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• How to convert HTML to PDF

  - by user349564

  I having a website developed in .net and need to get a HTML to PDF converter. Are there any open source or alternatives to http://www.html-to-pdf.net as it is quiet expensive.

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• Why did Sun develop the Java platform? [closed]

  - by nic28

  Why did Sun (now owned by Oracle, I know) develop the Java Plaform? How does it make business sense? It seems to me like it would be a very expensive project (also, any ideas on how much they spent/are spending to develop/maintain the platform?). Are they making money by selling support or something?

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• Can't get running JPA2 with Hibernate and Maven

  - by erlord

  Have been trying the whole day long and googled the ** out of the web ... in vain. You are my last hope: Here's my code: The Entity: package sas.test.model; import javax.persistence.Entity; import javax.persistence.Id; @Entity public class Employee { @Id private int id; private String name; private long salary; public Employee() {} public Employee(int id) { this.id = id; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public long getSalary() { return salary; } public void setSalary (long salary) { this.salary = salary; } } The service class: package sas.test.dao; import sas.test.model.Employee; import javax.persistence.*; import java.util.List; public class EmployeeService { protected EntityManager em; public EmployeeService(EntityManager em) { this.em = em; } public Employee createEmployee(int id, String name, long salary) { Employee emp = new Employee(id); emp.setName(name); emp.setSalary(salary); em.persist(emp); return emp; } public void removeEmployee(int id) { Employee emp = findEmployee(id); if (emp != null) { em.remove(emp); } } public Employee raiseEmployeeSalary(int id, long raise) { Employee emp = em.find(Employee.class, id); if (emp != null) { emp.setSalary(emp.getSalary() + raise); } return emp; } public Employee findEmployee(int id) { return em.find(Employee.class, id); } } And the main class: package sas.test.main; import javax.persistence.*; import java.util.List; import sas.test.model.Employee; import sas.test.dao.EmployeeService; public class ExecuteMe { public static void main(String[] args) { EntityManagerFactory emf = Persistence.createEntityManagerFactory("EmployeeService"); EntityManager em = emf.createEntityManager(); EmployeeService service = new EmployeeService(em); // create and persist an employee em.getTransaction().begin(); Employee emp = service.createEmployee(158, "John Doe", 45000); em.getTransaction().commit(); System.out.println("Persisted " + emp); // find a specific employee emp = service.findEmployee(158); System.out.println("Found " + emp); // find all employees // List<Employee> emps = service.findAllEmployees(); // for (Employee e : emps) // System.out.println("Found employee: " + e); // update the employee em.getTransaction().begin(); emp = service.raiseEmployeeSalary(158, 1000); em.getTransaction().commit(); System.out.println("Updated " + emp); // remove an employee em.getTransaction().begin(); service.removeEmployee(158); em.getTransaction().commit(); System.out.println("Removed Employee 158"); // close the EM and EMF when done em.close(); emf.close(); } } Finally my confs. pom.xml: <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>Test_JPA_CRUD</groupId> <artifactId>Test_JPA_CRUD</artifactId> <packaging>jar</packaging> <version>1.0</version> <name>Test_JPA_CRUD</name> <url>http://maven.apache.org</url> <repositories> <repository> <id>maven2-repository.dev.java.net</id> <name>Java.net Repository for Maven</name> <url>http://download.java.net/maven/2/ </url> <layout>default</layout> </repository> <repository> <id>maven.org</id> <name>maven.org Repository</name> <url>http://repo1.maven.org/maven2</url> <releases> <enabled>true</enabled> </releases> <snapshots> <enabled>true</enabled> </snapshots> </repository> </repositories> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.8.1</version> <scope>test</scope> </dependency> <!-- <dependency> <groupId>javax</groupId> <artifactId>javaee-api</artifactId> <version>6.0</version> </dependency> --> <!-- <dependency> <groupId>javax.persistence</groupId> <artifactId>persistence-api</artifactId> <version>1.0</version> </dependency> --> <!-- JPA2 provider --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>3.4.0.GA</version> </dependency> <!-- JDBC driver --> <dependency> <groupId>org.apache.derby</groupId> <artifactId>derby</artifactId> <version>10.5.3.0_1</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>3.3.2.GA</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>ejb3-persistence</artifactId> <version>3.3.2.Beta1</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-annotations</artifactId> <version>3.4.0.GA</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.5.2</version> </dependency> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.14</version> </dependency> </dependencies> <build> <plugins> <!-- compile with mvn assembly:assembly --> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-jar-plugin</artifactId> <version>2.2</version> </plugin> <!-- compile with mvn assembly:assembly --> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-assembly-plugin</artifactId> <version>2.2-beta-2</version> <configuration> <descriptorRefs> <descriptorRef>jar-with-dependencies</descriptorRef> </descriptorRefs> <archive> <manifest> <mainClass>sas.test.main.ExecuteMe</mainClass> </manifest> </archive> </configuration> <executions> <execution> <phase>package</phase> </execution> </executions> </plugin> <plugin> <!-- Force UTF-8 & Java-Version 1.6 --> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.6</source> <target>1.6</target> <!--<encoding>utf-8</encoding>--> </configuration> </plugin> </plugins> </build> </project> and the persistence.xml, which, I promise, is in the classpath of the target: <?xml version="1.0" encoding="UTF-8"?> <persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd http://java.sun.com/xml/ns/persistence "> <persistence-unit name="EmployeeService" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <class>sas.test.model.Employee</class> <properties> <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="hibernate.dialect" value="org.hibernate.dialect.DerbyDialect"/> <property name="hibernate.show_sql" value="true"/> <property name="javax.persistence.jdbc.url" value="jdbc:derby:webdb;create=true"/> </properties> </persistence-unit> </persistence> As you may have noticed from some commented code, I tried both, the Hibernate and the J2EE 6 implementation of JPA2.0, however, both failed. The above-mentioned code ends up with following error: log4j:WARN No appenders could be found for logger (org.hibernate.cfg.annotations.Version). log4j:WARN Please initialize the log4j system properly. Exception in thread "main" java.lang.UnsupportedOperationException: The user must supply a JDBC connection at org.hibernate.connection.UserSuppliedConnectionProvider.getConnection(UserSuppliedConnectionProvider.java:54) at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446) at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167) at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142) Any idea what's going wrong? Any "Hello World" maven/JPA2 demo that actually runs? I couldn't get any of those provided by google's search running. Thanx in advance.

