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  • ubuntu not logging in

    - by rakshith
    i am using ubuntu 11.10 and i once i logged in and the screen flashed for a sec and came back to the same screen it is happening again and again. i put the ubuntu cd and almost reinstalled it while i got this thought "lets try again" i tried again and luckly it came. i immediately came here without another log off and asked you guys. how do i correct it such that i wont be having problems in future?????

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  • C++ Exception Handling

    - by user1413793
    So I was writing some code and I noticed that apart from syntactical, type, and other compile-time errors, C++ does not throw any other exceptions. So I decided to test this out with a very trivial program: #include<iostream> int main() { std::count<<5/0<<std::endl; return 1 } When I compiled it using g++, g++ gave me a warning saying I was dividing by 0. But it still compiled the code. Then when I ran it, it printed some really large arbitrary number. When I want to know is, how does C++ deal with exceptions? Integer division by 0 should be a very trivial example of when an exception should be thrown and the program should terminate. Do I have to essentially enclose my entire program in a huge try block and then catch certain exceptions? I know in Python when an exception is thrown, the program will immediately terminate and print out the error. What does C++ do? Are there even runtime exceptions which stop execution and kill the program?

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  • iptables logging not working?

    - by vps_newcomer
    OS: Ubuntu 10.04 Logging daemon: rsyslog For some reason i'm not getting any iptables logs, even thought i don't look through them very often i'd still like to get it working for the sake of it working XD Here is my /etc/ryslog.d/iptables.conf :msg, contains, "[IPTABLES]" -/var/log/iptables.log & ~ My iptables logging prefix is "[IPTABLES]" followed by whatever else (example [IPTABLES] Denied xyz) the /var/log/iptables.log file is being created, however its not getting any entries. I can see the logging entries in dmesg but not in syslog or messages. Whats going on? EDIT: My iptables logging rules: # logging limit LoggingLimit=5/min LoggingPrefix=IPTABLES # Logging chain iptables -N LOG_REJECT iptables -A LOG_REJECT -j LOG # join INPUT to LOG_REJECT iptables -A INPUT -j LOG_REJECT # logging iptables -A LOG_REJECT -p tcp -m limit --limit $LoggingLimit -j LOG --log-prefix "$LoggingPrefix Denied TCP: " #--log-level 7 iptables -A LOG_REJECT -p udp -m limit --limit $LoggingLimit -j LOG --log-prefix "$LoggingPrefix Denied UDP: " #--log-level 7 iptables -A LOG_REJECT -p icmp -m limit --limit $LoggingLimit -j LOG --log-prefix "$LoggingPrefix Denied ICMP: " #--log-level 7 Update: I found a thread that has the same symptoms as i do, apparently is a kernel bug. I am using a VPS so could anyone point me on how to upgrade my kernel or apply a workaround? I couldn't find a 2.6.34 kernel listed in apt-cache. Thread: http://www.linode.com/forums/viewtopic.php?t=5533

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  • Catching an exception class within a template

    - by Todd Bauer
    I'm having a problem using the exception class Overflow() for a Stack template I'm creating. If I define the class regularly there is no problem. If I define the class as a template, I cannot make my call to catch() work properly. I have a feeling it's simply syntax, but I can't figure it out for the life of me. #include<iostream> #include<exception> using namespace std; template <class T> class Stack { private: T *stackArray; int size; int top; public: Stack(int size) { this->size = size; stackArray = new T[size]; top = 0; } ~Stack() { delete[] stackArray; } void push(T value) { if (isFull()) throw Overflow(); stackArray[top] = value; top++; } bool isFull() { if (top == size) return true; else return false; } class Overflow {}; }; int main() { try { Stack<double> Stack(5); Stack.push( 5.0); Stack.push(10.1); Stack.push(15.2); Stack.push(20.3); Stack.push(25.4); Stack.push(30.5); } catch (Stack::Overflow) { cout << "ERROR! The stack is full.\n"; } return 0; } The problem is in the catch (Stack::Overflow) statement. As I said, if the class is not a template, this works just fine. However, once I define it as a template, this ceases to work. I've tried all sorts of syntaxes, but I always get one of two sets of error messages from the compiler. If I use catch(Stack::Overflow): ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2316: 'Stack::Overflow' : cannot be caught as the destructor and/or copy constructor are inaccessible EDIT: I meant If I use catch(Stack<double>::Overflow) or any variety thereof: ch18pr01.cpp(89) : error C2061: syntax error : identifier 'Stack' ch18pr01.cpp(89) : error C2310: catch handlers must specify one type ch18pr01.cpp(95) : error C2317: 'try' block starting on line '75' has no catch handlers I simply can not figure this out. Does anyone have any idea?

