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Search found 562 results on 23 pages for 'robin williams'.

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  • How to properly siglongjmp out of signal handler?

    - by EpsilonVector
    Suppose I have the following code: In order to implement a context switch I activate ualarm and when it jumps to the handler it setjmp's the current context, and longjmps to the next, expecting to eventually return to the alarm handler and longjmped back into this context (the contexts are cycled through in a Round Robin). For this I need to keep SIGALRM unblocked in between alarm_handlers. I came up with the following code, which doesn't seem to work. What's wrong with it and what is the right way to do this? void alarm_handler(){ if(sigsetjmp(toc->threads[toc->RR_pointer].env, 0)){ ualarm(200, 0); signal(SIGALRM, alarm_handler); return; } get_next_context_number(toc->RR_pointer); //is a macro for (j=0; j<10; j++) printf("ALARM HANDLER\n"); siglongjmp(toc->threads[toc->RR_pointer].env, 1); }

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  • language to create flowcharts

    - by robintw
    Hi, This seems like something which must have been answered before, but I can't find anything appropriate in the question archives. Basically, I'm looking for a little Domain Specific Language to create flowcharts. I'm terrible at graphic design and making things look nice, and I'd really like a langauge where I could write something in code and it would produce a pretty flowchart. I've come across GraphViz, but it seems more suited to creating things like Finite State Machine diagrams, rather than process flowcharts. It also doesn't have the simple DSL-style front-end that would allow me to easily work it. Any ideas? I'm sure this must have been done before... Robin

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  • How to indefinitely pause a thread in Java and later resume it?

    - by Carlos Torres
    Maybe this question has been asked many times before, but I never found a satisfying answer. The problem: I have to simulate a process scheduler, using the round robin strategy. I'm using threads to simulate processes and multiprogramming; everything works fine with the JVM managing the threads. But the thing is that now I want to have control of all the threads so that I can run each thread alone by a certain quantum (or time), just like real OS processes schedulers. What I'm thinking to do: I want have a list of all threads, as I iterate the list I want to execute each thread for their corresponding quantum, but as soon the time's up I want to pause that thread indefinitely until all threads in the list are executed and then when I reach the same thread again resume it and so on. The question: So is their a way, without using deprecated methods stop(), suspend(), or resume(), to have this control over threads?

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  • Map the physical file path in asp.net mvc

    - by rmassart
    Hi, I am trying to read an XSLT file from disk in my ASP.Net MVC controller. What I am doing is the following: string filepath = HttpContext.Request.PhysicalApplicationPath; filepath += "/Content/Xsl/pubmed.xslt"; string xsl = System.IO.File.ReadAllText(filepath); However, half way down this thread on forums.asp.net there is the following quote HttpContext.Current is evil and if you use it anywhere in your mvc app you are doing something wrong because you do not need it. Whilst I am not using "Current", I am wondering what is the best way to determine the absolute physical path of a file in MVC? For some reason (I don't know why!) HttpContext doesn't feel right for me. Is there a better (or recommended/best practice) way of reading files from disk in ASP.Net MVC? Thanks for your help, Robin

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  • How to limit the wordpress tagcloud by date?

    - by Nordin
    Hello, I've been searching for quite a while now to find a way to limit wordpress tags by date and order them by the amount of times they appeared in the selected timeframe. But I've been rather unsuccesful. What I'm trying to achieve is something like the trending topics on Twitter. But in this case, 'trending tags'. By default the wordpress tagcloud displays the most popular tags of all time. Which makes no sense in my case, since I want to track current trends. Ideally it would be something like: Most popular tags of today Obama (18 mentions) New York (15 mentions) Iron Man (11 mentions) Robin Hood (7 mentions) And then multiplied for 'most popular this week' and 'most popular this month'. Does anyone know of a way to achieve this?

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  • Load balancer - how to write one for a custom application?

    - by Poni
    Hi! I've written a simple server application which will run distributed on several machines. My question is how does a network load balancer works, in general? I've heard of round-robin and other algorithms, but what I haven't got answer to is how does the process really goes? In socket terms. The client connects to one of the load balancer machines, asks for a "free-to-connect-to" server and simply connects to it? That's the simpliest way I can think of. .. or, does it use the load balancer as a proxy (that implies that all the NBs must be always connected to the application servers, and data is transferred through them)? It's more of a general question. How would you do this? Thank you all!