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• Basics of Join Predicate Pushdown in Oracle

  - by Maria Colgan

  Happy New Year to all of our readers! We hope you all had a great holiday season. We start the new year by continuing our series on Optimizer transformations. This time it is the turn of Predicate Pushdown. I would like to thank Rafi Ahmed for the content of this blog.Normally, a view cannot be joined with an index-based nested loop (i.e., index access) join, since a view, in contrast with a base table, does not have an index defined on it. A view can only be joined with other tables using three methods: hash, nested loop, and sort-merge joins. Introduction The join predicate pushdown (JPPD) transformation allows a view to be joined with index-based nested-loop join method, which may provide a more optimal alternative. In the join predicate pushdown transformation, the view remains a separate query block, but it contains the join predicate, which is pushed down from its containing query block into the view. The view thus becomes correlated and must be evaluated for each row of the outer query block. These pushed-down join predicates, once inside the view, open up new index access paths on the base tables inside the view; this allows the view to be joined with index-based nested-loop join method, thereby enabling the optimizer to select an efficient execution plan. The join predicate pushdown transformation is not always optimal. The join predicate pushed-down view becomes correlated and it must be evaluated for each outer row; if there is a large number of outer rows, the cost of evaluating the view multiple times may make the nested-loop join suboptimal, and therefore joining the view with hash or sort-merge join method may be more efficient. The decision whether to push down join predicates into a view is determined by evaluating the costs of the outer query with and without the join predicate pushdown transformation under Oracle's cost-based query transformation framework. The join predicate pushdown transformation applies to both non-mergeable views and mergeable views and to pre-defined and inline views as well as to views generated internally by the optimizer during various transformations. The following shows the types of views on which join predicate pushdown is currently supported. UNION ALL/UNION view Outer-joined view Anti-joined view Semi-joined view DISTINCT view GROUP-BY view Examples Consider query A, which has an outer-joined view V. The view cannot be merged, as it contains two tables, and the join between these two tables must be performed before the join between the view and the outer table T4. A: SELECT T4.unique1, V.unique3 FROM T_4K T4,            (SELECT T10.unique3, T10.hundred, T10.ten             FROM T_5K T5, T_10K T10             WHERE T5.unique3 = T10.unique3) VWHERE T4.unique3 = V.hundred(+) AND       T4.ten = V.ten(+) AND       T4.thousand = 5; The following shows the non-default plan for query A generated by disabling join predicate pushdown. When query A undergoes join predicate pushdown, it yields query B. Note that query B is expressed in a non-standard SQL and shows an internal representation of the query. B: SELECT T4.unique1, V.unique3 FROM T_4K T4,           (SELECT T10.unique3, T10.hundred, T10.ten             FROM T_5K T5, T_10K T10             WHERE T5.unique3 = T10.unique3             AND T4.unique3 = V.hundred(+)             AND T4.ten = V.ten(+)) V WHERE T4.thousand = 5; The execution plan for query B is shown below. In the execution plan BX, note the keyword 'VIEW PUSHED PREDICATE' indicates that the view has undergone the join predicate pushdown transformation. The join predicates (shown here in red) have been moved into the view V; these join predicates open up index access paths thereby enabling index-based nested-loop join of the view. With join predicate pushdown, the cost of query A has come down from 62 to 32.  As mentioned earlier, the join predicate pushdown transformation is cost-based, and a join predicate pushed-down plan is selected only when it reduces the overall cost. Consider another example of a query C, which contains a view with the UNION ALL set operator.C: SELECT R.unique1, V.unique3 FROM T_5K R,            (SELECT T1.unique3, T2.unique1+T1.unique1             FROM T_5K T1, T_10K T2             WHERE T1.unique1 = T2.unique1             UNION ALL             SELECT T1.unique3, T2.unique2             FROM G_4K T1, T_10K T2             WHERE T1.unique1 = T2.unique1) V WHERE R.unique3 = V.unique3 and R.thousand < 1; The execution plan of query C is shown below. In the above, 'VIEW UNION ALL PUSHED PREDICATE' indicates that the UNION ALL view has undergone the join predicate pushdown transformation. As can be seen, here the join predicate has been replicated and pushed inside every branch of the UNION ALL view. The join predicates (shown here in red) open up index access paths thereby enabling index-based nested loop join of the view. Consider query D as an example of join predicate pushdown into a distinct view. We have the following cardinalities of the tables involved in query D: Sales (1,016,271), Customers (50,000), and Costs (787,766).  D: SELECT C.cust_last_name, C.cust_city FROM customers C,            (SELECT DISTINCT S.cust_id             FROM sales S, costs CT             WHERE S.prod_id = CT.prod_id and CT.unit_price > 70) V WHERE C.cust_state_province = 'CA' and C.cust_id = V.cust_id; The execution plan of query D is shown below. As shown in XD, when query D undergoes join predicate pushdown transformation, the expensive DISTINCT operator is removed and the join is converted into a semi-join; this is possible, since all the SELECT list items of the view participate in an equi-join with the outer tables. Under similar conditions, when a group-by view undergoes join predicate pushdown transformation, the expensive group-by operator can also be removed. With the join predicate pushdown transformation, the elapsed time of query D came down from 63 seconds to 5 seconds. Since distinct and group-by views are mergeable views, the cost-based transformation framework also compares the cost of merging the view with that of join predicate pushdown in selecting the most optimal execution plan. Summary We have tried to illustrate the basic ideas behind join predicate pushdown on different types of views by showing example queries that are quite simple. Oracle can handle far more complex queries and other types of views not shown here in the examples. Again many thanks to Rafi Ahmed for the content of this blog post.

