This is about NodeJS and Express. I want to add an error handler that simply logs the error in my preferred way. This way also takes care of console output. I don't want, at this point in time anyway, to replace the functionality of the Express default error handler. I want the default error handler to continue doing its thing for the time being, with one exception: Since my logging already took place, and also covers console output, I want the default error handler to pretty much stop adding to the console.
My question is: How do I accomplish this? I did some searching and found nothing, so unsure if I may be using the wrong keywords.
Related
My goal is to influence the error descriptions that appear in BizTalk Administration Console in the Error Information tab of suspended instance windows, after errors occur in my custom functoids. If possible, I would also like the ErrorReport.Description promoted property to display this error description on the failed message.
I've read everything I can find about custom functoid development, but I can't find much about error handling within them. In particular, whenever my functoids throw exceptions, I see the boilerplate "Exception has been thrown at the target of an invocation" message that occurs whenever exceptions occur through reflection, rather than the message on the exception itself.
I had hoped to find something within the BaseFunctoid class framework that would allow me to submit an error string, so as to traverse the reflection boundary. Is there some way to pass error information from within a custom functoid, such that the BizTalk Administration Console will display it?
If I emulate the approach taken by DatabaseLookupFunctoid and DatabaseErrorExtractFunctoid, is there some way I can fail the map with the extracted error, rather than mapping it to a field on the destination schema as is shown in its examples?
The simplest way to do this is using custom C#, writing something like this in your code:
System.Diagnostics.EventLog.WriteEntry("EVENT_LOG_SOURCE", "Error message...", System.Diagnostics.EventLogEntryType.Error);
As Johns-305 mentions, you need to make sure your event source is registered (e.g. System.Diagnostics.EventLog.CreateEventSource("EVENT_LOG_SOURCE", "Application") - but this should really be done as part of your installation steps with an EventLogInstaller or some kind of script to set up the environment). It's certainly true that error handling in BizTalk is just .NET error handling, but one thing to keep in mind is that maps are actually executing as XSLT, and the context in which their executing can have a major impact on how exceptions and errors will be handled, particularly unhandled exceptions.
Orchestrations
If you're executing a transform in an orchestration that has exception handling in it, the exception thrown will be handled and may even fall into additional logging you have in the orchestration - in other words, executing a throw from a C# functiod will work the way you'd think it would work elsewhere in C#. However, I try to avoid this since you never know if a map will at some point be used else where and because exception handling in XSLT doesn't always work the way you'd think (see below).
Send/Receive Ports
Unfortunately, if you're executing a map on a send or receive port and throw an exception within it, you will almost definitely get very unhelpful error message in the event log and a suspended instance in the group hub. There is no easy, straightforward way to simple "cancel" a transform - XSLT 1.0 doesn't have any specified way of doing that (see for example Throwing an exception from XSLT). That leaves you with outputting an error string to a particular node in the output (and/or to the EventLog), or writing lots of completely custom XSLT to try to validate input, or designing your schemas properly and using a validating component where necessary. For example, if you have a node that must match a particular regex, or should never be empty, or should never repeat more than X times, make sure you set those restrictions on the schema and then make sure you pass it through the XmlValidator or similar before attempting to map.
The simplest answer is, you just do.
Keep in mind, there is nothing special at all about error handling in BizTalk apps, it's just regular plain old .Net error handling.
So, what you do is catch the error in you code, write the details to the Windows Event Log (be sure to create a custom Event Source) and...that's it. That is all I do. I don't worry about what appear in BT Admin specifically.strong text
I am trying to develop a standard when I code applications.
I was curious as to what other developers did when it comes to sql errors or general program errors. Do you output the error to the screen, write to a log file, or something else?
It really depends on the severity of the error.
Is it a show stopper?
Can the software automatically retry and get away with no message?
Can it be ignored?
You can log every exception, or just certain ones, or none. I have a custom Exception class which logs every exception created (of that type).
I have an unhandled exception handler which emails me when there is one.
I'd only send a message to the user when it will change the way the application works from the user's point of view.
Your question is a bit subjective and you would get opinion-based answers if the entire community bothered to answer.
If the error is relevant and important to the user (e.g.: invalid username/password) display it to the user using a message box.
If the error is relevant to the developer, or can be used in the debugging process, use a log or a console output.
The trick is to identify which and how the errors should be displayed to the user. You don't want to bombard the user with exceptions and complicated errors on which the user has no idea on how to act upon.
All of a sudden the errors that Dojo (1.8.3 from Google CDN) is spitting out empty errors, which makes debugging impossibly hard. For example, if I forget to require a dependent before using it, I get the usual
> dojo/parser::parse() error ReferenceError {}
... in the error console, but I remember getting more information in the ReferenceError (spindown arrow was present), giving me the arguments of the error as well as the message making it easy to figure out what I had done wrong.
I have isDebug : true in my dojoConfig, but it just doesn't want to tell me anything anymore.
What gives?
I've been having the same problem using Dojo 1.8.3 as well. When I close my developer tool's console and then re-open it the Error had the spindown and more details as expected. Seems stupid, but give it a try and see if that at "fixes" it for you. I planned on digging a little further into this later, so if I find any additional details I will make sure to update my answer with them.
I'm working on a site and to help catch errors that we may not hear about, I've created a custom 500 error page.
This page basically records information about the current situation and logs it including the following:
Request.Servervariables("URL")
But, the log seem to actually be providing information about the location of the error.asp file instead of the actual file causing the error. And it doesn't seem to pick up Server.GetLastError().
Any ideas on how to ensure these scripts pick up the errors and deatils about the page causing the error and not the page that is used for 500 errors?
NOTE: When there's an error, the url in the address bar is always the address fo the page causing the error, but the log shows the error handler page 'error.asp'.
I would follow what Dee said, but also be aware that there was something finicky with IIS7 (or 7.5). I can't remember exactly, but you have to do something special to make sure it works on IIS7. Check out this article. IIS7 breaks the server.getlasterror and there is a workaround provided.
Also a cool thing to do is to email yourself those errors. So in your custom 500 asp script just fire off an email with the details. Depends on how critical errors are to your program, but it's good to be in the loop rather than have another log to worry about.
Could someone provide info about error-handling in wxWidgets or a pointer to documentation?
Specifically, I discovered this behavior: I try to create a wxImage from a file. This is in an event-handler. The file is not present. The call to the image constructor does not throw an exception. (I understand that no wxWidgets code throws exceptions.) A call to image.Ok() returns false. Fine. But after my event-handler exits, wxWidgets gratuitously pops up an error message dialog. That's okay for this particular application, but I wonder how to stop that from happening if I want to handle the error myself. I suspect that the dialog is coming from an event-handler, but I search for things like EVT_ERROR, and came up empty.
There is the class wxLogNull for suppressing those log messages. See http://docs.wxwidgets.org/stable/wx_wxlognull.html#wxlognull where also an example is given.
Read the wxLog overview for more details on how wxWidgets handles this.
You can define your own log target which would throw an exception if an error message is logged. Of course, then you'd probably need to catch it in your event handler anyhow as you probably don't want to just give the user a relatively useless "File couldn't be opened" message but rather a "Image couldn't be opened" one. And if you do this, then why not just test for file.IsOk() directly and use wxLogError() yourself? IOW you can do what you want but I don't really see how is it better than the traditional exception-less way of doing things in this particular case.