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  • Horizontal Scaling of Tomcat in Microsoft Azure

    - by Fabe
    Hey everyone, I am working on this quiet a while, but still no conclustion. I want to do horizontal scaling of Tomcat instances in Microsoft Azure (1,2,3,... Tomcat instances for one service). I read lots of articles about session replication, clustering,... with Tomcat. Since Azure does not support Multicasts, there is no easy way to cluster Tomcat. Also sticky sessions is no options, because Azure does round robin load balancing. Setting up two services - one with Terracotta or Apache mod_jk - and the other with Tomcat instances seems overkill for me (if even doable)... Is this even possible? Thanks in advance for reading and answering my question. Every comment/idea is highly appreciated.

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  • Programmatically determine the relative "popularities" of a list of items (books, songs, movies, etc

    - by Horace Loeb
    Given a list of (say) songs, what's the best way to determine their relative "popularity"? My first thought is to use Google Trends. This list of songs: Subterranean Homesick Blues Empire State of Mind California Gurls produces the following Google Trends report: (to find out what's popular now, I restricted the report to the last 30 days) Empire State of Mind is marginally more popular than California Gurls, and Subterranean Homesick Blues is far less popular than either. So this works pretty well, but what happens when your list is 100 or 1000 songs long? Google Trends only allows you to compare 5 terms at once, so absent a huge round-robin, what's the right approach? Another option is to just do a Google Search for each song and see which has the most results, but this doesn't really measure the same thing

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  • Come see us at JavaU at JavaOne!

    - by tmcginn
    In just a little under a month, JavaOne will be in full swing (no pun intended) and thousands of Java developers will gather to hear the latest Java news, immerse themselves in Java technology and learn some new things. This year, I am fortunate enough to be able to attend, along with my Java curriculum development colleagues Matt Heimer and Mike Williams. We start our week at JavaOne teaching a one-day session at JavaU on Sunday morning. If you have never attended a training session through JavaU, you should check it out. There are some terrific sessions this year, and it might help to justify your trip to JavaOne if you can say it was for training! This year I am teaching a one day session on Java SE 7 New Features - a great session for anyone interested in the specific details of what is new in Java SE 7. Matt is teaching a one-day session on Developing Portable Java EE applications with the Enterprise JavaBeans 3.1 API and Java Persistence 2.0 API  EJB, and Mike is doing a one-day session on developing Rich Client applications with Java SE 7 using Java FX 2. I asked Matt and Mike to tell me what developers can expect from their sessions. Matt: "My session will get you up to speed on everything you need to know to create portable Java EE 6 applications using EJB 3.1 and JPA 2. I am going to cover why everyone can benefit from using EJBs (and why developers should relearn them if they haven't looked at them for years). Students who attend my session will see JPA examples showcasing how to use relational databases in an enterprise applications without programming to JDBC and without writing SQL statements. EJB and JPA benefit from being paired together, so I will also show how transaction management is easier in a container. I encourage students to bring a laptop and code as they learn!" Mike: "My session covers how to develop a rich client application using Java FX 2. Starting with the basic concepts of JavaFX, students will see how a JavaFX application is built from its layout, to its controls, to its data structures. In addition, more advanced controls like charts, smart tables, and transitions will be added to the application. Finally, a quick review of JavaFX concurrency and data binding is included. Blended with the core concepts the session will include some of the latest JavaFX technology. This includes using Scene Builder to create a JavaFX UI and connecting your XML UI definition to Java code.  In addition, packaging of the JavaFX application will be covered with some examples of the new native packaging features." As I mentioned, my session covers the changes in the Java for SE 7, including the  language changes that were voted into Java SE 7 from Project Coin. I will also look at how you can take advantage if the the new I/O library (NIO.2) for writing applications that work with files, directories and file systems. We will also look at the changes in Asynchronous I/O that are a part of the changes in NIO/2. We will spend some time looking at the changes to the Java Virtual Machine as well, including support for dynamically typed languages (JSR-292). We will spend some time looking at the Java Concurrency enhancements (JSR-166), including the new Fork/Join framework. And we'll round out the day with a look at changes in Swing, XML and a number of smaller changes in the API's. And, if these topics aren't grabbing your interest, take a look at the other 10 sessions that range from topics on architecture to how to pass the Oracle Certified Programmer I and II exams. See you soon!