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• Robotic Arm &ndash; Hardware

  - by Szymon Kobalczyk

  This is first in series of articles about project I've been building  in my spare time since last Summer. Actually it all began when I was researching a topic of modeling human motion kinematics in order to create gesture recognition library for Kinect. This ties heavily into motion theory of robotic manipulators so I also glanced at some designs of robotic arms. Somehow I stumbled upon this cool looking open source robotic arm: It was featured on Thingiverse and published by user jjshortcut (Jan-Jaap). Since for some time I got hooked on toying with microcontrollers, robots and other electronics, I decided to give it a try and build it myself. In this post I will describe the hardware build of the arm and in later posts I will be writing about the software to control it. Another reason to build the arm myself was the cost factor. Even small commercial robotic arms are quite expensive – products from Lynxmotion and Dagu look great but both cost around USD $300 (actually there is one cheap arm available but it looks more like a toy to me). In comparison this design is quite cheap. It uses seven hobby grade servos and even the cheapest ones should work fine. The structure is build from a set of laser cut parts connected with few metal spacers (15mm and 47mm) and lots of M3 screws. Other than that you’d only need a microcontroller board to drive the servos. So in total it comes a lot cheaper to build it yourself than buy an of the shelf robotic arm. Oh, and if you don’t like this one there are few more robotic arm projects at Thingiverse (including one by oomlout). Laser cut parts Some time ago I’ve build another robot using laser cut parts so I knew the process already. You can grab the design files in both DXF and EPS format from Thingiverse, and there are also 3D models of each part in STL. Actually the design is split into a second project for the mini servo gripper (there is also a standard servo version available but it won’t fit this arm).  I wanted to make some small adjustments, layout, and add measurements to the parts before sending it for cutting. I’ve looked at some free 2D CAD programs, and finally did all this work using QCad 3 Beta with worked great for me (I also tried LibreCAD but it didn’t work that well). All parts are cut from 4 mm thick material. Because I was worried that acrylic is too fragile and might break, I also ordered another set cut from plywood. In the end I build it from plywood because it was easier to glue (I was told acrylic requires a special glue). Btw. I found a great laser cutter service in Kraków and highly recommend it (www.ebbox.com.pl). It cost me only USD $26 for both sets ($16 acrylic + $10 plywood). Metal parts I bought all the M3 screws and nuts at local hardware store. Make sure to look for nylon lock (nyloc) nuts for the gripper because otherwise it unscrews and comes apart quickly. I couldn’t find local store with metal spacers and had to order them online (you’d need 11 x 47mm and 3 x 15mm). I think I paid less than USD $10 for all metal parts. Servos This arm uses five standards size servos to drive the arm itself, and two micro servos are used on the gripper. Author of the project used Modelcraft RS-2 Servo and Modelcraft ES-05 HT Servo. I had two Futaba S3001 servos laying around, and ordered additional TowerPro SG-5010 standard size servos and TowerPro SG90 micro servos. However it turned out that the SG90 won’t fit in the gripper so I had to replace it with a slightly smaller E-Sky EK2-0508 micro servo. Later it also turned out that Futaba servos make some strange noise while working so I swapped one with TowerPro SG-5010 which has higher torque (8kg / cm). I’ve also bought three servo extension cables. All servos cost me USD $45. Assembly The build process is not difficult but you need to think carefully about order of assembling it. You can do the base and upper arm first. Because two servos in the base are close together you need to put first with one piece of lower arm already connected before you put the second servo. Then you connect the upper arm and finally put the second piece of lower arm to hold it together. Gripper and base require some gluing so think it through too. Make sure to look closely at all the photos on Thingiverse (also other people copies) and read additional posts on jjshortcust’s blog: My mini servo grippers and completed robotic arm  Multiply the robotic arm and electronics Here is also Rob’s copy cut from aluminum My assembled arm looks like this – I think it turned out really nice: Servo controller board The last piece of hardware I needed was an electronic board that would take command from PC and drive all seven servos. I could probably use Arduino for this task, and in fact there are several Arduino servo shields available (for example from Adafruit or Renbotics).  However one problem is that most support only up to six servos, and second that their accuracy is limited by Arduino’s timer frequency. So instead I looked for dedicated servo controller and found a series of Maestro boards from Pololu. I picked the Pololu Mini Maestro 12-Channel USB Servo Controller. It has many nice features including native USB connection, high resolution pulses (0.25µs) with no jitter, built-in speed and acceleration control, and even scripting capability. Another cool feature is that besides servo control, each channel can be configured as either general input or output. So far I’m using seven channels so I still have five available to connect some sensors (for example distance sensor mounted on gripper might be useful). And last but important factor was that they have SDK in .NET – what more I could wish for! The board itself is very small – half of the size of Tic-Tac box. I picked one for about USD $35 in this store. Perhaps another good alternative would be the Phidgets Advanced Servo 8-Motor – but it is significantly more expensive at USD $87.30. The Maestro Controller Driver and Software package includes Maestro Control Center program with lets you immediately configure the board. For each servo I first figured out their move range and set the min/max limits. I played with setting the speed an acceleration values as well. Big issue for me was that there are two servos that control position of lower arm (shoulder joint), and both have to be moved at the same time. This is where the scripting feature of Pololu board turned out very helpful. I wrote a script that synchronizes position of second servo with first one – so now I only need to move one servo and other will follow automatically. This turned out tricky because I couldn’t find simple offset mapping of the move range for each servo – I had to divide it into several sub-ranges and map each individually. The scripting language is bit assembler-like but gets the job done. And there is even a runtime debugging and stack view available. Altogether I’m very happy with the Pololu Mini Maestro Servo Controller, and with this final piece I completed the build and was able to move my arm from the Meastro Control program.   The total cost of my robotic arm was: $10 laser cut parts $10 metal parts $45 servos $35 servo controller ----------------------- $100 total So here you have all the information about the hardware. In next post I’ll start talking about the software that I wrote in Microsoft Robotics Developer Studio 4. Stay tuned!

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• Azure, don't give me multiple VMs, give me one elastic VM

