is not much difference whether a job candidate is filtered out by race, gender or by personality features – it is all a bad habit. And in reality, there is no proven correlation between the technology knowledge paired with skills and the personal features (gender, race, age, optimism). It is true that a significantly greater number of Darwin awards were given to men than to women, but I am sure that somewhere there is a paper or theory explaining the genetics behind this. J This topic actually brings to mind one of my favorite work related stories. A while back I was working for a big company with many teams involved in their processes. One of the teams was occupying 2 rooms – one had the team members and was full of light, colorful posters, chit-chats and giggles, whereas the other room was dark, lighted only by a single monitor with a quiet person in front of it. Later on I realized that the ‘dark room’ person was the guru and the ultimate problem-solving-brain who did not like the chats and giggles and hence was in a separate room. In reality, all severe problems which the chatty and cheerful team members could not solve and all emergencies were directed to ‘the dark room’. And thus all worked out well. The moral of the story: Personality has nothing to do with technology knowledge and skills. End of story. Summary: I’d like to stress the fact that there is no ultimately perfect candidate for a job, and there is no such thing as ‘best-of-the-best’. From my personal experience, the main criteria by which I measure people (co-workers and bosses) is the curiosity factor; I know from experience that the more curious and inventive a person is, the better chances there are for great achievements in their field. Related stories: (for extra credit) 1) Get your priorities straight. A while back as a consultant I was working for a few days at a time at different offices and for different clients, and so I was able to compare and analyze the work environments. There were two different places which I compared and recently I asked a friend of mine the following question: “Which one would you prefer as a work environment: a noisy office full of people, or a quiet office full of faulty smells because the office is rarely cleaned?” My friend was puzzled for a while, thought about it and said: “Hmm, you are talking about two different kinds of pollution… I will probably choose the second, since I can clean the workplace myself a bit…” 2) The interview is a two-way street. One time, during a job interview, I met a potential boss that had a hard time phrasing a question. At that particular time it was clear to me that I would not have liked to work under this person. According to my work religion, the properly asked question contains at least half of the answer. And if I work with someone who cannot ask a question… then I’d be doing double or triple work. At another interview, after the technical part with the team leader of the department, I was introduced to one of the team members and we were left alone for 5 minutes. I immediately jumped on the occasion and asked the blunt question: ‘What have you learned here for the past year and how do you like your job?’ The team member looked at me and said ‘Nothing really. I like playing with my cats at home, so I am out of here at 5pm and I don’t have time for much.’ I was disappointed at the time and I did not take the job offer. I wasn’t that shocked a few months later when the company went bankrupt. 3) The right reasons to take a job: personality check. A while back I was asked to serve as a job reference for a coworker. I agreed, and after some weeks I got a phone call from the company where my colleague was applying for a job. The conversation started with the manager’s question about my colleague’s personality and about their social skills. (You can probably guess what my internal reaction was… J ) So, after 30 minutes of pouring common sense into the interviewer’s head, we finally agreed on the fact that a shy or quiet personality has nothing to do with work skills and knowledge. Some years down the road my former colleague is taking the manager’s position as the manager is demoted to a different department. Reference: Feodor Georgiev, Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, Readers Contribution, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• How to set up an FTP user on UBUNTU 9 server using vsftpd utility?

  - by Pavel

  Hi guys. I'm kinda new to this so bear with me. I've set up a server and now I need to create ftp user for it. I'm doing this by typing: useradd pavel passwd pavel And then I'm running iptables -I INPUT 1 -p tcp --dport 21 -j ACCEPT iptables-save > /etc/iptables.rules in order to open ftp ports and lastly, I'm changing the usermod by: usermod -s /bin/sh pavel So now tell me - what I'm doing wrong here? I just want to connect using FTP protocol. Please help...

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• Check if a Lat/Long point is on the GRoute

  - by Pavel

  I'm ploting a route between two points and I need to check if the route goes through a predefiend location. In the api, each GStep has a start and end points but the path doesn't have to be straight. Given a Lat/Long point, is there a way to check if it intersects with a route? -- Pavel

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• Silverlight Cream for April 05, 2010 -- #831

  - by Dave Campbell

  In this Issue: Rénald Nollet, Davide Zordan(-2-, -3-), Scott Barnes, Kirupa, Christian Schormann, Tim Heuer, Yavor Georgiev, and Bea Stollnitz. Shoutouts: Yavor Georgiev posted the material for his MIX 2010 talk: what’s new in WCF in Silverlight 4 Erik Mork and crew posted their This Week in Silverlight 4.1.2010 Tim Huckaby and MSDN Bytes interviewed Erik Mork: Silverlight Consulting Life – MSDN Bytes Interview From SilverlightCream.com: Home Loan Application for Windows Phone Rénald Nollet has a WP7 app up, with source, for calculating Home Loan application information. He also discusses some control issues he had with the emulator. Experiments with Multi-touch: A Windows Phone Manipulation sample Davide Zordan has updated the multi-touch project on CodePlex, and added a WP7 sample using multi-touch. Silverlight 4, MEF and MVVM: EventAggregator, ImportingConstructor and Unit Tests Davide Zordan has a second post up on MEF, MVVM, and Prism, oh yeah, and also Unit Testing... the code is available, so take a look at what he's all done with this. Silverlight 4, MEF and MVVM: MEFModules, Dynamic XAP Loading and Navigation Applications Davide Zordan then builds on the previous post and partitions the app into several XAPs put together at runtime with MEF. Silverlight Installation/Preloader Experience - BarnesStyle Scott Barnes talks about the install experience he wanted to get put into place... definitely a good read and lots of information. Changing States using GoToStateAction Kirupa has a quick run-through of Visual States, and then demonstrates using GoToStateAction and a note for a Blend 4 addition. Blend 4: About Path Layout, Part IV Christian Schormann has the next tutorial up in his series on Path Layout, and he's explaining Motion Path and Text on a Path. Managing service references and endpoint configurations for Silverlight applications Helping solve a common and much reported problem of managing service references, Tim Heuer details his method of resolving it and additional tips and tricks to boot. Some known WCF issues in Silverlight 4 Yavor Georgiev, a Program Manager for WCF blogged about the issues that they were not able to fix due to scheduling of the release How can I update LabeledPieChart to use the latest toolkit? Bea Stollnitz revisits some of her charting posts to take advantage of the unsealing of toolkit classes in labeling the Chart and PieSeries Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• Spring Webflow in Grails keeping plenty of hibernate sessions open