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  • Java Dynamic Binding

    - by Chris Okyen
    I am having trouble understanding the OOP Polymorphic principl of Dynamic Binding ( Late Binding ) in Java. I looked for question pertaining to java, and wasn't sure if a overall answer to how dynamic binding works would pertain to Java Dynamic Binding, I wrote this question. Given: class Person { private String name; Person(intitialName) { name = initialName; } // irrelevant methods is here. // Overides Objects method public void writeOutput() { println(name); } } class Student extends Person { private int studentNumber; Student(String intitialName, int initialStudentNumber) { super(intitialName); studentNumber = initialStudentNumber; } // irrellevant methods here... // overides Person, Student and Objects method public void writeOutput() { super.writeOutput(); println(studentNumber); } } class Undergaraduate extends Student { private int level; Undergraduate(String intitialName, int initialStudentNumber,int initialLevel) { super(intitialName,initialStudentNumber); level = initialLevel; } // irrelevant methods is here. // overides Person, Student and Objects method public void writeOutput() { super.writeOutput(); println(level); } } I am wondering. if I had an array called person declared to contain objects of type Person: Person[] people = new Person[2]; person[0] = new Undergraduate("Cotty, Manny",4910,1); person[1] = new Student("DeBanque, Robin", 8812); Given that person[] is declared to be of type Person, you would expect, for example, in the third line where person[0] is initialized to a new Undergraduate object,to only gain the instance variable from Person and Persons Methods since doesn't the assignment to a new Undergraduate to it's ancestor denote the Undergraduate object to access Person - it's Ancestors, methods and isntance variables... Thus ...with the following code I would expect person[0].writeOutput(); // calls Undergraduate::writeOutput() person[1].writeOutput(); // calls Student::writeOutput() person[0] to not have Undergraduate's writeOutput() overidden method, nor have person[1] to have Student's overidden method - writeOutput(). If I had Person mikeJones = new Student("Who?,MikeJones",44,4); mikeJones.writeOutput(); The Person::writeOutput() method would be called. Why is this not so? Does it have to do with something I don't understand about relating to arrays? Does the declaration Person[] people = new Person[2] not bind the method like the previous code would?

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  • It's All In The Cloud

    - by Natalia Rachelson
    People turned out in droves for Steve Miranda's Apps Cloud General Session. Steve, as engaging as ever, covered our Apps strategy in the cloud and reinforced that Oracle has a complete set of cloud services including: •    Human Capital Management•    Talent Management•    Sales and Marketing•    Customer Service and Support•    Financial Management•    Procurement, Sourcing, and Inventory•    Project Portfolio Management•    Governance, Risk, and Compliance... all delivered on top of the Social, Platform, and Common Infrastructure.Steve talked about Fusion being the centerpiece of our Cloud Services. The fact that Fusion is 100 percent standards based is a big, big deal! In addition, our ERP Cloud Service is the most complete cloud service on the market. And email marketing is dead -- social marketing is where the action is. It's also where Oracle is investing heavily from a Sales & Marketing Cloud perspective. Steve covered the strategic acquisitions Oracle has made to enhance our organic Cloud offering. Specifically, Oracle bought RightNow to make our Customer Service and Support Cloud service complete. We also bought Taleo to add Recruiting and Learning capabilities to our Talent Management Cloud. Steve talked about our customers and how they are benefiting from the use of a variety of our Cloud Services. Red Robin is driving lower labor and food costs with Oracle ERP Cloud Service. He used Elizabeth Arden as the profile customer for HCM and Talent Management Service, UBS for HCM and Talent Management Service, and Brocade for Talent Management. All these customers are benefiting from a comprehensive and fully integrated HR platform that aligns compensation with performance and enhances workforce motivation and retention. At the same time, Hitachi Data Systems is using Oracle Taleo Performance Management Cloud to recruit the right competencies, pinpoint areas of improvement, and develop and monitor employee goals to support the global account organization. KLM and Overstock.com are gaining the benefits of Oracle's Customer Service and Support Service from RightNow by better engaging and serving customer needs online and through call centers. And last but not least, Graco and Key Energy are leveraging mobility features and sales forecasting and territory management capabilities within the Oracle Sales and Marketing Service. They expect to gain better visibility to sales information and drive more efficient sales campaigns and empower their sales force with data they need to make sales. Overall, Oracle Apps Cloud Services are enjoying a significant momentum in the marketplace. Steve projected an air of confidence and enthusiasm highlighting Oracle's latest successes with Cloud services.

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  • Using Custom MapType with Google Maps API

    - by Pat Long - Munkii Yebee
    I realise there are a couple of examples such as Maoki's Add Your Own Custom Map and Mike Williams' [link text][Google Maps API Tutorial] however I have looked at these and still end up with a Grey box. The API will not call my "getTileUrl" callback function. This is the javascript I am using var map = new GMap2(document.getElementById("map")); map.setUIToDefault(); var copyCollection = new GCopyrightCollection('Map Data:'); var copyright = new GCopyright(1, new GLatLngBounds(new GLatLng(-90, -180), new GLatLng(90, 180)), 0, "©2006 RunwayFinder.com"); copyCollection.addCopyright(copyright); var tilelayers = [new GTileLayer(copyCollection, 3, 11)]; tilelayers[0].getTileUrl = function (a, b) { var z = 17 - b; var f = "http://localhost:25213/test.jpg?x=" + a.x + "&y=" + a.y + "&zoom=" + z + "&width=100&height=100"; return f; }; var custommap = new GMapType(tilelayers, new GMercatorProjection(12), "Chart", { errorMessage: "No chart data available" }); map.addMapType(custommap); Can anyone see what it is i am doing wrong?