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  • Tracking the user function that threw the exception

    - by makerofthings7
    I've been given a large application with only one try..catch at the outer most level. This application also throws exceptions all the time, and is poorly documented. Is there any pattern I can implement that will tell me what user method is being called, the exception being thrown, and also the count of exceptions? I'm thinking of using a dictionary with reflection to get the needed information, but I'm not sure if this will work. What do you think?

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  • C++ display stack trace on exception

    - by rlbond
    I want to have a way to report the stack trace to the user if an exception is thrown. What is the best way to do this? Does it take huge amounts of extra code? To answer questions: I'd like it to be portable if possible. I want information to pop up, so the user can copy the stack trace and email it to me if an error comes up.

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  • Where is this exception caught and handled?

    - by Zaki
    In some code I've been reading, I've come across this : class Someclass { public static void main(String[] args) throws IOException { //all other code here...... } } If main() throws an exception, in this case its an IOException, where is it caught and handled?

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  • Strengthening code with possibly useless exception handling

    - by rdurand
    Is it a good practice to implement useless exception handling, just in case another part of the code is not coded correctly? Basic example A simple one, so I don't loose everybody :). Let's say I'm writing an app that will display a person's information (name, address, etc.), the data being extracted from a database. Let's say I'm the one coding the UI part, and someone else is writing the DB query code. Now imagine that the specifications of your app say that if the person's information is incomplete (let's say, the name is missing in the database), the person coding the query should handle this by returning "NA" for the missing field. What if the query is poorly coded and doesn't handle this case? What if the guy who wrote the query handles you an incomplete result, and when you try to display the informations, everything crashes, because your code isn't prepared to display empty stuff? This example is very basic. I believe most of you will say "it's not your problem, you're not responsible for this crash". But, it's still your part of the code which is crashing. Another example Let's say now I'm the one writing the query. The specifications don't say the same as above, but that the guy writing the "insert" query should make sure all the fields are complete when adding a person to the database to avoid inserting incomplete information. Should I protect my "select" query to make sure I give the UI guy complete informations? The questions What if the specifications don't explicitly say "this guy is the one in charge of handling this situation"? What if a third person implements another query (similar to the first one, but on another DB) and uses your UI code to display it, but doesn't handle this case in his code? Should I do what's necessary to prevent a possible crash, even if I'm not the one supposed to handle the bad case? I'm not looking for an answer like "(s)he's the one responsible for the crash", as I'm not solving a conflict here, I'd like to know, should I protect my code against situations it's not my responsibility to handle? Here, a simple "if empty do something" would suffice. In general, this question tackles redundant exception handling. I'm asking it because when I work alone on a project, I may code 2-3 times a similar exception handling in successive functions, "just in case" I did something wrong and let a bad case come through.

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  • How to get more detail from an exception?

    - by cusimar9
    I have a .NET 4.0 web application which implements an error handler within the Application_Error event of Global.asax. When an exception occurs this intercepts it and sends me an email including a variety of information like the logged in user, the page the error occurred on, the contents of the session etc. This is all great but there is some fundamental detail missing which I seem unable to locate. For instance, this is a subset of an error I would receive and the associated stack trace: Source: Telerik.Web.UI Message: Selection out of range Parameter name: value Stack trace: at Telerik.Web.UI.RadComboBox.PerformDataBinding(IEnumerable dataSource) at Telerik.Web.UI.RadComboBox.OnDataSourceViewSelectCallback(IEnumerable data) at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) at Telerik.Web.UI.RadComboBox.OnDataBinding(EventArgs e) at Telerik.Web.UI.RadComboBox.PerformSelect() at System.Web.UI.WebControls.BaseDataBoundControl.DataBind() at Telerik.Web.UI.RadComboBox.DataBind() at System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() at Telerik.Web.UI.RadComboBox.OnPreRender(EventArgs e) at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) Now as lovely as this is I could do with knowing a) the name of the control and b) the value which caused the control to be 'out of range'. Any suggestions about how I could get this sort of information? I've run this in debug mode and the objects passed to Global.asax don't seem to hold any more detail that I can see.

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  • ASP.NET Web API Exception Handling