  - by Pavel P

  Hi, I have an Internet app running on Grails 1.1.2 and it integrates Spring WebFlow mechanism. The problem is that there are some bots ignoring robots.txt and are entering the flow quite often. Because second step of the flow needs some human intelligence, the bot leaves open flow after the first step. This causes a lot of open flows which leades to a lot of abandoned open hibernate sessions. Do you know some common clean-up mechanism for this kind of unattended flows (plus hibernate sessions) in Grails+Spring WebFlow? Thanks, Pavel

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• Disabling Windows Server 2008 firewall

  - by Vladimir Georgiev

  I am very stupid. I applied a windows firewall rule that blocks all tcp connection and thus kicking me out of remote desktop on a dedicated server. I managed to get into recovery via VNC, which is basically a windows xp recovery system. I have access to the physical files of the Windows Server 2008 R2 installation, but I don't know how to disable the firewall so I can reboot from recovery and connect to the W2K8 via remote desktop. Please, help.

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• Cannot access localhost without internet connection

  - by Pavel K.

  for some reason i cannot access localhost without internet connection in ubuntu, as soon as i disconnect from internet (with gui networkmanager), both "ping localhost" and "ping 127.0.0.1" return: ping: sendmsg: Operation not permitted i switched off iptables, "iptables -L" gives: Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination what could be the problem?

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• Network config with pppoe and Ubuntu 13.10

  - by Pavel

  I have an internet connection that is using pppoe. In my windows I do not assign an ip address for my network and I am able to connect using password and username. I installed Ubintu 13.10 today, and I did pppoeconf, and I setup an ip/network mask and changed the mac address in the options, and I was able to connect to the Internet. I restarted the computer, and I got a message saying that the wired connection is not managed. Internet was not working. I went to network manager file, and I changed the option to true, but I still can't connect to the Internet. I am pretty new to linux. How can I get my Internet working? Thanks

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• Netbeans and LibreOffice do not recognize the new fonts in /usr/share/fonts

  - by Pavel

  I installed some new fonts following this guide https://wiki.ubuntu.com/Fonts. Netbeans and LibreOffice do not recognize the new fonts in /usr/share/fonts and Mousepad recognizes them. Netbeans7.4(from Netbeans.com) recognizes the fonts if they are located in .fonts/ in my home folder. How can I make Netbeans and Libre Office recognize the new fonts located in /usr/share/fonts. I am using Xubuntu 13.10

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• Asynchronous connectToServer

  - by Pavel Bucek

  Users of JSR-356 – Java API for WebSocket are probably familiar with WebSocketContainer#connectToServer method. This article will be about its usage and improvement which was introduce in recent Tyrus release. WebSocketContainer#connectToServer does what is says, it connects to WebSocketServerEndpoint deployed on some compliant container. It has two or three parameters (depends on which representation of client endpoint are you providing) and returns aSession. Returned Session represents WebSocket connection and you are instantly able to send messages, register MessageHandlers, etc. An issue might appear when you are trying to create responsive user interface and use this method – its execution blocks until Session is created which usually means some container needs to be started, DNS queried, connection created (it’s even more complicated when there is some proxy on the way), etc., so nothing which might be really considered as responsive. Trivial and correct solution is to do this in another thread and monitor the result, but.. why should users do that? :-) Tyrus now provides async* versions of all connectToServer methods, which performs only simple (=fast) check in the same thread and then fires a new one and performs all other tasks there. Return type of these methods is Future<Session>. List of added methods: public Future<Session> asyncConnectToServer(Class<?> annotatedEndpointClass, URI path) public Future<Session> asyncConnectToServer(Class<? extends Endpoint>  endpointClass, ClientEndpointConfig cec, URI path) public Future<Session> asyncConnectToServer(Endpoint endpointInstance, ClientEndpointConfig cec, URI path) public Future<Session> asyncConnectToServer(Object obj, URI path) As you can see, all connectToServer variants have its async* alternative. All these methods do throw DeploymentException, same as synchronous variants, but some of these errors cannot be thrown as a result of the first method call, so you might get it as the cause ofExecutionException thrown when Future<Session>.get() is called. Please let us know if you find these newly added methods useful or if you would like to change something (signature, functionality, …) – you can send us a comment to [email protected] or ping me personally. Related links: https://tyrus.java.net https://java.net/jira/browse/TYRUS/ https://github.com/tyrus-project/tyrus