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  • JavaFx 2.1, 2.2 TableView update issue

    - by Lewis Liu
    My application uses JPA read data into TableView then modify and display them. The table refreshed modified record under JavaFx 2.0.3. Under JavaFx 2.1, 2.2, the table wouldn't refresh the update anymore. I found other people have similar issue. My plan was to continue using 2.0.3 until someone fixes the issue under 2.1 and 2.2. Now I know it is not a bug and wouldn't be fixed. Well, I don't know how to deal with this. Following are codes are modified from sample demo to show the issue. If I add a new record or delete a old record from table, table refreshes fine. If I modify a record, the table wouldn't refreshes the change until a add, delete or sort action is taken. If I remove the modified record and add it again, table refreshes. But the modified record is put at button of table. Well, if I remove the modified record, add the same record then move the record to the original spot, the table wouldn't refresh anymore. Below is a completely code, please shine some light on this. import javafx.application.Application; import javafx.beans.property.SimpleStringProperty; import javafx.collections.FXCollections; import javafx.collections.ObservableList; import javafx.event.ActionEvent; import javafx.event.EventHandler; import javafx.geometry.HPos; import javafx.geometry.Insets; import javafx.geometry.Pos; import javafx.scene.Group; import javafx.scene.Scene; import javafx.scene.control.*; import javafx.scene.control.cell.PropertyValueFactory; import javafx.scene.layout.GridPane; import javafx.scene.layout.HBox; import javafx.scene.layout.VBox; import javafx.scene.text.Font; import javafx.stage.Modality; import javafx.stage.Stage; import javafx.stage.StageStyle; public class Main extends Application { private TextField firtNameField = new TextField(); private TextField lastNameField = new TextField(); private TextField emailField = new TextField(); private Stage editView; private Person fPerson; public static class Person { private final SimpleStringProperty firstName; private final SimpleStringProperty lastName; private final SimpleStringProperty email; private Person(String fName, String lName, String email) { this.firstName = new SimpleStringProperty(fName); this.lastName = new SimpleStringProperty(lName); this.email = new SimpleStringProperty(email); } public String getFirstName() { return firstName.get(); } public void setFirstName(String fName) { firstName.set(fName); } public String getLastName() { return lastName.get(); } public void setLastName(String fName) { lastName.set(fName); } public String getEmail() { return email.get(); } public void setEmail(String fName) { email.set(fName); } } private TableView<Person> table = new TableView<Person>(); private final ObservableList<Person> data = FXCollections.observableArrayList( new Person("Jacob", "Smith", "[email protected]"), new Person("Isabella", "Johnson", "[email protected]"), new Person("Ethan", "Williams", "[email protected]"), new Person("Emma", "Jones", "[email protected]"), new Person("Michael", "Brown", "[email protected]")); public static void main(String[] args) { launch(args); } @Override public void start(Stage stage) { Scene scene = new Scene(new Group()); stage.setTitle("Table View Sample"); stage.setWidth(535); stage.setHeight(535); editView = new Stage(); final Label label = new Label("Address Book"); label.setFont(new Font("Arial", 20)); TableColumn firstNameCol = new TableColumn("First Name"); firstNameCol.setCellValueFactory( new PropertyValueFactory<Person, String>("firstName")); firstNameCol.setMinWidth(150); TableColumn lastNameCol = new TableColumn("Last Name"); lastNameCol.setCellValueFactory( new PropertyValueFactory<Person, String>("lastName")); lastNameCol.setMinWidth(150); TableColumn emailCol = new TableColumn("Email"); emailCol.setMinWidth(200); emailCol.setCellValueFactory( new PropertyValueFactory<Person, String>("email")); table.setItems(data); table.getColumns().addAll(firstNameCol, lastNameCol, emailCol); //--- create a edit button and a editPane to edit person Button addButton = new Button("Add"); addButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { fPerson = null; firtNameField.setText(""); lastNameField.setText(""); emailField.setText(""); editView.show(); } }); Button editButton = new Button("Edit"); editButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { if (table.getSelectionModel().getSelectedItem() != null) { fPerson = table.getSelectionModel().getSelectedItem(); firtNameField.setText(fPerson.getFirstName()); lastNameField.setText(fPerson.getLastName()); emailField.setText(fPerson.getEmail()); editView.show(); } } }); Button deleteButton = new Button("Delete"); deleteButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { if (table.getSelectionModel().getSelectedItem() != null) { data.remove(table.getSelectionModel().getSelectedItem()); } } }); HBox addEditDeleteButtonBox = new HBox(); addEditDeleteButtonBox.getChildren().addAll(addButton, editButton, deleteButton); addEditDeleteButtonBox.setAlignment(Pos.CENTER_RIGHT); addEditDeleteButtonBox.setSpacing(3); GridPane editPane = new GridPane(); editPane.getStyleClass().add("editView"); editPane.setPadding(new Insets(3)); editPane.setHgap(5); editPane.setVgap(5); Label personLbl = new Label("Person:"); editPane.add(personLbl, 0, 1); GridPane.setHalignment(personLbl, HPos.LEFT); firtNameField.setPrefWidth(250); lastNameField.setPrefWidth(250); emailField.setPrefWidth(250); Label firstNameLabel = new Label("First Name:"); Label lastNameLabel = new Label("Last Name:"); Label emailLabel = new Label("Email:"); editPane.add(firstNameLabel, 0, 3); editPane.add(firtNameField, 1, 3); editPane.add(lastNameLabel, 0, 4); editPane.add(lastNameField, 1, 4); editPane.add(emailLabel, 0, 5); editPane.add(emailField, 1, 5); GridPane.setHalignment(firstNameLabel, HPos.RIGHT); GridPane.setHalignment(lastNameLabel, HPos.RIGHT); GridPane.setHalignment(emailLabel, HPos.RIGHT); Button saveButton = new Button("Save"); saveButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { if (fPerson == null) { fPerson = new Person( firtNameField.getText(), lastNameField.getText(), emailField.getText()); data.add(fPerson); } else { int k = -1; if (data.size() > 0) { for (int i = 0; i < data.size(); i++) { if (data.get(i) == fPerson) { k = i; } } } fPerson.setFirstName(firtNameField.getText()); fPerson.setLastName(lastNameField.getText()); fPerson.setEmail(emailField.getText()); data.set(k, fPerson); table.setItems(data); // The following will work, but edited person has to be added to the button // // data.remove(fPerson); // data.add(fPerson); // add and remove refresh the table, but now move edited person to original spot, // it failed again with the following code // while (data.indexOf(fPerson) != k) { // int i = data.indexOf(fPerson); // Collections.swap(data, i, i - 1); // } } editView.close(); } }); Button cancelButton = new Button("Cancel"); cancelButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { editView.close(); } }); HBox saveCancelButtonBox = new HBox(); saveCancelButtonBox.getChildren().addAll(saveButton, cancelButton); saveCancelButtonBox.setAlignment(Pos.CENTER_RIGHT); saveCancelButtonBox.setSpacing(3); VBox editBox = new VBox(); editBox.getChildren().addAll(editPane, saveCancelButtonBox); Scene editScene = new Scene(editBox); editView.setTitle("Person"); editView.initStyle(StageStyle.UTILITY); editView.initModality(Modality.APPLICATION_MODAL); editView.setScene(editScene); editView.close(); final VBox vbox = new VBox(); vbox.setSpacing(5); vbox.getChildren().addAll(label, table, addEditDeleteButtonBox); vbox.setPadding(new Insets(10, 0, 0, 10)); ((Group) scene.getRoot()).getChildren().addAll(vbox); stage.setScene(scene); stage.show(); } }