    - by Fredrik N
    When I talk about exceptions in my product team I often talk about two kind of exceptions, business and critical exceptions. Business exceptions are exceptions thrown based on “business rules”, for example if you aren’t allowed to do a purchase. Business exceptions in most case aren’t important to log into a log file, they can directly be shown to the user. An example of a business exception could be "DeniedToPurchaseException”, or some validation exceptions such as “FirstNameIsMissingException” etc. Critical Exceptions are all other kind of exceptions such as the SQL server is down etc. Those kind of exception message need to be logged and should not reach the user, because they can contain information that can be harmful if it reach out to wrong kind of users. I often distinguish business exceptions from critical exceptions by creating a base class called BusinessException, then in my error handling code I catch on the type BusinessException and all other exceptions will be handled as critical exceptions. This blog post will be about different ways to handle exceptions and how Business and Critical Exceptions could be handled. Web API and Exceptions the basics When an exception is thrown in a ApiController a response message will be returned with a status code set to 500 and a response formatted by the formatters based on the “Accept” or “Content-Type” HTTP header, for example JSON or XML. Here is an example:   public IEnumerable<string> Get() { throw new ApplicationException("Error!!!!!"); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response message will be: HTTP/1.1 500 Internal Server Error Content-Length: 860 Content-Type: application/json; charset=utf-8 { "ExceptionType":"System.ApplicationException","Message":"Error!!!!!","StackTrace":" at ..."} .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The stack trace will be returned to the client, this is because of making it easier to debug. Be careful so you don’t leak out some sensitive information to the client. So as long as you are developing your API, this is not harmful. In a production environment it can be better to log exceptions and return a user friendly exception instead of the original exception. There is a specific exception shipped with ASP.NET Web API that will not use the formatters based on the “Accept” or “Content-Type” HTTP header, it is the exception is the HttpResponseException class. Here is an example where the HttpReponseExcetpion is used: // GET api/values [ExceptionHandling] public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response will not contain any content, only header information and the status code based on the HttpStatusCode passed as an argument to the HttpResponseMessage. Because the HttpResponsException takes a HttpResponseMessage as an argument, we can give the response a content: public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("My Error Message"), ReasonPhrase = "Critical Exception" }); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The code above will have the following response:   HTTP/1.1 500 Critical Exception Content-Length: 5 Content-Type: text/plain; charset=utf-8 My Error Message .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The Content property of the HttpResponseMessage doesn’t need to be just plain text, it can also be other formats, for example JSON, XML etc. By using the HttpResponseException we can for example catch an exception and throw a user friendly exception instead: public IEnumerable<string> Get() { try { DoSomething(); return new string[] { "value1", "value2" }; } catch (Exception e) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Adding a try catch to every ApiController methods will only end in duplication of code, by using a custom ExceptionFilterAttribute or our own custom ApiController base class we can reduce code duplicationof code and also have a more general exception handler for our ApiControllers . By creating a custom ApiController’s and override the ExecuteAsync method, we can add a try catch around the base.ExecuteAsync method, but I prefer to skip the creation of a own custom ApiController, better to use a solution that require few files to be modified. The ExceptionFilterAttribute has a OnException method that we can override and add our exception handling. Here is an example: using System; using System.Diagnostics; using System.Net; using System.Net.Http; using System.Web.Http; using System.Web.Http.Filters; public class ExceptionHandlingAttribute : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { if (context.Exception is BusinessException) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(context.Exception.Message), ReasonPhrase = "Exception" }); } //Log Critical errors Debug.WriteLine(context.Exception); throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: Something to have in mind is that the ExceptionFilterAttribute will be ignored if the ApiController action method throws a HttpResponseException. The code above will always make sure a HttpResponseExceptions will be returned, it will also make sure the critical exceptions will show a more user friendly message. The OnException method can also be used to log exceptions. By using a ExceptionFilterAttribute the Get() method in the previous example can now look like this: public IEnumerable<string> Get() { DoSomething(); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To use the an ExceptionFilterAttribute, we can for example add the ExceptionFilterAttribute to our ApiControllers methods or to the ApiController class definition, or register it globally for all ApiControllers. You can read more about is here. Note: If something goes wrong in the ExceptionFilterAttribute and an exception is thrown that is not of type HttpResponseException, a formatted exception will be thrown with stack trace etc to the client. How about using a custom IHttpActionInvoker? We can create our own IHTTPActionInvoker and add Exception handling to the invoker. The IHttpActionInvoker will be used to invoke the ApiController’s ExecuteAsync method. Here is an example where the default IHttpActionInvoker, ApiControllerActionInvoker, is used to add exception handling: public class MyApiControllerActionInvoker : ApiControllerActionInvoker { public override Task<HttpResponseMessage> InvokeActionAsync(HttpActionContext actionContext, System.Threading.CancellationToken cancellationToken) { var result = base.InvokeActionAsync(actionContext, cancellationToken); if (result.Exception != null && result.Exception.GetBaseException() != null) { var baseException = result.Exception.GetBaseException(); if (baseException is BusinessException) { return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Error" }); } else { //Log critical error Debug.WriteLine(baseException); return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Critical Error" }); } } return result; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can register the IHttpActionInvoker with your own IoC to resolve the MyApiContollerActionInvoker, or add it in the Global.asax: GlobalConfiguration.Configuration.Services.Remove(typeof(IHttpActionInvoker), GlobalConfiguration.Configuration.Services.GetActionInvoker()); GlobalConfiguration.Configuration.Services.Add(typeof(IHttpActionInvoker), new MyApiControllerActionInvoker()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   How about using a Message Handler for Exception Handling? By creating a custom Message Handler, we can handle error after the ApiController and the ExceptionFilterAttribute is invoked and in that way create a global exception handler, BUT, the only thing we can take a look at is the HttpResponseMessage, we can’t add a try catch around the Message Handler’s SendAsync method. The last Message Handler that will be used in the Wep API pipe-line is the HttpControllerDispatcher and this Message Handler is added to the HttpServer in an early stage. The HttpControllerDispatcher will use the IHttpActionInvoker to invoke the ApiController method. The HttpControllerDipatcher has a try catch that will turn ALL exceptions into a HttpResponseMessage, so that is the reason why a try catch around the SendAsync in a custom Message Handler want help us. If we create our own Host for the Wep API we could create our own custom HttpControllerDispatcher and add or exception handler to that class, but that would be little tricky but is possible. We can in a Message Handler take a look at the HttpResponseMessage’s IsSuccessStatusCode property to see if the request has failed and if we throw the HttpResponseException in our ApiControllers, we could use the HttpResponseException and give it a Reason Phrase and use that to identify business exceptions or critical exceptions. I wouldn’t add an exception handler into a Message Handler, instead I should use the ExceptionFilterAttribute and register it globally for all ApiControllers. BUT, now to another interesting issue. What will happen if we have a Message Handler that throws an exception?  Those exceptions will not be catch and handled by the ExceptionFilterAttribute. I found a  bug in my previews blog post about “Log message Request and Response in ASP.NET WebAPI” in the MessageHandler I use to log incoming and outgoing messages. Here is the code from my blog before I fixed the bug:   public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); var responseMessage = await response.Content.ReadAsByteArrayAsync(); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   If a ApiController throws a HttpResponseException, the Content property of the HttpResponseMessage from the SendAsync will be NULL. So a null reference exception is thrown within the MessageHandler. The yellow screen of death will be returned to the client, and the content is HTML and the Http status code is 500. The bug in the MessageHandler was solved by adding a check against the HttpResponseMessage’s IsSuccessStatusCode property: public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); byte[] responseMessage; if (response.IsSuccessStatusCode) responseMessage = await response.Content.ReadAsByteArrayAsync(); else responseMessage = Encoding.UTF8.GetBytes(response.ReasonPhrase); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If we don’t handle the exceptions that can occur in a custom Message Handler, we can have a hard time to find the problem causing the exception. The savior in this case is the Global.asax’s Application_Error: protected void Application_Error() { var exception = Server.GetLastError(); Debug.WriteLine(exception); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I would recommend you to add the Application_Error to the Global.asax and log all exceptions to make sure all kind of exception is handled. Summary There are different ways we could add Exception Handling to the Wep API, we can use a custom ApiController, ExceptionFilterAttribute, IHttpActionInvoker or Message Handler. The ExceptionFilterAttribute would be a good place to add a global exception handling, require very few modification, just register it globally for all ApiControllers, even the IHttpActionInvoker can be used to minimize the modifications of files. Adding the Application_Error to the global.asax is a good way to catch all unhandled exception that can occur, for example exception thrown in a Message Handler.   If you want to know when I have posted a blog post, you can follow me on twitter @fredrikn