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• Jersey non blocking client

  - by Pavel Bucek

  Although Jersey already have support for making asynchronous requests, it is implemented by standard blocking way - every asynchronous request is handled by one thread and that thread is released only after request is completely processed. That is OK for lots of cases, but imagine how that will work when you need to do lots of parallel requests. Of course you can limit (and its really wise thing to do, you do want control your resources) number of threads used for asynchronous requests, but you'll get another maybe not pleasant consequence - obviously processing time will incerase. There are few projects which are trying to deal with that problem, commonly named as async http clients. I didn't want to "re-implement a wheel" and I decided I'll use AHC - Async Http Client made by Jeanfrancois Arcand. There is also interesting implementation from Apache - HttpAsyncClient, but it is still in "very early stages of development" and others haven't been in similar or better shape as AHC. How this works? Non-blocking clients allow users to make same asynchronous requests as we can do with standard approach but implementation is different - threads are better utilized, they don't spend most of time in idle state. Simply described - when you make a request (send it over the network), you are waiting for reply from other side. And there comes main advantage of non-blocking approach - it uses these threads for further work, like making other requests or processing responses etc.. Idle time is minimized and your resources (threads) will be far better used. Who should consider using this? Everyone who is making lots of asynchronous requests. I haven't done proper benchmark yet, but some simple dumb tests are showing huge improvement in cases where lots of concurrent asynchronous requests are made in short period. Last but not least - this module is still experimental, so if you don't like something or if you have ideas for improvements/any feedback, feel free to comment this blog post, send mail to [email protected] or contact me personally. All feedback is greatly appreciated! maven dependency (will be present in java.net maven 2 repo by the end of the day): link: http://download.java.net/maven/2/com/sun/jersey/experimental/jersey-non-blocking-client <dependency> <groupId>com.sun.jersey.experimental</groupId> <artifactId>jersey-non-blocking-client</artifactId> <version>1.9-SNAPSHOT</version> </dependency> code snippet: ClientConfig cc = new DefaultNonBlockingClientConfig(); cc.getProperties().put(NonBlockingClientConfig.PROPERTY_THREADPOOL_SIZE, 10); // default value, feel free to change Client c = NonBlockingClient.create(cc); AsyncWebResource awr = c.asyncResource("http://oracle.com"); Future<ClientResponse> responseFuture = awr.get(ClientResponse.class); // or awr.get(new TypeListener<ClientResponse>(ClientResponse.class) { @Override public void onComplete(Future<ClientResponse> f) throws InterruptedException { ... } }); javadoc (temporary location, won't be updated): http://anise.cz/~paja/jersey-non-blocking-client/

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• Tyrus 1.3

  - by Pavel Bucek

  I’m pleased to announce that new version of Tyrus was released today. It contains some interesting features, like asynchronous handling of connectToServer method call, optimised broadcast support and lots of stability and performance improvements. As previously – I will follow with more blog posts about selected features later. Some of them are already described in updated User guide. Complete list of bugfixes and new featuresTYRUS-262: @OnOpen fails for programmatically deployed annotated endpoint.TYRUS-261: Text decoder disables Binary decoder if both are configured for the same server endpoint; endpoint cannot receive binary messages anymore.TYRUS-248: Consolidate Extension representationTYRUS-258: Tyrus always creates HTTP sessionTYRUS-251: DecodeException is not passed to @OnError methodTYRUS-252: encoder for primitive types cannot be overridden.TYRUS-250: Sec-WebSocket-Protocol header cannot be present when there is no negotiated subprotocolTYRUS-249: WebSocketContainer MaxSessionIdleTimeout is not propagated to Session (server side)TYRUS-257: Async timeout value set on WebSocketContainer is not propagated to RemoteEndpoints (Session#getAsyncRemote())TYRUS-253: DecodeException is not passed to @OnError method from session.getAsyncRemote().sendObjectTYRUS-243: WebSocketContainer.connectToServer can block for secondsTYRUS-227: Build failure : AsyncBinaryTestTYRUS-226: Tyrus build error : OnCloseTestTYRUS-247: Make all samples use TestContainer for testsTYRUS-238: Refactor WebSocketEngine (SPI and Impl)TYRUS-157: Submitting tasks to an injected ManagedExecutorService in a ServerEndpoint does not workTYRUS-137: Improve subprotocols/extensions headers parsingTYRUS-133: Some Broadcast(er) API is needed in order to opmtimize chat-like usecasesTYRUS-245: ServerEndpointConfig#getConfiigurator returns Configurator not used when getNegotiatedExtensions has been called.TYRUS-240: clean up duplicated static fields (strings)TYRUS-230: When Session is invalidated, the close reason is not 1006TYRUS-190: Remove TyrusServetServerContainer (merge with TyrusServerContainer)TYRUS-65: Implement common utilities for testingTYRUS-242: Tyrus does not run on JDK8 compact2 profileTYRUS-237: RemoteEndpoint.Async#sendBinary does not throw IllegalArgumentException when data is nullTYRUS-239: Improve WebSocketEngine ByteBuffer handlingTYRUS-232: Refactor grizzly/servlet container – Tyrus-SPITYRUS-235: Fix findbugs errors in tests/servletTYRUS-234: Remove support for older protocol versionTYRUS-229: Session#setMaxIdleTimeout() will kill the session whether or not the session actually timed outTYRUS-225: Invalidation of (Servlet) HttpSession does not invalidate WebSocket SessionTYRUS-153: Static map in TyrusRemotEndpointTYRUS-201: Wrong ServletInputStream#isReady() usage in TyrusHttpUpgradeHandlerTYRUS-224: Refactor Connection#write and ConnectionImpl to use CompletionHandler only (no Future)TYRUS-221: wss:// doesn’t appear to function correctly via a http proxy.TYRUS-146: Support request from client to secured services (“wss”)TYRUS-223: Message can be writen multiple times when running on Servlet container TYRUS-71: ErroCollector not properly used in AnnotatedEndpoint class. Tyrus 1.3 will be integrated in Glassfish trunk soon – you can download nightly build or upgrade to newer Tyrus manually (replace all Tyrus jars).