  - by FransBouma

  Yesterday, Microsoft revealed new major features for Windows Azure (see ScottGu's post). It all looks shiny and great, but after reading most of the material describing the new features, I still find the overall idea behind all of it flawed: why should I care on how much VMs my web app runs? Isn't that a problem to solve for the Windows Azure engineers / software? And what if I need the file system, why can't I simply get a virtual filesystem ? To illustrate my point, let's use a real example: a product website with a customer system/database and next to it a support site with accompanying database. Both are written in .NET, using ASP.NET and use a SQL Server database each. The product website offers files to download by customers, very simple. You have a couple of options to host these websites: Buy a server, place it in a rack at an ISP and run the sites on that server Use 'shared hosting' with an ISP, which means your sites' appdomains are running on the same machine, as well as the files stored, and the databases are hosted in the same server as the other shared databases. Hire a VM, install your OS of choice at an ISP, and host the sites on that VM, basically the same as the first option, except you don't have a physical server At some cloud-vendor, either host the sites 'shared' or in a VM. See above. With all of those options, scalability is a problem, even the cloud-based ones, though not due to the same reasons: The physical server solution has the obvious problem that if you need more power, you need to buy a bigger server or more servers which requires you to add replication and other overhead Shared hosting solutions are almost always capped on memory usage / traffic and database size: if your sites get too big, you have to move out of the shared hosting environment and start over with one of the other solutions The VM solution, be it a VM at an ISP or 'in the cloud' at e.g. Windows Azure or Amazon, in theory allows scaling out by simply instantiating more VMs, however that too introduces the same overhead problems as with the physical servers: suddenly more than 1 instance runs your sites. If a cloud vendor offers its services in the form of VMs, you won't gain much over having a VM at some ISP: the main problems you have to work around are still there: when you spin up more than one VM, your application must be completely stateless at any moment, including the DB sub system, because what's in memory in instance 1 might not be in memory in instance 2. This might sounds trivial but it's not. A lot of the websites out there started rather small: they were perfectly runnable on a single machine with normal memory and CPU power. After all, you don't need a big machine to run a website with even thousands of users a day. Moving these sites to a multi-VM environment will cause a problem: all the in-memory state they use, all the multi-page transitions they use while keeping state across the transition, they can't do that anymore like they did that on a single machine: state is something of the past, you have to store every byte of state in either a DB or in a viewstate or in a cookie somewhere so with the next request, all state information is available through the request, as nothing is kept in-memory. Our example uses a bunch of files in a file system. Using multiple VMs will require that these files move to a cloud storage system which is mounted in each VM so we don't have to store the files on each VM. This might require different file paths, but this change should be minor. What's perhaps less minor is the maintenance procedure in place on the new type of cloud storage used: instead of ftp-ing into a VM, you might have to update the files using different ways / tools. All in all this makes moving an existing website which was written for an environment that's based around a VM (namely .NET with its CLR) overly cumbersome and problematic: it forces you to refactor your website system to be able to be used 'in the cloud', which is caused by the limited way how e.g. Windows Azure offers its cloud services: in blocks of VMs. Offer a scalable, flexible VM which extends with my needs Instead, cloud vendors should offer simply one VM to me. On that VM I run the websites, store