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• A SelfHosted WCF Service over Basic HTTP Binding doesn't support more than 1000 concurrent requests

  - by Krishnan

  I have self hosted a WCF Service over BasicHttpBinding consumed by an ASMX Client. I'm simulating a concurrent user load of 1200 users. The service method takes a string parameter and returns a string. The data exchanged is less than 10KB. The processing time for a request is fixed at 2 seconds by having a Thread.Sleep(2000) statement. Nothing additional. I have removed all the DB Hits / business logic. The same piece of code runs fine for 1000 concurrent users. I get the following error when I bump up the number to 1200 users. System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags) at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) --- End of inner exception stack trace --- at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) at System.Net.PooledStream.Read(Byte[] buffer, Int32 offset, Int32 size) at System.Net.Connection.SyncRead(HttpWebRequest request, Boolean userRetrievedStream, Boolean probeRead) --- End of inner exception stack trace --- at System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(WebRequest request) at System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse(WebRequest request) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) at WCF.Throttling.Client.Service.Function2(String param) This exception is often reported on DataContract mismatch and large data exchange. But never when doing a load test. I have browsed enough and have tried most of the options which include, Enabled Trace & Message log on server side. But no errors logged. To overcome Port Exhaustion MaxUserPort is set to 65535, and TcpTimedWaitDelay 30 secs. MaxConcurrent Calls is set to 600, and MaxConcurrentInstances is set to 1200. The Open, Close, Send and Receive Timeouts are set to 10 Minutes. The HTTPWebRequest KeepAlive set to false. I have not been able to nail down the issue for the past two days. Any help would be appreciated. Thank you.

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• Why does my ko computed observable not update bound UI elements when its value changes?

  - by Allen

  I'm trying to wrap a cookie in a computed observable (which I'll later turn into a protectedObservable) and I'm having some problems with the computed observable. I was under the opinion that changes to the computed observable would be broadcast to any UI elements that have been bound to it. I've created the following fiddle JavaScript: var viewModel = {}; // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; return { 'write' : function (val) { privateZipcode = val; }, 'read': function () { return privateZipcode; } } }(); viewModel.zipcode = ko.computed({ read: function () { return cookie.read(); }, write: function (value) { cookie.write(value); }, owner: viewModel }); ko.applyBindings(viewModel);? HTML: zipcode: <input type='text' data-bind="value: zipcode"> <br /> zipcode: <span data-bind="text: zipcode"></span>? I'm not using an observable to store privateZipcode since that's really just going to be in a cookie. I'm hoping that the ko.computed will provide the notifications and binding functionality that I need, though most of the examples I've seen with ko.computed end up using a ko.observable underneath the covers. Shouldn't the act of writing the value to my computed observable signal the UI elements that are bound to its value? Shouldn't these just update? Workaround I've got a simple workaround where I just use a ko.observable along side of my cookie store and using that will trigger the required updates to my DOM elements but this seems completely unnecessary, unless ko.computed lacks the signaling / dependency type functionality that ko.observable has. My workaround fiddle, you'll notice that the only thing that changes is that I added a seperateObservable that isn't used as a store, its only purpose is to signal to the UI that the underlying data has changed. // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; // extra observable that isnt really used as a store, just to trigger updates to the UI var seperateObservable = ko.observable(privateZipcode); return { 'write' : function (val) { privateZipcode = val; seperateObservable(val); }, 'read': function () { seperateObservable(); return privateZipcode; } } }(); This makes sense and works as I'd expect because viewModel.zipcode depends on seperateObservable and updates to that should (and does) signal the UI to update. What I don't understand, is why doesn't a call to the write function on my ko.computed signal the UI to update, since that element is bound to that ko.computed? I suspected that I might have to use something in knockout to manually signal that my ko.computed has been updated, and I'm fine with that, that makes sense. I just haven't been able to find a way to accomplish that.

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• How do I refactor these two C# functions to abstract their logic from the specific class properties

  - by ObligatoryMoniker

  I have two functions whose underlying logic is the same but in one case it sets one property value on a class and in another case it sets a different one. How can I rewrite the following two functions to abstract away as much of the algorithm as possible so that I can make changes in logic in a single place? SetBillingAddress private void SetBillingAddress(OrderAddress newBillingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldBillingAddress = basketHelper.Basket.Addresses[basketHelper.BillingAddressID]; bool NewBillingAddressIsNotOldBillingAddress = ((oldBillingAddress == null) || (newBillingAddress.OrderAddressId != oldBillingAddress.OrderAddressId)); bool BillingAddressHasBeenPreviouslySet = (oldBillingAddress != null); bool BillingAddressIsNotSameAsShippingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewBillingAddressIsNotShippingAddress = (newBillingAddress.OrderAddressId != basketHelper.ShippingAddressID); if (NewBillingAddressIsNotOldBillingAddress && BillingAddressHasBeenPreviouslySet && BillingAddressIsNotSameAsShippingAddress) { basketHelper.Basket.Addresses.Remove(oldBillingAddress); } if (NewBillingAddressIsNotOldBillingAddress && NewBillingAddressIsNotShippingAddress) { basketHelper.Basket.Addresses.Add(newBillingAddress); } basketHelper.BillingAddressID = newBillingAddress.OrderAddressId; basketHelper.Basket.Save(); } And here is the second one: SetShippingAddress private void SetBillingAddress(OrderAddress newShippingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldShippingAddress = basketHelper.Basket.Addresses[basketHelper.ShippingAddressID]; bool NewShippingAddressIsNotOldShippingAddress = ((oldShippingAddress == null) || (newShippingAddress.OrderAddressId != oldShippingAddress.OrderAddressId)); bool ShippingAddressHasBeenPreviouslySet = (oldShippingAddress != null); bool ShippingAddressIsNotSameAsBillingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewShippingAddressIsNotBillingAddress = (newShippingAddress.OrderAddressId != basketHelper.BillingAddressID); if (NewShippingAddressIsNotOldShippingAddress && ShippingAddressHasBeenPreviouslySet && ShippingAddressIsNotSameAsBillingAddress) { basketHelper.Basket.Addresses.Remove(oldShippingAddress); } if (NewShippingAddressIsNotOldShippingAddress && NewShippingAddressIsNotBillingAddress) { basketHelper.Basket.Addresses.Add(newShippingAddress); } basketHelper.ShippingAddressID = newShippingAddress.OrderAddressId; basketHelper.Basket.Save(); } My initial thought was that if I could pass a class's property by refernce then I could rewrite the previous functions into something like private void SetPurchaseOrderAddress(OrderAddress newAddress, ref String CurrentChangingAddressIDProperty) and then call this function and pass in either basketHelper.BillingAddressID or basketHelper.ShippingAddressID as CurrentChangingAddressIDProperty but since I can't pass C# properties by reference I am not sure what to do with this code to be able to reuse the logic in both places. Thanks for any insight you can give me.

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• NSLinguisticTagger on the contents of an NSTextStorage- crashing bug