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• How do managers know if a person is a good or a bad programmer?

  - by Pavel Shved

  In most companies that do programming teams and divisions consist of programmers who design and write code and managers who... well, do the management stuff. Aside from just not writing code, managers usually do not even look at the code the team develops, and may even have no proper IDE installed on their work machines. Still, the managers are to judge if a person works well, if he or she should be put in charge of something, or if particular developer should be assigned to a task of the most importance and responsibility. And last, but not least: the managers usually assign the quarterly bonuses! To do the above effectively, a manager should know if a person is a good programmer—among other traits, of course. The question is, how do they do it? They don't even look at the code people write, they can't directly assess the quality of the components programmers develop... but their estimates of who is a good coder, and who is "not as good" are nevertheless correct in most cases! What is the secret?

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• 13.10 hangs on waking from suspend except when suspended from console

  - by Pavel

  I know waking from suspend is an issue, but this looks like a separate bug. When I suspend 13.10 on HP Pavillion dv6 (AMD 6770M/fglrx 13.10.10) from x, it suspends normally but freezes when waking. I get a black screen with a frozen cursor. But when I suspend from console with sudo pm-suspend, it wakes normally, and I can then get back my x with ctrl-alt-f7. If I suspend by closing lid under x, also freezes when waking up. If I suspend by closing lid under console, it wakes up into the x (?) login, then into a clean session.

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• Tyrus 1.8

  - by Pavel Bucek

  Another version of Tyrus, the reference implementation of JSR 356 – Java API for WebSocket is out! Complete list of fixes and features is below, but let me describe some of the new features in more detail. All information presented here is also available in Tyrusdocumentation. What’s new? First to mention is that JSR 356 Maintenance review Ballot is over and the change proposed for 1.1 release was accepted. More details about changes in the API can be found in this article. Important part is that Tyrus 1.8 implements this API, meaning you can use Lambda expressions and some features of Nashorn without the need for any workarounds. Almost all other features are related to client side support, which was significantly improved in this release. Firstly – I have to admit, that Tyrus client contained security issue – SSL Hostname verification was not performed when connecting to “wss” endpoints. This was fixed as part of TYRUS-339 and resulted in some changes in the client configuration API. Now you can control whether HostnameVerification should be performed (SslEngineConfigurator#setHostnameVerificationEnabled(boolean)) or even set your own HostnameVerifier (please use carefully): #setHostnameVerifier(…). Detailed description can be found in Host verification chapter. Another related enhancement is support for Http Basic and Digest authentication schemes. Tyrus client now enables users to provide credentials and underlying implementation will take care of everything else. Our implementation is strictly non pre-emptive, so the login information is sent always as a response to 401 Http Status Code. If the Basic and Digest are not good enough and there is a need to use some custom scheme or something which is not yet supported in Tyrus, custom Authenticator can be registered and the authentication part of the handshake process will be handled by it. Please seeClient HTTP Authentication chapter in the user guide for more details. There are other features, like fine-grain threadpool configuration for JDK client container, build-in Http redirect support and some reshuffling related to unifying the location of client configuration classes and properties definition – every property should be now part of ClientProperties class. All new features are described in the user guide – in chapterTyrus proprietary configuration. Update – Tyrus 1.8.1 There was another slightly late reported issue related to running in environments with SecurityManager enabled, so this version fixes that. Another noteworthy fixes are TYRUS-355 and TYRUS-361; the first one is about incorrect thread factory used for shared container timeout, which resulted in JVM waiting for that thread and not exiting as it should. The other issue enables relative URIs in Location header when using redirect feature. Links Tyrus homepage mailing list JIRA Complete list of changes: Bug [TYRUS-333] – Multiple endpoints on one client [TYRUS-334] – When connection is closed by a peer, periodic heartbeat pong is not stopped [TYRUS-336] – ReaderBuffer.getNextChars() keeps blocking a server thread after client has closed the session [TYRUS-338] – JDK client SSL filter needs better synchronization during handshake phase [TYRUS-339] – SSL hostname verification is missing [TYRUS-340] – Test PathParamTest are not stable with JDK client [TYRUS-341] – A control frame inside a stream of continuation frames is treated as the part of the stream [TYRUS-343] – ControlFrameInDataStreamTest does not pass on GF [TYRUS-345] – NPE is thrown, when shared container timeout property in JDK client is not set [TYRUS-346] – IllegalStateException is thrown, when using proxy in JDK client [TYRUS-347] – Introduce better synchronization in JDK client thread pool [TYRUS-348] – When a client and server close connection simultaneously, JDK client throws NPE [TYRUS-356] – Tyrus cannot determine the connection port for a wss URL [TYRUS-357] – Exception thrown in MessageHandler#OnMessage is not caught in @OnError method [TYRUS-359] – Client based on Java 7 Asynchronous IO makes application unexitable Improvement [TYRUS-328] – JDK 1.7 AIO Client container – threads – (setting threadpool, limits, …) [TYRUS-332] – Consolidate shared client properties into one file. [TYRUS-337] – Create an SSL version of Basic Servlet test New Feature [TYRUS-228] – Add client support for HTTP Basic/Digest Task [TYRUS-330] – create/run tests/servlet/basic via wss [TYRUS-335] – [clustering] – introduce RemoteSession and expose them via separate method (not include remote sessions in the getOpenSessions()) [TYRUS-344] – Introduce Client support for HTTP Redirect