my DB and my files. As it's a virtual machine, how this machine is actually ran on physical hardware (e.g. partitioned), I don't care, as that's the problem for the cloud vendor to solve. If I need more resources, e.g. I have more traffic to my server, way more visitors per day, the VM stretches, like I bought a bigger box. This frees me from the problem which comes with multiple VMs: I don't have any refactoring to do at all: I can simply build my website as if it runs on my local hardware server, upload it to the VM offered by the cloud vendor, install it on the VM and I'm done. "But that might require changes to windows!" Yes, but Microsoft is Windows. Windows Azure is their service, they can make whatever change to what they offer to make it look like it's windows. Yet, they're stuck, like Amazon, in thinking in VMs, which forces developers to 'think ahead' and gamble whether they would need to migrate to a cloud with multiple VMs in the future or not. Which comes down to: gamble whether they should invest time in code / architecture which they might never need. (YAGNI anyone?) So the VM we're talking about, is that a low-level VM which runs a guest OS, or is that VM a different kind of VM? The flexible VM: .NET's CLR ? My example websites are ASP.NET based, which means they run inside a .NET appdomain, on the .NET CLR, which is a VM. The only physical OS resource the sites need is the file system, however this too is accessed through .NET. In short: all the websites see is what .NET allows the websites to see, the world as the websites know it is what .NET shows them and lets them access. How the .NET appdomain is run physically, that's the concern of .NET, not mine. This begs the question why Windows Azure doesn't offer virtual appdomains? Or better: .NET environments which look like one machine but could be physically multiple machines. In such an environment, no change has to be made to the websites to migrate them from a local machine or own server to the cloud to get proper scaling: the .NET VM will simply scale with the need: more memory needed, more CPU power needed, it stretches. What it offers to the application running inside the appdomain is simply increasing, but not fragmented: all resources are available to the application: this means that the problem of how to scale is back to where it should be: with the cloud vendor. "Yeah, great, but what about the databases?" The .NET application communicates with the database server through a .NET ADO.NET provider. Where the database is located is not a problem of the appdomain: the ADO.NET provider has to solve that. I.o.w.: we can host the databases in an environment which offers itself as a single resource and is accessible through one connection string without replication overhead on the outside, and use that environment inside the .NET VM as if it was a single DB. But what about memory replication and other problems? This environment isn't simple, at least not for the cloud vendor. But it is simple for the customer who wants to run his sites in that cloud: no work needed. No refactoring needed of existing code. Upload it, run it. Perhaps I'm dreaming and what I described above isn't possible. Yet, I think if cloud vendors don't move into that direction, what they're offering isn't interesting: it doesn't solve a problem at all, it simply offers a way to instantiate more VMs with the guest OS of choice at the cost of me needing to refactor my website code so it can run in the straight jacket form factor dictated by the cloud vendor. Let's not kid ourselves here: most of us developers will never build a website which needs a truck load of VMs to run it: almost all websites created by developers can run on just a few VMs at most. Yet, the most expensive change is right at the start: moving from one to two VMs. As soon as you have refactored your website code to run across multiple VMs, adding another one is just as easy as clicking a mouse button. But that first step, that's the problem here and as it's right there at the beginning of scaling the website, it's particularly strange that cloud vendors refuse to solve that problem and leave it to the developers to solve that. Which makes migrating 'to the cloud' particularly expensive.

