Is there a way to pass any meaningful message, not “std::exception” to the promise’s fail callback? In the sources I found the following “void FB::variantDeferred::reject(std::exception e) const” specification. It seems when reject is called with any exception derived from std::exception the slicing happens and the right exception’s message is lost. Is there any workaround but to pass error through success callback?
std::exception is simply a base class for creating exceptions in C++. You can use a number of different methods to pass a specific string back; for example, you could throw a std::runtime_error, which accepts a message.
You could also subclass std::exception and provide an implementation of std::exception::what which returns a useful string representation of what you want.
FireBreath 2.0 will use the error message from e.what() when it creates the Error object. You can find this in the code, if you're curious how that works:
NPAPI
ActiveX
FireWyrm (used for Native Messaging)
Related
I'm just using NewRelic error trapping for my coldbox application. From OnException method, I'm just sending the error struct to log the error.
My code in onexception method
public function onException(event,rc,prc){
NewRelic.logError( prc.exception.getExceptionStruct());
}
The logerror() method resides in NewRelic.cfc and contains the following code
public boolean function logError(
required struct exception
) {
var cause = arguments.exception;
var params = {
error_id = createUUID(),
type: arguments.exception.type,
message: arguments.exception.message
};
writeDump(this.newRelic);
this.newRelic.noticeError(cause, params);abort;
return true;
}
So while error, I'm gettig the following error.
The noticeError method was not found.
You can see that, the noticeError() method is there in the object, but it is overloaded with arguments.
I'm using the same code for NewRelic error trapping in another coldfusion project without any frameworks.
Calling error.cfm through Cferror tag, and the code in error.cfm as follows
<cfset Application.newRelic.logError( variables.error )>
And in NewRelic.cfc, the logerror() method contains the same code as in the coldbox application. But it is logging errors in NewRelic without any issues.
This is the method I need to notice errors and log it in NewRelic.
noticeError(java.lang.Throwable, java.util.Map)
So I just thought to get the classname of the first argument Cause through the following code from both applications within logError() in NewRelic.cfc, to get the difference.
writeDump(cause.getClass().getName());
I'm getting
coldfusion.runtime.ExceptionScope for Coldbox application
and
coldfusion.runtime.UndefinedVariableException for normal coldfusion application
The cause argument is not throwable from coldbox application. So how to get the original error struct from coldbox application? and make it throwable to fix the noticeError method was not found issue.
The change in the underlying class happens when ColdBox duplicates the error object with CFML's duplicate() method. I doubt that ColdFusion behavior is documented anywhere, but I don't see an easy way to get around it right now other than creating your own instance of a java.langException and populating it with the details of the original error.
If you want to modify the ColdBox core code, this happens here:
https://github.com/ColdBox/coldbox-platform/blob/master/system/web/context/ExceptionBean.cfc#L43
I have entered this ticket for the ColdBox framework for us to review if we can stop duplicating the error object in future versions of the framework.
https://ortussolutions.atlassian.net/browse/COLDBOX-476
Update: Adam Cameron pointed out this ticket in the Adobe bug tracker that details this behavior in the engine. It was closed as "neverFix".
https://bugbase.adobe.com/index.cfm?event=bug&id=3976478
In CUDA we can get to know about errors simply by checking return type of functions such as cudaMemcpy(), cudaMalloc() etc. which is cudaError_t with cudaSuccess. Is there any method available in JCuda to check error for functions such as cuMemcpyHtoD(), cuMemAlloc(), cuLaunchKernel() etc.
First of all, the methods of JCuda (should) behave exactly like the corresponding CUDA functions: They return an error code in form of an int. These error codes are also defined in...
the cudaError class for the Runtime API
the CUresult class for the Driver API
the cublasStatus class for JCublas
the cufftResult class for JCufft
the curandStatus class for JCurand
the cusparseStatus class for JCusparse
and are the same error codes as in the respective CUDA library.
All these classes additionally have a static method called stringFor(int) - for example, cudaError#stringFor(int) and CUresult#stringFor(int). These methods return a human-readable String representation of the error code.
So you could do manual error checks, for example, like this:
int error = someCudaFunction();
if (error != 0= {
System.out.println("Error code "+error+": "+cudaError.stringFor(error));
}
which might print something like
Error code 10: cudaErrorInvalidDevice
But...
...the error checks may be a hassle. You might have noticed in the CUDA samples that NVIDIA introduced some macros that simplify the error checks. And similarly, I added optional exception checks for JCuda: All the libraries offer a static method called setExceptionsEnabled(boolean). When calling
JCudaDriver.setExceptionsEnabled(true);
then all subsequent method calls for the Driver API will automatically check the method return values, and throw a CudaException when there was any error.