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  • Logging Application Block

    - by Gordon Carpenter-Thompson
    I'm using the Logging Application Block in my ASP.NET application and want to convert the application to a Sharepoint WebPart. It all works fine as long as I change: <trust level="WSS_Minimal" originUrl="" /> to <trust level="Full" originUrl="" /> If not I get an exception in the logs: Failed to add webpart *************255Fcatalogs%252Fwp%252FSearchWebPart%252Ewebpart;SearchWebPart. Exception Microsoft.SharePoint.WebPartPages.WebPartPageUserException: The type initializer for 'Microsoft.Practices.EnterpriseLibrary.Logging.Logger' threw an exception. ---> System.TypeInitializationException: The type initializer for 'Microsoft.Practices.EnterpriseLibrary.Logging.Logger' threw an exception. ---> System.TypeInitializationException: The type initializer for 'Microsoft.Practices.EnterpriseLibrary.Common.Configuration.SystemConfigurationSource' threw an exception. ---> System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neut... ...ral, PublicKeyToken=b77a5c561934e089' failed. at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) at System.Security.CodeAccessPermission.Demand() at System.AppDomainSetup.VerifyDir(String dir, Boolean normalize) at System.AppDomainSetup.get_ConfigurationFile() at Microsoft.Practices.EnterpriseLibrary.Common.Configuration.SystemConfigurationSourceImplementation..ctor(Boolean refresh) at Microsoft.Practices.EnterpriseLibrary.Common.Configuration.SystemConfigurationSource..cctor() The action that failed was: Demand The type of the first permission that failed was: System.Security.Permissions.FileIOPermission The first permission that failed was: <IPermission class="System.Security.Permissions.FileIOPermi... ...ssion, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" PathDiscovery="D:\Inetpub\wwwroot\wss\VirtualDirectories\8686\web.config"/> The demand was for: <IPermission class="System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" PathDiscovery="D:\Inetpub\wwwroot\wss\VirtualDirectories\8686\web.config"/> The granted set of the failing assembly was: <PermissionSet class="System.Security.PermissionSet" version="1"> <IPermission class="System.Security.Permissions.SecurityPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Flags="Execution"/> <IPermission class="System.Security.Permissions.StrongNameIdentityPermis... ...sion, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" PublicKeyBlob="0024000004800000940000000602000000240000525341310004000001000100257FAE170ABB2AB4A8EF914DFEA757F7DB8C221F01850FC8753A4C6585C0B07749DA33DF4D64A721A070E7CDCDEFC8C786E3626418389BCF461E4300E6F4C477BE5CE64AD12C29D517208D6BA627D9F73A9066B7638BE1FEE3EABE6C3E537B546CB3B5DE5E436F95278BB1E9DBDE85C2A6B624010A8073841D467CC7A0A0C6C8" Name="Microsoft.Practices.EnterpriseLibrary.Common" AssemblyVersion="3.1.0.0"/> <IPermission class="System.Security.Permissions.UrlIdentityPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Url="file:///D:/Inetpub/wwwroot/wss/VirtualDirectories/8686/bin/Microsoft.Practices.EnterpriseLibrary.Common.DLL"/> <IPe... ...rmission class="System.Security.Permissions.ZoneIdentityPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Zone="MyComputer"/> <IPermission class="System.Web.AspNetHostingPermission, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Level="Minimal"/> <IPermission class="Microsoft.SharePoint.Security.WebPartPermission, Microsoft.SharePoint.Security, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" version="1" Connections="True"/> </PermissionSet> The assembly or AppDomain that failed was: Microsoft.Practices.EnterpriseLibrary.Common, Version=3.1.0.0, Culture=neutral, PublicKeyToken=a646907c4a695009 The Zone of the assembly that failed was: MyComputer The Url of the assem... ...bly that failed was: file:///D:/Inetpub/wwwroot/wss/VirtualDirectories/8686/bin/Microsoft.Practices.EnterpriseLibrary.Common.DLL --- End of inner exception stack trace --- at Microsoft.Practices.EnterpriseLibrary.Common.Configuration.SystemConfigurationSource..ctor() at Microsoft.Practices.EnterpriseLibrary.Common.Configuration.ConfigurationSourceFactory.Create() at Microsoft.Practices.EnterpriseLibrary.Logging.Logger..cctor() --- End of inner exception stack trace --- at Microsoft.Practices.EnterpriseLibrary.Logging.Logger.Write(LogEntry log) at com.okana.sharepoint.SearchWebPart.