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• How to Access a decendant object's internal method in C#

  - by Giovanni Galbo

  I'm trying to access a method that is marked as internal in the parent class (in its own assembly) in an object that inherits from the same parent. Let me explain what I'm trying to do... I want to create Service classes that return IEnumberable with an underlying List to non-Service classes (e.g. the UI) and optionally return an IEnumerable with an underlying IQueryable to other services. I wrote some sample code to demonstrate what I'm trying to accomplish, shown below. The example is not real life, so please remember that when commenting. All services would inherit from something like this (only relevant code shown): public class ServiceBase<T> { protected readonly ObjectContext _context; protected string _setName = String.Empty; public ServiceBase(ObjectContext context) { _context = context; } public IEnumerable<T> GetAll() { return GetAll(false); } //These are not the correct access modifiers.. I want something //that is accessible to children classes AND between descendant classes internal protected IEnumerable<T> GetAll(bool returnQueryable) { var query = _context.CreateQuery<T>(GetSetName()); if(returnQueryable) { return query; } else { return query.ToList(); } } private string GetSetName() { //Some code... return _setName; } } Inherited services would look like this: public class EmployeeService : ServiceBase<Employees> { public EmployeeService(ObjectContext context) : base(context) { } } public class DepartmentService : ServiceBase<Departments> { private readonly EmployeeService _employeeService; public DepartmentService(ObjectContext context, EmployeeService employeeService) : base(context) { _employeeService = employeeService; } public IList<Departments> DoSomethingWithEmployees(string lastName) { //won't work because method with this signature is not visible to this class var emps = _employeeService.GetAll(true); //more code... } } Because the parent class lives is reusable, it would live in a different assembly than the child services. With GetAll(bool returnQueryable) being marked internal, the children would not be able to see each other's GetAll(bool) method, just the public GetAll() method. I know that I can add a new internal GetAll method to each service (or perhaps an intermediary parent class within the same assembly) so that each child service within the assembly can see each other's method; but it seems unnecessary since the functionality is already available in the parent class. For example: internal IEnumerable<Employees> GetAll(bool returnIQueryable) { return base.GetAll(returnIQueryable); } Essentially what I want is for services to be able to access other service methods as IQueryable so that they can further refine the uncommitted results, while everyone else gets plain old lists. Any ideas?

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• Windows Server 2003 - Handling hundreds of simultaneous downloads

  - by Paul Hinett

  At the moment I have a single server with 4 1TB hard disks, daily I haver over 150 MP3 music files uploaded (around 80mb each). At busy periods there is over 300 people streaming / downloading these mixes all at once, 75% of the activity is on the most recently uploaded stuff which is all on a single hard disk. My read speads on the hard disk are very low due to such high activity of 200+ reads all happening at the same time on a single hard disk (ran some tests with HDTach). What would be a logical solution to solve this, a couple of ideas I had are: Load balance with another server Install faster hard disks (what are best these days? SCSI / SATA) Spread the most accessed files over the 4 drives so it is sharing the load between all 4 disks, instead of all the most accessed (most recent) all on the most recently installed drive. Obviouslly load balance is the most expensive option, but would it dramatically help? Some help on this situation would be great!

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• Upgrade from Vista 32 to Vista 64

  - by Lance Fisher

  I just ordered a laptop, and it came with Vista Home Premium 32. I want Vista Home Premium 64 on it. I'm planning a reinstall. Does anyone know if my product key for Vista 32 will also work for Vista 64 for an OEM copy? As far as I know, I just need to get the 64 bit media. Is this correct? Thanks. Update The laptop is a Dell XPS M1330, and its hardware is supported. Dell would even sell it with 64 bit. However, it was significantly more expensive for lower specs, and I couldn't get it in red.

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• Help me choose a desktop: which of these two should I buy?

  - by Sammy

  I just want the more powerful of the two: Choice 1: http://www.bestbuy.com/site/Gateway+-+Desktop+with+AMD+Phenom%26%23153%3B+II+Quad-Core+Processor/9698936.p?id=1218153428687&skuId=9698936 Choice 2: /site/HP+-+Pavilion+Desktop+with+AMD+Phenom%26%23153%3B+II+Quad-Core+Processor/9694506.p?id=1218150609828&skuId=9694506 I can't post more than one hyperlink since I am a new user, so please add bestbuy domain name before choice 2. The latter choice is a bit more expensive but not by much so I don't care about that. As for what I intend to use my machine for, just regular web surfing, light gaming, web development related work, etc. But that doesn't really matter, of these two I just want to know which is the better more powerful system and which you would buy if you were in my position.

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• Best choice for a personal "online backup" in Europe

  - by marc_s

  I'm looking for an online backup solution for personal use - besides all the usual requirements (like not too expensive, since it's for personal use), I'd like to add two requirements to it: data center should be in Europe (I don't want my personal data stored in the US, when the next crazed president comes along and wants to confiscate and rifle through everybody's files.....) the online backup store should be accessible through a drive letter in cmd.exe So far, I've looked at a few services, but none have totally convinced me: Dropbox is looking ok, but they insist on creating a silly "My Dropbox" directory in my data path - and there's no way I can choose that name. Sorry - "My everything" is for dummies - I don't like that, I like to name my files and folders according to my liking LiveDrive is OK, too - they offer European storage, drive letter and all - but those drive letters are only available in the Windows Explorer - and not on the cmd.exe command line :-( and since I do 99% of my work on the command line, this is a major drawback..... Any other services I haven't looked at worth checking out? Marc