  - by Remy Porter

  I'm trying to use an NSLinguisticTagger to monitor the contents of an NSTextStorage and provide some contextual information based on what the user types. To that end, I have an OverlayManager object, which wires up this relationship: -(void) setView:(NSTextView*) view { _view = view; _layout = view.layoutManager; _storage = view.layoutManager.textStorage; //get the TextStorage from the view [_tagger setString:_storage.string]; //pull the string out, this grabs the mutable version [self registerForNotificationsOn:self->_storage]; //subscribe to the willProcessEditing notification } When an edit occurs, I make sure to trap it and notify the tagger (and yes, I know I'm being annoyingly inconsistent with member access, I'm rusty on Obj-C, I'll fix it later): - (void) textStorageWillProcessEditing:(NSNotification*) notification{ if ([self->_storage editedMask] & NSTextStorageEditedCharacters) { NSRange editedRange = [self->_storage editedRange]; NSUInteger delta = [self->_storage changeInLength]; [_tagger stringEditedInRange:editedRange changeInLength:delta]; //should notify the tagger of the changes [self highlightEdits:self]; } } The highlightEdits message delegates the job out to a pool of "Overlay" objects. Each contains a block of code similar to this: [tagger enumerateTagsInRange:range scheme:NSLinguisticTagSchemeLexicalClass options:0 usingBlock:^(NSString *tag, NSRange tokenRange, NSRange sentenceRange, BOOL *stop) { if (tag == PartOfSpeech) { [self applyHighlightToRange:tokenRange onStorage:storage]; } }]; And that's where the problem is- the enumerateTagsInRange method crashes out with a message: 2014-06-04 10:07:19.692 WritersEditor[40191:303] NSMutableRLEArray replaceObjectsInRange:withObject:length:: Out of bounds This problem doesn't occur if I don't link to the mutable copy of the underlying string and instead do a [[_storage string] copy], but obviously I don't want to copy the entire backing store every time I want to do tagging. This all should be happening in the main run loop, so I don't think this is a threading issue. The NSRange I'm enumerating tags on exists both in the NSTextStorage and in the NSLinguisticTagger's view of the string. It's not even the fact that the applyHighlightToRange call adds attributes to the string, because it crashes before even reaching that line. I attempted to build a test case around the problem, but can't replicate it in those situations: - (void) testEdit { NSAttributedString* str = [[NSMutableAttributedString alloc] initWithString:@"Quickly, this is a test."]; text = [[NSTextStorage alloc] initWithAttributedString:str]; NSArray* schemes = [NSLinguisticTagger availableTagSchemesForLanguage:@"en"]; tagger = [[NSLinguisticTagger alloc] initWithTagSchemes:schemes options:0]; [tagger setString:[text string]]; [text beginEditing]; [[text mutableString] appendString:@"T"]; NSRange edited = [text editedRange]; NSUInteger length = [text changeInLength]; [text endEditing]; [tagger stringEditedInRange:edited changeInLength:length]; [tagger enumerateTagsInRange:edited scheme:NSLinguisticTagSchemeLexicalClass options:0 usingBlock:^(NSString *tag, NSRange tokenRange, NSRange sentenceRange, BOOL *stop) { //doesn't matter, this should crash }]; } That code doesn't crash.

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• How do I recover from an unchecked exception?

  - by erickson

  Unchecked exceptions are alright if you want to handle every failure the same way, for example by logging it and skipping to the next request, displaying a message to the user and handling the next event, etc. If this is my use case, all I have to do is catch some general exception type at a high level in my system, and handle everything the same way. But I want to recover from specific problems, and I'm not sure the best way to approach it with unchecked exceptions. Here is a concrete example. Suppose I have a web application, built using Struts2 and Hibernate. If an exception bubbles up to my "action", I log it, and display a pretty apology to the user. But one of the functions of my web application is creating new user accounts, that require a unique user name. If a user picks a name that already exists, Hibernate throws an org.hibernate.exception.ConstraintViolationException (an unchecked exception) down in the guts of my system. I'd really like to recover from this particular problem by asking the user to choose another user name, rather than giving them the same "we logged your problem but for now you're hosed" message. Here are a few points to consider: There a lot of people creating accounts simultaneously. I don't want to lock the whole user table between a "SELECT" to see if the name exists and an "INSERT" if it doesn't. In the case of relational databases, there might be some tricks to work around this, but what I'm really interested in is the general case where pre-checking for an exception won't work because of a fundamental race condition. Same thing could apply to looking for a file on the file system, etc. Given my CTO's propensity for drive-by management induced by reading technology columns in "Inc.", I need a layer of indirection around the persistence mechanism so that I can throw out Hibernate and use Kodo, or whatever, without changing anything except the lowest layer of persistence code. As a matter of fact, there are several such layers of abstraction in my system. How can I prevent them from leaking in spite of unchecked exceptions? One of the declaimed weaknesses of checked exceptions is having to "handle" them in every call on the stack—either by declaring that a calling method throws them, or by catching them and handling them. Handling them often means wrapping them in another checked exception of a type appropriate to the level of abstraction. So, for example, in checked-exception land, a file-system–based implementation of my UserRegistry might catch IOException, while a database implementation would catch SQLException, but both would throw a UserNotFoundException that hides the underlying implementation. How do I take advantage of unchecked exceptions, sparing myself of the burden of this wrapping at each layer, without leaking implementation details?

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• Gradual memory leak in loop over contents of QTMovie

  - by Benji XVI

  I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases. Instruments is not detecting any memory leaks per se, but the object trace shows certain General Data blocks to be increasing in size. [Edited out reference to slowdown as it doesn't seem to be as much of a problem as I thought.] Edit: let's knock out some parts of the code inside the loop & see what we find out... Test 1 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } Here we simply loop over the whole movie, creating the filename and logging it. Memory characteristics: remains at 15MB usage for the duration. Test 2 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; [sourceMovie stepForward]; [arp release]; } Here we add back in the creation of the NSImage from the current frame. Memory characteristics: gradually increasing memory usage. RSIZE is at 60MB by frame 200; 75MB by f300. Test 3 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; NSData *imageData = [image TIFFRepresentation]; [sourceMovie stepForward]; [arp release]; } We've added back in the creation of an NSData object from the NSImage. Memory characteristics: Memory usage is again increasing: 62MB at f200; 75MB at f300. In other words, largely identical. It looks like a memory leak in the underlying system QTMovie uses to do currentFrameImage, to me.

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• Go - Using a container/heap to implement a priority queue

  - by Seth Hoenig

  In the big picture, I'm trying to implement Dijkstra's algorithm using a priority queue. According to members of golang-nuts, the idiomatic way to do this in Go is to use the heap interface with a custom underlying data structure. So I have created Node.go and PQueue.go like so: //Node.go package pqueue type Node struct { row int col int myVal int sumVal int } func (n *Node) Init(r, c, mv, sv int) { n.row = r n.col = c n.myVal = mv n.sumVal = sv } func (n *Node) Equals(o *Node) bool { return n.row == o.row && n.col == o.col } And PQueue.go: // PQueue.go package pqueue import "container/vector" import "container/heap" type PQueue struct { data vector.Vector size int } func (pq *PQueue) Init() { heap.Init(pq) } func (pq *PQueue) IsEmpty() bool { return pq.size == 0 } func (pq *PQueue) Push(i interface{}) { heap.Push(pq, i) pq.size++ } func (pq *PQueue) Pop() interface{} { pq.size-- return heap.Pop(pq) } func (pq *PQueue) Len() int { return pq.size } func (pq *PQueue) Less(i, j int) bool { I := pq.data.At(i).(Node) J := pq.data.At(j).(Node) return (I.sumVal + I.myVal) < (J.sumVal + J.myVal) } func (pq *PQueue) Swap(i, j int) { temp := pq.data.At(i).(Node) pq.data.Set(i, pq.data.At(j).(Node)) pq.data.Set(j, temp) } And main.go: (the action is in SolveMatrix) // Euler 81 package main import "fmt" import "io/ioutil" import "strings" import "strconv" import "./pqueue" const MATSIZE = 5 const MATNAME = "matrix_small.txt" func main() { var matrix [MATSIZE][MATSIZE]int contents, err := ioutil.ReadFile(MATNAME) if err != nil { panic("FILE IO ERROR!") } inFileStr := string(contents) byrows := strings.Split(inFileStr, "\n", -1) for row := 0; row < MATSIZE; row++ { byrows[row] = (byrows[row])[0 : len(byrows[row])-1] bycols := strings.Split(byrows[row], ",", -1) for col := 0; col < MATSIZE; col++ { matrix[row][col], _ = strconv.Atoi(bycols[col]) } } PrintMatrix(matrix) sum, len := SolveMatrix(matrix) fmt.Printf("len: %d, sum: %d\n", len, sum) } func PrintMatrix(mat [MATSIZE][MATSIZE]int) { for r := 0; r < MATSIZE; r++ { for c := 0; c < MATSIZE; c++ { fmt.Printf("%d ", mat[r][c]) } fmt.Print("\n") } } func SolveMatrix(mat [MATSIZE][MATSIZE]int) (int, int) { var PQ pqueue.PQueue var firstNode pqueue.Node var endNode pqueue.Node msm1 := MATSIZE - 1 firstNode.Init(0, 0, mat[0][0], 0) endNode.Init(msm1, msm1, mat[msm1][msm1], 0) if PQ.IsEmpty() { // make compiler stfu about unused variable fmt.Print("empty") } PQ.Push(firstNode) // problem return 0, 0 } The problem is, upon compiling i get the error message: [~/Code/Euler/81] $ make 6g -o pqueue.6 Node.go PQueue.go 6g main.go main.go:58: implicit assignment of unexported field 'row' of pqueue.Node in function argument make: *** [all] Error 1 And commenting out the line PQ.Push(firstNode) does satisfy the compiler. But I don't understand why I'm getting the error message in the first place. Push doesn't modify the argument in any way.