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.AddedControl(Control control, Int32 index) at System.Web.UI.ControlCollection.Add(Con... ...trol child) at System.Web.UI.WebControls.WebParts.WebPartManager.WebPartManagerControlCollection.AddWebPartHelper(WebPart webPart) at System.Web.UI.WebControls.WebParts.WebPartManager.WebPartManagerControlCollection.AddWebPart(WebPart webPart) at System.Web.UI.WebControls.WebParts.WebPartManager.AddWebPart(WebPart webPart) at System.Web.UI.WebControls.WebParts.WebPartManagerInternals.AddWebPart(WebPart webPart) at Microsoft.SharePoint.WebPartPages.SPWebPartManager.AddWebPartWithRetry(WebPart webPart) at Microsoft.SharePoint.WebPartPages.SPWebPartManager.AddDynamicWebPart(WebPart webPart) at Microsoft.SharePoint.WebPartPages.SPWebPartManager.LoadWebPart(WebPart aspWebPart, String zoneId, Int32 zoneIndex, Boolean isClosed) at Microsoft.SharePoint.WebPartPages.... ...SPWebPartManager.AddWebPartInternalShared(WebPart webPart) at Microsoft.SharePoint.WebPartPages.SPWebPartManager.AddWebPartInternal(SPSupersetWebPart superset, Boolean throwIfLocked) --- End of inner exception stack trace --- at Microsoft.SharePoint.WebPartPages.SPWebPartManager.AddWebPartInternal(SPSupersetWebPart superset, Boolean throwIfLocked) at Microsoft.SharePoint.WebPartPages.SPWebPartManager.AddWebPartInternal(SPSupersetWebPart superset) at Microsoft.SharePoint.WebPartPages.WebPartQuickAdd.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) My log configuration is this: <loggingConfiguration name="Logging Application Block" tracingEnabled="true" defaultCategory="General" logWarningsWhenNoCategoriesMatch="true"> <listeners> <add fileName="XAE.log" rollSizeKB="0" timeStampPattern="yyyy-MM-dd" rollFileExistsBehavior="Overwrite" rollInterval="Day" formatter="Text Formatter" header="" footer="" listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.RollingFlatFileTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=3.1.0.0, Culture=neutral" traceOutputOptions="None" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.RollingFlatFileTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=3.1.0.0, Culture=neutral" name="Rolling Flat File Trace Listener" /> <add fileName="IDOL.log" rollSizeKB="0" timeStampPattern="yyyy-MM-dd" rollFileExistsBehavior="Overwrite" rollInterval="Day" formatter="Text Formatter" header="" footer="" listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.RollingFlatFileTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=3.1.0.0, Culture=neutral" traceOutputOptions="None" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.RollingFlatFileTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=3.1.0.0, Culture=neutral" name="IDOL Rolling Flat File Trace Listener" /> </listeners> <formatters> <add template="{timestamp(local)} : {category} : {message}" type="Microsoft.Practices.EnterpriseLibrary.Logging.Formatters.TextFormatter, Microsoft.Practices.EnterpriseLibrary.Logging, Version=3.1.0.0, Culture=neutral" name="Text Formatter" /> </formatters> <categorySources> <!-- For any log entries that you wish to suppress set "All" to "Off" --> <add switchValue="All" name="Communication"> <listeners> <add name="Rolling Flat File Trace Listener" /> </listeners> </add> <add switchValue="All" name="Debug"> <listeners> <add name="Rolling Flat File Trace Listener" /> </listeners> </add> <add switchValue="All" name="Exception"> <listeners> <add name="Rolling Flat File Trace Listener" /> </listeners> </add> <add switchValue="All" name="General"> <listeners> <add name="Rolling Flat File Trace Listener" /> </listeners> </add> <add switchValue="All" name="Warning"> <listeners> <add name="Rolling Flat File Trace Listener" /> </listeners> </add> <add switchValue="All" name="IDOL"> <listeners> <add name="IDOL Rolling Flat File Trace Listener" /> </listeners> </add> </categorySources> <specialSources> <allEvents switchValue="All" name="All Events" /> <notProcessed switchValue="All" name="Unprocessed Category" /> <errors switchValue="All" name="Logging Errors &amp; Warnings"> <listeners> <add name="Rolling Flat File Trace Listener" /> </listeners> </errors> </specialSources> </loggingConfiguration> Clearly this is because it's trying to create the log files and WSS_Minimal doesn't allow this. Is there a simple way to disable all logging for now? Removing the logging is problematic as it's used in the underlying libraries. I have tried setting all switchValue="All" to "Off" but it still throws the exception even though nothing should be logged