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• Samba4 advice for production use

  - by pgb

  I have an old Samba 3 + LDAP server installed that needs to be rebuilt. I'm weighting my options, and Windows Server seems too expensive at the moment, and Samba 4 appeared to be a nice option, coupled with the last Bind 9 that can dynamically add the computers to the DNS. I have about 30 workstations, so I still consider it a small network. My questions are: Is Samba 4 stable enough for production? It seems as if the Samba team is too cautious on when to call their version final, or even beta, as compared with other open source projects. What Linux distribution would you recommend to set it up? I usually use Ubuntu Server, but may use another one if installing / maintaining Samba 4 is better on that one.

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• 8Gb Fiber Channcel HBA vs. 10 Gb SPF+ Converged HBA

  - by Hossein Aarabi

  I am putting a Dell server together, more specifically R720. I have to select the correct Host Bus Adapter. This HBA on R710 will connect to a storage device. I am confused between these two: QLogic 2562, Dual Port 8Gb Optical Fiber Channel HBA (price $2,045) QLogic 8262, Dual Port 10Gb SFP+, Converged Network Adapter (price $1,618) I thought since the QLogic 2562 is a fiber channel and is more expensive then it is faster in terms of IOPS. But, it is a 8Gb as opposed to 10 Gb of SFP+. My questions: Which one is better (IOPS performance, etc.)? Why should I choose one over another?

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• Magento Community - Hosting :: Need Advice which sharing hosting will run magento fast

  - by user43353

  Hi, Need Advice which sharing hosting will run Magento Community fast or some other not expensive solution. This website will not have a lot of users, I only need that it will run fast for 100-20 users in same time. The problem with magento is database design that make this system very slow , also other staff not the best. I had hostmonster.com and justhost.com for previous website but it wasn't fast enough for single user that not located in USA (my customer areas: Asia, Africa). each action that involve database takes a lot of time. Thanks

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• How to hack airport extreme to support USB 3G modem?

  - by Mike Caron

  Has anyone out there ever tried to hack the Airport Extreme, specifically with regard to the USB port? There are many cellular routers available that provide WiFi sharing of a USB modem link. However, instead of buying yet another router, I'd like to use my expensive Airport Extreme with it. The AE has a USB port on the back, but it's been said that it only talks to printers. Is there a way to hack the USB driver on the AE to allow it to recognize a USB modem, then use that as the connectivity instead of the LAN? I would imagine that one could use OpenFirmware to boot something on the AE. If one can boot it, then one could provide access using SSH across the lan. Once access is granted, then let the hacking begin... but I don't know how to (a) get the mini-osx on to USB (is it the same as the ATV without a UI?) or (b) how to load up certain things once boot has begun.

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• Why is lassoing ink in OneNote so slow in general? Doesn't anyone care?

  - by GuoLiang Oon

  Now I understand that this is especially an (known) issue in the OneNote 2013 preview and that it will probably be fixed in the final release. But lassoing in OneNote 2010 was no sprightly affair either. I'm just perplexed really, why on earth is there such an issue? Is lassoing intrinsically computationally expensive? OneNote would be soooooooooooo much more useful if there's no lasso lag. And doing a laggy lasso on tablet pcs with weak processors is just so much worse. Or do most folks just don't use the lasso feature much? I use it primarily to shrink intermediate calculations for future retrieval.

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• Linux software raid robustness

  - by Waxhead

  I have a 4 disk 5TB raid5 setup where a disk is showing signs of going down the drain. It is reporting media errors and from dmesg I can see that several read errors are corrected. smartctl does report "notifications" but no panic so far. Since new disks are rather expensive at the moment I am starting to pondering exactly how robust the linux md layer is. I would appreciate if someone could shed some light on how md actually deals with disk errors. For example how does md deal with write and read errors - what does it (really) take for disk to be rejected from an array. I also read that recently md got support for mapping out bad blocks. Does this mean that the read errors I've had would have been mapped out if I where running kernel 3.1 or would md still try to "work on them" to make them usable.

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• Inexpensive Remote Assistance software?

  - by Jess

  Any recommendations for Remote Assistance software that does not require firewall modification for clients? To assist client with software problems and perform training, we currently use a tool called Remote Helpdesk to connect to their computers and guide them through the process. This tool was pretty cheap (~$400 onetime for 3 support staff), and worked great - the client's PC actually initiates the connection to us, so there's never any firewall issues (vs. Remote Desktop, VNC software, or many other similar tools). Unfortunately, the product doesn't work well with 64-bit O/S's and Vista in general (slows down by a factor of 10 or so). I am looking for alternatives that provide the same reverse connection capabilities to avoid firewall issues. The only solution I've found is WebEx's Remote Support, which is WAY too expensive ($449/month for us). Thanks for all the assistance!

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• NetApp and SQL Server?