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  • NSCollectionView: Can the same object not be in the array more than once or is this a bug?

    - by Sean
    I may be doing this all wrong, but I thought I was on the right track until I hit this little snag. Basically I was putting together a toy using NSCollectionView and trying to understand how to hook that all up using IB. I have a button which will add a couple of strings to the NSArrayController: The first time I press this button, my strings appear in the collection view as expected: The second time I press the button, the views scroll down and room is made - but the items don't appear to get added. I just see blank space: The button is implemented as follows (controller is a pointer to the NSArrayController I added in IB): - (IBAction)addStuff:(id)control { [controller addObjects:[NSArray arrayWithObjects:@"String 1",@"String 2",@"String 3",nil]]; } I'm not sure what I'm doing wrong. Rather than try to explain all the connections/binds/etc, if you need more info, I'd be grateful if you could just take a quick look at the toy project itself. UPDATE: After more experimentation as suggested by James Williams, it seems the problem stems from having multiple objects with the same memory address in the array. This confuses either NSArrayController or NSCollectionView (not sure which). Changing my addStuff: to this resulted in the behavior I originally expected: [controller addObjects:[NSArray arrayWithObjects:[NSMutableString stringWithString:@"String 1"],[NSMutableString stringWithString:@"String 2"],[NSMutableString stringWithString:@"String 3"],nil]]; So the question now, I guess, is if this is a bug I should report to Apple or if this is intended/documented behavior and I just missed it?