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• Poor man's "lexer" for C#

  - by Paul Hollingsworth

  I'm trying to write a very simple parser in C#. I need a lexer -- something that lets me associate regular expressions with tokens, so it reads in regexs and gives me back symbols. It seems like I ought to be able to use Regex to do the actual heavy lifting, but I can't see an easy way to do it. For one thing, Regex only seems to work on strings, not streams (why is that!?!?). Basically, I want an implementation of the following interface: interface ILexer : IDisposable { /// <summary> /// Return true if there are more tokens to read /// </summary> bool HasMoreTokens { get; } /// <summary> /// The actual contents that matched the token /// </summary> string TokenContents { get; } /// <summary> /// The particular token in "tokenDefinitions" that was matched (e.g. "STRING", "NUMBER", "OPEN PARENS", "CLOSE PARENS" /// </summary> object Token { get; } /// <summary> /// Move to the next token /// </summary> void Next(); } interface ILexerFactory { /// <summary> /// Create a Lexer for converting a stream of characters into tokens /// </summary> /// <param name="reader">TextReader that supplies the underlying stream</param> /// <param name="tokenDefinitions">A dictionary from regular expressions to their "token identifers"</param> /// <returns>The lexer</returns> ILexer CreateLexer(TextReader reader, IDictionary<string, object> tokenDefinitions); } So, pluz send the codz... No, seriously, I am about to start writing an implementation of the above interface yet I find it hard to believe that there isn't some simple way of doing this in .NET (2.0) already. So, any suggestions for a simple way to do the above? (Also, I don't want any "code generators". Performance is not important for this thing and I don't want to introduce any complexity into the build process.)

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• Java Best Practice for type resolution at runtime.

  - by Brian

  I'm trying to define a class (or set of classes which implement the same interface) that will behave as a loosely typed object (like JavaScript). They can hold any sort of data and operations on them depend on the underlying type. I have it working in three different ways but none seem ideal. These test versions only allow strings and integers and the only operation is add. Adding integers results in the sum of the integer values, adding strings concatenates the strings and adding an integer to a string converts the integer to a string and concatenates it with the string. The final version will have more types (Doubles, Arrays, JavaScript-like objects where new properties can be added dynamically) and more operations. Way 1: public interface DynObject1 { @Override public String toString(); public DynObject1 add(DynObject1 d); public DynObject1 addTo(DynInteger1 d); public DynObject1 addTo(DynString1 d); } public class DynInteger1 implements DynObject1 { private int value; public DynInteger1(int v) { value = v; } @Override public String toString() { return Integer.toString(value); } public DynObject1 add(DynObject1 d) { return d.addTo(this); } public DynObject1 addTo(DynInteger1 d) { return new DynInteger1(d.value + value); } public DynObject1 addTo(DynString1 d) { return new DynString1(d.toString()+Integer.toString(value)); } } ...and similar for DynString1 Way 2: public interface DynObject2 { @Override public String toString(); public DynObject2 add(DynObject2 d); } public class DynInteger2 implements DynObject2 { private int value; public DynInteger2(int v) { value = v; } @Override public String toString() { return Integer.toString(value); } public DynObject2 add(DynObject2 d) { Class c = d.getClass(); if(c==DynInteger2.class) { return new DynInteger2(value + ((DynInteger2)d).value); } else { return new DynString2(toString() + d.toString()); } } } ...and similar for DynString2 Way 3: public class DynObject3 { private enum ObjectType { Integer, String }; Object value; ObjectType type; public DynObject3(Integer v) { value = v; type = ObjectType.Integer; } public DynObject3(String v) { value = v; type = ObjectType.String; } @Override public String toString() { return value.toString(); } public DynObject3 add(DynObject3 d) { if(type==ObjectType.Integer && d.type==ObjectType.Integer) { return new DynObject3(Integer.valueOf(((Integer)value).intValue()+((Integer)value).intValue())); } else { return new DynObject3(value.toString()+d.value.toString()); } } } With the if-else logic I could use value.getClass()==Integer.class instead of storing the type but with more types I'd change this to use a switch statement and Java doesn't allow switch to use Classes. Anyway... My question is what is the best way to go about something thike this?

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• multithreading with database

  - by Darsin

  I am looking out for a strategy to utilize multithreading (probably asynchronous delegates) to do a synchronous operation. I am new to multithreading so i will outline my scenario first. This synchronous operation right now is done for one set of data (portfolio) based on the the parameters provided. The (psudeo-code) implementation is given below: public DataSet DoTests(int fundId, DateTime portfolioDate) { // Get test results for the portfolio // Call the database adapter method, which in turn is a stored procedure, // which in turns runs a series of "rule" stored procs and fills a local temp table and returns it back. DataSet resultsDataSet = GetTestResults(fundId, portfolioDate); try { // Do some local processing on the results DoSomeProcessing(resultsDataSet); // Save the results in Test, TestResults and TestAllocations tables in a transaction. // Sets a global transaction which is provided to all the adapter methods called below // It is defined in the Base class StartTransaction("TestTransaction"); // Save Test and get a testId int testId = UpdateTest(resultsDataSet); // Adapter method, uses the same transaction // Update testId in the other tables in the dataset UpdateTestId(resultsDataSet, testId); // Update TestResults UpdateTestResults(resultsDataSet); // Adapter method, uses the same transaction // Update TestAllocations UpdateTestAllocations(resultsDataSet); // Adapter method, uses the same transaction // It is defined in the base class CommitTransaction("TestTransaction"); } catch { RollbackTransaction("TestTransaction"); } return resultsDataSet; } Now the requirement is to do it for multiple set of data. One way would be to call the above DoTests() method in a loop and get the data. I would prefer doing it in parallel. But there are certain catches: StartTransaction() method creates a connection (and transaction) every time it is called. All the underlying database tables, procedures are the same for each call of DoTests(). (obviously). Thus my question are: Will using multithreading anyway improve performance? What are the chances of deadlock especially when new TestId's are being created and the Tests, TestResults and TestAllocations are being saved? How can these deadlocked be handled? Is there any other more efficient way of doing the above operation apart from looping over the DoTests() method repeatedly?

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• How do I do distributed UML development (à la FOSS)?

  - by James A. Rosen

  I have a UML project (built in IBM's Rational System Architect/Modeler, so stored in their XML format) that has grown quite large. Additionally, it now contains several pieces that other groups would like to re-use. I come from a software development (especially FOSS) background, and am trying to understand how to use that as an analogy here. The problem I am grappling with is similar to the Fragile Base Class problem. Let me start with how it works in an object-oriented (say, Java or Ruby) FOSS ecosystem: Group 1 publishes some "core" package, say "net/smtp version 1.0" Group 2 includes Group 1's net/smtp 1.0 package in the vendor library of their software project At some point, Group 1 creates a new 2.0 branch of net/smtp that breaks backwards compatibility (say, it removes an old class or method, or moves a class from one package to another). They tell users of the 1.0 version that it will be deprecated in one year. Group 2, when they have the time, updates to net/smtp 2.0. When they drop in the new package, their compiler (or test suite, for Ruby) tells them about the incompatibility. They do have to make some manual changes, but all of the changes are in the code, in plain text, a medium with which they are quite familiar. Plus, they can often use their IDE's (or text editor's) "global-search-and-replace" function once they figure out what the fixes are. When we try to apply this model to UML in RSA, we run into some problems. RSA supports some fairly powerful refactorings, but they seem to only work if you have write access to all of the pieces. If I rename a class in one package, RSA can rename the references, but only at the same time. It's very difficult to look at the underlying source (the XML) and figure out what's broken. To fix such a problem in the RSA editor itself means tons of clicking on things -- there is no good equivalent of "global-search-and-replace," at least not after an incomplete refactor. They real sticking point seems to be that RSA assumes that you want to do all your editing using their GUI, but that makes certain operations prohibitively difficult. Does anyone have examples of open-source UML projects that have overcome this problem? What strategies do they use for communicating changes?