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• Securing WebSocket applications on Glassfish

  - by Pavel Bucek

  Today we are going to cover deploying secured WebSocket applications on Glassfish and access to these services using WebSocket Client API. WebSocket server application setup Our server endpoint might look as simple as this: @ServerEndpoint("/echo") public class EchoEndpoint { @OnMessage   public String echo(String message) {     return message + " (from your server)";   } } Everything else must be configured on container level. We can start with enabling SSL, which will require web.xml to be added to your project. For starters, it might look as following: <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee">   <security-constraint>     <web-resource-collection>       <web-resource-name>Protected resource</web-resource-name>       <url-pattern>/*</url-pattern>       <http-method>GET</http-method>     </web-resource-collection>     <!-- https -->     <user-data-constraint>       <transport-guarantee>CONFIDENTIAL</transport-guarantee>     </user-data-constraint>   </security-constraint> </web-app> This is minimal web.xml for this task - web-resource-collection just defines URL pattern and HTTP method(s) we want to put a constraint on and user-data-constraint defines that constraint, which is in our case transport-guarantee. More information about these properties and security settings for web application can be found in Oracle Java EE 7 Tutorial. I have some simple webpage attached as well, so I can test my endpoint right away. You can find it (along with complete project) in Tyrus workspace: [webpage] [whole project]. After deploying this application to Glassfish Application Server, you should be able to hit it using your favorite browser. URL where my application resides is https://localhost:8181/sample-echo-https/ (may be different, depends on other configuration). My browser warns me about untrusted certificate (I use what freshly built Glassfish provides - self signed certificates) and after adding an exception for this site, I can see my webpage and I am able to securely connect to wss://localhost:8181/sample-echo-https/echo. WebSocket client Already mentioned demo application also contains test client, but execution of this is skipped for normal build. Reason for this is that Glassfish uses these self-signed "random" untrusted certificates and you are (in most cases) not able to connect to these services without any additional settings. Creating test WebSocket client is actually quite similar to server side, only difference is that you have to somewhere create client container and invoke connect with some additional info. Java API for WebSocket allows you to use annotated and programmatic way to construct endpoints. Server side shows the annotated case, so let's see how the programmatic approach will look. final WebSocketContainer client = ContainerProvider.getWebSocketContainer(); client.connectToServer(new Endpoint() {   @Override   public void onOpen(Session session, EndpointConfig EndpointConfig) {     try {       // register message handler - will just print out the       // received message on standard output.       session.addMessageHandler(new MessageHandler.Whole<String>() {       @Override         public void onMessage(String message) {          System.out.println("### Received: " + message);         }       });       // send a message       session.getBasicRemote().sendText("Do or do not, there is no try.");     } catch (IOException e) {       // do nothing     }   } }, ClientEndpointConfig.Builder.create().build(),    URI.create("wss://localhost:8181/sample-echo-https/echo")); This client should work with some secured endpoint with valid certificated signed by some trusted certificate authority (you can try that with wss://echo.websocket.org). Accessing our Glassfish instance will require some additional settings. You can tell Java which certificated you trust by adding -Djavax.net.ssl.trustStore property (and few others in case you are using linked sample). Complete command line when you are testing your service might need to look somewhat like: mvn clean test -Djavax.net.ssl.trustStore=$AS_MAIN/domains/domain1/config/cacerts.jks\ -Djavax.net.ssl.trustStorePassword=changeit -Dtyrus.test.host=localhost\ -DskipTests=false Where AS_MAIN points to your Glassfish instance. Note: you might need to setup keyStore and trustStore per client instead of per JVM; there is a way how to do it, but it is Tyrus proprietary feature: http://tyrus.java.net/documentation/1.2.1/user-guide.html#d0e1128. And that's it! Now nobody is able to "hear" what you are sending to or receiving from your WebSocket endpoint. There is always room for improvement, so the next step you might want to take is introduce some authentication mechanism (like HTTP Basic or Digest). This topic is more about container configuration so I'm not going to go into details, but there is one thing worth mentioning: to access services which require authorization, you might need to put this additional information to HTTP headers of first (Upgrade) request (there is not (yet) any direct support even for these fundamental mechanisms, user need to register Configurator and add headers in beforeRequest method invocation). I filed related feature request as TYRUS-228; feel free to comment/vote if you need this functionality.

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• How to mount NAS folders via direct wired connection?

  - by Pavel Vlasov

  There are two machines connected to each other via network cable. One is notebook Ubuntu 12.04. Another is NAS Western Digital with a Debian. The NAS has some files shared via samba. I am not sure how it is called but under Windows these files are accessible via path \mybooklive\public. I know there is NFS - probably it is preferable over samba... So, how to get my files accessible from Ubuntu when a cable is plugged?