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  • Why is Excel's 'Evaluate' method a general expression evaluator?

    - by jtolle
    A few questions have come up recently involving the Application.Evaluate method callable from Excel VBA. The old XLM macro language also exposes an EVALUATE() function. Both can be quite useful. Does anyone know why the evaluator that is exposed can handle general expressions, though? My own hunch is that Excel needed to give people a way to get ranges from string addresses, and to get the value of named formulas, and just opening a portal to the expression evaluator was the easiest way. (The help for the VBA version does say its purpose it to "convert a Microsoft Excel name to an object or a value".) But of course you don't need the ability to evaluate arbitrary expressions just to do that. (That is, Excel could provide a Name.Evaluate method or something instead.) Application.Evaluate seems kind of...unfinished. It's full behavior isn't very well documented, and there are quite a few quirks and limitations (as described by Charles Williams here: http://www.decisionmodels.com/calcsecretsh.htm) with what is exposed. I suppose the answer could be simply "why not expose it?", but I'd be interested to know what design decisions led to this feature taking the form that it does. Failing that, I'd be interested to hear other hunches.

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  • Strange results about C++11 memory model (Relaxed ordering)

    - by Dancing_bunny
    I was testing the example in the memory model of the Anthony Williams's book "C++ Concurrency" #include<atomic> #include<thread> #include<cassert> std::atomic_bool x,y; std::atomic_int z; void write_x_then_y() { x.store(true, std::memory_order_relaxed); y.store(true, std::memory_order_relaxed); } void read_y_then_x() { while(!y.load(std::memory_order_relaxed)); if(x.load(std::memory_order_relaxed)) { ++z; } } int main() { x = false; y = false; z = 0; std::thread a(write_x_then_y); std::thread b(read_y_then_x); a.join(); b.join(); assert(z.load()!=0); } According to the explanation, relaxed operations on difference variables (here x and y) can be freely reordered. However, I repeated running the problem for more than several days. I never hit the situation that the assertion (assert(z.load()!=0);) fires. I just use the default optimization and compile the code using g++ -std=c++11 -lpthread dataRaceAtomic.cpp Does anyone actually try it and hit the assertion? Could anyone give me an explanation about my test results? BTW, I also tried the version without using the atomic type, I got the same result. Currently, both programs are running healthily. Thanks.

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  • Understanding Linux SCSI queue depths

    - by Troels Arvin
    I'm experimenting with the effects of different SCSI queue depth values on a Dell server running CentOS Linux 5.4 (x86_64). The server has two QLogic QLE2560 FC HBAs connected via multipathing to a storage system. The storage system has allocated two LUNs to the server, each connected through four paths in an active-active-active-active round-robin configuration. All in all, the two LUNs exist as eight /dev/sdX devices, represented by two devices in /dev/mpath. I currently adjust the queue depth values in /etc/modprobe.conf and check the result (after rebooting) by looking in the seventh column of /proc/scsi/sg/devices. Two questions related to that: Is there a way to adjust queue depths without rebooting or unloading the qla2xxx kernel module? E.g., can I echo a new queue depth value into some /proc or /sys-like file to update the queue depth? If I set the queue depth to 128, is that 128 in total for all devices handled by the qla2xxx module?, or 128 for each HBA? (256 in total), or 128 for each of the eight /dev/sdX devices (1024 in toal)?, or 128 for each of the two /dev/mpath/... devices (256 in total)? This is important for me to know so that my server doesn't flood the storage system, affecting other servers connected to it.

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  • Mounting Replicated Gluster Multi-AZ Storage

    - by Roman Newaza
    I have Replicated Gluster Storage which is used by Auto scaling Servers. Both, Auto scaling and Storage are allocated in two Availability zones. Gluster: Number of Bricks: 4 x 2 = 8 Transport-type: tcp Bricks: Brick1: gluster01:/storage/1a # Zone A Brick2: gluster02:/storage/1b # Zone B Brick3: gluster03:/storage/2a # Zone A Brick4: gluster04:/storage/2b # Zone B Brick5: gluster01:/storage/3a # Zone A Brick6: gluster02:/storage/3b # Zone B Brick7: gluster03:/storage/4a # Zone A Brick8: gluster04:/storage/4b # Zone B I used Round Robin DNS for Gluster entry point, so DNS name resolves to all of the storage server addresses which are returned in different order all the time: # host storage.domain.com storage.domain.com has address xx.xx.xx.x1 storage.domain.com has address xx.xx.xx.x2 storage.domain.com has address xx.xx.xx.x3 storage.domain.com has address xx.xx.xx.x4 The Storage is mounted with Native Gluster Client: # grep storage /etc/fstab storage.domain.com:/storage /storage glusterfs defaults,log-level=WARNING,log-file=/var/log/gluster.log 0 0 I have heard Gluster might be mounted with the first Server IP and after that it will fetch its configuration with the rest of Servers. Personally, I never tested single Server mount setup and I don't know how Gluster handles this. On EC2, traffic among single Availability zone is free and between different zones is not. When Client in zone A writes to storage and IP of Storage in zone B is returned, it will cost me twice more for data transfer: Client (Zone A) - Storage Server (Zone B) - Replication to Storage Server (Zone A). Question: Would it be better to mount Storage Server of the same zone, so that data transfer charges apply only for replication (A - A - B)?