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• Using Core Data Concurrently and Reliably

  - by John Topley

  I'm building my first iOS app, which in theory should be pretty straightforward but I'm having difficulty making it sufficiently bulletproof for me to feel confident submitting it to the App Store. Briefly, the main screen has a table view, upon selecting a row it segues to another table view that displays information relevant for the selected row in a master-detail fashion. The underlying data is retrieved as JSON data from a web service once a day and then cached in a Core Data store. The data previous to that day is deleted to stop the SQLite database file from growing indefinitely. All data persistence operations are performed using Core Data, with an NSFetchedResultsController underpinning the detail table view. The problem I am seeing is that if you switch quickly between the master and detail screens several times whilst fresh data is being retrieved, parsed and saved, the app freezes or crashes completely. There seems to be some sort of race condition, maybe due to Core Data importing data in the background whilst the main thread is trying to perform a fetch, but I'm speculating. I've had trouble capturing any meaningful crash information, usually it's a SIGSEGV deep in the Core Data stack. The table below shows the actual order of events that happen when the detail table view controller is loaded: Main Thread Background Thread viewDidLoad Get JSON data (using AFNetworking) Create child NSManagedObjectContext (MOC) Parse JSON data Insert managed objects in child MOC Save child MOC Post import completion notification Receive import completion notification Save parent MOC Perform fetch and reload table view Delete old managed objects in child MOC Save child MOC Post deletion completion notification Receive deletion completion notification Save parent MOC Once the AFNetworking completion block is triggered when the JSON data has arrived, a nested NSManagedObjectContext is created and passed to an "importer" object that parses the JSON data and saves the objects to the Core Data store. The importer executes using the new performBlock method introduced in iOS 5: NSManagedObjectContext *child = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [child setParentContext:self.managedObjectContext]; [child performBlock:^{ // Create importer instance, passing it the child MOC... }]; The importer object observes its own MOC's NSManagedObjectContextDidSaveNotification and then posts its own notification which is observed by the detail table view controller. When this notification is posted the table view controller performs a save on its own (parent) MOC. I use the same basic pattern with a "deleter" object for deleting the old data after the new data for the day has been imported. This occurs asynchronously after the new data has been fetched by the fetched results controller and the detail table view has been reloaded. One thing I am not doing is observing any merge notifications or locking any of the managed object contexts or the persistent store coordinator. Is this something I should be doing? I'm a bit unsure how to architect this all correctly so would appreciate any advice.

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• Problem updating through LINQtoSQL in MVC application using StructureMap, Repository Pattern and UoW

  - by matt

  I have an ASP MVC application using LINQ to SQL for data access. I am trying to use the Repository and Unit of Work patterns, with a service layer consuming the repositories and unit of work. I am experiencing a problem when attempting to perform updates on a particular repository. My application architecture is as follows: My service class: public class MyService { private IRepositoryA _RepositoryA; private IRepositoryB _RepositoryB; private IUnitOfWork _unitOfWork; public MyService(IRepositoryA ARepositoryA, IRepositoryB ARepositoryB, IUnitOfWork AUnitOfWork) { _unitOfWork = AUnitOfWork; _RepositoryA = ARepositoryA; _RepositoryB = ARepositoryB; } public PerformActionOnObject(Guid AID) { MyObject obj = _RepositoryA.GetRecords() .WithID(AID); obj.SomeProperty = "Changed to new value"; _RepositoryA.UpdateRecord(obj); _unitOfWork.Save(); } } Repository interface: public interface IRepositoryA { IQueryable<MyObject> GetRecords(); UpdateRecord(MyObject obj); } Repository LINQtoSQL implementation: public class LINQtoSQLRepositoryA : IRepositoryA { private MyDataContext _DBContext; public LINQtoSQLRepositoryA(IUnitOfWork AUnitOfWork) { _DBConext = AUnitOfWork as MyDataContext; } public IQueryable<MyObject> GetRecords() { return from records in _DBContext.MyTable select new MyObject { ID = records.ID, SomeProperty = records.SomeProperty } } public bool UpdateRecord(MyObject AObj) { MyTableRecord record = (from u in _DB.MyTable where u.ID == AObj.ID select u).SingleOrDefault(); if (record == null) { return false; } record.SomeProperty = AObj.SomePropery; return true; } } Unit of work interface: public interface IUnitOfWork { void Save(); } Unit of work implemented in data context extension. public partial class MyDataContext : DataContext, IUnitOfWork { public void Save() { SubmitChanges(); } } StructureMap registry: public class DataServiceRegistry : Registry { public DataServiceRegistry() { // Unit of work For<IUnitOfWork>() .HttpContextScoped() .TheDefault.Is.ConstructedBy(() => new MyDataContext()); // RepositoryA For<IRepositoryA>() .Singleton() .Use<LINQtoSQLRepositoryA>(); // RepositoryB For<IRepositoryB>() .Singleton() .Use<LINQtoSQLRepositoryB>(); } } My problem is that when I call PerformActionOnObject on my service object, the update never fires any SQL. I think this is because the datacontext in the UnitofWork object is different to the one in RepositoryA where the data is changed. So when the service calls Save() on it's IUnitOfWork, the underlying datacontext does not have any updated data so no update SQL is fired. Is there something I've done wrong in the StrutureMap registry setup? Or is there a more fundamental problem with the design? Many thanks.

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• Circular database relationships. Good, Bad, Exceptions?

  - by jim

  I have been putting off developing this part of my app for sometime purely because I want to do this in a circular way but get the feeling its a bad idea from what I remember my lecturers telling me back in school. I have a design for an order system, ignoring the everything that doesn't pertain to this example I'm left with: CreditCard Customer Order I want it so that, Customers can have credit cards (0-n) Customers have orders (1-n) Orders have one customer(1-1) Orders have one credit card(1-1) Credit cards can have one customer(1-1) (unique ids so we can ignore uniqueness of cc number, husband/wife may share cc instances ect) Basically the last part is where the issue shows up, sometimes credit cards are declined and they wish to use a different one, this needs to update which their 'current' card is but this can only change the current card used for that order, not the other orders the customer may have on disk. Effectively this creates a circular design between the three tables. Possible solutions: Either Create the circular design, give references: cc ref to order, customer ref to cc customer ref to order or customer ref to cc customer ref to order create new table that references all three table ids and put unique on the order so that only one cc may be current to that order at any time Essentially both model the same design but translate differently, I am liking the latter option best at this point in time because it seems less circular and more central. (If that even makes sense) My questions are, What if any are the pros and cons of each? What is the pitfalls of circular relationships/dependancies? Is this a valid exception to the rule? Is there any reason I should pick the former over the latter? Thanks and let me know if there is anything you need clarified/explained. --Update/Edit-- I have noticed an error in the requirements I stated. Basically dropped the ball when trying to simplify things for SO. There is another table there for Payments which adds another layer. The catch, Orders can have multiple payments, with the possibility of using different credit cards. (if you really want to know even other forms of payment). Stating this here because I think the underlying issue is still the same and this only really adds another layer of complexity.

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• How does Sentry aggregate errors?

  - by Hugo Rodger-Brown

  I am using Sentry (in a django project), and I'd like to know how I can get the errors to aggregate properly. I am logging certain user actions as errors, so there is no underlying system exception, and am using the culprit attribute to set a friendly error name. The message is templated, and contains a common message ("User 'x' was unable to perform action because 'y'"), but is never exactly the same (different users, different conditions). Sentry clearly uses some set of attributes under the hood to determine whether to aggregate errors as the same exception, but despite having looked through the code, I can't work out how. Can anyone short-cut my having to dig further into the code and tell me what properties I need to set in order to manage aggregation as I would like? [UPDATE 1: event grouping] This line appears in sentry.models.Group: class Group(MessageBase): """ Aggregated message which summarizes a set of Events. """ ... class Meta: unique_together = (('project', 'logger', 'culprit', 'checksum'),) ... Which makes sense - project, logger and culprit I am setting at the moment - the problem is checksum. I will investigate further, however 'checksum' suggests that binary equivalence, which is never going to work - it must be possible to group instances of the same exception, with differenct attributes? [UPDATE 2: event checksums] The event checksum comes from the sentry.manager.get_checksum_from_event method: def get_checksum_from_event(event): for interface in event.interfaces.itervalues(): result = interface.get_hash() if result: hash = hashlib.md5() for r in result: hash.update(to_string(r)) return hash.hexdigest() return hashlib.md5(to_string(event.message)).hexdigest() Next stop - where do the event interfaces come from? [UPDATE 3: event interfaces] I have worked out that interfaces refer to the standard mechanism for describing data passed into sentry events, and that I am using the standard sentry.interfaces.Message and sentry.interfaces.User interfaces. Both of these will contain different data depending on the exception instance - and so a checksum will never match. Is there any way that I can exclude these from the checksum calculation? (Or at least the User interface value, as that has to be different - the Message interface value I could standardise.) [UPDATE 4: solution] Here are the two get_hash functions for the Message and User interfaces respectively: # sentry.interfaces.Message def get_hash(self): return [self.message] # sentry.interfaces.User def get_hash(self): return [] Looking at these two, only the Message.get_hash interface will return a value that is picked up by the get_checksum_for_event method, and so this is the one that will be returned (hashed etc.) The net effect of this is that the the checksum is evaluated on the message alone - which in theory means that I can standardise the message and keep the user definition unique. I've answered my own question here, but hopefully my investigation is of use to others having the same problem. (As an aside, I've also submitted a pull request against the Sentry documentation as part of this ;-)) (Note to anyone using / extending Sentry with custom interfaces - if you want to avoid your interface being use to group exceptions, return an empty list.)