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  • How to implement exception chaining in PHP

    - by Josef Sábl
    Constructor for PHP's exception has third parameter, documentation says: $previous: The previous exception used for the exception chaining. But I can't make it work. My code looks like this: try { throw new Exception('Exception 1', 1001); } catch (Exception $ex) { throw new Exception('Exception 2', 1002, $ex); } I expect Exception 2 to be thrown and I expect that it will have Exception 1 attached. But all I get is: Fatal error: Wrong parameters for Exception([string $exception [, long $code ]]) in ... What am I doing wrong?

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  • How do I configure the Python logging module in Django?

    - by mipadi
    I'm trying to configure logging for a Django app using the Python logging module. I have placed the following bit of configuration code in my Django project's settings.py file: import logging import logging.handlers import os date_fmt = '%m/%d/%Y %H:%M:%S' log_formatter = logging.Formatter(u'[%(asctime)s] %(levelname)-7s: %(message)s (%(filename)s:%(lineno)d)', datefmt=date_fmt) log_dir = os.path.join(PROJECT_DIR, "var", "log", "my_app") log_name = os.path.join(log_dir, "nyrb.log") bytes = 1024 * 1024 # 1 MB if not os.path.exists(log_dir): os.makedirs(log_dir) handler = logging.handlers.RotatingFileHandler(log_name, maxBytes=bytes, backupCount=7) handler.setFormatter(log_formatter) handler.setLevel(logging.DEBUG) logging.getLogger().setLevel(logging.DEBUG) logging.getLogger().addHandler(handler) logging.getLogger(__name__).info("Initialized logging subsystem") At startup, I get a couple Django-related messages, as well as the "Initialized logging subsystem", in the log files, but then all the log messages end up going to the web server logs (/var/log/apache2/error.log, since I'm using Apache), and use the standard log format (not the formatter I designated). Am I configuring logging incorrectly?