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• WebSocket API 1.1 released!

  - by Pavel Bucek

  Its my please to announce that JSR 356 – Java API for WebSocket maintenance release ballot vote finished with majority of “yes” votes (actually, only one eligible voter did not vote, all other votes were “yeses”). New release is maintenance release and it addresses only one issue:  WEBSOCKET_SPEC-226. What changed in the 1.1? Version 1.1 is fully backwards compatible with version 1.0, there are only two methods added to javax.websocket.Session: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 /** * Register to handle to incoming messages in this conversation. A maximum of one message handler per * native websocket message type (text, binary, pong) may be added to each Session. I.e. a maximum * of one message handler to handle incoming text messages a maximum of one message handler for * handling incoming binary messages, and a maximum of one for handling incoming pong * messages. For further details of which message handlers handle which of the native websocket * message types please see {@link MessageHandler.Whole} and {@link MessageHandler.Partial}. * Adding more than one of any one type will result in a runtime exception. * * @param clazz   type of the message processed by message handler to be registered. * @param handler whole message handler to be added. * @throws IllegalStateException if there is already a MessageHandler registered for the same native *                               websocket message type as this handler. */ public void addMessageHandler(Class<T> clazz, MessageHandler.Whole<T> handler); /** * Register to handle to incoming messages in this conversation. A maximum of one message handler per * native websocket message type (text, binary, pong) may be added to each Session. I.e. a maximum * of one message handler to handle incoming text messages a maximum of one message handler for * handling incoming binary messages, and a maximum of one for handling incoming pong * messages. For further details of which message handlers handle which of the native websocket * message types please see {@link MessageHandler.Whole} and {@link MessageHandler.Partial}. * Adding more than one of any one type will result in a runtime exception. * * * @param clazz   type of the message processed by message handler to be registered. * @param handler partial message handler to be added. * @throws IllegalStateException if there is already a MessageHandler registered for the same native *                               websocket message type as this handler. */ public void addMessageHandler(Class<T> clazz, MessageHandler.Partial<T> handler); Why do we need to add those methods? Short and not precise version: to support Lambda expressions as MessageHandlers. Longer and slightly more precise explanation: old Session#addMessageHandler method (which is still there and works as it worked till now) does rely on getting the generic parameter during the runtime, which is not (always) possible. The unfortunate part is that it works for some common cases and the expert group did not catch this issue before 1.0 release because of that. The issue is really clearly visible when Lambdas are used as message handlers: 1 2 3 session.addMessageHandler(message -> { System.out.println("### Received: " + message); }); There is no way for the JSR 356 implementation to get the type of the used Lambda expression, thus this call will always result in an exception. Since all modern IDEs do recommend to use Lambda expressions when possible and MessageHandler interfaces are single method interfaces, it basically just scream “use Lambdas” all over the place but when you do that, the application will fail during runtime. Only solution we currently have is to explicitly provide the type of registered MessageHandler. (There might be another sometime in the future when generic type reification is introduced, but that is not going to happen soon enough). So the example above will then be: 1 2 3 session.addMessageHandler(String.class, message -> { System.out.println("### Received: " + message); }); and voila, it works. There are some limitations – you cannot do 1 List<String>.class , so you will need to encapsulate these types when you want to use them in MessageHandler implementation (something like “class MyType extends ArrayList<String>”). There is no better way how to solve this issue, because Java currently does not provide good way how to describe generic types. The api itself is available on maven central, look for javax.websocket:javax.websocket-api:1.1. The reference implementation is project Tyrus, which implements WebSocket API 1.1 from version 1.8.

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• Python response parse [migrated]

  - by Pavel Shevelyov

  When I'm sending some data on host: r = urllib2.Request(url, data = data, headers = headers) page = urllib2.urlopen(r) print page.read() I have something like this: [{"command":"settings","settings":{"basePath":"\/","ajaxPageState":{"theme":"spsr","theme_token":"kRHUhchUVpxAMYL8Y8IoyYIcX0cPrUstziAi8gSmMYk","css":[]},"ajax":{"edit-submit":{"callback":"spsr_calculator_form_ajax","wrapper":"calculator_form","method":"replaceWith","event":"mousedown","keypress":true,"url":"\/ru\/system\/ajax","submit":{"_triggering_element_name":"submit"}}}},"merge":true},{"command":"insert","method":null,"selector":null,"data":"\u003cdiv id=\"calculator_form\"\u003e\u003cform action=\"\/ru\/service\/calculator\" method=\"post\" id=\"spsr-calculator-form\" accept-charset=\"UTF-8\"\u003e\u003cdiv\u003e\u003cinput id=\"edit-from-ship-region-id\" type=\"hidden\" name=\"from_ship_region_id\" value=\"\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_build_id\" value=\"form-0RK_WFli4b2kUDTxpoqsGPp14B_0yf6Fz9x7UK-T3w8\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_id\" value=\"spsr_calculator_form\" \/\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"bg_p\"\u003e \n\u0421\u0435\u0439\u0447\u0430\u0441 \u0412\u044b... bla bla bla but I want have something, like this: <html><h1>bla bla bla</h1></html> How can I do it?