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• Minutia on Objective-C Categories and Extensions.

  - by Matt Wilding

  I learned something new while trying to figure out why my readwrite property declared in a private Category wasn't generating a setter. It was because my Category was named: // .m @interface MyClass (private) @property (readwrite, copy) NSArray* myProperty; @end Changing it to: // .m @interface MyClass () @property (readwrite, copy) NSArray* myProperty; @end and my setter is synthesized. I now know that Class Extension is not just another name for an anonymous Category. Leaving a Category unnamed causes it to morph into a different beast: one that now gives compile-time method implementation enforcement and allows you to add ivars. I now understand the general philosophies underlying each of these: Categories are generally used to add methods to any class at runtime, and Class Extensions are generally used to enforce private API implementation and add ivars. I accept this. But there are trifles that confuse me. First, at a hight level: Why differentiate like this? These concepts seem like similar ideas that can't decide if they are the same, or different concepts. If they are the same, I would expect the exact same things to be possible using a Category with no name as is with a named Category (which they are not). If they are different, (which they are) I would expect a greater syntactical disparity between the two. It seems odd to say, "Oh, by the way, to implement a Class Extension, just write a Category, but leave out the name. It magically changes." Second, on the topic of compile time enforcement: If you can't add properties in a named Category, why does doing so convince the compiler that you did just that? To clarify, I'll illustrate with my example. I can declare a readonly property in the header file: // .h @interface MyClass : NSObject @property (readonly, copy) NSString* myString; @end Now, I want to head over to the implementation file and give myself private readwrite access to the property. If I do it correctly: // .m @interface MyClass () @property (readonly, copy) NSString* myString; @end I get a warning when I don't synthesize, and when I do, I can set the property and everything is peachy. But, frustratingly, if I happen to be slightly misguided about the difference between Category and Class Extension and I try: // .m @interface MyClass (private) @property (readonly, copy) NSString* myString; @end The compiler is completely pacified into thinking that the property is readwrite. I get no warning, and not even the nice compile error "Object cannot be set - either readonly property or no setter found" upon setting myString that I would had I not declared the readwrite property in the Category. I just get the "Does not respond to selector" exception at runtime. If adding ivars and properties is not supported by (named) Categories, is it too much to ask that the compiler play by the same rules? Am I missing some grand design philosophy?

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• Poor performance / speed of regex with lookahead

  - by Hugo Zaragoza

  I have been observing extremely slow execution times with expressions with several lookaheads. I suppose that this is due to underlying data structures, but it seems pretty extreme and I wonder if I do something wrong or if there are known work-arounds. The problem is determining if a set of words are present in a string, in any order. For example we want to find out if two terms "term1" AND "term2" are somewhere in a string. I do this with the expresion: (?=.*\bterm1\b)(?=.*\bterm2\b) But what I observe is that this is an order of magnitude slower than checking first just \bterm1\b and just then \bterm2\b This seems to indicate that I should use an array of patterns instead of a single pattern with lookaheads... is this right? it seems wrong... Here is an example test code and resulting times: public static void speedLookAhead() { Matcher m, m1, m2; boolean find; int its = 1000000; // create long non-matching string char[] str = new char[2000]; for (int i = 0; i < str.length; i++) { str[i] = 'x'; } String test = str.toString(); // First method: use one expression with lookaheads m = Pattern.compile("(?=.*\\bterm1\\b)(?=.*\\bterm2\\b)").matcher(test); long time = System.currentTimeMillis(); ; for (int i = 0; i < its; i++) { m.reset(test); find = m.find(); } time = System.currentTimeMillis() - time; System.out.println(time); // Second method: use two expressions and AND the results m1 = Pattern.compile("\\bterm1\\b").matcher(test); m2 = Pattern.compile("\\bterm2\\b").matcher(test); time = System.currentTimeMillis(); ; for (int i = 0; i < its; i++) { m1.reset(test); m2.reset(test); find = m1.find() && m2.find(); } time = System.currentTimeMillis() - time; System.out.println(time); } This outputs in my computer: 1754 150

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• Can I use the [] operator in C++ to create virtual arrays

  - by Shane MacLaughlin

  I have a large code base, originally C ported to C++ many years ago, that is operating on a number of large arrays of spatial data. These arrays contain structs representing point and triangle entities that represent surface models. I need to refactor the code such that the specific way these entities are stored internally varies for specific scenarios. For example if the points lie on a regular flat grid, I don't need to store the X and Y coordinates, as they can be calculated on the fly, as can the triangles. Similarly, I want to take advantage of out of core tools such as STXXL for storage. The simplest way of doing this is replacing array access with put and get type functions, e.g. point[i].x = XV; becomes Point p = GetPoint(i); p.x = XV; PutPoint(i,p); As you can imagine, this is a very tedious refactor on a large code base, prone to all sorts of errors en route. What I'd like to do is write a class that mimics the array by overloading the [] operator. As the arrays already live on the heap, and move around with reallocs, the code already assumes that references into the array such as point *p = point + i; may not be used. Is this class feasible to write? For example writing the methods below in terms of the [] operator; void MyClass::PutPoint(int Index, Point p) { if (m_StorageStrategy == RegularGrid) { int xoffs,yoffs; ComputeGridFromIndex(Index,xoffs,yoffs); StoreGridPoint(xoffs,yoffs,p.z); } else m_PointArray[Index] = p; } } Point MyClass::GetPoint(int Index) { if (m_StorageStrategy == RegularGrid) { int xoffs,yoffs; ComputeGridFromIndex(Index,xoffs,yoffs); return GetGridPoint(xoffs,yoffs); // GetGridPoint returns Point } else return m_PointArray[Index]; } } My concern is that all the array classes I've seen tend to pass by reference, whereas I think I'll have to pass structs by value. I think it should work put other than performance, can anyone see any major pitfalls with this approach. n.b. the reason I have to pass by value is to get point[a].z = point[b].z + point[c].z to work correctly where the underlying storage type varies.

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• How does System.TraceListener prepend message with process name?

  - by btlog

  I have been looking at using System.Diagnostics.Trace for doing logging is a very basic app. Generally it does all I need it to do. The downside is that if I call Trace.TraceInformation("Some info"); The output is "SomeApp.Exe Information: 0: Some info". Initally this entertained me but no longer. I would like to just output "Some info" to console. So I thought writing a cusom TraceListener, rather than using the inbuilt ConsoleTraceListener, would solve the problem. I can see a specific format that I want all the text after the second colon. Here is my attempt to see if this would work. class LogTraceListener : TraceListener { public override void Write(string message) { int firstColon = message.IndexOf(":"); int secondColon = message.IndexOf(":", firstColon + 1); Console.Write(message); } public override void WriteLine(string message) { int firstColon = message.IndexOf(":"); int secondColon = message.IndexOf(":", firstColon + 1); Console.WriteLine(message); } } If I output the value of firstColon it is always -1. If I put a break point the message is always just "Some info". Where does all the other information come from? So I had a look at the call stack at the point just before Console.WriteLine was called. The method that called my WriteLine method is: System.dll!System.Diagnostics.TraceListener.TraceEvent(System.Diagnostics.TraceEventCache eventCache, string source, System.Diagnostics.TraceEventType eventType, int id, string message) + 0x33 bytes When I use Reflector to look at this message it all seems pretty straight forward. I can't see any code that changes the value of the string after I have sent it to Console.WriteLine. The only method that could posibly change the underlying string value is a call to UnsafeNativeMethods.EventWriteString which has a parameter that is a pointer to the message. Does anyone understand what is going on here and whether I can change the output to be just my message with out the additional fluff. It seems like evil magic that I can pass a string "Some info" to Console.WriteLine (or any other method for that matter) and the string that output is different.