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  • DAL Exception handling in a MVP application

    - by Chathuranga
    In a MVP win forms application I'm handling exceptions as follows in DAL. Since the user messaging is not a responsibility of DAL, I want to move it in to my Presentation class. Could you show me a standard way to do that? public bool InsertAccount(IBankAccount ba) { string selectStatement = @"IF NOT EXISTS (SELECT ac_no FROM BankAccount WHERE ac_no=@ac_no) BEGIN INSERT INTO BankAccount ..."; using (SqlConnection sqlConnection = new SqlConnection(db.ConnectionString)) { using (SqlCommand sqlCommand = new SqlCommand(selectStatement, sqlConnection)) { try { sqlConnection.Open(); sqlCommand.Parameters.Add("@ac_no", SqlDbType.Char).Value = ba.AccountNumber; // // sqlCommand.ExecuteNonQuery(); return true; } catch (Exception e) { MessageBox.Show(("Error: " + e.Message)); } if (sqlConnection.State == System.Data.ConnectionState.Open) sqlConnection.Close(); return false; } } }

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  • Best way to throw exception and avoid code duplication

    - by JF Dion
    I am currently writing code and want to make sure all the params that get passed to a function/method are valid. Since I am writing in PHP I don't have access to all the facilities of other languages like C, C++ or Java to check for parameters values and types public function inscriptionExists($sectionId, $userId) // PHP vs. public boolean inscriptionExists(int sectionId, int userId) // Java So I have to rely on exceptions if I want to make sure that my params are both integers. Since I have a lot of places where I need to check for param validity, what would be the best way to create a validation/exception machine and avoid code duplication? I was thinking on a static factory (since I don't want to pass it to all of my classes) with a signature like: public static function factory ($value, $valueType, $exceptionType = 'InvalidArgumentException'); Which would then call the right sub process to validate based on the type. Am I on the right way, or am I going completely off the road and overthinking my problem?

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  • Best exception handling practices or recommendations?

    - by user828584
    I think the two main problems with my programs are my code structure/organization and my error handling. I'm reading Code Complete 2, but I need something to read for working with potential problems. For example, on a website, if something can only happen if the user tampers with data via javascript, do you write for that? Also, when do you not catch errors? When you write a class that expects a string and an int as input, and they aren't a string and int, do you check for that, or do you let it bubble up to the calling method that passed incorrect parameters? I know this is a broad topic that can't be answered in a single answer here, so what I'm looking for is a book or resource that's commonly accepted as teaching proper exception handling practice.

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  • How python logging get it's configuration

    - by Andrew_1510
    I used to Python logging, it works fine. The logging.basicConfig(...) set in one module (a some.py file), then we can use logging every where. Obviously, logging is global. The question is how logging find it's settings, when we not call the module where basicConfig(...) appeared (in some.py file )? Is logging scan all the packages? Even the logging.basicConfig(...) put into an any.py and the module (any.py) never get imported, or not used anywhere, the logging setting take effect!

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  • MySQL and User level logging

    - by Adraen
    I have been looking at logging only certain users activity in MySQL. I found that the logging could be enabled or disabled for all users but one of the service using the db does a lot of queries and therefore I would like to only log specific users. Google told me that a flag can be SET to enable disable logging, however, I cannot modify the service DB connection code and asking every single user to enable logging before they do anything might not be as reliable as I want. So, do you know if there is any way to log only a set of users queries ? Thanks !

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  • What is likely cause of Android runtime exception "No suitable Log implementation" related to loggin

    - by M.Bearden
    I am creating an Android app that includes a third party jar. That third party jar utilizes internal logging that is failing to initialize when I run the app, with this error: "org.apache.commons.logging.LogConfigurationException: No suitable Log implementation". The 3rd party jar appears to be using org.apache.commons.logging and to depend on log4j, specifically log4j-1.2.14.jar. I have packaged the log4j jar into the Android app. The third party jar was packaged with a log4j.xml configuration file, which I have tried packaging into the app as an XML resource (and also as a raw resource). The "No suitable Log implementation" error message is not very descriptive, and I have no immediate familiarity with Java logging. So I am looking for likely causes of the problem (what class or configuration resources might I be missing?) or for some debugging technique that will result in a different error message that is more explicit about the problem. I do not have access to source code for the 3rd party jar. Here is the exception stack trace. When I run the app, I get the following exception as soon as one of the third party jar classes attempts to initialize its internal logging. DEBUG/AndroidRuntime(15694): Shutting down VM WARN/dalvikvm(15694): threadid=3: thread exiting with uncaught exception (group=0x4001b180) ERROR/AndroidRuntime(15694): Uncaught handler: thread main exiting due to uncaught exception ERROR/AndroidRuntime(15694): java.lang.ExceptionInInitializerError ERROR/AndroidRuntime(15694): Caused by: org.apache.commons.logging.LogConfigurationException: No suitable Log implementation ERROR/AndroidRuntime(15694): at org.apache.commons.logging.impl.LogFactoryImpl.discoverLogImplementation(LogFactoryImpl.java:842) ERROR/AndroidRuntime(15694): at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:601) ERROR/AndroidRuntime(15694): at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:333) ERROR/AndroidRuntime(15694): at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:307) ERROR/AndroidRuntime(15694): at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:645) ERROR/AndroidRuntime(15694): at org.apache.commons.configuration.ConfigurationFactory.<clinit>(ConfigurationFactory.java:77)