(Note that this method exists separately for all libraries. E.g. the call would be JCublas.setExceptionsEnabled(true) when using JCublas)
The samples usually enable exception checks right at the beginning of the main method. And I'd recommend to also do this, at least during the development phase. As soon as it is clear that the program does not contain any errors, one could disable the exceptions, but there's hardly a reason to do so: They conveniently offer clear information about which error occurred, whereas otherwise, the calls may fail silently.
I created a custom component for a proprietary service. If this service is down i get noticed via a call of a callback function. I am throwing a custom exception at this point.
Sending exchanges to the producer/ consumer will yield no errors or exceptions (all seems to fine).
So i need to implement an emergency stop if my custom exception is thrown. I read a bit about exception handling in camel. I think i need a context-scoped onException(MyException.class).??? but what then?
Is this working on exceptions that are called without relation to an exchange? If this is working how to handle it. I want to stop certain routes in this case.
here you can find to stop routes from a route: http://camel.apache.org/how-can-i-stop-a-route-from-a-route.html.
If you do the call of the proprietary service in a route you do have an exchange btw.
kind regards,
soilworker
I created a little workaround: I set a boolean i the callback method is called. On each call of process i check this boolean and if true i throw an exception.
With this the exception is within normal camel exception handling and onException could be used.
I found questions here Should a retrieval method return 'null' or throw an exception when it can't produce the return value? and Should functions return null or an empty object?, but I think my case is quite different.
I'm writing an application that consists of a webservice and a client. The webservice is responsible to access data, and return data to the client. I design my app like this:
//webservice
try
{
DataTable data = GetSomeData(parameter);
return data
}
catch (OopsException ex)
{
//write some log here
return null;
}
//client:
DataTable data = CallGetSomeData(parameter);
if(data == null)
{
MessageBox.Show("Oops Exception!");
return;
}
Well, there is a rule of not returning null. I don't think that I should just rethrow an exception and let the client catch SoapException. What's your comment? Is there better approach to solve this problem?
Thank you.
In your case, an exception has already been thrown and handled in some manner in your web service.
Returning null there is a good idea because the client code can know that something errored out in your web service.
In the case of the client, I think the way you have it is good. I don't think there is a reason to throw another exception (even though you aren't in the web service anymore).
I say this, because, technically, nothing has caused an error in your client code. You are just getting bad data from the web service. This is just a matter of handling potentially bad input from an outside source.
Personally, as a rule of thumb, I shy away from throwing exceptions when I get bad data since the client code can't control that.
Just make sure you handle the data == null condition in such a way that it doesn't crash your client code.
In general i try to design my webservices in such way that they return a flag of some sort that indicates whether there was a technical/functional error or not.
additionally i try to return a complex object for result not just a string, so that i can return things like:
result->Code = "MAINTENANCE"
result->MaintenanceTill = "2010-10-29 14:00:00"
so for a webservice that should get me a list of dataEntities i will return something like:
<result>
<result>
<Code>OK</Code>
</result>
<functionalResult>
<dataList>
<dataEntity>A</dataEntity>
</dataList>
</functionalResult>
</result>
so every failure that can occur behind my webservice is hidden in a error result.
the only exceptions that developers must care about while calling my webservice are the exceptions or errors that can occur before the webservice.
All the WebServices that I've used return objects, not simple data types. These objects usually contain a bool value named Success that lets you test very quickly whether or not to trust the data returned. In either event, I think any errors thrown should be untrappable (i.e. unintentional) and therefore signify a problem with the service itself.
I think there may be a few factors to consider when making a decision:
what is the idiomatic way to do this in the language your using (if it wasn't a webservice)
how good your soap/webservice library is (does it propogate exceptions or no)
what's the easiest thing for the client to do
I tend to make the client do the easiest, idiomatic thing, within the limitations of the library. If the client lib doesn't take care of auto restoring serialized exceptions I would probably wrap it with a lib that did so I could do the following.
Client:
try:
# Restore Serialized object, rethrow if exception
return CallGetSomeData(parameter);
except Timeout, e:
MessageBox.Show("timed out")
except Exception, e:
MessageBox.Show("Unknown error")
exit(1)
WebService:
try:
return GetSomeData(parameter) # Serialized
except Exception, e:
return e # Serialized
Your first problem is "a rule of not returning null". I would strongly suggest reconsidering that.
Returning a SoapException is a possibility, but like hacktick already mentioned, it would be better to return a complex object with a status flag {Success,Fail} with every response from the web service.
I think it all boils down to the question whether or not your client can use any info as to why no data was returned.
For example - if no data was returned because the (say sql) server that is called in GetSomeData was down, and the client can actually do something with that information (e.g. display an appropriate message) - you don't want to hide that information - throwing an error is more informative.
Another example - if parameter is null, and that causes an exception.. (although you probably should have taken care of that earlier in the code.. But you get the idea) - should have throw an appropriate (informative) exception.