  - by Edinor

  Do you have any good or bad experiences to share running SQL Server OLTP Systems on NetApp appliances? I have been working with a small, relatively low-volume cluster with a lower-end NetApp device, and I have found the environment to be generally unstable, at least compared to my experiences with other SANs, iSCSI arrays, and DAS setups. I struggle to believe that RAID DP and WAFL are more than fairy-dust technologies. A solution has been proposed to me that I just need a bigger, better NetApp, with PAM cards and other cool technology I've not heard of, and I feel like I would be better off spending a quarter of that on good direct-attached drives and a beefy server. At the same time, I feel that an Enterprise-class SAN should be something I can count on to be consistently a more stable, better performer than the less expensive solution I might propose. Are you a SQL Server DBA in an OLTP environment and love your NetApp? If you don't like them, why not?

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• Magento Community - Hosting :: Need Advice which sharing hosting will run magento fast

  - by user43353

  Hi, Need Advice which sharing hosting will run Magento Community fast or some other not expensive solution. This website will not have a lot of users, I only need that it will run fast for 100-20 users in same time. The problem with magento is database design that make this system very slow , also other staff not the best. I had hostmonster.com and justhost.com for previous website but it wasn't fast enough for single user that not located in USA (my customer areas: Asia, Africa). each action that involve database takes a lot of time. Thanks

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• Can a usb cable carry 12v?

  - by zm15

  Here's what i'm wanting to do. I have a Acer Iconia A500 tablet. I want to plug it in, in the car, but it has a barrel plug and I don't want to buy an inverter. The car adapters are expensive for what they do. I already have a 2.1 amp usb car charger meant for the iPad: http://www.amazon.com/Kensington-K33497US-PowerBolt-Charger-Compatible/dp/tech-data/B003PU01M4/ref=de_a_smtd And i want to use this usb cable from the 2.1 amp port to plug into the A500: http://www.amazon.com/gp/product/B00304DZ7I/ref=ox_sc_act_title_2?ie=UTF8&m=A1HPBDJJIXKXS7 Here are the specs on the original wall charger if that helps: http://www.phihong.com/assets/pdf/PSA18R.pdf The usb cable says it's 5v, but the original charger says it outputs 12v. But since it's just a cable... wasn't sure if that really made a whole lot of difference since it's only 1.5 amps from the wall charger. Is it possible to use that usb cable through the powerbolt car charger, to charge the A500?

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• Software for failover across multiple external hosts

  - by Lin

  I have multiple webservers with the same content, hosted across different providers. However, I can't seem to find a nice, simple failover solution. Load-balancing software (Pound, HAProxy, etc.) are unnecessary, and I need the flexibility to manage over 100+ domains, so the paid DNS failover solutions I've found are too expensive. So far the simplest solution I've thought of is just to set a very low TTL (30min - 1hr) in each zone entry on my nameservers (running BIND). Then, continuously monitor each server, and temporarily remove failed servers from zone entries. But this seems like something that should be currently available. I only have root access to different VPSes running CentOS. Any suggestions? Thanks!

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• Mini DisplayPort to DVI-D Dual Link up to 2560 * 1600

  - by Steinway Wu

  I have a ThinkPad T530 with Mini DP++ and NVS 5400M, which are said to support 2560 * 1600 resolution. The display is Dell 3007WFP, which also supports 2560 * 1600. But, I have never seen any cables or adapters that can connect them with full support to 2560 * 1600. Do you have any idea? THANK YOU! In addition, I found that mDP++ means I can use a passive adapter. No need for active adapter which is much more expensive. This is the only one that meets my needs, but it is not sold in the US. And this one seems to be OK, but I am not sure because it says "2.5 Gbps per channel", which may not be enough.

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• On Server Disk Storage VS SAN Storage

  - by Justin

  Hello, I am looking at buying three servers, and trying to figure out which storage solution makes the most sense in terms of performance and cost. Total budget is around: $10,000. OPTION 1: Dell servers with RAID 10 (4 Drives) each 7200RPM SAS 500GB, for a total capacity of 1TB. Each server is approx: $3000. Total storage then across all three servers is 3TB. OPTION 2: Same Dell servers with a cheap single drive no RAID for $2000 and go with a centralized SAN solution. The biggest problem is that I haven't been able to even find a SAN solution that is a reasonable price. Dell entry level storage servers are like $15,000. I am thinking just iSCSI, not fiber (too expensive). What do you guys recommend?

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• Dell R510 vs R710

  - by AX1

  Hello, the Dell R510 and R710 can both hold regular configurations (e.g. X5650, 24 GB RAM, etc.) and these usually come out to about the same price. Is there a particular reason why one would choose the R510 over the R710 or vice versa? There really appears a lack of differentiating factors. The only 'major' factor I found, which doesn't apply to me though, is that the R510 can hold up to 12 3.5in HDDs while the R710 (which is slightly more expensive) can only hold up to 6 3.5in HDDs. Maybe you guys have some input and bought either of these machines (or both) to shed some light on other differences and why someone should choose one over the other as the pricing is pretty much the same with my configuration. Thanks!

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