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• Tyrus 1.1

  - by Pavel Bucek

  It might seem like there is not much time passed since Tyrus 1.0 (Java API for WebSocket reference implementation) release, but the fact is it was frozen several weeks before going public and development in the trunk continued. Tyrus 1.1 brings some new features and improvements: client-side proxy support simple command line client various stability/performance fixes (see below for complete list) Individual blog posts about highlighted features will follow, same as related user guide chapters.. stay tuned! Tyrus 1.1 is already integrated in Glassfish trunk - you can download nightly build or upgrade to newer Tyrus manually (replace all Tyrus jars; I know this is not very user friendly, so I'll try to come up with some better solution or at least simple guide). Complete list of bugfixes/improvements: TYRUS-180 TYRUS-176 TYRUS-192 TYRUS-186 TYRUS-191 TYRUS-187 TYRUS-172 TYRUS-194 TYRUS-179 TYRUS-178 TYRUS-200 TYRUS-177 TYRUS-181 TYRUS-203 TYRUS-205 TYRUS-198 TYRUS-202 TYRUS-188 TYRUS-149 Related links: https://tyrus.java.net https://java.net/jira/browse/TYRUS/

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• Silverlight Firestarter Wrap Up and WCF RIA Services Talk Sample Code

  - by dwahlin

  I had a great time attending and speaking at the Silverlight Firestarter event up in Redmond on December 2, 2010. In addition to getting a chance to hang out with a lot of cool people from Microsoft such as Scott Guthrie, John Papa, Tim Heuer, Brian Goldfarb, John Allwright, David Pugmire, Jesse Liberty, Jeff Handley, Yavor Georgiev, Jossef Goldberg, Mike Cook and many others, I also had a chance to chat with a lot of people attending the event and hear about what projects they’re working on which was awesome. If you didn’t get a chance to look through all of the new features coming in Silverlight 5 check out John Papa’s post on the subject. While at the Silverlight Firestarter event I gave a presentation on WCF RIA Services and wanted to get the code posted since several people have asked when it’d be available. The talk can be viewed by clicking the image below. Code from the talk follows as well as additional links. I had a few people ask about the green bracelet on my left hand since it looks like something you’d get from a waterpark. It was used to get us access down a little hall that led backstage and allowed us to go backstage during the event. I thought it looked kind of dorky but it was required to get through security. Sample Code from My WCF RIA Services Talk (To login to the 2 apps use “user” and “P@ssw0rd”. Make sure to do a rebuild of the projects in Visual Studio before running them.) View All Silverlight Firestarter Talks and Scott Guthrie’s Keynote WCF RIA Services SP1 Beta for Silverlight 4 WCF RIA Services Code Samples (including some SP1 samples) Improved binding support in EntitySet and EntityCollection with SP1 (Kyle McClellan’s Blog) Introducing an MVVM-Friendly DomainDataSource: The DomainCollectionView (Kyle McClellan’s Blog) I’ve had the chance to speak at a lot of conferences but never with as many cameras, streaming capabilities, people watching live and overall hype involved. Over 1000 people registered to attend the conference in person at the Microsoft campus and well over 15,000 to watch it through the live stream.  The event started for me on Tuesday afternoon with a flight up to Seattle from Phoenix. My flight was delayed 1 1/2 hours (I seem to be good at booking delayed flights) so I didn’t get up there until almost 8 PM. John Papa did a tech check at 9 PM that night and I was scheduled for 9:30 PM. We basically plugged in my laptop backstage (amazing number of servers, racks and audio devices back there) and made sure everything showed up properly on the projector and the machines recording the presentation. In addition to a dedicated show director, there were at least 5 tech people back stage and at least that many up in the booth running lights, audio, cameras, and other aspects of the show. I wish I would’ve taken a picture of the backstage setup since it was pretty massive – servers all over the place. I definitely gained a new appreciation for how much work goes into these types of events. Here’s what the room looked like right before my tech check– not real exciting at this point. That’s Yavor Georgiev (who spoke on WCF Services at the Firestarter) in the background. We had plenty of monitors to reference during the presentation. Two monitors for slides (right and left side) and a notes monitor. The 4th monitor showed the time and they’d type in notes to us as we talked (such as “You’re over time!” in my case since I went around 4 minutes over :-)). Wednesday morning I went back on campus at Microsoft and watched John Papa film a few Silverlight TV episodes with Dave Campbell and Ryan Plemons.   Next I had the chance to watch the dry run of the keynote with Scott Guthrie and John Papa. We were all blown away by the demos shown since they were even better than expected. Starting at 1 PM on Wednesday I went over to Building 35 and listened to Yavor Georgiev (WCF Services), Jaime Rodriguez (Windows Phone 7), Jesse Liberty (Data Binding) and Jossef Goldberg and Mike Cook (Silverlight Performance) give their different talks and we all shared feedback with each other which was a lot of fun. Jeff Handley from the RIA Services team came afterwards and listened to me give a dry run of my WCF RIA Services talk. He had some great feedback that I really appreciated getting. That night I hung out with John Papa and Ward Bell and listened to John walk through his keynote demos. I also got a sneak peak of the gift given to Dave Campbell for all his work with Silverlight Cream over the years. It’s a poster signed by all of the key people involved with Silverlight: Thursday morning I got up fairly early to get to the event center by 8 AM for speaker pictures. It was nice and quiet at that point although outside the room there was a huge line of people waiting to get in.     At around 8:30 AM everyone was let in and the main room was filled quickly. Two other overflow rooms in the Microsoft conference center (Building 33) were also filled to capacity. At around 9 AM Scott Guthrie kicked off the event and all the excitement started! From there it was all a blur but it was definitely a lot of fun. All of the sessions for the Silverlight Firestarter were recorded and can be watched here (including the keynote). Corey Schuman, John Papa and I also released 11 lab exercises and associated videos to help people get started with Silverlight. Definitely check them out if you’re interested in learning more! Level 100: Getting Started Lab 01 - WinForms and Silverlight Lab 02 - ASP.NET and Silverlight Lab 03 - XAML and Controls Lab 04 - Data Binding Level 200: Ready for More Lab 05 - Migrating Apps to Out-of-Browser Lab 06 - Great UX with Blend Lab 07 - Web Services and Silverlight Lab 08 - Using WCF RIA Services Level 300: Take me Further Lab 09 - Deep Dive into Out-of-Browser Lab 10 - Silverlight Patterns: Using MVVM Lab 11 - Silverlight and Windows Phone 7