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  • BGP Multihomed/Multi-location best practice

    - by Tom O'Connor
    We're in the process of designing a new iteration of our network where we improve resilliency by adding a second datacentre. We'll be adding a second datacentre, with an identical configuration of servers as our primary location. To achieve network connectivity, we're looking into a couple of possible methods. See earlier questions http://serverfault.com/questions/86736/best-way-to-improve-resilience and http://serverfault.com/questions/101582/dns-round-robin-failover-and-load-balancing I'm pretty convinced that BGP is the right way to go about this, and this question is not about RRDNS. 1) If we have 2 locations, do we announce the same IP address block from both locations? 2) If we did this, but had a management ssh interface on x.x.x.50 from datacentre A, but it was on x.x.x.150 in datacentre B. What is the best practice mechanism for achieving this? Because if I were nearest to A, then all my traffic would go to x.50, but if i attempted to connect to x.150, I'd not be able to connect, because this address wouldn't be valid at A, but only at B. Is the best solution to announce 2 different netblocks, one at each location, facilitating the need for RRDNS, or to announce a single block, and run some form of VPN between the two sites for managment traffic?

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  • how to design pound -> varnish -> jboss for ha + loadbalancing

    - by andreash
    Hello, I'm planning a new infrastructure for our web application. We have two JBossAS5 servers, running in a cluster. Session state will be replicated via JBoss Cache. In front of that, there should be some cache, to speed up delivery of static elements. However, most of the traffic to our app will be via HTTPS. So far, I had been thinking of two Varnish caches in front of the JBossASs, each being configured for loadbalancing to the two JBossASs via round-robin. Since Varnish doesn't handle HTTPS, then there would need to be two pound proxies in front of the Varnishs, dealing with the HTTPS. The two pounds would be made high-available with Heartbeat/LinuxHA. The traffic to www.example.com would then be going through our firewall, from there to the virtual IP of the pounds, from there to the Varnishs, and from there to the JBossASs. Question 1: Does this make sense? Or is it overly complicated, and the same goal can be reached with simpler methods? Question 2: If my layout is fine, how do I configure the pound - Varnish step? Should I a) make the Varnish service high-available through Heartbeat/LinuxHA as well and direct traffic from pound to the virtual IP of the Varnishs, or should I rather b) Configure two independent Varnishs and use load-balancing in pound to address the different Varnishs? Thanks a lot for your insight! Andreas.

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  • Multi-IP address zimbra server DNS PTR records and spam

    - by David Fraser
    We have a mail server running Zimbra (ZCS 6.0.8). The server has 5 active public IP addresses in the same subnet. (.226-.230). I currently have A records for each of these (host0.domain.com..host4.domain.com), with the main host.domain.com of the machine pointing to .226. Our host has ended up being listed on the SORBS DUHL list (even though it's in a server farm). According to them you can get removed quickly by checking that your host has an MX record, an A record, and a PTR record that points back to the hostname given in the MX record. I tried setting the PTR records so that each of these addresses resolved back to their A record (i.e. .228 had a PTR to host2.domain.com). However, I then got mail being rejected from other servers because when Postfix (under Zimbra control) sends out mail, it uses the main hostname for the HELO - there doesn't seem to be any way to override it. So the PTR records currently say host.domain.com for all 5 IP addresses. What's the correct way to handle this? Should I have an A record for the domain that points to all the IP addresses (for round-robin handling)? I'm nervous of changes that could cause problems, so I'm wondering what the standard way to handle a multiple-IP-address mail server is.