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  • Query Logging in Analysis Services

    - by MikeD
    On a project I work on, we capture the queries that get executed on our Analysis Services instance (SQL Server 2008 R2) and use the table for helping us to build aggregations and also we aggregate the query log daily into a data warehouse of operational data so we can track usage of our Analysis databases by users over time. We've learned a couple of helpful things about this logging that I'd like to share here.First off, the query log table automatically gets cleaned out by SSAS under a few conditions - schema changes to the analysis database and even regular data and aggregation processing can delete rows in the table. We like to keep these logs longer than that, so we have a trigger on the table that copies all rows into another table with the same structure:Here is our trigger code:CREATE TRIGGER [dbo].[SaveQueryLog] on [dbo].[OlapQueryLog] AFTER INSERT AS       INSERT INTO dbo.[OlapQueryLog_History] (MSOLAP_Database, MSOLAP_ObjectPath, MSOLAP_User, Dataset, StartTime, Duration)      SELECT MSOLAP_Database, MSOLAP_ObjectPath, MSOLAP_User, Dataset, StartTime, Duration FROM inserted Second, the query logging process is "best effort" - if SSAS cannot connect to the database listed in the QueryLogConnectionString in the Analysis Server properties, it just stops logging - it doesn't generate any errors to the client at all, which is a good thing. Once it stops logging, it doesn't retry later - an hour, a day, a week, or even a month later, so long as the service doesn't restart.That has burned us a couple of times, when we have made changes to the service account that is used for SSAS, and that account doesn't have access to the database we want to log to. The last time this happened, we noticed a while later that no logging was taking place, and I determined that the service account didn't have sufficient permissions, so I made the necessary changes to give that service account access to the logging database. I first tried just the db_datawriter role and that wasn't enough, so I granted the service account membership in the db_owner role. Yes, that's a much bigger set of permissions, but I didn't want to search out the specific permissions at the time. Once I determined that the service account had the appropriate permissions, I wanted to get query logging restarted from SSAS, and I wondered how to do that? Having just used a larger hammer than necessary with the db_owner role membership, I considered just restarting SSAS to get it logging again. However, this was a production server, and it was in the middle of business hours, and there were active users connecting to that SSAS instance, so I thought better of it.As I considered the options, I remembered that the first time I set up query logging, by putting in a valid connection string to the QueryLogConnectionString server property, logging started immediately after I saved the properties. I wondered if I could make some other change to the connection string so that the query logging would start again without restarting the service. I went into the connection string dialog, went to the All page, and looked at the properties I could change that wouldn't affect the actual connection. Aha! The Application Name property would do just nicely - I set it to "SSAS Query Logging" (it was previously blank) and saved the changes to the server properties. And the query logging started up right away. If I need to get this running again in the future, I could just make a small change in the Application Name property again, save it, and even change it back again if I wanted to.The other nice side effect of setting the Application Name property is that now I can see (and possibly filter for or filter out) the SQL activity in that database that is related to the query logging process in Profiler:  To sum up:The SSAS Query Logging process will automatically delete rows from the QueryLog table, so if you want to keep them longer, put a trigger on the table to copy the rows to another tableThe SSAS service account requires more than db_datawriter role membership (and probably less than db_owner) in the database specified in the QueryLogConnectionString server property to successfully insert log rows to the QueryLog  table.Query logging will stop quietly whenever it encounters an error. Make a change to the QueryLogConnectionString server property (such as the Application Name attribute) to get query logging to restart and you won't have to restart the service.

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  • How to simulate inner exception in C++

    - by Siva Chandran
    Basically I want to simulate .NET Exception.InnerException in C++. I want to catch exception from bottom layer and wrap it with another exception and throw again to upper layer. The problem here is I don't know how to wrap the catched exception inside another exception. struct base_exception : public std::exception { std::exception& InnerException; base_exception() : InnerException(???) { } // <---- what to initialize with base_exception(std::exception& innerException) : InnerException(innerException) { } }; struct func1_exception : public base_exception { const char* what() const throw() { return "func1 exception"; } }; struct func2_exception : public base_exception { const char* what() const throw() { return "func2 exception"; } }; void func2() { throw func2_exception(); } void func1() { try { func2(); } catch(std::exception& e) { throw func2_exception(e); // <--- is this correct? will the temporary object will be alive? } } int main(void) { try { func1(); } catch(base_exception& e) { std::cout << "Got exception" << std::endl; std::cout << e.what(); std::cout << "InnerException" << std::endl; std::cout << e.InnerException.what(); // <---- how to make sure it has inner exception ? } } In the above code listing I am not sure how to initialize the "InnerException" member when there is no inner exception. Also I am not sure whether the temporary object that is thrown from func1 will survive even after func2 throw?

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