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• IPhone app with SSL client certs

  - by Pavel Georgiev

  I'm building an iphone app that needs to access a web service over https using client certificates. If I put the client cert (in pkcs12 format) in the app bundle, I'm able to load it into the app and make the https call (largely thanks to stackoverflow.com). However, I need a way to distribute the app without any certs and leave it to the user to provide his own certificate. I thought I would just do that by instructing the user to import the certificate in iphone's profiles (settings-general-profiles), which is what you get by opening a .p12 file in Mail.app and then I would access that item in my app. I would expect that the certificates in profiles are available through the keychain API, but I guess I'm wrong on that. 1) Is there a way to access a certificate that I've already loaded in iphone's profile in my app? 2) What other options I have for loading a user specified certificate in my app? The only thing I can come up with is providing some interface where the user can give an URL to his .p12 cerificate, which I can then load into the app's keychain for later use, but thats not exactly user-friednly. I'm looking for something that would allow the user to put the cert on phone (email it to himself) and then load it in my app.

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• Eclipse IDE Learning Curve

  - by Vladimir Georgiev

  I am a C# guy with pretty good grasp of Visual Studio IDE usage (using it since VS2003). Right now, I am doing a proof of concept app using Eclipse 3.4.1. Is there any good reference or book which describes the usage of Eclipse IDE, compared to Visual Studio. Is there any Eclipse guide for Visual Studio users :) Thanks, in advance.

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• Can I constrain a template parameter class to implement the interfaces that are supported by other?

  - by K. Georgiev

  The name is a little blurry, so here's the situation: I'm writing code to use some 'trajectories'. The trajectories are an abstract thing, so I describe them with different interfaces. So I have a code as this: namespace Trajectories { public interface IInitial < Atom > { Atom Initial { get; set; } } public interface ICurrent < Atom > { Atom Current { get; set; } } public interface IPrevious < Atom > { Atom Previous { get; set; } } public interface ICount < Atom > { int Count { get; } } public interface IManualCount < Atom > : ICount < Atom > { int Count { get; set; } } ... } Every concrete implementation of a trajectory will implement some of the above interfaces. Here's a concrete implementation of a trajectory: public class SimpleTrajectory < Atom > : IInitial < Atom >, ICurrent < Atom >, ICount < Atom > { // ICount public int Count { get; private set; } // IInitial private Atom initial; public Atom Initial { get { return initial; } set { initial = current = value; Count = 1; } } // ICurrent private Atom current; public Atom Current { get { return current; } set { current = value; Count++; } } } Now, I want to be able to deduce things about the trajectories, so, for example I want to support predicates about different properties of some trajectory: namespace Conditions { public interface ICondition &lt Atom, Trajectory &gt { bool Test(ref Trajectory t); } public class CountLessThan &lt Atom, Trajectory &gt : ICondition &lt Atom, Trajectory &gt where Trajectory : Trajectories.ICount &lt Atom &gt { public int Value { get; set; } public CountLessThan() { } public bool Test(ref Trajectory t) { return t.Count &lt Value; } } public class CurrentNormLessThan &lt Trajectory &gt : ICondition &lt Complex, Trajectory &gt where Trajectory : Trajectories.ICurrent &lt Complex &gt { public double Value { get; set; } public CurrentNormLessThan() { } public bool Test(ref Trajectory t) { return t.Current.Norm() &lt Value; } } } Now, here's the question: What if I wanted to implement AND predicate? It would be something like this: public class And &lt Atom, CondA, TrajectoryA, CondB, TrajectoryB, Trajectory &gt : ICondition &lt Atom, Trajectory &gt where CondA : ICondition &lt Atom, TrajectoryA &gt where TrajectoryA : // Some interfaces where CondB : ICondition &lt Atom, TrajectoryB &gt where TrajectoryB : // Some interfaces where Trajectory : // MUST IMPLEMENT THE INTERFACES FOR TrajectoryA AND THE INTERFACES FOR TrajectoryB { public CondA A { get; set; } public CondB B { get; set; } public bool Test(ref Trajectory t){ return A.Test(t) && B.Test(t); } } How can I say: support only these trajectories, for which the arguments of AND are ok? So I can be able to write: var vand = new CountLessThan(32) & new CurrentNormLessThan(4.0); I think if I create an orevall interface for every subset of interfaces, I could be able to do it, but it will become quite ugly.

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