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• Java: Is there a way to efficiently insert or remove many elements from the middle of a LinkedList?

  - by allyourcode

  I was expecting to find this in Java's LinkedList, since the point of linked lists is to be able to efficiently insert (and remove) anywhere (assuming you have some kind of pointer to the location where you want to insert or remove). I'm not finding anything in the API though. Am I overlooking something? The closest thing I can find to this are the add and remove method in ListIterator. This has some limitations though. In particular, other iterators become invalid as soon as the underlying LinkedList is modified via remove, according to the API. This is born out in my tests as well; the following program results in a IllegalStateException: import java.util.*; public class RemoveFromLinkedList { public static void main(String[] args) { LinkedList<Integer> myList= new LinkedList<Integer>(); for (int i = 0; i < 10; ++i) { myList.add(i); } ListIterator<Integer> i1 = myList.listIterator(); ListIterator<Integer> i2 = myList.listIterator(); for (int i = 0; i < 3; ++i) { i1.next(); i2.next(); } System.out.println("i1.next() should be 3: " + i1.next()); i1.remove(); i1.remove(); // Exception! System.out.println("i2.next() should be 5: " + i2.next()); } } Ideally, what I'm expecting is something like this: // In my imagination only. This is the way Java actually works, afaict. // Construct two insertion/deletion points in LinkedList myLinkedList. myIterator = myLinkedList.iterator(); for (...) { myIterator.next(); } start = myIterator.clone(); for (...) { myIterator.next(); } // Later... after = myLinkedList.spliceAfter(myIterator, someOtherLinkedList); // start, myIterator, and after are still all valid; thus, I can do this: // Removes everything I just spliced in, as well as some other stuff before that. myLinkedList.remove(start, after); // Now, myIterator is invalid, but not start, nor after. C++ has something like this for its list class (template). Only iterators pointing to moved elements become invalidated, not ALL iterators.

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• Several C# Language Questions

  - by Water Cooler v2

  1) What is int? Is it any different from the struct System.Int32? I understand that the former is a C# alias (typedef or #define equivalant) for the CLR type System.Int32. Is this understanding correct? 2) When we say: IComparable x = 10; Is that like saying: IComparable x = new System.Int32(); But we can't new a struct, right? or in C like syntax: struct System.In32 *x; x=>someThing = 10; 3) What is String with a capitalized S? I see in Reflector that it is the sealed String class, which, of course, is a reference type, unlike the System.Int32 above, which is a value type. What is string, with an uncapitalized s, though? Is that also the C# alias for this class? Why can I not see the alias definitions in Reflector? 4) Try to follow me down this subtle train of thought, if you please. We know that a storage location of a particular type can only access properties and members on its interface. That means: Person p = new Customer(); p.Name = "Water Cooler v2"; // legal because as Name is defined on Person. but // illegal without an explicit cast even though the backing // store is a Customer, the storage location is of type // Person, which doesn't support the member/method being // accessed/called. p.GetTotalValueOfOrdersMade(); Now, with that inference, consider this scenario: int i = 10; // obvious System.object defines no member to // store an integer value or any other value in. // So, my question really is, when the integer is // boxed, what is the *type* it is actually boxed to. // In other words, what is the type that forms the // backing store on the heap, for this operation? object x = i; Update Thank you for your answers, Eric Gunnerson and Aaronought. I'm afraid I haven't been able to articulate my questions well enough to attract very satisfying answers. The trouble is, I do know the answers to my questions on the surface, and I am, by no means, a newbie programmer. But I have to admit, a deeper understanding to the intricacies of how a language and its underlying platform/runtime handle storage of types has eluded me for as long as I've been a programmer, even though I write correct code.

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• ASP.NET MVC 3 Hosting :: New Features in ASP.NET MVC 3

  - by mbridge

  Razor View Engine The Razor view engine is a new view engine option for ASP.NET MVC that supports the Razor templating syntax. The Razor syntax is a streamlined approach to HTML templating designed with the goal of being a code driven minimalist templating approach that builds on existing C#, VB.NET and HTML knowledge. The result of this approach is that Razor views are very lean and do not contain unnecessary constructs that get in the way of you and your code. ASP.NET MVC 3 Preview 1 only supports C# Razor views which use the .cshtml file extension. VB.NET support will be enabled in later releases of ASP.NET MVC 3. For more information and examples, see Introducing “Razor” – a new view engine for ASP.NET on Scott Guthrie’s blog. Dynamic View and ViewModel Properties A new dynamic View property is available in views, which provides access to the ViewData object using a simpler syntax. For example, imagine two items are added to the ViewData dictionary in the Index controller action using code like the following: public ActionResult Index() {          ViewData["Title"] = "The Title";          ViewData["Message"] = "Hello World!"; } Those properties can be accessed in the Index view using code like this: <h2>View.Title</h2> <p>View.Message</p> There is also a new dynamic ViewModel property in the Controller class that lets you add items to the ViewData dictionary using a simpler syntax. Using the previous controller example, the two values added to the ViewData dictionary can be rewritten using the following code: public ActionResult Index() {     ViewModel.Title = "The Title";     ViewModel.Message = "Hello World!"; } “Add View” Dialog Box Supports Multiple View Engines The Add View dialog box in Visual Studio includes extensibility hooks that allow it to support multiple view engines, as shown in the following figure: Service Location and Dependency Injection Support ASP.NET MVC 3 introduces improved support for applying Dependency Injection (DI) via Inversion of Control (IoC) containers. ASP.NET MVC 3 Preview 1 provides the following hooks for locating services and injecting dependencies: - Creating controller factories. - Creating controllers and setting dependencies. - Setting dependencies on view pages for both the Web Form view engine and the Razor view engine (for types that derive from ViewPage, ViewUserControl, ViewMasterPage, WebViewPage). - Setting dependencies on action filters. Using a Dependency Injection container is not required in order for ASP.NET MVC 3 to function properly. Global Filters ASP.NET MVC 3 allows you to register filters that apply globally to all controller action methods. Adding a filter to the global filters collection ensures that the filter runs for all controller requests. To register an action filter globally, you can make the following call in the Application_Start method in the Global.asax file: GlobalFilters.Filters.Add(new MyActionFilter()); The source of global action filters is abstracted by the new IFilterProvider interface, which can be registered manually or by using Dependency Injection. This allows you to provide your own source of action filters and choose at run time whether to apply a filter to an action in a particular request. New JsonValueProviderFactory Class The new JsonValueProviderFactory class allows action methods to receive JSON-encoded data and model-bind it to an action-method parameter. This is useful in scenarios such as client templating. Client templates enable you to format and display a single data item or set of data items by using a fragment of HTML. ASP.NET MVC 3 lets you connect client templates easily with an action method that both returns and receives JSON data. Support for .NET Framework 4 Validation Attributes and IvalidatableObject The ValidationAttribute class was improved in the .NET Framework 4 to enable richer support for validation. When you write a custom validation attribute, you can use a new IsValid overload that provides a ValidationContext instance. This instance provides information about the current validation context, such as what object is being validated. This change enables scenarios such as validating the current value based on another property of the model. The following example shows a sample custom attribute that ensures that the value of PropertyOne is always larger than the value of PropertyTwo: public class CompareValidationAttribute : ValidationAttribute {     protected override ValidationResult IsValid(object value,              ValidationContext validationContext) {         var model = validationContext.ObjectInstance as SomeModel;         if (model.PropertyOne > model.PropertyTwo) {            return ValidationResult.Success;         }         return new ValidationResult("PropertyOne must be larger than PropertyTwo");     } } Validation in ASP.NET MVC also supports the .NET Framework 4 IValidatableObject interface. This interface allows your model to perform model-level validation, as in the following example: public class SomeModel : IValidatableObject {     public int PropertyOne { get; set; }     public int PropertyTwo { get; set; }     public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) {         if (PropertyOne <= PropertyTwo) {            yield return new ValidationResult(                "PropertyOne must be larger than PropertyTwo");         }     } } New IClientValidatable Interface The new IClientValidatable interface allows the validation framework to discover at run time whether a validator has support for client validation. This interface is designed to be independent of the underlying implementation; therefore, where you implement the interface depends on the validation framework in use. For example, for the default data annotations-based validator, the interface would be applied on the validation attribute. Support for .NET Framework 4 Metadata Attributes ASP.NET MVC 3 now supports .NET Framework 4 metadata attributes such as DisplayAttribute. New IMetadataAware Interface The new IMetadataAware interface allows you to write attributes that simplify how you can contribute to the ModelMetadata creation process. Before this interface was available, you needed to write a custom metadata provider in order to have an attribute provide extra metadata. This interface is consumed by the AssociatedMetadataProvider class, so support for the IMetadataAware interface is automatically inherited by all classes that derive from that class (notably, the DataAnnotationsModelMetadataProvider class). New Action Result Types In ASP.NET MVC 3, the Controller class includes two new action result types and corresponding helper methods. HttpNotFoundResult Action The new HttpNotFoundResult action result is used to indicate that a resource requested by the current URL was not found. The status code is 404. This class derives from HttpStatusCodeResult. The Controller class includes an HttpNotFound method that returns an instance of this action result type, as shown in the following example: public ActionResult List(int id) {     if (id < 0) {                 return HttpNotFound();     }     return View(); } HttpStatusCodeResult Action The new HttpStatusCodeResult action result is used to set the response status code and description. Permanent Redirect The HttpRedirectResult class has a new Boolean Permanent property that is used to indicate whether a permanent redirect should occur. A permanent redirect uses the HTTP 301 status code. Corresponding to this change, the Controller class now has several methods for performing permanent redirects: - RedirectPermanent - RedirectToRoutePermanent - RedirectToActionPermanent These methods return an instance of HttpRedirectResult with the Permanent property set to true. Breaking Changes The order of execution for exception filters has changed for exception filters that have the same Order value. In ASP.NET MVC 2 and earlier, exception filters on the controller with the same Order as those on an action method were executed before the exception filters on the action method. This would typically be the case when exception filters were applied without a specified order Order value. In MVC 3, this order has been reversed in order to allow the most specific exception handler to execute first. As in earlier versions, if the Order property is explicitly specified, the filters are run in the specified order. Known Issues When you are editing a Razor view (CSHTML file), the Go To Controller menu item in Visual Studio will not be available, and there are no code snippets.