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  • Managing multiple Apache proxies simultaneously (mod_proxy_balancer)

    - by Hank
    The frontend of my web application is formed by currently two Apache reverse proxies, using mod_proxy_balancer to distribute traffic over a number of backend application servers. Both frontend reverse proxies, running on separate hosts, are accessible from the internet. DNS round robin distributes traffic over both. In the future, the number of reverse proxies is likely to grow, since the webapplication is very bandwidth-heavy. My question is: how do I keep the state of both reverse balancers / proxies in sync? For example, for maintenance purposes, I might want to reduce the load on one of the backend appservers. Currently I can do that by accessing the Balancer-Manager web form on each proxy, and change the distribution rules. But I have to do that on each proxy manually and make sure I enter the same stuff. Is it possible to "link" multiple instances of mod_proxy_balancer? Or is there a tool out there that connects to a number of instances, and updates all with the same information? Update: The tool should retrieve the runtime status and make runtime changes, just like the existing Balancer-Manager, only for a number of proxies - not just for one. Modification of configuration files is not what I'm interested in (as there are plenty tools for that).

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  • How many reverse proxies (nginx, haproxy) is too many?

    - by Alysum
    I'm setting up a HA (high availability) cluster using nginx, haproxy & apache. I've been reading great things about nginx and haproxy. People tend to choose one or the other but I like both. Haproxy is more flexible for load balancing than nginx's simple round robin (even with the upstream-fair patch). But I'd like to keep nginx for redirecting non-https to https among other things right at the point of entry to the cluster. On the other hand, nginx is a lot faster for serving static contents and would reduce the load on the powerful apache which loves to eat a lot of RAM! Here is my planned setup: Load balancer: nginx listens on port 80/443 and proxy_forwards to haproxy on 8080 on the same server to load balance between the multiple nodes. Nodes: nginx on the node listens to requests coming from haproxy on 8080, if the content is static, serve it. But if it's a backend script (in my case PHP), proxy forward to apache2 on the same node server listenning on a different port number. Technically this setup works but my concerns are whether having the requests going through several proxies is going to slow down requests? Most of the requests will be PHP requests as the backends are services (which means groing from nginx - haproxy - nginx - apache). Thoughts? Cheers

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  • Can a pool of memcache daemons be used to share sessions more efficiently?

    - by Tom
    We are moving from a 1 webserver setup to a two webserver setup and I need to start sharing PHP sessions between the two load balanced machines. We already have memcached installed (and started) and so I was pleasantly surprized that I could accomplish sharing sessions between the new servers by changing only 3 lines in the php.ini file (the session.save_handler and session.save_path): I replaced: session.save_handler = files with: session.save_handler = memcache Then on the master webserver I set the session.save_path to point to localhost: session.save_path="tcp://localhost:11211" and on the slave webserver I set the session.save_path to point to the master: session.save_path="tcp://192.168.0.1:11211" Job done, I tested it and it works. But... Obviously using memcache means the sessions are in RAM and will be lost if a machine is rebooted or the memcache daemon crashes - I'm a little concerned by this but I am a bit more worried about the network traffic between the two webservers (especially as we scale up) because whenever someone is load balanced to the slave webserver their sessions will be fetched across the network from the master webserver. I was wondering if I could define two save_paths so the machines look in their own session storage before using the network. For example: Master: session.save_path="tcp://localhost:11211, tcp://192.168.0.2:11211" Slave: session.save_path="tcp://localhost:11211, tcp://192.168.0.1:11211" Would this successfully share sessions across the servers AND help performance? i.e save network traffic 50% of the time. Or is this technique only for failovers (e.g. when one memcache daemon is unreachable)? Note: I'm not really asking specifically about memcache replication - more about whether the PHP memcache client can peak inside each memcache daemon in a pool, return a session if it finds one and only create a new session if it doesn't find one in all the stores. As I'm writing this I'm thinking I'm asking a bit much from PHP, lol... Assume: no sticky-sessions, round-robin load balancing, LAMP servers.

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  • What's the best way to run Drupal and Django sites behind the same Varnish server?

    - by Alexis Bellido
    I have a high traffic website running with Drupal and Apache, five web servers behind a Varnish server load balancing. Let's say this site is example.com. I'm using five backends and a director like this in my default.vcl: director balancer round-robin { { .backend = web1; } { .backend = web2; } { .backend = web3; } { .backend = web4; } { .backend = web5; } } Now I'm working on a new Django project that will be a new section of this site running on example.com/new-section. After checking the documentation I found I can do something like this: sub vcl_recv { if (req.url ~ "^/new-section/") { set req.backend = newbackend; } else { set req.backend = default; } } That is, using a different backend for a subdirectory /new-section under the same domain. My question is, how do I make something like this work with my director and load balancing setup? I'm probably going to run two or more web servers (backends) with my new Django project, each one with a mix of Gunicorn, Nginx, and a few Python packages, and would like to put all of those in their own Varnish director to load balance. Is it possible to do use the above approach to decide which director to use?, like this: sub vcl_recv { if (req.url ~ "^/new-section/") { set req.director = newdirector; } else { set req.director = balancer; } } All suggestions welcome. Thanks!

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