If the client doesn't care at all why he didn't get any data back, you may return null, he'll ignore the error text anyhow and he's code will look the same..
If your client and service are running on different machines or different processes, it will be impossible to throw an error from the service and catch it on the client. If you insist on using exceptions, the best you can hope for is some proxy on the client to detect the error condition (either null or some other convention) and re-throw a new exception.
The general practice in handling exception is, when the sequence of flow is expected in the normal circumstance where as the sequence could not be completed due to non-availability of resources or expected input.
In your case, you still need to decide how do you want your client side code to react for null or exception.
How about passing in a delegate to be invoked when anything bad happens? The delegate could throw an exception if that's what the outside could would like, or let the function return null (if the outside code will check for that), or possibly take some other action. Depending upon the information passed to the delegate, it may be able to deal with problem conditions in such a way as to allow processing to continue (e.g. the delegate might set a 'retry' flag the first few times it's called, in case flaky network connections are expected). It may also be possible for a delegate to log information that wouldn't exist by the time an exception could get caught.
PS--It's probably best to pass a custom class to the problem-detected delegate. Doing that will allow for future versions of the method to provide additional information to the delegate, without breaking any implementations that expect the simpler information.
Exceptions are recommended in the same process space. Across processes, it is only through information that a success/failure is evaluated.
Since you are the client to your webservice, you can log the exception at the service layer and return null to the client, yet the client should still know if the CallGetSomeData returned null because a) data is not available, or b) there is a database exception as the table is locked. Hence its always good to know what has caused the error for easier reporting at client side. You should have a error code and description as part of your message.
If you are not consuming your webservice then you should definetly throw exception for the same reasons mentioned above, client should know what has happened and its upto them to decide to what to do with that.
When I design a class I often have trouble deciding if I should throw an exception or have 2 func with the 2nd returning an err value. In the case of 2 functions how should I name the exception and non exception method?
For example if I wrote a class that decompresses a stream and the stream had errors or incomplete I would throw an exception. However what if the app is trying to recover data from the stream and excepts an error? It would want a return value instead? So how should I name the 2nd function?
Or should I not have both an exception method and a nonexception method?
Or should I not have both an exception method and a nonexception method?
That. Unless you really have time to burn maintaining two separate but mostly-identical methods.
If you really need to allow for clients that won't consider errors exceptional, then just indicate them with a return value and be done with it... Otherwise, just write the exception-throwing version and let the odd error-eating client handle the exception.
It depends on the language, but...
In my opinion, two versions of each potentially failing method imposes too high a cognitive burden on the API user, and too high a burden on the API maintainer. My personal preference is for exceptions, since that's fewer parameters to remember the order of.
I believe that you should try to use exceptions even if you're not going to exit program in some cases. You just need to create a specific exception type for your errors. And catch only them when you need to do some spefic logic. All other exceptions will go to upper level of your code.
For example you've created function which throws exception on any error. And you don't want to exit program if user specified incorrect file name. Here is how it can look:
## this is top level try/catch block
try {
## your main code is here
...
## somewhere deep in your code
try {
## we trying to open file specified by user
}
catch (FileNotFoundException) {
## we are not going to exit on this error
## let's just show a user an error message
## and try to ask different file to open
}
} catch (Exception) {
## catch all exceptions here
## the best thing we can do here is save exception to log and quit }
}
We just need to create hierarchy of exceptions (if your language allows it):
Exception <-- MoreSpecificException
This approach is used in Java
Exceptions should normally be used for exceptional conditions, whatever they may be. Being unable to decompress a file is probably an exceptional condition (unless, for example, you're writing a program to scan for badly compressed files). Bad data may or may not be exceptional.
If you've got a class decompressing a stream, then what it should do is decompress the stream, and not try to interpret its contents. Another class should use the first class to get decompressed input, and do the interpretation. That gives you separation of functionality, and good cohesion. Avoid classes where you're tempted to put an "And" in their names: "DecompressAndParseInput" is a bad class name.
Given two classes, there's no particular reason why you have to use the same error-reporting
method for both. The decompressor could throw, and the parser could return an error code.
I would only throw an exception on the decompression function if the results were not usable. If they were usable, return the results and then the function that reads those results can throw an exception instead. IE
try
{
results = decompress(file); // only throws exceptions on non-usable files
} catch (FileNotFoundException) {
// file was not usable, can't recover anything, insert nuclear error handling here
}
try
{
read(results);
} catch (ErrorThatIsRecoverableException) {
partialRead(results);
}
so read() is the function you call on normal data, partialRead is the function that handles trying to recover screwed-up-but-still-usable data. And of course, you don't necessarily need exceptions or separate functions at all- you could do the error handling all within the read() function.