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• This task is currently locked by a running workflow and cannot be edited. Limitation to both Nintex and SPD workflow

  - by ybbest

  Note, this post is from Nintex Forum here. These limitations apply to both SharePoint designer Workflow and Nintex Workflow as Nintex using the SharePoint workflow engine. The common cause that I experience is that ‘parent’ workflow is generating more than one task at once. This is common as you can have multiple approvers for certain approval process. You could also have workflow running when the task is created, one of the common scenario is you would like to set a custom column value in your approval task. For me this is huge limitation, as Nintex lover I really hope Nintex could solve this problem with Microsoft going forward. Introduction “This task is currently locked by a running workflow and cannot be edited” is a common message that is seen when an error occurs while the SharePoint workflow engine is processing a task item associated with a workflow. When a workflow processes a task normally, the following sequence of events is expected to occur: 1.       The process begins. 2.       The workflow places a ‘lock’ on the task so nothing else can change the values while the workflow is processing. 3.       The workflow processes the task. 4.       The lock is released when the task processing is finished. When the message is encountered, it usually indicates that an error occurred between step 2 and 4. As a result, the lock is never released. Therefore, the ‘task locked’ message is not an error itself, rather a symptom of another error – the ‘task locked’ message does not indicate what went wrong. In most cases, once this message is encountered, the workflow cannot be made to continue and must be terminated and started again. The following is a guide that can help troubleshoot the cause of these messages.  Some initial observations to narrow down the potential causes are: Is the error consistent or intermittent? When the error is consistent, it will happen every time the workflow is run. When it is intermittent, it may happen regularly, but not every time. Does the error occur the first time the user tries to respond to a task, or do they respond and notice the workflow does not continue, and when they respond again the error occurs? If the message is present when the user first responds to the task, the issue would have occurred when the task was created. Otherwise, it would have occurred when the user attempted to respond to the task. Causes Modifying the task list A cause of this error appearing consistently the first time a user tries to respond to a task is a modification to the default task list schema. For example, changing the ‘Assigned to’ field in a task list to be a multiple selection will cause the behaviour. Deleting the workflow task then restoring it from the Recycle bin If you start a workflow, delete the workflow task then restore it from the Recycle Bin in SharePoint, the workflow will fail with the ‘task locked’ error.  This is confirmed behaviour whether using a SharePoint Designer or a Nintex workflow.  You will need to terminate the workflow and start it again. Parallel simultaneous responses A cause of this error appearing inconsistently is multiple users responding to tasks in parallel at the same time. In this scenario, one task will complete correctly and the other will not process. When the user tries again, the ‘task locked’ message will display. Nintex included a workaround for this issue in build 11000. In build 11000 and later, one of the users will receive a message on the task form when they attempt to respond, stating that they need to try again in a few moments. Additional processing on the task A cause of this error appearing consistently and inconsistently is having an additional system running on the items in the task list. Some examples include: a workflow running on the task list, an event receiver running on the task list or another automated process querying and updating workflow tasks. Note: This Microsoft help article (http://office.microsoft.com/en-us/sharepointdesigner/HA102376561033.aspx#5) explains creating a workflow that runs on the task list to update a field on the task. Our experience shows that this causes the ‘Task Locked’ issues when the ‘parent’ workflow is generating more than one task at once. Isolated system error If the error is a rare event, or a ‘one off’ event, then an isolated system error may have occurred. For example, if there is a database connectivity issue while the workflow is processing the task response, the task will lock. In this case, the user will respond to a task but the workflow will not continue. When they respond again, the ‘task locked’ message will display. In this case, there will be an error in the SharePoint ULS Logs at the time that the user originally responded. Temporary delay while workflow processes If the workflow is taking a long time to process after a user submits a task, they may notice and try to respond to the task again. They will see the task locked error, but after a number of attempts (or after waiting some time) the task response page eventually indicates the task has been responded to. In this case, nothing actually went wrong, and the error message gives an accurate indication of what is happening – the workflow temporarily locked the task while it was processing. This scenario may occur in a very large workflow, or after the SharePoint application pool has just started. Modifying the task via a web service with an invalid url If the Nintex Workflow web service is used to respond to or delegate a task, the site context part of the url must be a valid alternative access mapping url. For example, if you access the web service via the IP address of the SharePoint server, and the IP address is not a valid AAM, the task can become locked. The workflow has become stuck without any apparent errors This behaviour can occur as a result of a bug in the SharePoint 2010 workflow engine.  If you do not have the August 2010 Cumulative Update (or later) for SharePoint, and your workflow uses delays, “Flexi-task”, State machine”, “Task Reminder” actions or variables, you could be affected. Check the SharePoint 2010 Updates site here: http://technet.microsoft.com/en-us/sharepoint/ff800847.  The October CU is recommended http://support.microsoft.com/kb/2553031.   The fix is described as “Consider the following scenario. You add a Delay activity to a workflow. Then, you set the duration for the Delay activity. You deploy the workflow in SharePoint Foundation 2010. In this scenario, the workflow is not resumed after the duration of the Delay activity”. If you find this is occurring in your environment, install the October CU, terminate all the running workflows affected and run them afresh. Investigative steps The first step to isolate the issue is to create a new task list on the site and configure the workflow to use it.  Any customizations that were made to the original task list should not be made to the new task list. If the new task list eliminates the issue, then the cause can be attributed to the original task list or a change that was made to it. To change the task list that the workflow uses: In Workflow Designer select Settings -> Startup Options Then configure the task list as required If any of the scenarios above do not help, check the SharePoint logs for any messages with a category of ‘Workflow Infrastructure’. Conclusion The information in this article has been gathered from observations and investigations by Nintex. The sources of these issues are the underlying SharePoint workflow engine. This article will be updated if further causes are discovered. From <http://connect.nintex.com/forums/thread/6503.aspx>

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• Database users in the Oracle Utilities Application Framework

  - by Anthony Shorten

  I mentioned the product database users fleetingly in the last blog post and they deserve a better mention. This applies to all versions of the Oracle Utilities Application Framework. The Oracle Utilities Application Framework uses up to three users initially as part of the base operations of the product. The type of database supported (the framework supports Oracle, IBM DB2 and Microsoft SQL Server) dictates the number of users used and their permissions. For publishing brevity I will outline what is available for the Oracle database and, in summary, mention where it differs for the other database supported. For Oracle database customers we ship three distinct database users: Administration User (SPLADM or CISADM by default) - This is the database user that actually owns the schema. This user is not used by the product to do any DML (Data Manipulation Language) SQL other than that is necessary for maintenance of the database. This database user performs all the DCL (Data Control Language) and DDL (Data Definition Language) against the database. It is typically reserved for Database Administration use only. Product Read Write User (SPLUSER or CISUSER by default) - This is the database user used by the product itself to execute DML (Data Manipulation Language) statements against the schema owned by the Administration user. This user has the appropriate read and write permission to objects within the schema owned by the Administration user. For databases such as DB2 and SQL Server we may not create this user but use other DCL (Data Control Language) statements and facilities to simulate this user. Product Read User (SPLREAD or CISREAD by default) - This is the database that has read only permission to the schema owned by the Administration user. It is used for reporting or any part of the product or interface that requires read permissions to the database (for example, products that have ConfigLab and Archiving use this user for remote access). For databases such as DB2 and SQL Server we may not create this user but use other DCL (Data Control Language) statements and facilities to simulate this user. You may notice the words by default in the list above. The values supplied with the installer are the default and can be changed to what the site standard or implementation wants to use (as long as they conform to the standards supported by the underlying database). You can even create multiples of each within the same database and pointing to same schema. To manage the permissions for the users, there is a utility provided with the installation (oragensec (Oracle), db2gensec (DB2) or msqlgensec (SQL Server)) that generates the security definitions for the above users. That can be executed a number of times for each schema to give users appropriate permissions. For example, it is possible to define more than one read/write User to access the database. This is a common technique used by implementations to have a different user per access mode (to separate online and batch). In fact you can also allocate additional security (such as resource profiles in Oracle) to limit the impact of specific users at the database. To facilitate users and permissions, in Oracle for example, we create a CISREAD role (read only role) and a CISUSER role (read write role) that can be allocated to the appropriate database user. When the security permissions utility, oragensec in this case, is executed it uses the role to determine the permissions. To give you a case study, my underpowered laptop has multiple installations on it of multiple products but I have one database. I create a different schema for each product and each version (with my own naming convention to help me manage the databases). I create individual users on each schema and run oragensec to maintain the permissions for each appropriately. It works fine as long I have setup the userids appropriately. This means: Creating the users with the appropriate roles. I use the common CISUSER and CISREAD role across versions and across Oracle Utilities Application Framework products. Just remember to associate the CISUSER role with the database user you want to use for read/write operations and the CISREAD role with the user you wish to use for the read only operations. The role is treated as a tag to indicate the oragensec utility which appropriate permissions to assign to the user. The utilities for the other database types essentially do the same, obviously using the technology available within those databases. Run oragensec against the read write user and read only user against the appropriate administration user (I will abbreviate the user to ADM user). This ensures the right permissions are allocated to the right users for the right products. To help me there, I use the same prefix on the user name for the same product. For example, my Oracle Utilities Application Framework V4 environment has the administration user set to FW4ADM and the associated FW4USER and FW4READ as the users for the product to use. For my MWM environment I used MWMADM for the administration user and MWMUSER and MWMREAD for my associated users. You get the picture. When I run oragensec (once for each ADM user), I know what other users to associate with it. Remember to rerun oragensec against the users if I run upgrades, service packs or database based single fixes. This assures that the users are in synchronization with the ADM user. As a side note, for those who do not understand the difference between DML, DCL and DDL: DDL (Data Definition Language) - These are SQL statements that define the database schema and the structures within. SQL Statements such as CREATE and DROP are examples of DDL SQL statements. DCL (Data Control Language) - These are the SQL statements that define the database level permissions to DDL maintained objects within the database. SQL Statements such as GRANT and REVOKE are examples of DCL SQL statements. DML (Database Manipulation Language) - These are SQL statements that alter the data within the tables. SQL Statements such as SELECT, INSERT, UPDATE and DELETE are examples of DML SQL statements. Hope this has clarified the database user support. Remember in Oracle Utilities Application Framework V4 we enhanced this by also supporting CLIENT_IDENTIFIER to allow the database to still use the administration user for the main processing but make the database session more traceable.

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• Top 10 Reasons SQL Developer is Perfect for Oracle Beginners

  - by thatjeffsmith

  Learning new technologies can be daunting. If you’ve never used a Mac before, you’ll probably be a bit baffled at first. But, you’re probably at least coming from a desktop computing background (Windows), so you common frame of reference. But what if you’re just now learning to use a relational database? Yes, you’ve played with Access a bit, but now your employer or college instructor has charged you with becoming proficient with Oracle database. Here’s 10 reasons why I think Oracle SQL Developer is the perfect vehicle to help get you started. 1. It’s free No need to break into one of these… No start-up costs, no need to wrangle budget dollars from your company. Students don’t have any money after books and lab fees anyway. And most employees don’t like having to ask for ‘special’ software anyway. So avoid all of that and make sure the free stuff doesn’t suit your needs first. Upgrades are available on a regular base, also at no cost, and support is freely available via our public forums. 2. It will run pretty much anywhere Windows – check. OSX (Apple) – check. Unix – check. Linux – check. No need to start up a windows VM to run your Windows-only software in your lab machine. 3. Anyone can install it There’s no installer, no registry to be updated, no admin privs to be obtained. If you can download and extract files to your machine or USB storage device, you can run it. You can be up and running with SQL Developer in under 5 minutes. Here’s a video tutorial to see how to get started. 4. It’s ubiquitous I admit it, I learned a new word yesterday and I wanted an excuse to use it. SQL Developer’s everywhere. It’s had over 2,500,000 downloads in the past year, and is the one of the most downloaded items from OTN. This means if you need help, there’s someone sitting nearby you that can assist, and since they’re in the same tool as you, they’ll be speaking the same language. 5. Simple User Interface Up-up-down-down-Left-right-left-right-A-B-A-B-START will get you 30 lives, but you already knew that, right? You connect, you see your objects, you click on your objects. Or, you can use the worksheet to write your queries and programs in. There’s only one toolbar, and just a few buttons. If you’re like me, video games became less fun when each button had 6 action items mapped to it. I just want the good ole ‘A’, ‘B’, ‘SELECT’, and ‘START’ controls. If you’re new to Oracle, you shouldn’t have the double-workload of learning a new complicated tool as well. 6. It’s not a ‘black box’ Click through your objects, but also get the SQL that drives the GUI As you use the wizards to accomplish tasks for you, you can view the SQL statement being generated on your behalf. Just because you have a GUI, doesn’t mean you’re ceding your responsibility to learn the underlying code that makes the database work. 7. It’s four tools in one It’s not just a query tool. Maybe you need to design a data model first? Or maybe you need to migrate your Sybase ASE database to Oracle for a new project? Or maybe you need to create some reports? SQL Developer does all of that. So once you get comfortable with one part of the tool, the others will be much easier to pick up as your needs change. 8. Great learning resources available Videos, blogs, hands-on learning labs – you name it, we got it. Why wait for someone to train you, when you can train yourself at your own pace? 9. You can use it to teach yourself SQL Instead of being faced with the white-screen-of-panic, you can visually build your queries by dragging and dropping tables and views into the Query Builder. Yes, ‘just like Access’ – only better. And as you build your query, toggle to the Worksheet panel and see the SQL statement. Again, SQL Developer is not a black box. If you prefer to learn by trial and error, the worksheet will attempt to suggest the next bit of your SQL statement with it’s completion insight feature. And if you have syntax errors, those will be highlighted – just like your misspelled words in your favorite word processor. 10. It scales to match your experience level You won’t be a n00b forever. In 6-8 months, when you’re ready to tackle something a bit more complicated, like XML DB or Oracle Spatial, the tool is already there waiting on you. No need to go out and find the ‘advanced’ tool. 11. Wait, you said this was a ‘Top 10′ list? Yes. Yes, I did. I’m using this ‘trick’ to get you to continue reading because I’m going to say something you might not want to hear. Are you ready? Tools won’t replace experience, failure, hard work, and training. Just because you have the keys to the car, doesn’t mean you’re ready to head out on the race track. While SQL Developer reduces the barriers to entry, it does not completely remove them. Many experienced folks simply do not like tools. Rather, they don’t like the people that pick up tools without the know-how to properly use them. If you don’t understand what ‘TRUNCATE’ means, don’t try it out. Try picking up a book first. Of course, it’s very nice to have your own sandbox to play in, so you don’t upset the other children. That’s why I really like our Dev Days Database Virtual Box image. It’s your own database to learn and experiment with.

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